# Question about "Motion Mach Number" in "Dynamic Mesh Definition" SU2 version3

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 March 2, 2014, 20:19 #2 Super Moderator   Thomas D. Economon Join Date: Jan 2013 Location: Stanford, CA Posts: 271 Rep Power: 14 Hi Jin, In going to version 3.0, we made a lot of upgrades and standardized much of the dynamic mesh capabilities in the code. This included incorporating the rotating frame mode into the rest of the dynamic mesh framework (and consolidating options). We added the motion mach number option to decouple the force coefficient calculation from the free-stream definition for moving mesh applications, as sometimes you might want to non-dim. based on a tip mach number for a rotor, for instance. It also allows you to compute force coefficients that make sense if your free-stream Mach number is zero (rotor in hover, for example). In order to compute forces for any type of dynamic mesh simulation, see the code on lines ~3500-3525 in solution_direct_mean.cpp, or /*--- For dynamic meshes, use the motion Mach number as a reference value for computing the force coefficients. Otherwise, use the freestream values, which is the standard convention. ---*/ if (grid_movement) { Gas_Constant = config->GetGas_ConstantND(); Mach2Vel = sqrt(Gamma*Gas_Constant*config->GetTemperature_FreeStreamND()); Mach_Motion = config->GetMach_Motion(); RefVel2 = (Mach_Motion*Mach2Vel)*(Mach_Motion*Mach2Vel); } else { RefVel2 = 0.0; for (iDim = 0; iDim < nDim; iDim++) RefVel2 += Velocity_Inf[iDim]*Velocity_Inf[iDim]; } RefDensity = Density_Inf; RefPressure = Pressure_Inf; factor = 1.0 / (0.5*RefDensity*RefAreaCoeff*RefVel2); Note also that the RefAreaCoeff is the value that set in the following config option: % Reference area for force coefficients (0 implies automatic calculation) REF_AREA= 1.0 Between setting the motion mach number to an appropriate value of your choice and entering the correct area, you should be able to recover the type of non-dim. for the force coefficients that you expect. Hope this helps, Tom

 December 2, 2016, 18:02 #3 New Member   California Join Date: Nov 2016 Posts: 10 Rep Power: 9 Just to keep this current, this data is now in solver_direct_mean.cpp, starting at line 4523.

 March 4, 2022, 00:27 su2 propellersimulation #4 New Member   Sushil Nepal Join Date: Feb 2022 Posts: 3 Rep Power: 4 Hi Jin, Hi Tom; I am also doing a su2 cfd simulation for a propeller blade but facing some difficulties. It seems like I can get a good idea from your project. If its not a problem can you please share you pointwise mesh file and su2 configuration file? Thank you!