Computational Fluid Dynamics (CFD) Modeling Of Turbulence Induced Drag In Vehicle Aerodynamics

ABSTRACT

This research work focused on the use of an hybrid RANS-LES turbulence model in simulating and checking the drag performance characteristics of an aerodynamic vehicle. The Spalart-Allmaras shear stress transport (SST)- Scale Adaptive Simulation (SAS) Turbulence model was selected for use, and with the help of OpenFOAM Finite Volume Computational Fluid Dynamic Solver the simulation algorithm was set and carried out in a total time step of 4000. Convergence was achieved under the stipulated time step based on our set convergence criteria. The geometries were downloaded in their stereolitography (STL) format, then SnappyHex Mesh meshing tool was used to generate our mesh grid. The first simulation which took 674870secs to run gave a coefficient of drag value of 0.522497. Then with the help of FreeCAD Open Source Software, the vehicle shape was carefully altered and on running the simulation on the new shape it produced a drag coefficient value of 0.415411 in 669116secs, which represents a coefficient of drag reduction of about 20.49%. Thus OpenFOAM CFD Solver helped to carry out analysis on the turbulent flow over a motorbike and aided in reducing the drag coefficient of the motorbike. Further optimal shape analysis studies if carried out can help an aerodynamic engineer produce more fuel economical vehicles for consumer use.