PIV investigation of flow over a transverse square rib in pressure gradients

Abstract

This paper reports on experiments conducted to study the characteristics of separated and reattached turbulent flows experiencing adverse and favorable pressure gradients. The adverse and favorable pressure gradients were produced, respectively, in asymmetric diverging and converging channels, and the flow separation was caused by transverse square rib attached to the lower wall of the channels. A high-resolution particle image velocimetry was used to conduct detailed velocity measurements in the separated and redevelopment regions. Reference measurements were also conducted in a parallel-walled channel for which the pressure gradient is small compared to those produced in the diverging and converging for comparison. From these measurements, iso-contour plots of the mean velocity, spanwise vorticity and turbulence production in the vicinity of the rib were reported. The profiles of the mean velocities and vorticity, Reynolds stresses, triple correlations, production terms in the transport equations for the turbulent kinetic energy and Reynolds shear stress, mixing length and eddy viscosity were obtained in the separated and redevelopment regions as far downstream as 120 rib heights.

Keywords:

• separated flows
• turbulent flow
• pressure gradient
• particle image velocimetry

Acknowledgements

Financial support provided by Canada Foundation for Innovation, Manitoba Hydro and Natural Sciences and Engineering Research Council of Canada is gratefully acknowledged.

Notes

^†Measurements have been reported in separated as well as redevelopment region;

*measurements have been reported in redevelopment region only.

^a */θ) is the shape parameter; Re _k = U _o k/ν; Re _θ = U _o k/ν; k is the rib height and ν is the kinematic viscosity.