# CFL ramp option

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 March 30, 2013, 04:54 CFL ramp option #1 New Member   Milosz Join Date: Jan 2013 Posts: 14 Rep Power: 13 Hi, I would like to dectrease CFL number during iterations. In the example configuration file there is an option CFL_RAMP: % CFL ramp (factor, number of iterations, CFL limit) CFL_RAMP= ( 1.0, 50, 2.0 ) I have tried this but it looks like CFL limit is only upper boundary. When I set: CFL_NUMBER= 100.0 CFL_RAMP= ( 0.8, 100, 0.1 ) program don't use ramp option and all iterations use CFL=100. When I set: CFL_NUMBER= 100.0 CFL_RAMP= ( 0.8, 100, 100 ) program use ramp option but in every 100 steps it change CFL. In a result I almost get convergence but CFL is so small that I can't reach it. Is there any solution to set lower boundary of CFL number in ramp option?

 April 11, 2013, 13:25 #2 New Member   Amrita Lonkar Join Date: Nov 2012 Posts: 14 Rep Power: 13 Hi, Thanks for your question. I understand that you are trying to decrease the CFL as the number of iterations increases. This option is not available in SU2, but it's a very easy to implement. I suggest you go to the file config_structure.cpp in the folder trunk/Common/src Then, go to the method, UpdateCFL of class CConfig. The very first set of lines are: if ((val_iter % int(CFLRamp[1]) == 0 ) && (val_iter != 0)) { change = false; for (iCFL = 0; iCFL <= nMultiLevel; iCFL++) { coeff = pow(MG_CFLRedCoeff, double(iCFL)); if (Adjoint) coeff = coeff * Adj_CFLRedCoeff; if (CFL[iCFL]*CFLRamp[0] < CFLRamp[2]*coeff) { CFL[iCFL] = CFL[iCFL]*CFLRamp[0]; change = true; } } For your case in which you want to decrease the CFL, these lines of code should be replaced by, if ((val_iter % int(CFLRamp[1]) == 0 ) && (val_iter != 0)) { change = false; for (iCFL = 0; iCFL <= nMultiLevel; iCFL++) { coeff = pow(MG_CFLRedCoeff, double(iCFL)); if (Adjoint) coeff = coeff * Adj_CFLRedCoeff; if (CFL[iCFL]*CFLRamp[0] > CFLRamp[2]*coeff) { CFL[iCFL] = CFL[iCFL]*CFLRamp[0]; change = true; } } Hope this helps, Amrita amitkamboj likes this.