Flow characteristics over forward facing step and through abrupt contraction pipe and drag reduction

The flow through a circular pipe with an abrupt contraction has two distinguished vortex regions just before and after the contraction. The latter vortex makes the eective crosssectional area of the downstream constracted pipe reduce, and then the flow resistance, drag, is increased. In this study, first the flow chracteristics over the forward facing step (corresponds to a two dimensional case of an abrupt contraction pipe) and through abrapt constractin pipe and then the flow control, suppression, of the vortex over the forward facing step by a new simple method, mounting a small obstacle on the wall just before the step. As a result, a considerable drag reduction of the abrapt contrction pipe by the new simple method was made clear.