The flow downstream of multiple bodies placed in the flow has many practical engineering applications. A row of bodies is often used to screen strong and sudden winds in order to change them to weak and gentle ones. Cascades of bodies, with a narrow spacing between them, are often used in wind tunnels to obtain a uniform velocity distribution. The flow past a row of bodies is of interest in situations such as turning vanes in duct elbows, multi-slotted airfoils, and flow around closely spaced electrical power poles. Similarly, birds have been observed to fly in V-formation but the reason for this behaviour is not understood.
The flow around multiple bodies is a spatially developing flow problem, where several rich phenomena are observed (see figure). Change in the flow behaviour has implications on the instantaneous and mean forces experienced by the bodies. In our work, we have numerically and experimentally studied flow around multiple bodies arranged in different configurations. We proposed that certain flow regimes will always be present, irrespective of how the bodies are placed. This hypothesis was proved for bodies placed row-wise, column-wise, in V-shape, and when transversely oscillated. This is particularly important because no such previous attempt was made prior to his work.
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