Experimental and numerical studies of flows over forward facing steps in pressure gradients

Abstract

This thesis reports experimental and numerical studies of the effects of adverse pressure gradients (APG) and Reynolds numbers on flows over forward facing steps (FFS). For the experimental work, particle image velocimetry was used to conduct velocity measurements at several locations downstream of the FFS. Proper orthogonal decomposition and two-point correlation were applied to the experimental data to study the large scale structures. For the numerical analysis, turbulence models in ANSYS Fluent were used to study the reattachment length XL for blockage ratios from 5.8% to 29.5% and step inclination angles from 22.5˚ to 135˚. The experimental results show that XL increases with the increase in Reynolds number without APG, but remains nearly constant for increasing APG. The CFD results show that as the step angle is increased, XL decreased. Furthermore, increasing the blockage at constant Reynolds number, the XL values decrease.