Numerical modeling and prediction of the effect of cooling drag on the total vehicle drag

The effect of the engine cooling on the total drag is evaluated by numerical analyses using CFD methods for a light commercial vehicle. The numerical mesh includes both exterior and interior (engine compartment, under hood components) parts of the vehicle. The effects of radiator and fan on the total drag were calculated separately. The initial and boundary conditions were supported by in house experiments (radiators pressure drop) and manufacturer data (mass-flow rate information of radiator fan) that are used as inputs for the RANS based CFD analyses. The effect of the wheels motion and cruise speed on the cooling drag and total drag is also investigated. Predicted cooling drag corresponds to 6.9% of the total drag which is consistent with the measurements.