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Abstract

In this paper, laminar flows through axisymmetric confined annular geometries with sudden expansions have been studied numerically using a third-order accurate upstream biased quadratic scheme to investigate the recirculating eddy characteristics, following the expansion, in terms of recirculation length and eddy intensity. Two variations of annular geometry have been considered. In the first geometry, a smaller annulus abruptly expands inwardly into a larger one, whereas in the second case an abrupt inward expansion of the smaller annulus leads to a coaxial pipe. Fully developed inflow has been observed to separate immediately after the expansion plane forming a recirculating eddy. The variations in the size and intensity of the recirculating eddy are studied at different Reynolds numbers and expansion ratio for both the geometries. The effect of the presence of an inner solid wall after the expansion plane on the behaviour of the eddy is investigated. A secondary wall recirculation has been observed under specific flow situations in both the geometries. The characteristics of the secondary eddy have also been analysed and compared.

Keywords

annular backstep recirculation eddy intensity

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On the eddy characteristics of laminar axisymmetric flows through confined annular geometries with inward expansion

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