702-04

EP-702 Wind Tunnel Setup Procedure (ANSYS Design Modeler & Meshing)

Revision for “EP-702 Wind Tunnel Setup Procedure (ANSYS Design Modeler & Meshing)” created on November 30, 2015 @ 19:26:49

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EP-702 Wind Tunnel Setup Procedure (ANSYS Design Modeler & Meshing)
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Date: <strong>May 28, 2015</strong> <h1><a name="_Toc357579789"></a><strong>1. </strong><strong>PURPOSE</strong><strong> / DESCRIPTION</strong></h1> <ul> <li><strong>To set a standard procedure for NX Drone and other subjects to prepare a mesh for a headwind wind tunnel simulation in ANSYS Fluent</strong></li> <li>Useful resources: <ul> <li>ANSYS Customer Portal and full course videos on Fluent and Meshing</li> <li>“Workshop 07b: Auto Ext Aero” from ANSYS Meshing 16.0 full course materials</li> <li>“Workshop 04: Airfoil” from ANSYS Fluent 16.0 full course materials</li> <li>Workshops from full course for Design Modeler on ANSYS Customer Portal</li> </ul> </li> </ul> <strong> </strong> <h1><strong>2. </strong><strong>PROCEDURE</strong></h1> <ul> <li><strong>ANSYS Workbench</strong> <ul> <li>Drag and drop Fluid Flow (Fluent) system under Analysis Systems to create a standalone Fluent system.</li> <li>Double click on Geometry cell to open Design Modeler.<img class="alignnone wp-image-253 size-full" src="http://wiki.vairdo.com/wp-content/uploads/2015/11/702-01.png" alt="702-01" width="573" height="360" /></li> </ul> </li> </ul> <ul> <li><strong>ANSYS Design Modeler</strong> <ul> <li>File &gt; Import External Geometry File… &gt; find the CAD model file <ul> <li>Generate (F5)</li> <li>Make sure that the generated object is not a surface but rather a body (if it is a surface, choose a different CAD version)</li> <li>Double click on imported body and name it Drone.</li> </ul> </li> <li>Check that the geometry of the model is <strong>moderately clean</strong>. If not, subject-specific cleanup in DM may be necessary (use learning resources), or the CAD model should be sent back to the designer to simplify geometry. The judgment should be based on Meshing and CFD courses.</li> <li>(Optional) Create &gt; Body Transformation &gt; Rotate <ul> <li>Preserve Bodies? = No</li> <li>Bodies = select Drone</li> <li>Axis Selection = choose appropriate axis <ul> <li>Selecting one of the planes in Outlines will show the corresponding axes of that plane.</li> <li>Choose the desired axis on the Model View window and click Apply.</li> </ul> </li> <li>Angle = desired angle of rotations</li> <li>Generate (F5)</li> </ul> </li> <li>Tools &gt; Enclosure <ul> <li>Shape = Box</li> <li><span style="line-height: 1.5">Determine appropriate dimensions of enclosure depending on the dimensions of the geometry. You can use the diagram below to have applicable dimensions for external flow domain.</span><img class="alignnone wp-image-254" style="line-height: 1.5" src="http://wiki.vairdo.com/wp-content/uploads/2015/11/702-02.png" alt="702-02" width="611" height="199" /></li> <li>Merge Parts? = No</li> <li>Body = Tunnel</li> <li>Generate (F5)</li> </ul> </li> </ul> </li> </ul> <ul> <li>Create &gt; Boolean <ul> <li>Operation = Subtract</li> <li>Target Bodies = select first enclosure</li> <li>Tool Bodies = select Drone</li> <li>Preserve Tool Bodies? = Yes</li> <li>Generate (F5)</li> </ul> </li> <li>RMB test subject in outline &gt; Suppress Body</li> <li>Create &gt; Primitives &gt; Box <ul> <li>Dimension the box so that it encloses Drone tightly (up to about 10% cushion) as seen in the example shown below.<img class="alignnone wp-image-255" src="http://wiki.vairdo.com/wp-content/uploads/2015/11/702-03.png" alt="702-03" width="655" height="464" /> <img class="alignnone wp-image-256" src="http://wiki.vairdo.com/wp-content/uploads/2015/11/702-04.png" alt="702-04" width="387" height="415" /></li> <li>Fluid/Solid = Solid</li> <li>Generate (F5)</li> </ul> </li> <li>Close Design Modeler</li> <li>Double click on Mesh cell to open Meshing</li> </ul> &nbsp; &nbsp; <!--nextpage--> <ul> <li><strong>ANSYS Meshing</strong> <ul> <li>Click on <strong>Solid</strong> (the box created above) in Outline <ul> <li>Graphics Properties &gt; Transparency = 0.2</li> </ul> </li> <li>Figure to the right is what the setup should look similar to</li> <li>RMB on <strong>Solid</strong> in Outline &gt; Suppress Body</li> <li>Basic options <ul> <li>Mouse selection:<img class="alignnone size-full wp-image-257" src="http://wiki.vairdo.com/wp-content/uploads/2015/11/702-05.png" alt="702-05" width="114" height="26" /> these allow seleciton of vertices, edges, faces, and bodies</li> <li>View controls: <img class="alignnone size-full wp-image-258" src="http://wiki.vairdo.com/wp-content/uploads/2015/11/702-06.png" alt="702-06" width="175" height="26" /> the leftmost button is the most useful because it allows you to set the center of rotation for the view by left clicking.</li> </ul> </li> <li>Click on <strong>Mesh</strong> &gt; Statistics &gt; Mesh Metric = Orthogonal Quality <ul> <li>Make sure that you can see the Metric Graph by clicking the button <img class="alignnone size-full wp-image-259" src="http://wiki.vairdo.com/wp-content/uploads/2015/11/702-07.png" alt="702-07" width="121" height="25" /></li> <li>It is important to check the quality of the Mesh each change and update through Orthogonal Quality and Metric Graph. (a surface mesh’s Min should be above about .4, and a full mesh’s Min should be above about .05) There is no reason to generate the full mesh when the surface mesh’s quality is not satisfactory.</li> </ul> </li> <li>Select the 6 faces of the enclosure &gt; RMB on graphics window &gt; Hide Face (F8) <ul> <li>This is to be able to select and work with the surface of Drone</li> <li>When you need to select the enclosure’s faces, RMB on graphics window &gt; Show Hidden Face(s)</li> </ul> </li> <li>RMB on <strong>Mesh</strong> in Outline &gt; Preview &gt; Surface Mesh <ul> <li>Use Surface Mesh to observe the mesh before generating the entire mesh. If the surface mesh has a bad quality there is no point in generating the entire mesh.</li> </ul> </li> <li>Click on New Section Plane <img class="alignnone size-full wp-image-260" src="http://wiki.vairdo.com/wp-content/uploads/2015/11/702-08.png" alt="702-08" width="29" height="20" /> <ul> <li>Make a section plane as shown below by drawing a vertical line slightly off the center of the front face.<img class="alignnone wp-image-270 " src="http://wiki.vairdo.com/wp-content/uploads/2015/11/702-091.png" alt="702-09" width="682" height="569" /></li> <li>Create more section planes as needed throughout the steps</li> </ul> </li> <li>Click on <strong>Mesh</strong> <ul> <li>Change settings:</li> </ul> </li> </ul> </li> </ul> <table border="1"> <tbody> <tr> <td rowspan="2" width="128">Defaults</td> <td width="255">Physics Preference</td> <td width="405">CFD</td> </tr> <tr> <td width="255">Solver Preference</td> <td width="405">Fluent</td> </tr> <tr> <td rowspan="5" width="128">Sizing</td> <td width="255">Use Advanced Sizing Function</td> <td width="405">On: Proximity and Curvature</td> </tr> <tr> <td width="255">Relevance Center</td> <td width="405">Fine</td> </tr> <tr> <td width="255">Span Angle Center</td> <td width="405">Fine</td> </tr> <tr> <td width="255">Curvature Normal Angle</td> <td width="405">10° (should be adjusted depending on geometry)</td> </tr> <tr> <td width="255">Min Size</td> <td width="405">.7 mm This should be adjusted after examining the surface mesh. If there are features that are not well resolved because the cell size is not small enough, then decrease the size. However, wing features will be dealt with later, so if there are no problems except the wings, then leave this as default. Check the Orthogonal Quality after each change.</td> </tr> <tr> <td width="128">Patch Conforming Options</td> <td width="255">Triangle Surface Mesher</td> <td width="405">Advancing Front</td> </tr> <tr> <td width="128">Defeaturing</td> <td width="255">Automatic Mesh Based Defeaturing</td> <td width="405">On</td> </tr> </tbody> </table> <ul> <li>Creating Named Selections <ul> <li>Select the faces on Drone that are not part of the wing (or parts that need more refining). <ul> <li>RMB on graphics window &gt; Create Named Selection</li> <li>Name it ‘wall_body’</li> </ul> </li> <li>Select the faces of the wings <ul> <li>RMB on graphics window &gt; Create Named Selection</li> <li>Name it ‘wall_wing’</li> </ul> </li> <li>RMB on graphics window &gt; Show Hidden Face(s) <ul> <li>Using the same procedure as above, name the front side of the enclosure ‘inlet’.</li> <li>Name the back side ‘outlet’.</li> <li>Name the 4 remaining sides ‘walls’.</li> </ul> </li> <li>RMB on <strong>Mesh</strong> &gt; Insert &gt; Sizing</li> </ul> </li> </ul> <table border="1"> <tbody> <tr> <td rowspan="2" width="128">Scope</td> <td width="255">Scoping Method</td> <td width="405">Name Selection</td> </tr> <tr> <td width="255">Named Selection</td> <td width="405">wall_wing</td> </tr> <tr> <td rowspan="2" width="128">Definition</td> <td width="255">Element Size</td> <td width="405">1 mm Use appropriate size to get accurate results on the wings</td> </tr> <tr> <td width="255">Behavior</td> <td width="405">Soft</td> </tr> <tr> <td width="128"></td> <td width="255">Curvature Normal Angle</td> <td width="405">3°</td> </tr> </tbody> </table> <ul> <li>RMB on <strong>Solid</strong> (the suppressed box) &gt; Unsuppress Body <ul> <li>RMB on <strong>Mesh</strong> &gt; Insert &gt; Sizing</li> </ul> </li> </ul> <table border="1"> <tbody> <tr> <td width="128">Scope</td> <td width="255">Scoping Method</td> <td width="405">Geometry Selection</td> </tr> <tr> <td width="128"></td> <td width="255">Geometry</td> <td width="405">Select Tunnel</td> </tr> <tr> <td width="128">Definition</td> <td width="255">Type</td> <td width="405">Body of Influence</td> </tr> <tr> <td width="128"></td> <td width="255">Bodies of Influence</td> <td width="405">Select the box</td> </tr> <tr> <td width="128"></td> <td width="255">Element Size</td> <td width="405">8.0 mm Use appropriate size to refine the mesh around Drone.</td> </tr> </tbody> </table> <ul> <li>RMB on <strong>Mesh</strong> &gt; Insert &gt; Inflation</li> </ul> <table border="1"> <tbody> <tr> <td width="128">Scope</td> <td width="255">Scoping Method</td> <td width="405">Geometry Selection</td> </tr> <tr> <td width="128"></td> <td width="255">Geometry</td> <td width="405">Select the entire body of the system</td> </tr> <tr> <td width="128">Definition</td> <td width="255">Boundary Scoping Method</td> <td width="405">Named Selections</td> </tr> <tr> <td width="128"></td> <td width="255">Boundary</td> <td width="405">wall_wing, wall_body (Ctrl to select multiple)</td> </tr> <tr> <td width="128"></td> <td width="255">Inflation Option</td> <td width="405">Smooth Transition</td> </tr> </tbody> </table> <ul> <li>This example that the procedure follows employs Smooth Transition to inflate the subject because the resulting grid was found to be sufficient; however, it is recommended that you calculate the <strong>desired first cell height</strong> and use the other methods instead of Smooth Transition. Cases in which aerodynamic drag is important require y+ values less than 10 in order to resolve the viscous sublayer, so use First Cell Height Calculator.xlsx provided or an online tool to calculate the first cell height using appropriate values.</li> </ul> <ul> <li>Click on <strong>Mesh</strong> <ul> <li>Inflation &gt; View Advanced Options = Yes</li> <li>Inflation &gt; Maximum Angle = 180.0°</li> </ul> </li> <li>RMB on <strong>Mesh</strong> &gt; Preview &gt; Inflation <ul> <li>Check that the Min for Orthogonal Quality is above .05.</li> </ul> </li> <li>Click on Generate Mesh</li> </ul> &nbsp; <a style="font-family: Bitter, Georgia, serif;font-size: 48px;line-height: 1.3" name="_Toc357579793"></a><strong>NOTE</strong>: Options chosen and changed depend on the geometry of the model and the characteristics of the problem. Judgment should be based on what is learned in the courses and comparison of different settings. Other options for inflation and sizing should be explored for improvement. <h1><strong>3. </strong><strong>Example Result<img class="alignnone size-full wp-image-262" src="http://wiki.vairdo.com/wp-content/uploads/2015/11/702-10.png" alt="702-10" width="1449" height="687" /></strong></h1> <ul> <li>Orthogonal Quality Min value should be above .05</li> </ul> &nbsp; <h1><strong>4. </strong><strong>TEST RECORDS</strong></h1> <ul> <li>1<sup>st</sup> setup</li> </ul> <img class="alignnone size-full wp-image-263" src="http://wiki.vairdo.com/wp-content/uploads/2015/11/702-11.png" alt="702-11" width="337" height="756" /> &nbsp; &nbsp;
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