![]() Both these factors depend on the bend angle, the curvature ratio and the Reynolds Number. The pressure losses suffered in a bend are caused by both friction and momentum exchanges resulting from a change in the direction of flow. Even for fairly large-radius bends, the flow field in the bend will be severely distorted as illustrated by the data of Rowe (1970) shown in Figure 2. If the bend curvature is strong enough, the adverse pressure gradient near the outer wall in the bend and near the inner wall just after the bend may lead to flow separation at these points, giving rise to a large increase in pressure losses. This creates a double spiral flow field shown schematically in Figure 1. Because of this, the fluid at the center of the pipe moves towards the outer side and comes back along the wall towards the inner side. ![]() ![]() The main feature of flow through a bend is the presence of a radial pressure gradient created by the centrifugal force acting on the fluid.
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