I get negative drag coefficient when I set the REF_DIMENSIONALIZATION
HL-ZHI opened this issue · 3 comments
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Describe the bug
To be honest, I haven't care about the dimensionalization since today I got a negative CD for a very very simple case. The case setup is:
- NACA0012 airfoil, structured grid
- Freestream condition: Re=1E6, AoA=5, Mach=0.1
- Solver: RANS with S-A model, Roe upwind scheme.
Every other thing can be default. The drag coefficients I got are:
REF_DIMENSIONALIZATION=DIMENSIOAL: 0.005
REF_DIMENSIONALIZATION=FREESTREAM_VEL_EQ_MACH: -0.025
It is interesting. I am gonna check the code in CEulerSolver::SetNondimensionalization.
Desktop (please complete the following information):
- OS: WINDOWS & Ubuntu
- C++ compiler and version: [e.g., g++ (GCC) 4.8.5]
- MPI implementation and version: [e.g., OpenMPI 4.1.3]
- SU2 Version: 7.3.1 & 7.5.1
You have a negative mach number, that doesn't sound right.
You have a negative mach number, that doesn't sound right.
I'm sorry. My mach number is 0.1. When I set REF_DIMENSIONALIZATION=FREESTREAM_VEL_EQ_MACH, I got CD=-0.025.
I found ENTROPY_FIX_COEFF is of great influence on the CD, I got the negative CD when it is small.