Impacts of the gap size between two bluff bodies on the flow field within the gap

Abstract

When two bluff bodies is in close tandem, i.e, the distance between blocks D is less than half of the height of the body H, the flow field is very similar to that in the gap between tractor and trailer in a truck, and hence understanding such a flow field would help to reduce the gap drag of a truck. This paper presents a numerical study of the flow field in the gap between two identical cubes in tandem arrangement, in particular, focusing on the impact of gap size on the flow field within the gap and around the two cubes. Simulations have been carried out for four different gap sizes. The numerical model has been validated first against a test case before further studies are carried out to study the impact of gap width on the flow field. The predicted mean velocity profiles compare well against the experimental data for the validation test case. Detailed analysis has been carried out to reveal the change of the flow fields when the gap size changes, leading to a better understanding of the drag coefficient variations for the four cases studied.