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oneram6 [2012/02/29 06:40]
ramcdona old revision restored
oneram6 [2018/04/01 14:41]
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-====== Geometry Generation for Cart3D Tutorial ====== 
  
-This component of the Cart3D tutorial will walk through the process of creating a simple geometry to analyze with Cart3D. ​ For this example, we will build a model of the Onera M6 wing. 
- 
-==== Onera M6 Definition ==== 
- 
-The Onera M6 wing is a standard transonic test case frequently used to demonstrate CFD codes. ​ The geometry, experimental setup, and experimental results are documented in AGARD AR-138. ​ These results are also summarized by the [[http://​www.grc.nasa.gov/​WWW/​wind/​valid/​m6wing/​m6wing.html|NASA NPARC Alliance Validation Archive]]. 
- 
-The Onera M6 wing uses uses an Onera D airfoil normal to the 40.18% chord line.  VSP generally works with airfoils specified in the streamwise direction. ​ The NPARC Alliance web site includes a Fortran program to transform the airfoil coordinates;​ it also includes an airfoil file which results from the transformation. ​ That file was modified to create an airfoil in the [[files#​af|VSP airfoil format]]. ​ The Onera M6 airfoil file is available [[http://​www.openvsp.org/​files/​m6foil.af|here]]. 
- 
-The planform of the Onera M6 wing is depicted in the following figure pulled from AGARD AR-138. ​ This image has been cropped and rotated slightly so it is ready-to-use as a background image in VSP; you may want to save a copy of the image for that purpose. ​ The simplicity of the Onera M6 makes use of a background image somewhat unnecessary,​ but this does provide a good example of using a background image. 
- 
-{{ :​oneram6_planform.jpg?​nolink&​ |}} 
- 
-The Onera M6 wing is described by the following parameter values 
- 
-  * Semispan 1.1963 m 
-  * Root chord 0.8059 m 
-  * Taper ratio 0.562 
-  * Aspect ratio 3.8 
-  * Sweep (LE) 30 deg 
- 
-==== Building the Onera M6 ==== 
- 
-As you proceed through the tutorial to build the Onera M6, remember that images have been included as thumbnails, so any place you see a picture, click on it for a larger version. 
- 
-  - Run OpenVSP 
-     * Launch OpenVSP ready to create a new model. \\ {{:​1_blank_start.png?​direct&​200|}} \\ 
-  - Add wing component 
-     * Add a MS_Wing component to your model. ​ Depending on your defaults file, your new MS_Wing component may look different from this one.  
-     - In 'Geom Browser',​ choose 'MS WING' from the component type pulldown. 
-     - Click '​Add'​ to add the component to the model. \\ {{:​2_ms_wing.png?​direct&​200|}} 
-  - Delete unneeded wing sections 
-     * The Onera M6 wing has no planform or twist breaks and therefore can be modeled with only one wing section. 
-     - In 'Multi Section Wing Geom', select the '​Sect'​ tab. 
-     - Repeatedly click the right-facing arrow by '​Section ID:' until the most outboard wing section is active. 
-     - Repeatedly click the '​Del'​ button until only one wing section remains. ​ VSP will not let you delete the last wing section. \\ {{:​3_single_section.png?​direct&​200|}} 
-  - Change model view 
-     * You may wish to rotate, zoom, or pan the model view to provide a different perspective on the model. ​ This can be done at any time in VSP. \\ {{:​4_rotated_single.png?​direct&​200|}} 
-  - Add background image 
-     * VSP can display a background image in the main graphics window. ​ This is often a good way to start a model when all you have is a three-view drawing. ​ The Onera M6 geometry is well specified, so this step is not strictly needed. ​ However, it still provides a good sanity check. 
-     - Save the Onera M6 planform drawing above to your hard drive. 
-     - Go to the '​Window'​ menu and then select '​Background...'​. \\ {{:​5_click_background.png?​direct&​200|}} 
-     - In the '​Background'​ window, click the 'JPEG Image' button to activate a background image \\ {{:​5.5_activate_background.png?​direct&​200|}} 
-     - In the '​Select File' window, navigate to the location where you stored the background image, select the file, and click '​Accept'​. ​ \\ {{:​6_select_background.png?​direct&​200|}} 
-     - If needed, you can scale and offset the background image so that it fits well in the display window. ​ Close the '​Background'​ window when you are satisfied with the background display. 
-     - In the '​View'​ window, click '​Top'​ (or press F5) to change the view orientation to a top-view of the model. ​ 
-  - Change driver group 
-     * There are six canonical interdependent parameters frequently used to describe a trapezoidal wing -- aspect ratio (AR), taper ratio (TR), Area, Span, tip chord (TC), and root chord (RC).  Usually, if three of these parameters are specified, the other three can be calculated. ​ VSP lets the user choose which parameters to specify when building the model. 
-     - In the 'Multi Section Wing Geom' window, on the '​Sect'​ tab, in the '​Section Planform'​ area, click the '​Driver:'​ pulldown and then select '​AR-TR-Span'​. ​ This will activate aspect ratio, taper ratio, and span as the independent variables. \\ {{:​7_change_driver.png?​direct&​200|}} 
-  - Set span and adjust view 
-     * As the model is updated, the view can be adjusted such that the model and the background image coincide. 
-     - In the '​Section Planform'​ area, enter '​1.1963'​ into the box next to '​Span'​. ​ This is the semi-span of the Onera M6 wing in meters. 
-     - Adjust the pan and zoom of the model view until the wing root and tip match the background image. ​ If you accidentally rotate the model, just press '​F5'​ to reset to the top view. \\ {{:​8_scale_span.png?​direct&​200|}} 
-  - Set wing planform 
-     * The published Onera M6 wing parameters over-specify the wing shape and because of the limited precision included in the report, the published parameters are not perfectly self-consistent. ​ Consequently some amount of compromise is required when modeling this wing.  Each independent parameter is set by entering the value into the box to the right of the parameter. 
-     - Set the sweep to 30 degrees. 
-     - Set the taper ratio to 0.562. 
-     - Set the aspect ratio to 1.9.  VSP uses the aspect ratio of a single section instead of the whole wing.  Consequently,​ the aspect ratio is 1.9 instead of the published value of 3.8. 
-     - Pan the model until the leading edge origin aligns with the background image. \\ {{:​9_onera_planform.png?​direct&​200|}} 
-  - Change driver group 
-     * Notice that the calculated root chord (0.8062) does not perfectly agree with the published value (0.8059). ​ This is a direct result of the limited precision of the specified parameters of the Onera M6 wing. 
-     - Click the '​Driver:'​ pulldown and select '​Span-TC-RC'​ as the driver group. ​ This will activate span, tip chord, and root chord as the independent variables. ​ Aspect ratio, taper ratio, and area will be calculated to agree. \\ {{:​10_change_driver.png?​direct&​200|}} 
-     - Set the root chord to 0.8059. 
-     * Note that the aspect ratio is now 1.9004 (instead of 1.9) and the taper ratio is now 0.5622 (instead of 0.562). ​ Increasing the tip chord will drive aspect ratio closer to the target value - but will also drive taper ratio further from the target value. 
-  - Set airfoil section 
-     * As described above, the Onera M6 uses the Onera D section orthogonal to the 40.18% chord line.  This section has been transformed into a streamwise airfoil and put into VSP airfoil format. 
-     - Download the [[http://​www.openvsp.org/​files/​m6foil.af|transformed Onera M6 airfoil]] and save it to your hard drive. 
-     - In the 'Multi Section Wing Geom' window, on the '​Foil'​ tab, click the 'Read File' button to pull up a '​Select File' dialog. \\ {{:​11_pick_foil.png?​direct&​200|}} 
-     - In the '​Select File' window, navigate to the location where you stored the airfoil, select the file, and click '​Accept'​. ​ This will set the root airfoil section. 
-     - Click the right-facing arrow by '​Airfoil'​ to change control to the tip airfoil section. 
-     - Repeat the 'Read File', navigate, '​Accept'​ sequence to set the tip airfoil to the Onera M6 section. 
-  - Round the wingtips 
-     * The Onera M6 has rounded wing tips -- while the VSP default is a truncated wing tip.  Fortunately,​ VSP also has built-in support for rounded wing tips. 
-     - In the 'Multi Section Wing Geom' window, at the bottom of the the '​Plan'​ tab, click the '​Rounded Tips' button. \\ {{:​12_rounded_tips.png?​direct&​200|}} 
-  - Change part name 
-     * Although this model only has one component, it is a good practice to give each component in a model a meaningful name. 
-     - In the 'Multi Section Wing Geom' window, on the '​Gen'​ tab, enter '​OneraWing'​ in the text field next to '​Name:'​. \\ {{:​13_name.png?​direct&​200|}} 
-     * In this example, the background image has also been deactivated by clicking '​Window',​ '​Background...',​ 'JPEG Image',​ and then '​Cancel'​. 
-  - Save model 
-     * The basic definition of the Onera M6 model is now complete, so this is probably a good time to save your work. 
-     - In the '​File'​ window, click '​Save'​ to bring up a '​Select File' dialog to navigate the hard drive and specify an appropriate file name. \\ {{:​14_save.png?​direct&​200|}} 
-     - When you are satisfied, click '​Accept'​ 
- 
-===== Next Steps ===== 
- 
-Once the geometry definition is complete, the next step is to generate a triangulated surface mesh for analysis in Cart3D. ​ This process is detailed on the [[MeshOverview|Mesh Generation]] page. 
- 
-Or, feel free to jump to your topic of choice. 
- 
-  - Geometry Generation (This Page) 
-  - [[MeshOverview|Mesh Generation]] 
-    * [[TutGenMesh|Isotropic Generated Mesh]] 
-    * [[TutUnint|Unintersected Component Wireframe]] 
-    * [[TutCompGeom|Intersected Component Wireframe]] 
-  - [[TutSTLtoTRI|STL to TRI Conversion]] 
-  - [[TutSetup|Cart3D Setup]] 
-  - [[TutRunCart3D|Cart3D Execution]] 
oneram6.txt ยท Last modified: 2018/04/01 14:41 (external edit)