Topology of flow and heat transfer from prisms in square array

Abstract

Structures in an array with multiple rows and columns may undergo both inline and side-by-side interferences. A system of nine square prisms in a 3 × 3 square array is numerically investigated for pitch ratio L/D = 1.2 – 7.0 at a Reynolds number of 150, where L is the spacing between the centers of two adjacent prisms, and D is the side width of a square prism. The focus is given on investigating the effect of L/D on flow topology, fluid forces, heat transfer, vortex shedding, and recirculation bubbles. An increase in L/D from 1.2 to 7.0 leads to evolutions of five distinct flows: single bluff body flow (L/D < 1.6), reattachment flow (1.6 < L/D < 3.3), lateral-interaction-induced coshedding flow (3.3 < L/D < 4.1), mixed flow (4.1 < L/D < 4.6) and free coshedding flow (4.6 < L/D < 7.0). The reattachment flow corresponds to small fluid forces while the lateral-interaction-induced coshedding flow induces large fluid forces. The time-mean drag force coefficient of the center prism drastically increases from 0.09 to 1.0 as the flow evolves from the reattachment flow to the lateral-interaction-induced coshedding flow. The maximum heat transfer from the center prism, 10% higher than that from a standalone prism, occurs for the lateral-interaction-induced coshedding flow where the flow around the center prism resembles creeping flow, no recirculation bubble forming on the front or rear surface of the prism. The coherence between heat transfer and flow patterns is discussed, including the impacts of shear layer reattachment, flow recirculation, and vortex shedding on heat transfer.