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The applicability of high-performance computing (HPC) to vehicle aerodynamics is presented using a Cartesian grid approach of computational fluid dynamics. Methodology that allows the user to avoid a large amount of manual work in preparing geometry is indispensable in HPC simulation whereas conventional methodologies require much manual work. The new frame work allowing a solver to treat ‘dirty’ computer-aided-design data directly was developed with a modified immersed boundary method. The efficiency of the calculation of the vehicle aerodynamics using HPC is discussed. The validation case of flow with a high Reynolds number around a sphere is presented. The preparation time for the calculation is approximately 10 minutes. The calculation time for flow computation is approximately one-tenth of that of conventional unstructured code.

In vehicle aerodynamics analysis considering actual traveling conditions, it is known that the flow around the rotating wheel interferes with the wake of the wheel arch, the flow ejected from the engine room, and the flow under the floor. This significantly affects the aerodynamic drag value. In particular, the fuel consumption measurement method by the World Wide Harmonized Light Vehicle Test Procedure has been carried out since FY 2018 in Japan. A calculation condition on computational fluid dynamics is required to be accompanied with wheel rotation. However, it is not easy to carry out simulations with wheel rotation for a full-vehicle model using a general-purpose method with an unstructured grid or voxel lattice. This method has difficulty in performing calculations faster and easier.