Experimental Investigation of the Three-Dimensional Nature of Turbulent Flow over a Rectangular Cavity

Abstract

This paper presents results of an experimental study on incompressible turbulent flow over a rectangular cavity. The experiment was carried out to clarify the strength and three-dimensional nature of cavity oscillations for fully turbulent inflow. Particle image velocimetry (PIV) and fluctuating pressure measurements were made in a closed, re-circulating water tunnel for cavity length-depth ratio from L/D=1 to 4 at a momentum thickness based Reynolds number, Re θ =8,300. Measured power spectra of pressure fluctuations show dominant frequencies with broad peak width indicating the absence of resonant oscillations. Pressure fluctuations at two spanwise separated locations are well correlated at the frequency range in which dominant peaks are found. Instantaneous flow fields reveal strong three-dimensional distortions. Although formation and passage of turbulent eddies are observed in the instantaneous x (streamwise)-y (vertical) plane flow field, instantaneous x-z (spanwise) plane flow fields show strong spanwise variations.

LDV and PIV Measurements of the Organized Oscillations of Turbulent Flow over a Rectangular Cavity

“…It should be addressed that these vortical structures are strongly distorted in the spanwise direction. As reported previously (3) , high and low speed streaks were observed in the cavity shear layer. In the case of the cavity with L/D=2, mean spanwise spacing of the high speed streaks was 0.35D (~δ ω ).…”

“…To assess the strength of shear layer-trailing edge interaction, measurements were also made for a backward facing step (BFS) flow. The results reported in this paper will provide a comprehensive data set on unsteady characteristics of turbulent cavity flows when combined with the results on three-dimensional characteristics in a previous paper (3) .…”

“…The test section of the tunnel is 233 mm (W) × 233mm (H) × 1160mm (L). Figure 1 shows experimental setup (3) . By varying the location of the downstream liner, cavity length was varied.…”

“…The velocity profiles at the upstream edge are essentially identical between the three geometrical configurations. The momentum thickness θ of the boundary layer was determined to be 1.6mm (3) , and Reynolds number based on momentum thickness was 8,300±300 considering the variation of water temperature.…”

Probabilistic entrainment of particles from a rectangular cavity in turbulent open channel flows

“…Numerous experimental studies (Lin et al, 2004;Lin et al, 2008;Haigermoser et al, 2009;Lin et al, 2009;Mori and Naganuma, 2009;Cicca et al, 2013;Fernando et al, 2013;etc. ) have also been conducted to characterize flows in cavities or over vertical drop pools without involving the process of sediment entrainment.…”