Three-dimensional flow within shallow, narrow cavities

Abstract

The three-dimensional structure of incompressible flow in a narrow, open rectangular cavity in a flat plate was investigated with a focus on the flow topology of the time-averaged flow. The ratio of cavity length (in the direction of the flow) to width to depth was l:w:d = 6:2:1. Experimental surface pressure data (in air) and particle image velocimetry data (in water) were obtained at low speed with free-stream Reynolds numbers of Re l = 3.4×10 5 in air and Re l = 4.3×10 4 in water. The experimental results show that the three-dimensional cavity flow is of the 'open' type, with an overall flow structure that bears some similarity to the structure observed in nominally twodimensional cavities, but with a high degree of three-dimensionality both in the flow near the walls and in the unsteady behaviour. The defining features of an open-type cavity flow include a shear layer that traverses the entire cavity opening ultimately impinging on the back surface of the cavity, and a large recirculation zone within the cavity itself. Other flow features that have been identified in the current study include two vortices at the back of the cavity, of which one is barely visible, a weak vortex at the front of the cavity, and a pair of counter-rotating streamwise vortices along the sides of the cavity near the cavity opening. These vortices are generally symmetric about the cavity centre-plane. However, the discovery of a single tornado vortex, located near the cavity centreline at the front of the cavity, indicated that the flow within the cavity is asymmetric. It is postulated that the observed asymmetry in the time-averaged flow field is due to the asymmetry in the instantaneous flow field, which switches between two extremes at large time scales.

Zamana Bağli Sikiştirilamaz Kavi̇te Akişinin Aeroakusti̇k Anali̇zi̇

“…Düşük Mach ve Reynolds Sayısı için yeteri kadar deneysel çalışma gerçekleştirilmemiş olsa da son dönemlerde Parçacık Görüntülemeli Akış Ölçümü (Particle Image Velocimetry-PIV) tekniğinin gelişmesine bağlı olarak farklı kavite geometrileri için deney sonuçları literatüre kazandırılmaktadır [6]. Bu çalışmada kavite akış sonuçları, L/D oranı 4 için PIV ölçüm tekniği ile elde edilen deneysel verilerle karşılaştırılmıştır.…”

Three-Dimensional Measurement of Edge Effects in Open Cavities of Finite-Span

“…The existence of this rear vortex was attributed by Crook et al to being a function of Reynolds number and thickness of the on-coming boundary layer just prior to separation at the leading edge. 15 However, no similar structure was shown within the work of Beresh et al 12,29 or Wagner et al, 30 which were conducted in similar conditions, albeit for a smaller length cavity. It is possible that the presence of this secondary rear vortex is evidence (in the time-average) of a transitional cavity flow, where the mixing layer may, at times impinge on the floor of the cavity.…”

“…Crook et al 15 made measurements in water using multiple 2C PIV planes in various orientations, exploring the flow topology. Likewise, Haigermoser et al used tomographic PIV to make flow field measurements within deep rectangular 25 and circular cavities, 26 albeit in low-speed flows.…”

“…Work by Arunajatesan et al 14 showed that the spanwise influence of the spillage vortices was dependent on the width of the cavity, resulting in either a net inflow or outflow at centerline, near the aft end of the cavity. In addition, Crook et al 15 used multiple PIV measurements to construct a diagram explaining the existence of all vorticity within a finite-span cavity in low-speed conditions, theorizing that the spillage vortices were two legs of a horseshoe vortex structure.…”

Control of flow instabilities in an open aircraft bay model cavity

“…The periodic spanwise structural formation were in good agreement with with the numerical visualizations by Faureet al [13][14][15][16] and experimental observations. 17 Many studies [18][19][20][21][22][23] emphasize the existence of more complex cavity flow structures in a realistic open cavity configuration, i.e., bounded by lateral walls, and at high Reynolds number. In this context, Liu et al 6 were the first to unravel the mechanisms ultimately responsible for laminar-turbulent transition of the long rectangular parallelepipedic open cavity using TriGlobal linear instability analysis.…”