Development and Prediction of Vehicle Drag Coefficient Using OpenFoam CFD Tool 2019-26-0235

Vehicle aerodynamic design has a critical impact on fuel efficiency of the vehicle. Reducing aerodynamic wind resistance of the vehicle's exterior shape and reducing losses associated with requirements for engine compartment cooling through vehicle front openings plays key role in achieving desired aerodynamic efficiency.

Today fairly large number of computational fluid dynamics (CFD) simulations are being performed during the vehicle aerodynamic design and development process and it is rapidly increasing day by day. Vehicle aerodynamic design and development process involves mainly aerodynamic shape development, aerodynamic optimizations of vehicle external components (side view mirror, spoilers, underbody shield etc.) and number of” what if studies during preliminary design process.

Licensing costs of the available commercial CFD simulation solver has significant impact on product development cost when numbers of aerodynamic simulations expand. To address this aspects, open source code “OpenFoam” CFD have become popular in the aerodynamic community.

This papers summarizes CFD simulation results for three standard MIRA body configurations (Notchback, Fastback and Estate back) using OpenFoam solver. In this study, steady state simulations with Realizable K-epsilon turbulence models were performed on MIRA body. Aerodynamic drag coefficient (C_d) of above three configurations are compared against experimental data. It is observed that OpenFoam simulation results matches well with experimental values for drag coefficient for Estateback and Notchback configurations and for Fastback configuration more than 5% deviation is observed which is to be studied further. This shows that OpenFoam simulation prediction quality is at par with commercial software tools like ANSYS Fluent, Star CCM+ etc. The simulation methodology presented in this paper will help OEMs and engineering service providers to reduce product development cost as OpenFoam is open source code which subsequently help to reduce physical validations and product development timeline.