The Study of Two Dimensional Bluff Body Wake Flows With The Effect Of Underneath Wavy Surface

Abstract

The present study observes the effect of wave-like structure on flow after a bluff body. Particle Image Velocimetry (PIV) technique has been employed to measure the flow velocity and to capture the flow pattern in various wavy surface conditions, positions of bluff body of which has height to width ratio of two, and Reynolds numbers. Two-dimensional numerical solution for the same test condition has been performed by employing the turbulent model of RNG k -e . Sinusoidal surfaces were chosen for wavy condition to represent the wavy boundary. Range of Reynolds numbers were 1480 to 3300 and the wave amplitudes were 0.13 of the bluff body height (0.13D), 0.33D and 0.67D. Comparisons were made against flow over the flat surface for the same flow condition. For most cases studied, two vortices always present in the region in the vicinity close to the bluff body. Larger size of vortices appears in the upper area than those in the lower area of the flow. For low amplitude wave, the flow tends to follow the wave and resulted in large U-component negative velocity zone behind the bluff body. As the wave amplitude increases, the size of this negative velocity region will reduce. Low amplitude wave also increases the fluctuation of the flow as the Reynolds number increases. However, higher wave amplitude suppresses the flow to the same order of fluctuations. In general, the numerical solutions were in good agreement with the experimental results.