Underhood thermal management is an important area in new vehicle design, consuming substantial engineering resources and requiring extensive access to costly prototype vehicles throughout a development programme. Simulation-based design methods and computational tools have been validated for steady-state investigations of forced flows within engine bays. However, transient analyses with a long timescale, such as the simulation of natural convective flow under the hood during heat soak, are still unfeasible due to the high computing requirements.
The present paper intends to define a reliable computation procedure that will enable time-marching Computational Fluid Dynamic (CFD) simulations to be performed with significantly reduced CPU time usage.
The performance of the proposed methodology was evaluated through model comparison with a fully transient CFD solution. The methodology was then refined and implemented for the investigation of a half-scale underhood compartment model simulated in heat soak condition and the results were compared with experimental measurements.
The commercial CFD software VECTIS was employed for the numerical simulations. VECTIS incorporated all three modes of heat transfer, including radiation. The laboratory data comprised measurements of the temperature distribution on underhood component surfaces and air planes and Particle Image Velocimetry (PIV) measurements of the airflow patterns induced by buoyancy.
The devised procedure was successful in efficiently providing detailed pseudo transient flow and thermal predictions that would not have been otherwise obtainable with a typical CFD time-dependent simulation, especially on computing resources found in a typical engineering analysis group.