Experimental observation of boundary layer of the turbulent flow over a bluff body inside rectangular diffuser

摘要

The turbulent fluid flow with different velocity over a bluff body is important for the analysis and design of structure of high rise buildings as well as flow passage having flow obstruction. The main aim of present work is to investigate experimentally the flow field of air in a rectangular diffuser with different inlet velocity. From experimental results it has been found the displacement thickness and momentum thickness by numerical integration. The flow field considered is the field before and after the bluff body in a rectangular diffuser. The result also contained detailed velocity distributions, which have been investigated thoroughly in the direction normal to the test section at different axial positions. From the experimental results it is concluded that the boundary layer thickness is lower for higher inlet velocity. Displacement thickness is fluctuating at upstream and top of bluff body and at downstream it decreases with increase of inlet velocity. Momentum thickness decreases according to increase inlet velocity. The variation of momentum thickness is higher for high inlet velocity. Near the bluff body, momentum thickness decreases, which denotes maximum momentum transfer and as it becomes negative, it corresponds to recirculation zone. The recirculation length and height increases with increase inlet velocity.