Accuracy in Computational Aerodynamics Part 1: Stagnation Pressure 980037
For the computation of the flow around a car there is typically an overprediction of stagnation and base pressure coefficient by 0.02 and 0.07 respectively causing an underprediction of total drag by about 0.01 - 0.02.
To determine the cause of the error in stagnation pressure several different effects have been investigated: length of inlet section, boundary conditions on the floor, mesh resolution, turbulence models and different flow solvers.
One major effect was found to be a short inlet section in the computational model, which caused an overprediction of the stagnation pressure.
The second major effect was insufficient resolution of the mesh along the stagnation line. More than 100 nodes along the stagnation line were necessary to avoid a significant pressure drop.
Finally the k-ε turbulence model caused overprediction of total pressure very close to the stagnation point. The use of an explicit algebraic Reynolds stress model removed this error. This turbulence model also improved prediction of pressure development along the front, in the spoiler region and at the front of the hood.