Executive Summary - Portland State Universityweb.cecs.pdx.edu/~far/Past Capstone Projects/2010/Wind...Optical Mounting System for Laboratory Research Final Design Report 1 Executive

Optical Mounting System for Laboratory Research

Final Design Report

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Executive Summary

Portland State University is receiving a closed-loop, subsonic wind tunnel to aid in the

research of boundary layer effects, turbulent kinetic energy, and heat transfer effects.

Each of these effects changes the density of the surrounding fluid and may be visually

represented by utilizing Schlieren imaging techniques. Schlieren imaging uses a light

source, convex collimating lenses, concave spherical mirror, and a knife edge to capture

images through a medium. The light travels through the medium, is reflected by a mirror,

travels back through a double convex collimating lens, past the knife edge, and into a

camera. Light refracts differently through various densities of the same fluid. The knife

edge blocks light not refracted through a density gradient, and the camera captures the

density profile as illustrated by captured image. This method provides a very useful

qualitative description of the fluid phenomena occurring through transparent media.

The optical components of this system require precise calibration. To decrease

adjustment time between tests, a frame was needed to hold all of the optical equipment.

With all of the optics mounted to one frame, the entire system may be moved in concert

rather than moving each component individually. This removes the need for adjustment

when moving the system in a single focal plane. Once the focal length is changed, the

system must be recalibrated. Space in the lab is limited, making it difficult for multiple

people to maneuver in the space available. Due to this space restriction, movement and

calibration of the system must be achieved by a single user and be assembled and

disassembled by no more than two people. Only one side of the wind tunnel is easily

accessible, therefore, access to the other side is achieved only by traveling under the test

area. Taking this into account, the optical mounting system was designed such that once

the focal plane is established, calibration and operation may be completed from the user

side of the wind tunnel.

The final design enables the execution of Schlieren imaging by one user and minimizes

adjustments needed by the individual components. Due to the modular properties of the

material used, future integration of additional components and functions will be simple.


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Table of Contents

Introduction: .................................................................................................................................... 4

Mission Statement: ......................................................................................................................... 5

Summary of Main Design Requirements:........................................................................................ 6

Ease of Use .................................................................................................................................. 6

Optical Component Mounting ..................................................................................................... 6

Mounting Structure and Mobility of Optical Plane ..................................................................... 7

Base Structure ............................................................................................................................. 7

Storage ........................................................................................................................................ 8

Cost .............................................................................................................................................. 8

Top Level Design Alternatives: ........................................................................................................ 8

Final Design Evaluation: ................................................................................................................ 10

Material Selection: ........................................................................................................................ 11

Final Design: .................................................................................................................................. 11

Clamps ....................................................................................................................................... 13

Linear Guide Rails ...................................................................................................................... 15

Optical Mounting Frame ........................................................................................................... 16

Optical Component Mounting ................................................................................................... 17

Cost Analysis .............................................................................................................................. 18

Future Design Considerations: ...................................................................................................... 19

Conclusion: .................................................................................................................................... 20

Appendix A: Components and Equipment for Schlieren Photography ........................................ 21

Appendix B: Initial Design Considerations .................................................................................... 22

Appendix C: Decision Matrices ..................................................................................................... 25

Appendix D: Bill of Materials (BOM) and Quotes ......................................................................... 26

Appendix E: Calculations .............................................................................................................. 29

Appendix E1: Fastener Calculations for Leg Clamps ................................................................. 29

Appendix E2: Deflection Calculation for Linear Guide Rails ..................................................... 32

Appendix E3: Torsional Deflection of Vertical Rise Members .................................................. 35

Appendix E4: Loaded Clamp Deflection Calculation ................................................................ 38

Appendix E5: Calculation for Line-of-sight Deflection .............................................................. 41


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Appendix F: Additional Technical and Parts Drawings ................................................................. 46

Appendix G: Procedures ............................................................................................................... 56

Appendix G1: Assembly Procedure .......................................................................................... 56

Appendix G2: Operation Manual ............................................................................................. 57

Appendix H: References ............................................................................................................... 60


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Introduction: Schlieren photography is a method of identifying and imaging many phenomena common

in the fluid sciences. This setup for optics is functional in any of a number of different

configurations. One such configuration is being built and tested for future integration

with the wind tunnel in the Portland State University’s (PSU) Daimler Wind Tunnel

Laboratory. As techniques associated with schlieren photography become increasingly

quantitative, schlieren imaging systems become more advantageous in the laboratory

environment. Figure 1 on the next page shows a schematic of the current optics

arrangement for reference.

Although a relatively simple configuration of optics, schlieren imaging requires a number

of components that need to be carefully aligned in order to function at maximum

potential. In its proposed use with the wind tunnel at PSU, the system will be required to

resolve images in different areas along the entire length of the test area and operate at a

variety of focal depths. In order to collect any meaningful quantitative or qualitative data

from this imaging system, the optics, including a spherical mirror, up to two double-

convex collimating lenses, a camera, and a variety of filters, must be carefully calibrated

and aligned. Appendix A has a complete list of optics currently being used and some

potential components for future experimentation.

In order to mitigate the process of setup and calibration of the optics, Dr. Raul Cal,

Assistant Professor at PSU, has requested that an optics mounting system be designed

and constructed for the laboratory. This mounting system is to add mobility to the optics

without altering the calibration of the optics or changing their relative spacing unless

determined by the user. Additionally, the system should interface with other equipment

intended for lab use and facilitate the future construction of other potential experimental

apparatus where feasible.

Interviews with Dr. Cal have revealed a number of experiments to take place in the wind

tunnel laboratory that will interface or require the use of some of the mounting system


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designed here. These experiments are discussed more extensively in the Future Design

Considerations section.

Test Area

Spherical M

irro

r Collimating

Lens

Camera

Light

Source

Test Chamber Width 1.2 m

Knife Edge

“Important”

Central 50% of

test area = .6 m

X X

Absolute minimum distance Xis 0.3 m.

Figure 1: Schematic of a schlieren imaging system. Shown is the single-mirror off-axis

configuration selected for use in the PSU wind tunnel.

Mission Statement: This design is to provide a mounting system for all optical components necessary in

schlieren imaging used in the wind tunnel research laboratory at PSU. The mounting

system will be designed to simplify and expedite the setup and calibration of optical

components by allowing such components to move in concert. The mounting system will

minimize the need to recalibrate with any change in focal plane and adhere to all aspects

of the product design specification (PDS). The mounting system is to traverse the length

of the test area on rails that will be used to house additional equipment for other

experiments to be performed in the Daimler Laboratory.


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Summary of Main Design Requirements: The main customers for this project are Dr. Cal, his research partners, and assistants, who

will be collecting data with this apparatus and training others in future use. Based on

interviews with Dr. Cal throughout the project, the product requirements were divided in

to subsections in order to streamline the design process. Table 1 later in this section

summarizes the PDS targets and the performance generated by the prototype. The

summaries of each subsection of the design requirements are described below in order of

relative importance.

Ease of Use Of the design requirements, the operability of the system is the most important. When

the wind tunnel laboratory is fully operational, there will likely be no more than one or

two researchers present at any given time. Given this constraint, it is important that any

equipment, data acquisition system, or imaging apparatus to be used in the lab be

operable by a single user. The specific requirements for this design were that the system

be calibrated, moved into all functional configurations including the exchange of optical

components, or be moved once disassembled by a single user. The assembly of the

mounting device from its component parts is to be performed by a maximum of two

people in 5 hours or less.

Optical Component Mounting The components used in schlieren photography require careful tuning and calibration.

Optical components may change depending on the nature of the experiment in progress

or the size of the image being resolved. It is required that the individual mounting for

each component be adjustable to accommodate different diameters and focal capabilities

of mirrors, lenses, and cameras. The original requirements listed in the PDS were that

mirrors and lenses of diameters ranging from 7.5 cm to 25.4 cm (3 in. to 10 in.) be

useable with the system. This requirement has been changed by the customer following

successive work with the optics. The range of mirror diameters is now from 15.2 cm to

30.4 cm (6 in. to 12 in.) and the range of lens diameters is now 7.5 cm to 15.2 cm (3 in. to

6 in.). The need for angular mobility (pitch and yaw) adjustable to 10 for the lens


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remains but has been removed for the mirror as it will remain essentially fixed except for

the ability to translate vertically.

Mounting Structure and Mobility of Optical Plane The original specification for the mounting apparatus stated that the focal plane of any

optics used in experiments need to be mobile about much of the test area. Specifically,

the focal plane of the optics needs to traverse the entire 5-meter length of the test area (x-

direction), the central 50% of the test area (y-direction) and the entire 0.8 m (20 in.)

height of the test area (z-direction). Figure 2 shows the test area with an imposed

coordinate system. The original design requirements stated that the mounting apparatus

was to allow the optical setup to image experiments through the tunnel in a vertical

orientation. This requirement was removed by the customer and allows for a more sleek

design. Regardless of orientation, the assembled mounting structure will span the test

area of the wind tunnel to a maximum of 2 meters.

Figure 2: Schematic of the wind tunnel test area with coordinate system. For the test

area, the doors open to the user side. The inlet is the upper left portion of the test area

and the outlet is the lower right as shown.

Base Structure Initial interviews indicated the base of the mounting device needed to be mobile down the

length of the entire test area. Further, it would need to be sufficiently resilient to support

a wide variety of experimental equipment. If possible, the base is to absorb background

vibration that would otherwise be imparted to the optics from sources such as the fan and

motor of the wind tunnel or from automotive traffic outside the building. At a minimum,


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the structure would need to support its own weight and up to 20 kg (44 lbs) worth of

optics or equipment. In its fully extended configuration, this could include a moment of

up to 20 N-m (15 ft-lbs). Optics of this nature are sensitive to vibration and change of

alignment. For this reason, the frame should exhibit only minimal deflection under

expect loads.

Storage The Daimler Wind Tunnel Laboratory will be almost entirely occupied by the wind

tunnel itself. This leaves little space in the room for the storage of other equipment.

Thus, the system needs to be removable from the wind tunnel when not in use. All

components of the system must be stored safely and out of the way. If possible the entire

system should fit into a corner of the lab or slide under an elevated section of the wind

tunnel when disassembled.

Cost In all engineering projects, a balance of system performance versus cost needs to be

established. This project was funded by contributions from ASME, Don Mueller

(Director of Student Services and Facilities), and Dr. Cal’s research grant and startup

moneys. Initial estimates on funding indicated resources totaling $1750 for the

completion of the project.

Top Level Design Alternatives:

During the initial round of group design, external searches including a patent search

showed that there were no existing systems that provided a complete solution to the PDS

requirements. Following this search, several rounds of internal searches were undertaken

in order to develop designs capable of satisfying all requirements. This process began

with a series of brainstorming sessions. The major components of the design were

identified as being the base, mounting system, and materials. Two minutes were

dedicated to each of these components in which each team member created a list of

possible solutions. Each idea was evaluated by the team after which a design was


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generated by each member of the team and submitted to the group for evaluation.

Examples of initial designs can be found in Appendix B.

Prior to performing the final design decision matrix (Appendix C) for overall system

design the combined ideas and concepts were shown to the customer. At this point, the

customer expressed concern regarding several aspects of the proposed designs. Noted in

the Storage subsection, the wind tunnel footprint encompasses most of the usable area in

the laboratory which limits available working space, as illustrated in Figure 3. The

customer concluded the proposed designs were not compatible with the space available.

Figure 3: 3-D rendering of wind tunnel installation in the PSU fluids laboratory. Test

area not shown in the figure. When disassembled, the mounting structure should fit in

back corner (top right of figure) or under part of the tunnel itself.

Dr. Cal decided that simplicity of the optical mounting fixture and conservative use of

space were paramount. A meeting was held Wednesday, 10 March, 2010 to revise the

product design specifications. Upon reviewing the updated design requirements, the

following were eliminated: the ability to resolve images vertically through the test area,

the need for the mounting structure to support itself, and the requirement for individual

optical component motion laterally along the length of the test area. These changes were

finalized with customer approval. A final design was chosen using a weighted scoring

matrix and can be found in Appendix C.


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Final Design Evaluation: Table 1: Final PDS Summary

Performance

Requirements Customer Priority Metric Target Basis Verification

Working Prototype Cal High Yes/No Yes Team Req. Prototype

Manual Control Cal Low Yes/No Yes Cust. Req. Prototype

Horizontal

Adjustment (Optics)

Cal Med. Distance 5 cm Cust. Req. Prototype

Translate along

Chamber Length

Cal High Time Yes Cust. Req. Prototype

Stable with Rotation

Moment

Cal High Torque 50 Nm Team Req. Experiment

Ease of Use


Number of

Operators

Cal Med. People 1 Cust. Req. Prototype

Documentation


Detailed Drawings Cal High Yes/No Yes Team./Cust.

Req.

Cap. Faculty

Dr. Cal

Bill of Materials Cal High Yes/No Yes Cust. Req. Dr. Cal

Cost


Low Construction

Cost

Cal High Dollars <$1750 Cust. Req. Invoices

Installation


Install/Remove with

Chamber In Place

Cal High Yes/No Yes Cust. Req. Prototype

Removal or

Installation Time

Cal High Time < 5 hrs Cust. Req. Set up

Zero Facility

Modifications

Cal High Yes/No Yes Cust. Req. Prototype


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Material Selection: Once the requirements were finalized, the process of material selection began. From

the initial rounds of design, it was determined that the overall material selection would

dramatically impact the system. Several materials were identified as possible

candidates: (1) square steel tube, (2) UnistrutTM

, and (3) T-SlotTM

(an extruded,

modular aluminum product). An experiment, utilizing strain gauges coupled with

various input loading conditions was devised to compare the materials according to the

following criteria:

Maximum strength per unit mass (corresponds to minimum strain per unit

length)

Greatest self-damping within the material (limits the external damping

necessary for the system as a whole)

Cost, manufacturability, and customer preference were identified as differentiating

criteria. T-SlotTM

was identified as the material of choice through use of a decision

matrix (Appendix C). Although the most expensive solution, T-SlotTM

presented the

greatest versatility in manufacturability with the added advantage of overall maximum

strength per unit mass. Additionally, some portions of the wind tunnel test chamber

already incorporate T-SlotTM

. This presents an opportunity for future compatibility with

other research equipment in the lab.

Final Design: The material selection enabled the final design to progress rapidly. Futura Industries, the

manufacturer of T-SlotTM

, provided an add-in toolbox for SolidWorksTM

which allowed

for virtual design with accurate material dimensions. The add-in also provided guidance

on design limitations of the materials, the ability to address issues concerning

connectivity, a complete bill of materials (BOM), and instructions for fabrication by the

material manufacturer. The complete bill of materials can be found in Appendix D.

Figure 4 depicts a SolidWorksTM

rendering of the final design and its orientation to the

wind tunnel structure utilizing appropriate T-SlotTM

materials and accurate dimensions.


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Two horizontal guide rails span the length of the wind tunnel test area. These two

members allow the mounting apparatus to travel linearly along the length of the test area

while maintaining a planar relationship with an established line of sight. The support

rails also provide a constant base for location and calibration of the optics.

Figure 4: Rendered final design with relation to wind tunnel test area. For clarity, the

main body of the test area has been hidden; only the support structure to which the

clamps mount is shown.

Figure 5 depicts the final design in greater detail. The upper right corner of the figure

shows the schlieren imaging components attached to an optical mount allowing

adjustment along its length, perpendicular to the test area. In the lower left corner, a

convex spherical mirror is depicted in a 3-point mounting apparatus which can

accommodate mirrors of various sizes.


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Figure 5: Detailed rendered final design system mounting

Clamps After reviewing the design drawings of the wind tunnel, four 6 in. square tube legs were

identified as support for the test area. To ensure that the wind tunnel is not permanently

modified, compression/friction clamps were designed to attach the horizontal beam

members to the square tube legs. Extreme conditions were considered to determine the

normal force required to sufficiently and safely attach the clamps. The imaging system,

estimated to be 90 kg (200 lbs), was located to one extreme of the test area. Then, an

additional 90 kg (200 lbs) vertical load was added for an additional factor of safety. All

values assumed are worst case estimates of actual loading scenarios. In this situation,

135 kg (300 lbs) of downward force per clamp was estimated. Given the estimated

coefficient of friction for the rubber isolation between the clamps and the legs, 195 kg

(430 lbs) of normal force is required for each clamp [Shigley]. The calculation for

fastener sizing and clamp deflections are shown in Appendix E1.

Initial designs were configured using SolidWorksTM

and Finite Element Analysis (FEA)

was used to determine appropriate material selection. Iterative FEA models determined

1080 steel plate with a minimum 10 gauge thickness was the best choice. This thickness


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produced material stresses within the elastic range of the steel while remaining easily

positioned by a single operator (Appendix E4).

Fastener sizing was calculated using the desired normal force for the clamps [Shigley].

Various fastener-hole patterns were analyzed resulting in three holes per tab being chosen

to evenly distribute the fastener forces. One quarter inch (1/4”) fasteners were

determined to be sufficient; however, 5/16” were chosen for reliability and to increase the

factor of safety against bolt failure (Appendix E1).

The initial “bucket” design utilized four-fastener holes within the linear rail supports of

the clamps; however, the commercial manufacturing consultant, Ecklund Industries, Inc.,

determined the four-fastener design would need to be fabricated in two pieces to

accommodate the desired hole pattern. The depth of the bucket in the original design was

greater than the width and would require special tooling to manufacture. The proposed

two-piece design would require significant surface preparation prior to welding thus,

dramatically increasing overall production costs. The final design, depicted in Figure 6,

utilizes a simpler to manufacture two-hole bucket, which would be hydraulically press

broken. The figure also includes a photograph of the completed two-piece clamp

assembly. The pocket tab has been welded to the “hat” of the clamp for structural

rigidity. The reverse side of the clamp was designed and fabricated without the front side

mounting bucket. Part drawings are provided in Appendix F.

Figure 6: Detailed rendering of final clamp design and photograph of manufactured

mounting clamps.


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Linear Guide Rails Two T-Slot

TM ts15-30 beams were chosen to span the distance between clamps. This

material provides compatibility with the imaging structure material, weight savings over

steel and high moment of inertia when orientated correctly. Figure 7 depicts an exploded

view of a wind tunnel test area support leg with support clamps and guide rail.

Figure 7: Detailed rendering of linear guide rail/clamp/test area leg orientation

Vertical deflection was of concern as minimal deviation from an established imaging

plane is desired. The entire imaging system was FEA modeled as a point load (worst

case). Two members spanning 5.25 m (208 in.), the entire length of the test area, support

the optical frame and equipment. One member was modeled as the two beams are

identical and support equal loads. The single member was modeled as a wire frame

beam, simply supported at each end, with two concentrated point loads in the center.

These point loads were separated by 0.46 m (18 in.), the approximate width of the frame.

The frame was conservatively estimated to have a total weight of 45 kg (100 lbs). In the

analysis, each of the two point loads was approximated to be 11.3 kg (25 lbs). The

support beam calculations can be found in Appendix E2.

T-SlotTM

has a complex cross-section; data for the moments of inertial and cross-

sectional areas provided by the manufacturer were used to model the members as a

general profile in AbaqusTM

. Through this method it was determined that the spanning

member will have a maximum deflection of 2 cm (0.78 in.). This deflection was deemed

acceptable as the overall resolution of the system is equal to the radius of the spherical


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mirror. The radius is greater than the maximum expected deflection, thus affects to the

field of view will not remove the desired focal plane from the calibrated line of sight.

Optical Mounting Frame The optical mounting frame consists of an inner closed loop structure and an outer sleeve

design and is depicted in Figure 8. The loop-sleeve design allows the extreme ends of the

frame to be manually adjusted closer or further away from the wind tunnel test area. This

adjustment is necessary as the internal dimension must vary depending on the focal

length of the mirror used in the schlieren imaging setup. The mirror determines the focal

length of the system and can differ depending on the size of the desired final image.

Figure 8: Detailed rendering of optical frame design.

There are six linear bearings depicted in Figure 8. Four bearings, mounted directly to the

loop-sleeve frame, allowing linear translation along the length of the horizontal beam

member clamped to the square tube legs. Two larger linear bearings are orientated

vertically on the ends of the loop-sleeve design. These bearings facilitate vertical

adjustment of the optical components. Bearings were sized to overcome moments

created by the mass of the optical components affixed to their respective mounting

structures.


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Optical Component Mounting The mirror optical mount is fabricated from the T-Slot

TM. As shown in Figures 9 and 10,

a vertical member is connected to the optical frame by one of the previously discussed

vertically mounted linear bearings. The vertical member allows travel of approximately

0.8 m (20 in.) for each optical assembly. The linear bearing also acts as a break and

allows for precise line-of-sight adjustment.

Figure 9: Rendered mirror optical mount assembly (left) and rendered camera/light

source optical mount assembly (right).

Figure 10: Detail images of mirror mount showing front (left), back (center), and

exploded view (right) with spherical mirror.

Also depicted in Figure 9, a collimating lens is housed in a double-gimbal structure. This

structure allows for tuning the collimating lens and allows the light returning from the

circular mirror to be focused and conditioned prior to imaging. The assembly was

modeled in SolidWorksTM

to determine viability and compatibility. The two concentric

rings were milled from 1 inch thick 6000 series aluminum using a computer numerical

controlled (CNC) end mill. Once milled, the surface was ground and polished manually.


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Exact dimensions for all parts of the double-gimbal lens holder may be found in

Appendix F. These dimensions had to be modified from the original SolidWorksTM

design due to the CNC machines inability to machine parts exceeding 26 cm (10.5 in.) in

diameter. Figure 11 features the fabricated final design.

Figure 11: Modeled and fabricated double-gimbal collimating lens assembly.

The fastener holes were located and fabricated using manual measurement and tap and

die tools. The base plate was fabricated from the remnants of the concentric ring

fabrication. The base plate allows for integration with the optical mount assembly

depicted in Figure 9.

Cost Analysis Throughout the project, several iterations of the final design were required to balance the

total cost of the mounting apparatus versus the functionality of the system. The final

design concept approved by Dr. Cal was submitted to Futura Industries. The quote

received was over budget and required modification. An interview with the customer

revealed a preference to compromise the ease of use of the system to accommodate

budget constraints. In order to conform to the cost limit, several linear bearings were

removed or replaced by simple joining plates. While this change means that the system

will require two users to adjust the focal position in some orientations, it does not limit

the degrees of freedom of the system. As the mounting apparatus incurs more use and


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future funding can be allocated, components will be added back to the system to fully

expand its usability.

Several components and/or the their materials were donated to the project. The

manufacturing and materials for the clamps were donated by Ecklund Industries, Inc.

The aluminum plate from which the double-gimbal lens holder was manufactured was

donated by Colin Kirkendall. With the mentioned donations, the total cost for the project

amounted to $1850, approximately $100 beyond the original estimate for funding. The

budget overrun was approved and covered by Dr. Cal.

Future Design Considerations: The mounting apparatus outlined here was designed to accommodate a variety of optical

components as outlined in the PDS. There are a number of filters that can replace the

knife-edge using the same simple fixture. Cameras may also change; ranging from

digital cameras with telephoto lenses, to Charge Coupled Device (CCD) cameras with

computer interface to high-speed video cameras. All of these have a standard tripod

mount that will work with the current camera mount. The only alteration concern for

cameras is the vertical position for calibration. If adjustments are necessary, a new stand

may need to be manufactured. The PDS outlined that mirror diameters from 15.2 cm to

30.4 cm (6 in. to 12 in.) and lens diameters from 7.5 cm to 15.2 cm (3 in. to 6 in.) be

useable with the mounting device. Any change beyond these diameters could require

additional structural support. To accommodate the addition of a second collimating lens,

another lens holder would need to be purchased or manufactured.

In successive interviews with Dr. Cal, it was proposed that the design be robust enough to

accommodate other research projects or equipment beyond the optics used in schlieren

photography. One such project involves mounting the four cameras necessary for

tomographic particle image velocimetry (tomo-PIV) to the structure. As the mounting

structure already enables changing the position of equipment, adding tomo-PIV would

save time in locating and calibrating equipment. An extension of the proposed PIV work

involves creating a Lagrangian imaging system in which the equipment moves with the

air flows in the tunnel. It may be desirable to automate the system for this research.


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Automation would involve the addition of an electric motor or drive system to move the

equipment at constant rates and syncing the cameras to the movement with Labview or

another such instrumentation package.

Another proposed set of experiments for the wind tunnel includes modeling off-shore

conditions for wind turbines. To model these conditions, a wave generator and water

tank are being contracted to attach to the floor of the wind tunnel at the exit side. The

support rails have been positioned at the outside of the legs to accommodate this addition.

With the water tank there is a proposed collaborative research project between Dr. Cal

and Dr. Randy Zelick of the PSU Biology department. In this project a support platform

could be constructed to interface with the support rails (and possibly the automation

system mentioned above) to investigate the swimming dynamics and neural response of

fish.

Conclusion: The final design of the optical mounting system met all PDS requirements with the

exceptions of the cost and installation. Future plans for the wind tunnel made a modular

design essential, which required use of the most expensive of potential material selections

for construction.

The final changes to the design were made to limit the overall cost of the system while

maintaining other requirements of the PDS. Additionally, many of the requirements for

verification of the system could not be met. For example, the installation requirement,

“Install/Remove with chamber in place” could not be verified as the wind tunnel delivery

date has been delayed, however, SolidWorks™ models show that the design meets the

requirement. Other verifications delayed include, setup/disassembly time, maximum

system span, and complete mobility of the focal area for schlieren imaging. In the case of

all but the setup/disassembly time, requirements have been verified through design

calculations but still require physical verification upon the completion of the wind tunnel.


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Appendix A: Components and Equipment for Schlieren Photography Current optical components

Spherical Mirror FL = 1524 mm, Diam = 152.4 mm

serial #: NT71-026

DCX lenses, FL = 381 mm, Diam = 107 mm

serial #: AX20827

Achromatic lenses, FL = 245 mm, Diam = 58 mm

serial #: AX20876

Diffraction gratings

Apertures:

serial #: AX39523

4x13mm aperture

serial #: AX39521

20 mm diameter apertures

Custom LED light source:

serial #: RL5-W18015

Super Bright White LED, 18000 mcl

serial #: RL5-IR2730

Super Bright Infra-Red LED, 15000 mcl

serial #: 276-005

Ultra-High Brightness White LED 28500 mcl

Potential Optics for Future Experimentation

Parabolic Mirror FL = 1524 mm, Diam = 254 mm

serial #: NT32-274-533

Parabolic Mirror FL = 2032 mm, Diam = 412.75 mm

serial #: NT32-725-533

Bi-Convex Spherical Lenses, FL = 149 mm, Diam = 150 mm

serial #: LNBX023

Spherical Aberration Plates, up to Diam = 75 mm

serial #: NT66-765


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Appendix B: Initial Design Considerations Design 1

The optical frame in Figure B1 (dark grey) is mounted to a mobile base envisioned to

safely house all optical components. On the top surface of the base, linear bearings allow

the frame to translate in the x and z direction of the test area (Figure 2). The vertical

stanchions of the optical frame were designed to run parallel with either side of the wind

tunnel test area and hold the optical mount in varying orientations. The u-shaped optical

frame can be detached and rotated, on end, to allow for imaging in the vertical

orientation.

Figure B1: Design 1

Design 2

Design 2, depicted in Figure B2, is similar in concept to Design 1. The optical frame is

supported by a scissor jack. This allows the frame to roll under the tunnel and into

position, then elevate to the appropriate imaging height. The optical frame is intended to

house the optical mount riding on linear bearings. Utilizing the bearings, the optical

mount can be positioned anywhere within the plane of the optical frame. The base

structures on either side of the scissor jack are intended to store all optical components as

well as any additional mounting fixtures.


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Figure B2: Design 2

Design 3

Figure B3 shows two optical frames, mounted vertically on two independent base

structures, positioned on either side of the wind tunnel test chamber. Each vertical frame

is slightly larger than one of the four access panels of the wind tunnel (Figure 2).

Telescoping members span the distance between the base structures above and below the

test area. These members may be adjusted to accommodate any width needed between

the optical frames and the test area. The optical components are intended to be attached

to vertical members within the frames. Linear bearings enable positioning of the optics

anywhere within the plane of the frame. This orientation allows for imaging along the

length of the test area. For vertical imaging, the optical mount can be positioned using

the telescoping members running above and below the test area.

Figure B3: Design 3


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Design 4

The half hoop concept, shown in Figure B4, is intended to allow the optical mounts to

rotate about the tunnel test area. Curved, extruded aluminum I-beam is the major

component of this design and allows rotation through a bearing system designed similarly

to gantry systems currently using I-beams as the load-bearing element. The optical

mounting brackets would be attached to each end. Again, like in previous concepts, the

base structure was conceptualized to hold the varied optical components.

Figure B4: Design 4


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Appendix C: Decision Matrices Table C1: Decision matrix for design schemes.

Design Weight Cost Ease of

Assembly

Ease of

Adjustment Stability

Range of

Movement

Weighting 0.1 0.3 0.1 0.2 0.15 0.15 Totals

Kukla 4

2

4.5

3

5

3 3.25

Hamilton 3

4

4

3

5

4 3.85

Mastin 3

2

4

3

4

4.5 3.175

Martin 4

2

3.5

3.5

4

4 3.25

Table C2: Decision matrix for construction materials.

Material Cost Manufacturability Modular Strength Weight Aesthetics Compatibility Score

Square tube

steel

10 4 1 7 6 3 2 32

Uni-Strut™ 7 8 10 6 6 4 6 47

T-Slot™ 3 8 10 8 3 10 9 51


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Appendix D: Bill of Materials (BOM) and Quotes


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Appendix E: Calculations

Appendix E1: Fastener Calculations for Leg Clamps Given:

Fasteners for Linear Guide Rail Clamps of the 2010 Optical Mounting Fixture are to be

sized. The two-piece clamp design is used to attach linear guide rails to the legs of the

wind tunnel test area. The clamps are designed to produces a normal force capable of

allowing the frictional forces generated to solely carry the vertically applied loads. The

brackets have been designed using 10 gauge plate steel and a friction/damping

intermediate material (rubber) sandwiched between the bracket and the chamber legs.

Sketch:

See Figure Bracket…..

Data:

Area (A) = 9.894 sq. in.

Area (B) = 28.733 sq. in.

Optical System Weight ~ 200 lb

Load Factor = 3

Find:

Determine the minimal size and grade requirements for the fasteners securing the two

halves of the given clamp design.

Assumptions:

µs(rubber) ~ 0.7


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Researchers Weight ~ 200 lb

Worst Case: Researcher leans on system while the imaging frame is located to one

extreme of the test area. In this scenario, assume all weight of the imaging system is

carried by two brackets but the entire weight of the researcher is carried by one bracket.

Solution:

In this scenario, each of the two brackets experiences 300 lbs shear (vertical downward).

Find the normal force (N) required to resist this force.

(Eq. TT)

Where

Ff = Force of friction

µs = Coefficient of friction

Solving for N we get:

N = 430 lb

Given the brackets overall size, the design wants to incorporate two or three fasteners per

tab.

The load carried by each fastener:

72 lb (6 fasteners) and 108 lb (4 fasteners)

For nonpermanent (reused fastener) connections the force per faster is calculated by:

(Eq. TY)

(Eq. TU)

Where

Fi = Load Allowed for Reuse of Fastener

Fp = Proof Load

At = Tensile Stress Area

Sp = Proof Strength


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Fi (4 fasteners) ~ 325 lb

Solving the equation for the proof load

[Fp = (4 bolts) ~ 435 lb]

Fi (6 fasteners) ~ 216 lb

Solving the equation for the proof load

[Fp = (6 bolts) ~ 288 lb]

These values will help size the fasteners

From the Shigley’s [Ref] Table 8-1, 2, 10, the smallest size lowest grade fastener will

support this application. In the end,


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Appendix E2: Deflection Calculation for Linear Guide Rails Given:

Linear Guide Rails for the 2010 Optical Mounting System are to be tested. The rails are

used to guide the Optical Mount along the length of the wind tunnel test area. The rails

are an extruded aluminum material produced under T-SlotTM

brand name. The vertical

deflection must be quantified to determine limitations of the material and determine

possible design considerations and solutions.

Sketch:

Data:

Length ~ 208 inches

Distributed Load (weight of beam) = 0.2155 lb / in


Find:

Determine the maximum deflection for the material chosen.

Assumptions:

Worst Case: The imaging frame located in the exact middle of the span. In this scenario,

assume all weight is distributed over two point on each rail 18 inches apart straddling the

exact midpoint of the rails.


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Solution:

Using the below equations (assuming a point load), manual calculations for the deflection

results by summing the deflections given for each loading condition.

(Eq. TT)

Where

F = Vertical Force

E = Young’s Modulus for Material

I = Area Moment of Inertia

W = Distributed Load

Solving for δ we get:

δ = 0.78 inches

**NOTE: This calculation is to compare with the subsequent FEA model that accurately

distribute the load over two points – it is not the assumed deflection**

AbaqusTM

will be used to determine the deflection given the assumed worst case loading

condition.


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Boundary conditions (orange triangles) limit translation in x and y. The point loads are

represented by the red triangles and are 25 pounds each. The yellow triangles represent

the weight of the rail.

The overall deflection is noted below as 0.774 inches and matches the hand calculations

very nicely.


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Appendix E3: Torsional Deflection of Vertical Rise Members Given:

Optical frame vertical adjustments for the 2010 Optical Mounting System’s vertical

adjustments are to be tested. The vertical adjustment must be compatible with varied

optical applications; some may require an imbalance of optical components and result in

a moment about the vertical linear bearing. The entire assembly is constructed from an

extruded aluminum material produced under T-SlotTM

brand name.

Sketch:

CCD Camera

Knife Edge

Custom LED Light Source

Lens Mount

Vertical Riser for Optics MountUser Side

Vertical Riser for Optics MountMirror Side

6” Spherical Mirror

120˚ Mirror Supports

Locking Linear Bearing

Diagonal Supports

38” Total Vertical Travel

Data:

For T-SlotTM

P/N 15-30

For T-SlotTM

P/N 15-15

Load to produce 50 N*m (442.5 in*lbs) moment as per PDS

Find:

Determine the maximum deflection.

Assumptions:

Worst Case: The imaging frame is fully extended in the vertical orientation and the

applied load produces a maximum 50 N*m (442.5 in*lbs) moment.


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Solution:

Inputting the two different geometries for the given material, AbaquaTM

returns a wire

frame model with assumed boundary conditions (zero x-axis translation) and applied load

(22.13 lbs).

To ensure correct material orientation, a rendered wire frame was made.


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Once all information was verified, AbaqusTM provided the maximum deflection due to

the indicated loading.

Maximum deflection (δ) = 0.0137 inches

This value will be examined and confirmed once the final prototype evaluation takes

place.


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Appendix E4: Loaded Clamp Deflection Calculation Given:

Minimum Material thickness for the Linear Guide Rail Clamps of the 2010 Optical

Mounting Fixture is to be determined. The two-piece clamp design is used to attach

linear guide rails to the legs of the wind tunnel test area and the baseline material

thickness will be 10 gauge steel plate. The clamps are designed to produces a normal

force capable of allowing the frictional forces generated to solely carry the vertically

applied loads.

Sketch:

Data:

Area (A) = 9.894 sq. in.

Area (B) = 28.733 sq. in.


Load Factor = 3

Find:

Determine the yield criteria (Von Mises) for the minimum selected material thickness

(10-gauge) sheet steel.

Assumptions:

The three fasteners per side force are assumed to be a point load for the given FEA

model. Additionally, the highest loads will be imposed by the fasteners, not the linear

guide rails. To this end, the cap “pockets” are not modeled.


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Solution:

After entering the physical parameters into AbaqusTM

as a 2-D wire beam element, the

following boundary conditions and loading were applied. Orange arrows limit translation

and yellow arrows indicate loading conditions. A normal load of 430 lbs was split

between the two clamp tabs.

To ensure the orientation was correct within the program, a rendered view was generated.

After rendering, AbaqusTM

was ran to determine Von Mises stress for the given material

and thickness.


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According to the model, 10-guage sheet steel experiences 9234 lbs/sq. in. (psi).

Yield strenght for steel is approximately 58000 psi. A bracket of this design with a

miminum


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Appendix E5: Calculation for Line-of-sight Deflection Given:

Optical frame for the 2010 Optical Mounting System is to be virtually tested to determine

deviation from the optimal line-of-sight. The entire assembly is constructed from an

extruded aluminum material produced under T-SlotTM

brand name.

Sketch:



Optics Mounting ApparatusSide View

Platform operable at spans from 83.5” to 120”

Vertical Risers operate independently with graduations to provide easy calibration. Risers can be repositioned to vary location of focal plane along the height of the wind tunnel. Platform segments connected with joining plates. Joining plates can be unlocked allowing platform to expand or contract to desired span adjusting depth of focal plane in wind tunnel.

Mounting Platform

Linear bearings allow platform to traverse the length of the wind tunnel on aluminum extrusion rails. Portions of the platform are locked in place by square joining plates that can be released to adjust span of the platform. Vertical rise sections mount directly to mounting platform.

Joining Plates

Linear Bearings

Vertical Rise Mounting(Mirror Side)

Vertical Rise Mounting(User Side)

Linear Bearings

Joining Plates

Data:

For T-SlotTM

P/N 15-30

For T-SlotTM

P/N 15-15


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Load to produce 20 lbs downward force at the ends (simulating weight of optical mounts)

Find:

Determine the maximum deflection and associated line-of-sight change.

Assumptions:

Worst Case: The imaging frame is in current configuration, using current mirror, and in

an extended configuration, simulating a larger mirror and the required change in focal

length. Weight of optical mounts was calculated using manufacturer information and

rounded up to 20 lbs (almost double actual weight).

Solution:

Inputting the geometries for the given material, AbaquaTM

returned a wire frame model

with assumed boundary conditions (zero x and y-axis translation at the linear bearings)

and applied load (20 lbs).

NOTE: The wire frame only changes slightly for the two configurations, only one is

shown

To ensure correct material orientation, a rendered wire frame was made.


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The difference in cross-section indicates the sections identified with four cross lengths

and those with two cross lengths (see Sketch above).

Once all information was verified, AbaqusTM

provided the maximum deflection due to

the indicated loading based on the current configuration.

Maximum total deflection (δ) = 0.006183 inches


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Maximum deflection x-axis (δx) = 0.006068 inches

Using the law of sines, the change from vertical orientation (ϴ) = 0.01738o

Calculating the line of sight change, the change in x-axis dimensions were divided by

vertical height of the optical vertical risers to get a change per inch. This resulted in

0.0003034 inch per inch change. Then, multiplying by the horizontal separation of the

two vertical risers, ~ 85.25 inches, the total line of sight change = 0.026 inch deviation

from nominal line-of-sight.

This process was repeated for an Optical Frame resize of an additional 2 feet. The

boundary conditions remained the same; however, the relationship was verified by a

rendered image.

The analysis produced a maximum deflection in the x-axis of 0.03672 inches.


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As in the preceding calculations, the line-of-sight change in angle was determined to be

0.1052o. This resulted in 0.03672 inch per inch change. Then, multiplying by the

horizontal separation of the two vertical risers, ~ 109.25 inches, the total line of sight

change = 0.20 inch deviation from nominal line-of-sight.

Result: These dimensions are well within the resolving capability of the mirror and the

optical equipment to be used. An attempt to verify the validity of this model will be

attempted during prototype installation and testing.


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Appendix F: Additional Technical and Parts Drawings



Optics Mounting ApparatusSide View


Vertical Risers operate independently with graduations to provide easy calibration. Risers can be repositioned to vary location of focal plane along the height of the wind tunnel. Platform segments connected with joining plates. Joining plates can be unlocked allowing platform to expand or contract to desired span adjusting depth of focal plane in wind tunnel.

Figure F1: Side view of mounting apparatus with descriptions.



Optics Mounting ApparatusTop View


Joining Plates

Linear Bearings Linear Bearings

Figure F2: Top view of mounting apparatus.


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Mounting Platform

Linear bearings allow platform to traverse the length of the wind tunnel on aluminum extrusion rails. Portions of the platform are locked in place by square joining plates that can be released to adjust span of the platform. Vertical rise sections mount directly to mounting platform.

Joining Plates

Linear Bearings



Linear Bearings

Joining Plates

Figure F3: Perspective view of mounting platform with description.



Linear Bearings

Joining Plates

Linear Bearings

Figure F4: Side and top views of support platform. Shown with linear bearings for

longitudinal and vertical translation.


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CCD Camera

Knife Edge


Lens Mount

Vertical Riser for Optics MountUser Side Vertical Riser for Optics Mount

User SideFront View


Diagonal Supports

20” Vertical Travel

Figure F5: Perspective and front views of user side vertical rise member.

Vertical Riser for Optics MountUser SideSide View


Diagonal Supports

20” Vertical Travel

Figure F6: Side view of user side vertical rise member.


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6” Spherical Mirror

120˚ Mirror Supports


Diagonal Supports

38” Total Vertical Travel


Front View Side View

Figure F7: Perspective, front, and side views of mirror side vertical rise member.


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Figure F8: Detailed drawing of the mounting clamp shown configured to hold the

support rail at the left side of the wind tunnel.


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Figure F9: Detailed drawing of the mounting clamp shown configured to hold the

support rail at the right side of the wind tunnel.


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Figure F10: Detailed drawing of the mounting clamp shown configured to attach the

backside of both the left- and right-side clamps in Figure GGG8 and Figure GGGp.


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Double Gimbal Lens Holder

Figure F11: Projected views of the prototype double-gimbal lens holder.

Figure F12: Detailed Drawing of inner ring of the double-gimbal lens holder.


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Figure F13: Detailed drawings of inner ring of the double-gimbal lens holder.

Figure F14: Detailed drawing of base plate of the double-gimbal lens holder.


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Figure F15: Custom LED light source with description

Figure F16: Projected views of the custom LED light source.


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Appendix G: Procedures

Appendix G1: Assembly Procedure 1. Mount the clamps onto the legs of the wind tunnel test area.

Each leg requires two clamp components: one with a section to hold the

rails (“bucket”) and one without. Choose the clamp components such that

the bucket opens toward the center of the test area (x-direction, refer to

Figure 2).

The top of the clamps should be positioned such that the top edge is

located 6 in. below the bottom of the test area.

Make sure all clamps are level and fasteners are securely applied.

2. Mount the rails to the clamps. Clamps have fastener holes. Specialized hardware

to mount to the aluminum extrusion is available.

3. Assemble and attach the spanning members of the platform to one another as

shown in assembly drawings. Refer to Figures F1 through F4 for orientations of

pieces.

Joining plates should be on the bottom of the connected spanning

members for ease of future adjustment.

The internal crosspiece should be toward the user side of the test area.

Attach vertical members and diagonal supports.

Attach the two 6” linear bearings to the vertical members.

4. Affix the four linear bearings to the rails.

Bearings with locking mechanisms should be on the user side of the wind

tunnel.

Connect the assembled spanning platform to the four linear bearings.

5. Assemble the vertical rise portions.

User Side:

Attach all cross-members and diagonal supports to the vertical

member. With this complete add the risers and arms to position

the camera, knife-edge, and light source. Fix all members in place


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with provided fasteners. Omit the lens mount and the actual optics

until the mounting apparatus is complete.

Mirror Side:

Attach mirror-mounting pieces to the side of the vertical member

facing the test area. Fix all members in place with provided

fasteners. Omit the spherical or parabolic mirror until the

mounting apparatus is complete.

Attach vertical rise sections to the 6” linear bearings and lock into place.

6. Add optics:

Mirror to be secured by the 120 supports.

Lens to be secured by the mounting screws of the double-gimbal lens

holder.

Camera to be mounted on riser with ¼”-20 thread (standard tripod mount).

Knife-edge (razor blade) clamped between L-brackets.

Light source mounted on support arm with power cord secured to

mounting structure.

Appendix G2: Operation Manual The operation of the mounting device for wind tunnel optics is described in terms of three

subsections: Installing and swapping optical components, calibrating optics and

alignment, and positioning the focal plane in the wind tunnel. Once particular optics

have been selected and calibrated. The system is capable of resolving images in any

position within the same focal plane. While positions at any location down the length of

the wind tunnel and at locations along the vertical height of the test area (x-y plane) do

not require recalibration, changing the depth of focus across the tunnel (z-direction) will

require fine-tuning of the knife edge and camera.

Installing and swapping optical components: It will be the case that the optics

used to collect images in the test area of the wind tunnel will be exchanged

for others during the course of proposed experimentation. Each component


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will be added or exchanged individually. With all optical components it is

important to keep all surfaces clean. Components should be handled with

appropriate cloths to prevent fingerprints, oils, and dust from being

transferred to optical surfaces.

o The mirror is held by three supports at positions 120 about the

circumference of the mirror. The support at the top of the mirror should

be released first when installing or removing a mirror. This will allow the

two lower supports to hold the mirror while adjustments are made. The

edge of any mirror used should be wrapped in rubber or felt tape to

provide grip and protection to the mirror itself. When the mirror is

removed, or before it is placed, reposition the bottom supports such that

the center of the mirror will be at the marked position on the vertical rise

member. Place the mirror, reposition the top support, and tighten

connective hardware.

o The lens is supported by three set screws in a similar fashion to the mirror.

To install a lens in the holder, position the bottom screws at the desired

radius. Holding the lens in an appropriate cloth, position the lens such that

it is supported on the lower screws. Tighten the top screw until the lens is

secure. Do not over tighten screws. Excessive torque on the screws can

permanently damage lenses. As with the mirror, the edge should be

wrapped in rubber or felt for grip and protection. To remove a lens, hold

the body with an appropriate cloth while the top screw is loosened.

Remove the lens and store in a protected, dust free environment.

o The knife-edge is held vertically between two L-brackets. To change or

reposition the edge, loosen the screw and move the edge into desired

location. Take care, razors are sharp and can cause injury if not treated

appropriately.

o The camera mount is fitted with a standard ¼”-20 thread screw. Any

tripod-ready camera should fit on the mount. Vertical adjustments can be

made by switching vertical riser.


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Calibrating Optical Components: To make sure all optics are in alignment, place

a laser pointer at the light source or turn on a LED in the light source.

Position the light source such that the center of projection from the light is in

the center of the mirror. Using a hand or a sheet of paper, make sure that the

light reflected from the mirror is centered in the lens. If not, adjust the

alignment of the mirror until this is the case. Using a hand or a sheet of

paper, locate the position of focus of the light coming through the lens. This

is the point where the light is the smallest possible dot. Place the knife edge

at the position of focus, blocking approximately 75% of the light. Place the

camera lens as close to the knife-edge as possible. Check focus to ensure

that light is passing through the lens to the film or CCD.

Positioning the Focal Plane: To change position of the mounting apparatus in-

plane, loosen the locks on the linear bearings attached to the support rails

first. With these unlocked, the entire device should translate easily down the

length of the test area (x-direction). When desired position is reached,

simply relock the bearings. To adjust vertically, each vertical rise member

must be adjusted individually. Adjust the mirror side first. There are

graduations along the vertical members indicating the distance from the

center of focus from the floor of the wind tunnel. Unlock the bearing with

the vertical support firmly held, reposition to desired height (y-direction), and

relock the bearing. Repeat for the user side vertical rise member. Check to

ensure optics are still in focus. If not adjust the user side vertical rise

member. When changing the focal depth of the optics, two users are

required. Loosen the spanning platform from the linear bearings on the user

side. Loosen the fasteners in the joining plates underneath the spanning

platform. Pull the user side vertical member out from or push in toward test

area to desired distance between vertical members. Tighten fasteners in

joining plates. Adjust position of the platform (z-direction) and tighten all

fasteners between linear bearings on the support rails and the spanning

platform. Recalibrate optics as explained above.


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Appendix H: References

Richard, Budynas and Nesbett, Kieth. Shigley's Mechanical Engineering Design.

McGraw-Hill College, 8th Edition.

"T-Slot". Futura Industries. 2 March 2010 <http://www.tslots.com/>.

Elsinga, G.E., van Oudheusden, B.W., Scarano, F., Watt, D.W. (2004) Assessment and

application of quantitative schlieren methods: Calibrated color schlieren and background

oriented schlieren. Experiments in Fluids. 309-325

Gopal, V., Klosowiak, J. L., Jaeger, R., Selimkhanov, T., and Hartmann, M. J. Z. (2008)

Visualizing the Invisible: the Construction of Three Low-Cost Schlieren Imaging

Systems for the Undergraduate Laboratory. European Journal of Physics. 607- 617

Settles, Gary S. (2001) Schlieren and Shadowgraph Techniques. Springer Berlin Heidelberg,

New York.

Documents

Executive Summary - Portland State Universityweb.cecs.pdx.edu/~far/Past Capstone Projects/2010/Wind...Optical Mounting System for Laboratory Research Final Design Report 1 Executive