The Decay of a Turbulent Swirl of a Circular Pipe

Abstract

Comparison with the theoretical analysis of the decay of a turbulent swirling flow in a pipe and the results of experiments are presented. An angular momentum equation is guided from Navier-Stokes equations. Here, Reynolds shearing stress is treated with Boussinesq's expression. The second derivative of angular momentum respects to radius needs to be negative from the decay of moment. Therefore, at the boundary of forced and free vortex, an attention to the solution of equation must be payed. Near the wall, shearing stress for laminer flow is applied. And angular momentum equations in each region are numerically solved and that solutions are connected smoothly on each boundary. As the results, the prediction of the decay agrees much with the results of experiments.