tutsetup

# Differences

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 tutsetup [2012/02/27 22:25]ramcdona [Cart3D Setup With VSP] tutsetup [2018/04/01 14:41] Line 1: Line 1: - ====== 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>​ - $__Case_Information: ​ # ...Specify Free Stream Quantities - - Mach 0.8395 ​ # (double) - alpha 3.06 # (double) - angle of attack - beta ​0.0 ​ # (double) - sideslip angle - ​ - - === Control Volume Boundary Conditions === - - The far-field boundary conditions and the symmetry wall condition must be specified. ​ Because the +Y direction runs out the wing, the symmetry condition is applied to the Low end of direction 1. - - <​file>​ -$__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 - ​ - - === 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 - ​ - - 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 - ​ - - === 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 - ​ - - === 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 - ​ - - === 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 - ​ - - - ==== 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>​ - # 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 - ​ - - - === 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 - ​ - - ===== Next Steps ===== - - Once you have these input files set up for your case, proceed to the [[TutRunCart3D|Cart3D Execution]] tutorial. -
tutsetup.txt · Last modified: 2018/04/01 14:41 (external edit)