Status of 3D Ice Shape Measurement Effort

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National Aeronautics and Space Administration

www.nasa.gov

Status of 3D Ice Shape Measurement Effort

Sam Lee

ASRC Aerospace, Inc.

2011 Annual Technical Meeting

May 10–12, 2011

St. Louis, MO


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Outline

• Introduction

• Research Plan

• Project Status

• Future Plans


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Introduction• Main goal of the Airframe Icing Technical Challenge is to

achieve acceptance of experimental and computational icing simulation tools– Supercooled Large Droplet Icing (SLD) conditions

– 3D airframe components including swept wings.

• It is necessary to develop suitable means of recording and archiving fully 3D descriptions of experimental ice accretion geometry.

• Past research has shown that commercial laser scanners have the potential to be adapted to this task.

• A research plan has been developed to implement and validate the use of this technology for experimental ice accretions.


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Introduction (cont’d)• Phase 1 – Identify most suitable scanning system

– Focus specifically upon measuring ice accreted in the NASA Icing Research Tunnel (IRT).

– Built on recent demonstration tests of portable scanners in IRT.

– Follow-on IRT testing and demonstrations conducted to complete a down-selection process to the most promising and suitable technology.

• Phase 2 – Validation exercises to define scanning capability.– Calibration block

– 2D geometric and aerodynamic comparisons

– Swept-wing geometric comparisons


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NASA Milestones

• Level 3 milestone– “Select Candidate Laser Scanning System”

– Q1 FY2012

• Level 1 milestone– “Declare 3D Ice Accretion Measurement Capability”

– Q4 FY2013


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Research Plan – 1st Phase• Evaluate candidate laser scanning system in IRT.

– Demonstrate capability to operate in the IRT environment.

– Evaluated on the basis of criteria having to do with operations, scanning capability/accuracy and cost.

• Evaluate candidate software used to post-process the scanner data .– Demonstrate ability to create “water-tight” surface.

– Evaluated on the basis of criteria having to do with operations, efficiency, ease of use, and cost.

• Assessment of rapid-prototyping capability. – Scan data of ice accretion will be processed to water-tight surface.

– Various RPM (rapid-prototype model) vendors will be contacted to ascertain the current state of capability to manufacture artificial ice shapes.


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Research Plan – 1st Phase (cont’d)

• The outcome of Phase I will be a selection of both laser scanning hardware system and post-processing software.– This will satisfy the AEST level 3 milestone.

Define

Scanner

Selection

Criteria

Evaluate

Scanners

in IRT

Define

Software

Selection

Criteria

Down-

Select &

Purchase

Scanner

Evaluate

Software

Down-

Select &

Purchase

Software

RPM

Assessment

Phase I Roadmap

Evaluate

Scan

Data

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1st Phase Research Task

• Define evaluation/selection criteria for scanner hardware and software.

• Define specific laser scanner systems (hardware) and post-processing software to be evaluated.

• Develop test and evaluation plans.

• Evaluate candidate current laser-scanning systems in IRT.

• Evaluate candidate software systems.

• Conduct assessment of Rapid Prototype Method (RPM) capability.

• Down-select one hardware system and one software system for Phase II.

• Purchase hardware and software.


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Selection Criteria - Hardware

• IRT test section capability– Environment - operate in a wide range of IRT test section

environment.

– Usability

• Portability

• Ease of use.

• Convenience of measurement procedure

• Scanning capability– Scan resolution

– Scan speed

– Ability to scan gaps and holes.

– Accuracy

• Cost vs. capability


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Selection Criteria - Software

• Scanner compatibility

• Water-tight modeling ability

• Noise filtering

• Efficiency– Ease of use

– Speed

– Processing time

– Large file capability

• Cost vs. capability


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Research Plan – 2nd Phase• Implementation and validation of the selected system.

• Validation exercise with known geometry to define the measurement capability. – Benchmark measurements performed on the metal calibration blocks.

– These data can be used as a type of check standard to ensure uniform capability over time.


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Research Plan – 2nd Phase (cont’d)• “Circular” validation along with aerodynamic assessment

based upon a 2D airfoil geometry.– Perform laser scans and pour molds of selected ice accretion.

– Use scan data to create high-fidelity (RPM) artificial ice shapes along with castings from molds.

– Compare scanned and cast geometries


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Research Plan – 2nd Phase (cont’d)• A closely related 2D aerodynamic evaluation will also be

conducted– RPM artificial shapes made from ice scans will be tested against

castings.

– Use methods established during NASA/ONERA/UIUC Aerosim Project

– These validations (both geometric and aerodynamic) should be conducted for each of the four basic categories of ice accretion: roughness, horn, streamwise and spanwise ridge.

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Research Plan – 2nd Phase (cont’d)

• Geometric validation test on a swept-wing model.– This exercise will consist of scanning an ice accretion, making a mold

and casting of that ice accretion.

– The scan data used to create an RPM artificial shape that can be scanned and compared to the original ice accretion.

– A scan of the casting can also be compared to the original ice accretion scan.

– Aerodynamic assessment not possible at this time due to lack of established method.


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Research Plan – 2nd Phase (cont’d)• Develop procedures for using the scanner in the IRT as well as

for post-processing the data.– Document to serve as an internal reference guide for continued IRT

testing and use of the scanner and software system.

– Include all aspects of the measurement

• Preparation of the ice accretion (e.g., “painting”)

• Set-up of the scanning (e.g., any in-situ calibration or homing)

• Scanning of the ice (e.g., software settings, resolution vs. time and desired accuracy)

• Saving of the data (e.g., file types and sizes)

• Post-processing of the data (e.g., procedures for hole-filing, software settings, extracting tracings, etc.).

• The outcome of Phase II will be declaration of 3D ice accretion measurement capability.– This will satisfy the AEST level 1 milestone.


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Research Plan – 2nd Phase (cont’d)

Benchmark

Measurements

Rqmts

Met?

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Declare

Swept

Wing

Capability

Y

N

Phase II Roadmap

RPM of

Scan

Shapes

Mold/Cast

Ice Shapes

IRT Ice

Accretion

Test

Aero test/

Comparisons

Geometric

Comparisons

Geometric

Comparisons

RPM of

Scan

Shapes

Mold/Cast

Ice Shapes

2D Airfoil Validation

Swept Wing Validation

IRT Ice

Accretion

Test

Declare 2D

Capability

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2nd Phase Research Tasks

• Benchmark scanner with calibration blocks

• 2D airfoil model evaluation– Geometry comparisons

– Aerodynamic comparisons

• Swept wing model evaluation– Geometry comparisons

• Standardize methods for laser scan data acquisition and post-processing.– Write process description with quantifiable standards

• Declare 3D ice accretion measurement capability.– Satisfy AEST Level 1 milestone.


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Project Status

• Hardware/software selection criteria established

• Evaluated candidate scanners in IRT– Creaform – Oct 2009

– Faro Arm– Nov 2009, March and April 2011

– Romer – March 2011

– nVision – April 2011

• Tested ice shapes from identical model and icing conditions– Glaze, rime, roughness on straight NACA 0012

– Scallop ice shape on 45 deg swept NACA 0012

• Purchased software to evaluate scan data (Geomagic)


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IRT Scanner Evaluation Procedure

1. Accrete ice on test article

2. Photograph ice

3. Spray paint accreted ice using airbrush

4. Install/set up laser scanner

5. Scan ice

6. Cut ice and make tracing


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IRT Scanner Evaluation

Painting ice with air brush paint

Painted ice


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Scanning ice shape with 3D scanner.


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Hand tracing of ice shapes for

comparison to scanner.


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Water Tight Scanned DataGlaze Ice


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Water Tight Scanned DataRime ice


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Scanned Data3D Scallop Ice


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Comparison of 3D Scanned Data to Hand Tracing

x (in)

-1 0 1 2 3 4 5

y (

in)

-2

-1

0

1

2

Clean Model

Hand Traced

3D Scanner

Glaze ice

x (in)

-1 0 1 2 3 4 5

y (

in)

-2

-1

0

1

2

Clean Model

Hand Traced

3D Scanner

Rime ice

x (in)

-2 0 2 4 6

y (

in)

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-2

-1

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1

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3

Clean Model

Hand Traced

3D Scanner

3D scallop ice


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Future Plans

• Evaluate data from candidate scanners

• Down-select and purchase scanner

– Q1 FY2012 (L3 milestone)

• Assess and validate scanning system and methods

– Straight and swept wing geometry

– Compare aero results with scanned and cast ice shapes

• Declare 3D ice shape scanning capability

– Q4 FY 2013 (L1 milestone)

Documents

Status of 3D Ice Shape Measurement Effort