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tutsetup [2012/02/27 22:25]
ramcdona [Cart3D Setup With VSP]
tutsetup [2018/04/01 14:41]
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-====== Cart3D Setup With VSP ====== 
- 
-Using Cart3D with a model created in VSP is mostly just like using Cart3D with any other model. ​ However, VSP and Cart3D use different axis conventions by default. ​ In VSP, +X runs from nose to tail, +Y runs out the right wing, and +Z is up.  In this example, we will analyze a symmetrical flow condition with a symmetry condition on the XZ plane. 
- 
-Cart3D v1.4 includes an adjoint based mesh adaptation capability which is extremely effective at efficiently generating a mesh which is good for your purposes. ​ In this example, we will use adjoint based adaptation with drag coefficient as the adaptation functional. 
- 
-The Cart3D v1.4 adjoint calculation capability is not available on MPI-based clusters. ​ If you have a large case to run with the adjoint calculation,​ you must use a shared memory computer. ​ This tutorial example should run acceptably on a modern laptop. 
-==== input.cntl ==== 
- 
-The Cart3D '​input.cntl'​ file requires some modifications to work with a VSP oriented geometry and also some modifications to match our Onera M6 test case.  These modifications will be detailed below or you can download a ready-to-go '​[[http://​www.openvsp.org/​files/​input.cntl|input.cntl]]'​. 
- 
-=== Flow Conditions === 
- 
-The freestream flow conditions must be set to match the Onera M6 test conditions. ​ Test 2308 was conducted at Mach 0.8395 at 3.06 degrees angle of attack. 
- 
-<​file>​ 
-$__Case_Information: ​         # ...Specify Free Stream Quantities 
- 
-Mach  0.8395 ​ #  (double) 
-alpha    3.06  #  (double) - angle of attack 
-beta     ​0.0 ​ #  (double) - sideslip angle 
-</​file>​ 
- 
-=== Control Volume Boundary Conditions === 
- 
-The far-field boundary conditions and the symmetry wall condition must be specified. ​ Because the +Y direction runs out the wing, the symmetry condition is applied to the Low end of direction 1. 
- 
-<​file>​ 
-$__Boundary_Conditions:​ # BC types: 0 = FAR FIELD  
-                        #           1 = SYMMETRY 
-                        #           2 = INFLOW ​ (specify all) 
-                        #           3 = OUTFLOW (simple extrap) 
-Dir_Lo_Hi ​    ​0 ​  0 0   # (int) (0/1/2) direction ​ (int) Low BC   (int) Hi BC 
-Dir_Lo_Hi ​    ​1 ​  1 0   # (int) (0/1/2) direction ​ (int) Low BC   (int) Hi BC 
-Dir_Lo_Hi ​    ​2 ​  0 0   # (int) (0/1/2) direction ​ (int) Low BC   (int) Hi BC 
-</​file>​ 
- 
-=== Reference Quantities === 
- 
-Although we aren't going to compare force and moment coefficients in this example, it is always a good idea to set the reference quantities appropriately. ​ Because we are analyzing a half wing, the reference area is the area of the half wing.  These reference quantities match the values specified in AGARD-AR-138. 
- 
-<​file>​ 
-refArea ​   0.7532 
-refLength ​ 0.64607 
-momentCtr ​ 0.0 0.0 0.0 
-</​file>​ 
- 
-The reference quantities appear in two places in the '​input.cntl'​ file.  Don't forget to set them in both locations. ​ The second location appears a bit later in the file, so when you change this, scroll back up to make the next change. 
- 
-<​file>​ 
-# ... reference area and length specifications 
- 
-Reference_Area ​   0.7532 ​ all 
- 
-Reference_Length ​ 0.64607 ​ all 
- 
-# ... Force Info 
- 
-Force entire 
- 
-# Moment_Point Xctr(%f) Yctr(%f) Zctr(%f) CompName or CompNumber 
-Moment_Point 0.0 0.0 0.0 entire 
-</​file>​ 
- 
-=== Cut Planes === 
- 
-The Onera M6 wing had a few rows of pressure taps.  Although most visualization tools can extract the pressure distribution on any cut through a surface, it is a good idea to have Cart3D place cut planes at the pressure tap locations. ​ The pressure tap locations are specified in AGARD-AR-138. 
- 
-<​file>​ 
-#                                   ​Pretty printed cutplanes 
-Xslices ​ 0.0 
-Yslices ​ 0.001   ​0.23926 ​  ​0.526372 ​  ​0.777595 ​  ​0.95704 ​  ​1.07667 ​  ​1.136485 ​  ​1.184337 
-Zslices ​ 0.0 
-#                                      ...general format 
-#​Xslices ​ (float) (float) ...(float) ​    -- any number of locations 
-#​Yslices ​ (float) (float) ...(float) ​    -- any number of locations 
-#​Zslices ​ (float) (float) ...(float) ​    -- any number of locations 
-</​file>​ 
- 
-=== Axis Definition === 
- 
-Cart3D needs the axis system defined so that lift, drag, and moment coefficients will be reported with the expected meaning. 
- 
-<​file>​ 
- 
-# ... Axis definitions (with respect to body axis directions (Xb,Yb,Zb) 
-#                       w/ usual stability and control orientation) 
-Model_X_axis ​ -Xb  
-Model_Y_axis ​  ​Yb ​ 
-Model_Z_axis ​ -Zb  
-</​file>​ 
- 
-=== Adaptation Metric === 
- 
-Cart3D provides a flexible means for constructing objective functionals which may be used to drive the adjoint based adaptation. ​ In this example, we construct a simple functional equal to the drag coefficient. 
- 
-<​file>​ 
-# Objective Function: SUM of functionals (J) 
-# J = 0 -> W(P-T)^N 
-# J = 1 -> W(1-P/T)^N 
- 
-# Ref. Frame = 0 Aerodynamic Frame 
-#            = 1 Aircraft (Body) Frame 
- 
-# Force coefficients 
-# Force Codes: CD=0 Cy=1 CL=2 in Aerodynamic Frame 
-# Force Codes: CA=0 CY=1 CN=2 in Aircraft (Body) Frame 
-# Format: ​ 
-#         ​Name ​   Force   ​Frame ​   J      N    Target ​  ​Weight ​ Bound  GMP Comp 
-#        (String) (0,1,2) (0,1) (0,1,2) (int)  (dble) ​  ​(dble) (-1,0,1) 
-# ----------------------------------------------------------------------------- 
-optForce ​  ​CD ​       0      0      0      1      0.     ​1.0 ​      ​0 ​    ​entire 
-</​file>​ 
- 
- 
-==== aero.csh ==== 
- 
-The Cart3D '​aero.csh'​ file requires very little modification to work with a VSP oriented geometry. ​ In addition, the file will be modified to limit the solution procedure so this example will comfortably run on a typical laptop computer. ​ These modifications will be detailed below or you can download a ready-to-go '​[[http://​www.openvsp.org/​files/​aero.csh|aero.csh]]'​. 
- 
-=== Adaptation Limits === 
- 
-When first working with a new analysis case - or when working on a computer with limited resources - it is often a good idea to limit the adaptation procedure. ​ The following limits should keep most cases small enough to run on a modern laptop. ​ When you go to run a '​real'​ case, be sure to increase these limits in concert. 
- 
-<​file>​ 
-# choose functional error tolerance 
-set etol = 0.005 
-</​file>​ 
- 
-<​file>​ 
-# max number of cells allowed in mesh 
-# if the new mesh exceeds this limit, the adaptation terminates 
-set max_nCells = 1000000 
- 
-# number of adaptation cycles 
-set n_adapt_cycles = 7 
-</​file>​ 
- 
- 
-=== Spanwise Orientation === 
- 
-The only **required** change to '​aero.csh'​ for using VSP geometries is to set the spanwise orientation parameter. 
- 
-<​file>​ 
-# spanwise orientation:​ set -y_is_spanwise (default null) 
-# set y_is_spanwise ​ 
-set y_is_spanwise = -y_is_spanwise 
-</​file>​ 
- 
-===== Next Steps ===== 
- 
-Once you have these input files set up for your case, proceed to the [[TutRunCart3D|Cart3D Execution]] tutorial. 
- 
  
tutsetup.txt ยท Last modified: 2018/04/01 14:41 (external edit)