Investigating the influence of dimples on side of Ahmed body skin friction using Computational Fluid Dynamics (CFD) analysis

Kamarullzaman, Shafiq Danial (2025) Investigating the influence of dimples on side of Ahmed body skin friction using Computational Fluid Dynamics (CFD) analysis. Project Report. Universiti Teknikal Malaysia Melaka, Melaka, Malaysia. (Submitted)

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Abstract

Aerodynamic drag significantly contributes to vehicle performance, fuel efficiency, and ecological friendliness; hence, it is the most important field in auto-body engineering. Despite the overwhelming research in Ahmed bodies, the amenability of side dimples to drag and skin friction remains unexploited. In this regard, this work investigates the effect of side dimples on the aerodynamics of the Ahmed body using CFD methods. The steps that have been carried out systematically were 3D modeling, mesh generation, setting of boundary conditions, and CFD analyses. The number of elements identified for mesh sensitivity analysis was 12 million, as this number had the best fitting where the computational cost and accuracy were well balanced. It was observed that the drag coefficient decreased by 8.46% from its benchmark value of 0.306 to 0.277 in this modified model, while the skin friction coefficient slightly reduced from 0.014 to 0.0135. Statistical analysis and pressure distribution comparisons supported the stability of the modified model aerodynamics, with negligible deviation over the benchmark configuration. Lift and moment coefficients after their initial transients stabilized into a consistent value of aerodynamics. This finding confirms that side dimples act to increase the aerodynamic performance by reducing flow detachment and hence turbulence. Such modifications provide practical ways in which the fuel economy could be improved and emissions reduced, thus having economic and environmental benefits. The research forms a basis for new and innovative optimization in aerodynamics toward achieving sustainable engineering solutions in the automotive sector.

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