Optimization of Boundary Layer Separation Reduction Induced by The Addition of a Dimple Grid on Top of a Bluff Body

Abstract

In recent years, there has been an increasing interest bluff body vehicle aerodynamic. Bluff body vehicle is the vehicle segment category comprising buses, van, multipurpose vehicle (MPV), small utility vehicle (SUV), truck and lorry. The bulky size of these bluff body experienced a large aerodynamics drag when travelling at high speed. These aerodynamic drags are contributed by large pressure drag at front and boundary layer separation on vehicle wall and wake region at the back of the vehicle. It is becoming increasingly difficult to ignore the effect of boundary layer separation on top of the bluff body towards the aerodynamic drag. Recent developments in the field of vehicle aerodynamic have led to a renewed interest in boundary layer separation phenomena on bluff body. Most studies in boundary layer separation have only been carried out on the wake region at the rear of the bluff body due to shape limitation of the bluff body itself. This research will focus on examine the boundary layer separation on top of bluff body by the adaptation of golf ball dimple grid which will be introduced on top of a generic bluff body in various location. The dimple grid will be further optimize using design of experiment (DOE) approaches. The computational fluid dynamic (CFD) simulation method is one of the more practical ways of validating the bluff body model and this will be further validate using physical wind tunnel experimental. It is possible to hypothesize that the dimple depth, size, grid pattern and location most likely have influential effect to the boundary layer separation. In general, therefore, it seems that drag reduction was possible by the alteration of flow on top of the bluff body. The optimized design shows prominent result as it contributes around 36.5% of drag reduction.