Investigation of a Coupled CFD and Thermal Modelling Methodology for Prediction of Vehicle Underbody Temperatures

A coupled steady-state CFD and thermal study was undertaken at full-vehicle scale using the Low-Reynolds formulation of the k-epsilon turbulence model, with hybrid wall function modification. The separate thermal model included radiative and conductive heat transfer. Road testing (simulated hill climb using towing dynamometer) was performed to provide both boundary conditions for exhaust temperature and detailed local temperatures (air and surface) to enable correlation. CFD and thermal models were alternately iterated until overall convergence was achieved. Measured air temperatures were utilized in the “control” thermal model to provide a best possible non-CFD solution.

Coupled model results show reduction in local surface temperature prediction error due to the inclusion of the detailed convection modeling, but cause concerns that the heat transfer mechanism in the exhaust tunnel is not correctly represented. The model additionally increased qualititative understanding of the flow conditions surrounding the vehicle underbody. The modeling process was very time-consuming due to geometry and mesh manipulation and proposals are made to reduce this in future.