STAR-CCM+ TUTORIAL Whitcomb Area Rule: Modeling …...STAR-CCM+ TUTORIAL Whitcomb Area Rule: Modeling Geometry STAR-CCM+ 13.06.011 844-756-7638 (844-PLM-SOFT)

STAR-CCM+ TUTORIAL

Whitcomb Area Rule: ModelingGeometry

STAR-CCM+ 13.06.011

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Whitcomb Area Rule Tutorial in STAR-CCM+

Content subject to change without notice. © 2020 ATA Engineering, Inc. STAR-CCM+ and HEEDS are trademarks of Siemens Digital Industries Software

Overview

This tutorial series walks through the workflow of utilizing HEEDS optimization software and the STAR-CCM+ flow solver to demonstrate the Whitcomb area rule on a simplified model of the Convair F-102 aircraft. The goal is to minimize the total drag coefficient on the aircraft by manipulating the radii of five discrete sections of the fuselage midsection.

This tutorial is part one of three and leads users through modeling the aircraft using the STAR-CCM+ native CAD package. The next tutorials cover meshing, solving, and post-processing with the STAR-CCM+ flow solver and performing optimization using HEEDS. Each section of the tutorial has a file demonstrating the completed steps to allow users to complete individual sections as desired.

Required files and completed example models are available in the Supplementary_Materials.zip file.

Software:STAR-CCM+ 13.06.011HEEDS 2018.10

Difficulty Level:Beginner

Preceding Tutorial:None

Succeeding Tutorials:Setting Up the SimulationOptimization with HEEDS

Input files required:airfoilCL.csvairfoilTip.csv

Additional Documents:Supplementary_Materials.zip

This tutorial is part of a series of free Siemens Digital Industries Software training resources provided by ATA. For more tutorials, whitepapers, videos, and macros, visit ATA’s PLM Software website: http://www.ata-plmsoftware.com/resources.




Content subject to change without notice. © 2020 ATA Engineering, Inc. STAR-CCM+ and HEEDS are trademarks of Siemens Digital Industries Software

Contents of This Tutorial

• Navigating the Star-CCM+ user interface

• Using the 2D Sketch environment

• Creating 3D-CAD features

• Importing sketches from .csv files

Contents of Succeeding Tutorials

• Setting up a physics model for transonic flows

• Creating prism-layer and polyhedral meshes

• Defining mesh parameters

• Generating reports and stopping criteria

• Creating STAR-CCM+ post-processing scenes

• Connecting STAR-CCM+ to HEEDS

• Generating a HEEDS study

• Evaluating HEEDS results



1 Content subject to change without notice. © 2020 ATA Engineering, Inc. STAR-CCM+ and HEEDS are trademarks of Siemens Digital Industries Software

ContentsTutorial 21. Modeling Geometry in STAR-CCM+ 2

1.1. Launching STAR-CCM+ CAD 21.2. Setting Design Parameters 31.3. Setting Up the Sketch Environment 41.4. Creating Fuselage Sketch: Overall Profile 51.5. Creating Fuselage Sketch: Elliptical Nose 71.6. Creating Fuselage Sketch: Midsection Lines 91.7. Creating Fuselage Body 121.8. Creating the Delta Wing Sketch 131.9. Creating the Delta Wing Loft 161.10. Sketching the Fluid Domain 191.11. Defining the Fluid Domain 211.12. Setting Up Fluid Surfaces and Curves 22




Tutorial

1. Modeling Geometry in STAR-CCM+The steps of this tutorial walk through producing a simplified model of the F-102 aircraft using the STAR-CCM+ native CAD package. The intent of the model is to have the diameter of midsections of the aircraft fuselage be variable so that the effect of the fuselage shape on the drag coefficient can be evaluated. A completed geometry model as shown in Figure 1-1 can be found in the zipped folder Supplementary_Materials/AreaRule_1.sim.

1.1. Launching STAR-CCM+ CAD1. Create a new STAR-CCM+ simulation, select File → Save-As… and

save the file as areaRule_1.sim.2. Expand and right-click the Geometry → 3D-CAD Models node

and select New. This should launch the 3D-CAD environment, shown in Figure 1-2.

3. Right-click 3D-CAD Model 1 and select Rename….4. Rename node to fluidModel.

Figure 1-1: ▶ The final 3D-CAD model represents the fluid domain of the STAR-CCM+ simulation.




1.2. Setting Design ParametersDesign Parameters are used here to make geometrical features modifiable from outside the STAR-CCM+ native 3D-CAD modeling tool. These externally alterable parameters will enable HEEDS to later make geometrical modifications in the design-space exploration of the aircraft fuselage.1. Right-click the Design Parameters node and select New →

Length.2. Right-click the newly created Length node and select Rename…

to rename the node to fuselageRadius.3. Repeat the previous steps until a total of eight length parameter

nodes have been created and renamed as shown in Figure 1-3.

4. Right-click on the Design Parameters node and select Edit… to open the Design Parameters Manager window.

Figure 1-2: ▶The left-hand panel is the 3D-CAD feature tree, and the right-hand side is the 3D-CAD graphics window.

Figure 1-3: ▶These Design Parameters will later be used to define the shape of the fuselage, and they can be accessed by HEEDS to manipulate the 3D-CAD geometry.




5. Expand fuselageRadius and set the Value definition to 1.08 m, as shown in Figure 1-4.

6. Repeat previous steps using the values listed in Table 1-1.

7. 7. Click Close to exit the Design Parameter Manager

1.3. Setting Up the Sketch Environment

1. In the 3D-CAD feature tree, expand the Features node, right-click the ZX sketch plane, and select Create Sketch to open up the Edit Sketch Environment shown in Figure 1-5.

Figure 1-4: ▶These values will be used to evaluate dimensions for different aspects of the fuselage later on.

Table 1-1: ▶These design parameter values specify the initial fuselage shape.




2. Under the Display Options, enable (Snap to Grid). Select

(Grid Spacing) and set the Grid spacing value to 0.5 m and the Number of fine grid divisions to 5.0 as shown in Figure 1-6. Select OK.

3. Select (View Normal to Sketch Plane) to reorient the view.

1.4. Creating Fuselage Sketch: Overall Profile

1. Under Create Sketch Entities, enable (Create Line). In the Sketch graphics window, move the mouse cursor to the origin [0,0] and left-click to define the line segment start point. Make

sure (Snap to Grid) is still enabled or the start point may not snap to the origin.

Figure 1-5: ▶The Sketch panel allows the creation and manipulation of 2D geometry on a sketch plane in the Sketch graphics window.

Figure 1-6: ▶Grid spacing is a useful tool for conceptualizing the approximate dimensions of a sketch and helps snap points to the grid if the Snap to Grid tool is enabled.




2. Move the mouse cursor approximately 15 m to the right of the origin and left-click when the line segment is horizontal as shown in Figure 1-7.

3. Once the first line segment is created, the end point of the first line segment will automatically define the start point of the second line segment; create another horizontal line segment that extends an arbitrary distance to the right of the first line segment.

4. Once the two line segments are created, press the [Esc] key to exit the line tool.

5. In the Sketch graphics window, hover over the point located at the origin, right-click the selection, and select Apply Fixation Constraint; a small icon representing a fixation constraint should appear above the point. This fixes the line segment relative to the origin.

6. Enable (Create Line) again and create a third line segment starting from the origin [0,0] and ending at an arbitrary point directly vertical to the start point as shown in Figure 1-8. Press [Esc] to exit the line tool.

7. Enable (Create Line) again and create a fourth line segment starting from the shared intersection point between the first and second line and ending at an arbitrary point directly vertical to the start point. Press [Esc] to exit the line tool.

8. In the Sketch graphics window, right-click the fourth line segment and select Set as Construction as shown in Figure 1-9.

Figure 1-7: ▶When you are defining the end point of a line segment, if the line is oriented horizontal to the sketch plane, the line will turn yellow and a small icon representing a horizontal constraint will appear above the second point.

Figure 1-8: ▶When defining the end point of a line segment, if the line is oriented vertical to the sketch plane, the line will turn red and a small icon representing a vertical constraint will appear above the second point.




9. Right-click the second line segment, select Apply Length Dimension, and set the dimension to $noseLength as shown in Figure 1-10. Select OK; this will set the length of the line segment to the value previously defined by the 3D-CAD design parameter noseLength.

10. Right-click the third line segment, select Apply Length Dimension, and set the dimension to $fuselageRadius. Press OK and repeat for the fourth line segment, which will have its length dimension set to $fuselageRadius as well. The result is shown in Figure 1-11.

1.5. Creating Fuselage Sketch: Elliptical Nose

1. To assist in the creation of the elliptical nose, some tangent

construction lines will need to be made; enable (Create Line) and create an approximately vertical line by starting at the end of the second line segment and extending upward until it is approximately in line with the third and fourth line segments.

Figure 1-9: ▶The sketch should look similar to this; a construction line is used only to assist in the sketch process and is not used to define geometries.

Figure 1-10: ▶The dimension will be valid for any positive scalar value, including variables and algebraic expressions.

Figure 1-11: ▶Dimensions indicated by black arrows constrain the overall length of the lines they reference.




2. Create an approximately horizontal line starting at the end point of the previous line and finishing at the end point of the fourth line segment.

3. Right-click on each line to apply a Vertical Constraint and a Horizontal Constraint, respectively; the icons for each constraint should appear at the center of each line.

4. Right-click and select Set Line as Construction for both lines, shown in Figure 1-12.

5. In the Sketch Panel under Create Sketch Entities, select (Ellipse). Select the intersection point between the first and second line segments; this point defines the center of the ellipse.

6. Continue by moving the cursor to the right and snapping the second point onto the end point of the second line segment; this point defines the major diameter.

7. Finish the ellipse by snapping the third point to the end point of the fourth line segment; this point defines the minor diameter. The new ellipse is shown in Figure 1-13.

8. In the Sketch Panel, enable (Trim and Delete Primitives) and select the upper-left quadrant and bottom half of the ellipse; this will delete both sections, leaving the upper-right quadrant

Figure 1-12: ▶The construction lines used to create the ellipse.

Figure 1-13: ▶The guidelines assist in defining the ellipse by automatically creating tangent relationships between the ellipse curve and the guidelines.




intact; under Quick Trim, select OK to confirm changes as shown in Figure 1-14.

9. If the tangent curve icon is no longer shown beside the guidelines like in Figure 1-15, the tangent relationship has been deleted; reapply the tangent relationship by holding the [Ctrl] key while selecting the elliptical curve and the vertical guideline; right-click and select Apply Tangent Constraint.

1.6. Creating Fuselage Sketch: Midsection Lines

1. The midsection of the fuselage is split into six sections with radii defined by the design parameters r1 through r5 and lengths defined by the midsectionLength parameter.

2. In the Sketch panel, enable (Create Line) and create five approximately evenly spaced and approximately vertical lines between the third line segment and the fourth line segment; ensure that the starting point of each new line segment snaps somewhere along the length of the first line segment.

3. While holding down [Ctrl], select each of the five newly created line segments until all five are selected, right-click, and select Apply Vertical Constraint; this will apply a vertical constraint relationship to all the line segments at once.

4. Hold down [Ctrl] and multi-select all five newly created lines. Right-click and select Set as Construction; this turns all lines into construction line entities.

Figure 1-14: ▶The Quick Trim tool automatically identifies points of intersection and allows sections of a sketch entity to be removed based on selection.

Figure 1-15: ▶The tangent relationship is needed to fully define the position and shape of the ellipse.




5. Multi-select two consecutive lines by holding down [Ctrl], and select Apply Distance Dimension as shown in Figure 1-16.

6. Set dimension to $midsectionLength as shown in Figure 1-17; this should evaluate to 2.4 m as previously defined in the design parameters.

7. Repeat the previous two steps for the remaining five midsections until a total of six midsection lengths have been defined as shown in Figure 1-18; several lines may need to be dragged relative to each other prior to dimensioning depending on the distribution of the vertical line segments.

Figure 1-16: ▶The multi-select function can be used to define a distance between two parallel lines; the multi-select function is also useful for applying constraints to multiple sketch entities, such as defining a vertical constraint for a series of lines.

Figure 1-17: ▶Midsection length is defined by the parameter midsectionLength.

Figure 1-18: ▶The sketch should resemble this after the lengths have been defined.




8. Select the leftmost of the five newly created lines that define the first midsection, right-click, select Apply Length Dimension, and set value to $r1.

9. Repeat previous step for the remaining four lines and set their values to $r2, $r3, $r4, and $r5, respectively, as shown in Figure 1-19.

10. In the Sketch panel, under Create Sketch Entities, select (Create Spline), and in the graphics window, create a seven-point spline entity whose points lie somewhere near, but not on, each of the seven vertical lines that define the midsection, as shown in Figure 1-20; press the [Esc] key after creating the seventh point; this will automatically exit the Spline creation tool.

11. Multi-select one of the spline points and the corresponding line segment end point, right-click, and select Apply Coincidence Constraint as shown in Figure 1-21; the spline point should snap to the line’s end point.

Figure 1-19: ▶All five radii have been defined by the respective design parameters; the entities in black are fully defined relative to the origin;

this view is enabled by toggling (Show status of Sketch Primitives).

Figure 1-20: ▶The spline points created should be coincident to the line segment end points shown in pink but are not snapped onto those points, as the coincident relationship between the spline points and the end points is not created by default; keeping these points separate makes it easier to apply the coincident relationship later.




12. Click anywhere on the graphics window to deselect the two points.

13. Repeat the previous two steps for the remaining six spline points; the spline should resolve to a single straight line that spans the entire midsection as in Figure 1-22; if the line is not straight, right-click the spline curve and select Relax All Spline Tangent Handles.

14. Select OK on the bottom of the Sketch panel window to save the sketch; this should take you back to the 3D-CAD feature tree.

1.7. Creating Fuselage Body

1. In the 3D-CAD feature tree, under Features, right-click on Sketch 1 and select Rename… and rename the sketch to fuselageSketch.

2. Right-click on fuselageSketch and select Revolve; this should open the Edit Revolve panel.

3. Set Angle to 180.0 deg, Axis Type to Specified, and Axis Direction to [0,0,1.0] m as shown in Figure 1-23; select OK to exit the Edit Revolve panel.

Figure 1-21: ▶Adding a coincidence constraint will ensure that the spline will change its profile to match any change in length of r1 through r5.

Figure 1-22: ▶The completed sketch should resemble this; all entities should be fully defined except for the spline entity, which is still variable due to curvature controls available at each spline point.




4. Right-click on Revolve 1 and select Rename… to rename the feature to fuselageRevolve.

1.8. Creating the Delta Wing Sketch

In the following steps, we will create a delta wing similar to that on the Convair F-102 by creating lofting between two sketches of NACA 0004-64 symmetric airfoils defining the wing root and tip shapes. Pre-generated CSV files of the airfoil coordinates will be imported into the 3D-CAD modeler to define the geometry.

1. In the 3D-CAD feature tree, under the Features node, right-click the ZX plane and select Create Sketch; this should open the Sketch panel.

2. In the Sketch panel, select OK on the bottom of the panel to save the current sketch; this sketch should be empty.

3. In the 3D-CAD feature tree, under Features, right-click on Sketch 1 and select Rename… and rename the sketch to airfoilCenterSketch.

4. Right-click on airfoilCenterSketch and select Import Curves; this will open the Star-CCM+ browser dialog box.

5. Select the airfoilCL.csv as shown in Figure 1-24 and select Open to continue.

Figure 1-23: ▶This Edit Revolve panel shows the settings for creating the revolved feature; revolve feature creates a 3D geometry by projecting a 2D sketch about a defined axis.




6. In the Import Curve Options dialog box, keep Import as spline selected, enable Close the Curve, and select OK to import the curve. The resulting curve is shown in Figure 1-25.

7. In the 3D-CAD tree, right-click the Features node and select Reference Geometry → Create Plane → By Definition.

8. In the Plane by Definition panel, set Origin to [0,5.81,0] m, set X-Axis Direction to [0,0,1.0] m, and Vector on X-Y Plane to [1.0,0,0] m as shown in Figure 1-26; select OK to return to the 3D-CAD view.

Figure 1-24: ▶Curves are imported into STAR-CCM+ sketches in a .csv file format.

Figure 1-25: ▶The curve profile is a NACA 004-64 symmetric airfoil.




9. In the 3D-CAD feature tree, right-click on Plane 1 and rename to airfoilTipPlane.

10. Right-click on airfoilTipPlane and select Create Sketch, click OK in the Sketch panel to save and exit the sketch.

11. Rename the sketch to airfoilTipSketch.12. Import airfoilTip.csv into the airfoilTipSketch while keeping

Import as spline selected and enabling Close the Curve. The new curve is shown in Figure 1-27.

Figure 1-26: ▶The plane reference geometry can be used to allow sketching outside the default sketch planes.

Figure 1-27: ▶The two imported sketches are shown highlighted in pink.




1.9. Creating the Delta Wing Loft

1. To produce a loft between the two airfoil profiles, a guideline needs to be made for the loft to follow; right-click on the YZ plane and select Create Sketch to create a new sketch.

2. In the graphics window, expand the Model Visibility tool in the visibility toolbar on the top-middle of the graphics window and deselect Solid Bodies as in Figure 1-28 to hide the revolved geometry.

3. Using (Create Line), create a line segment such that each end of the line lies close to the leading edge of the imported airfoil curve as shown in Figure 1-29.

4. Multi-select one end point of the line with the nearby airfoil curve; right-click on one of the selections and select Apply Pierce Constraint as shown in Figure 1-30.

Figure 1-28: ▶The model visibility toolbar provides control over how 3D-CAD geometry is displayed in the graphics window.

Figure 1-29: ▶The line segment should be placed in close proximity to where the line should intersect with the airfoil curve.




5. Repeat the previous step for the other end point; click OK to save and exit the sketch.

6. In the graphics window, expand the Model Visibility tool in the visibility toolbar on the top-middle of the graphics window and reselect Solid Bodies, which result in a view similar to Figure 1-31.

7. In the 3D-CAD tree, rename Sketch 1 to airfoilGuideSketch.8. Multi-select airfoilCenterSketch and airfoilTipSketch on the

3D-CAD tree; right-click and select Loft.9. In the Edit Loft panel, make sure the Profile Sketches include the

two sketches only. Select the Guide Sketches selection window, and on the graphics window, select the line representing the airfoilGuideSketch; set Alignment Type to Airfoil as shown in Figure 1-32.

Figure 1-30: ▶The Pierce constraint allows two sketch entities on different intersecting planes to be fixed relative to each other.

Figure 1-31: ▶The three sketches should look like this.




10. Press OK to exit the Loft panel view.11. In the 3D-CAD feature tree, expand Body Groups and rename

Body 2 to plane; under the Features node, rename Loft 1 to airfoilLoft. The final geometry of the airplane model is shown in Figure 1-33.

Figure 1-32: ▶The Loft feature is used to produce a continuous body between two profile sketches; the guideline is used to control the shape of the profile along the length of the loft.

Figure 1-33: ▶The final geometry of the airplane model.




1.10. Sketching the Fluid Domain

1. Now that the aircraft body has been modeled, the fluid domain needs to be defined; because the aircraft model has quarter symmetry, the fluid domain will be represented by one quarter of a sphere with a 300 meter radius, and because the flow is transonic, any disturbances are not expected to propagate upstream, so the center of the sphere will be offset 100 m downstream from the aircraft.

2. Right-click on the ZX plane in the 3D-CAD feature tree and create a new sketch.

3. Select (View Normal to Sketch Plane) to align the sketch graphics window.

4. 4. In the Sketch panel, select (Create Circle) and position the center at [-100.0,0] m; this can be accomplished by creating a circle somewhere in free space and selecting the center point of the circle and editing the Point Properties located in the Sketch panel as shown in Figure 1-34.

5. Once the center point is positioned, right-click on it and select Apply Fixation Constraint.

6. Right-click on the curve of the circle and select Apply Radius Dimension and set the value equal to 300.0 m.

7. Create a line segment with its end points coincident to the curve of the circle and its line segment with a horizontal constraint and a coincident relation with the center of the circle as shown in Figure 1-35.

Figure 1-34: ▶The position of the point can be adjusted with Point Properties.




8. Enable (Trim and Delete Primitives) and remove the bottom curve of the circle as shown in Figure 1-36; select OK to confirm changes.

9. Select OK on the bottom of the Sketch panel to exit the 2D sketch view.

10. Rename Sketch 1 to fluidDomainSketch.

Figure 1-35: ▶The geometry should resemble this.

Figure 1-36: ▶The geometry should now resemble this.




1.11. Defining the Fluid Domain

1. Right-click on fluidDomainSketch and select Revolve.2. In the Edit Revolve Panel set Angle to 90.0 deg, set Axis Type to

Specified, set Axis Direction to [0,0,1.0] m and Body Interaction to None as shown in Figure 1-37; select OK to confirm.

3. Rename Revolve 1 to fluidDomainRevolve.4. Under the Body Groups node, rename the newly created body

to fluid.5. In the feature tree under Body Groups, multi-select by first

selecting fluid and then selecting plane; right-click and select Boolean → Subtract.

6. Make sure Target Bodies is set to fluid and Tool Bodies is set to plane as shown in Figure 1-38; select OK to confirm settings.

Figure 1-37: ▶The settings for creating the revolved feature; Body Interaction is disabled because further operations are needed to modify the geometry.




7. Only the fluid body group should remain, and a new feature SubtractBodies 1 should be created. The final fluid domain resembles the inverted profile of the plane shown in Figure 1-39.

1.12. Setting Up Fluid Surfaces and Curves

1. Several parts of the geometry will need to be referenced in the simulation, so it is useful to define these geometries in the 3D-CAD environment; in the graphics window, select the trailing edge of the aircraft, right-click, and select Rename as shown in Figure 1-40. Set the name to trailingEdge and press OK to confirm.

Figure 1-38: ▶The settings for creating the Boolean subtraction; this operation cuts away the geometry that defined the plane body from the geometry that defined the fluid body.

Figure 1-39: ▶The final fluid domain should resemble the inverted profile of the plane.




2. Individually select each face on the fluid body and rename the faces as shown in Figure 1-41. The named faces will be shown under the fluid body as shown in Figure 1-42.

Figure 1-40: ▶The renamed edge will be referenced during mesh refinement.

Figure 1-41: ▶The faces are named as follows: freestream, xSymm, ySymm, nose, fuselage, base, deltaWing, and wingTip.

Figure 1-42: ▶All the renamed faces and edges will automatically be added under the fluid body.




3. Select Close 3D-CAD to exit the 3D-CAD modeling environment. At the completion of this step of the tutorial, the file should be identical to the AreaRule_1.sim file found in the Supplementary_Materials.zip file.

The STAR-CCM+/HEEDS Witcomb area rule tutorial continues with part two, covering setting up the simulation, and part three, on integrating HEEDS into the workflow.

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