Abstract
The wakes of wall-mounted small (square) and large (long) depth-ratio rectangular prisms are numerically studied at Reynolds numbers of 50–250. The large depth-ratio significantly alters the dominance of lateral secondary flow (upwash and downwash) in the wake due to the reattachment of leading-edge separated flow on the surfaces of the prism. This changes the wake topology by varying the entrained flow in the wake region and changing the distribution of vorticity. Thus, the magnitude of vorticity significantly decreases by increasing the prism depth-ratio. Furthermore, the length of the recirculation region and the orientation of near wake flow structures are altered for the larger depth-ratio prism compared to the square prism. Drag and lift coefficients are also affected due to the change of pressure distributions on the rear face of the prism and surface friction force. This behavior is consistently observed for the entire range of Reynolds numbers considered here. The wake size is scaled with Re1/2, whereas drag coefficient scaled with Re−0.3.
Highlights
The flow structures around wall-mounted rectangular cylinders or prisms have been extensively studied in the literature, partly due to their broad engineering applications and partly because of their complex dynamics
This study focuses mainly on characterizing the wake of a large depth-ratio prism at the highest Reynolds number (Re) considered here, while comparing the wake topology to well-established wake of small depth-ratio prisms
The results showed that drag and lift coefficients are altered by the larger depth-ratio of the rectangular prims compared to the square prism
Summary
The flow structures around wall-mounted rectangular cylinders or prisms have been extensively studied in the literature, partly due to their broad engineering applications and partly because of their complex dynamics. At low Reynolds numbers, understanding the wake of a wall-mounted long prism has major implications in improving the design of electronic chips for better cooling, biomedical devices, vortex generators, pipe roughness elements, and small heat exchangers [1]. In these applications, the detail understanding of the flow field around the prism is critical in optimizing the design and performance of various devices, for example fast response accurate measuring equipments such as hotwire. Wang et al (2004) [6] proposed a comprehensive model for the wake of a wall-mounted rectangular cylinder. Later on Wang et al (2009) [3]
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