LOW REYNOLDS NUMBER FLOW OVER A SQUARE RIB

Abstract

Laminar flow over a square rib placed in a fully developed channel flow is investigated over the Reynolds number range 80-350. The effect of Reynolds number on the flow and the variation of the primary reattachment length with Reynolds number are investigated using flow visualization and laser-Doppler velocimetry. The primary recirculation region length is found to increase in a slightly non-linear fashion with Reynolds number up to Reh = 250, at which point shear layer instabilities first appear downstream of the rib. Increasing the Reynolds number further, first results in continuing growth of the separation bubble, and then for Reh ≳ 300, in the appearance of three dimensional vortices and gradual shortening of the bubble. The measurements are complemented by two- and three-dimensional numerical simulations using a finite volume method with a high-order descretization scheme. These simulations yield excellent agreement with the measured reattachment lengths and velocity profiles over the steady laminar flow régime.