CFD Simulation of the Volvo Cars Slotted Walls Wind Tunnel

Sammanfattning: When CFD simulations are performed at Volvo Cars, a case which resemblesthe condition for a car traveling on a open road is simulated. The results fromthese simulations have often proved to be different compared to the results from theexperiments in the Volvo Cars slotted walls wind tunnel. To investigate the reasonbehind these differences a number of CFD simulations of the Volvo Cars wind tunnelhave been performed. The simulations have been focused on three main cases, emptytunnel, tunnel with a simplified S60 and tunnel with a detailed S80. The resultshave been compared to ordinary CFD simulations and to newly made experimentsin the wind tunnel. The flow produced by the numerical simulations in the emptywind tunnel has proved to be largely asymmetric due to the asymmetric geometryof the slotted walls’ support structure. This has greatly affected the flow around acar in the tunnel resulting in a different flow field compared to the standard CFDsimulation. The drag and lift coefficient of the S60 and S80 have been lower in theCFD simulations of the wind tunnel compared to the ordinary CFD simulations,which is the opposite to what have been found when comparing the standard CFDsimulations to the real experiments in the tunnel. The reason behind this is believedto be mainly due to the geometry simplifications of the simulated tunnel and theuniform inlet boundary condition, which have resulted in a very much more uniformflow in the CFD simulations compared to the experiments.