Unsteady Flow Analysis Method for Automobile LED Headlamp Based on Massively Parallel CFD Considering the External Environment

The aims of this study are to understand the mechanism of dew condensation and try to prevent it on automobile headlamp. In this case, it is necessary to build the computational model of the headlamp with all details accurately. In addition, the simulation framework for predicting the turbulent flow field has to be accompanied with the high temperature heat source and consider high accuracy of the wall heat transfer in the running environment of a vehicle. Moreover, it is a challenging task that using CFD (Computational Fluid Dynamics) to understand the mechanism of the flow field inside the light emitting diode (LED) headlamp with a rotating fan to cool the light sources because of the complicated internal structures and significant heat transfer. In this paper, the method of compressible turbulence has been constructed which based on hierarchical cartesian grid using the HPC (High Performance Computing) environment. At first, the ventilation phenomenon of the lamp has been interpreted under the uniform flow condition and then, by changing the position and number of the vents, the relationship between the ventilation of the lamp and these two relative parameters has been shown clearly. The calculation results have been verified by wind tunnel experiments. This makes it possible to consider the external environment that LED headlamps mounted on the vehicle in the future. Next, the calculation method for moving boundary such as a rotating fan has been constructed with the adoption of the immersed boundary method (IBM) in the HPC environment. Then, the comparison between the numerical simulation and particle image velocimetry (PIV) experiment results shows a good agreement with each other. Additionally, to simulate the real situation in the near future, where the extremely larger physical time (>10 seconds) should be taken into account, the trade-off between the accuracy and the computational resource is investigated.