Power dissipation and time-averaged pressure in oscillating flow through a sudden area change.

Experiments on oscillating flow at the abrupt transition between a two-dimensional channel and essentially infinite space are presented. It is shown that phenomena associated with the transition are functions of three independent dimensionless parameters including the dimensionless radius rounding the edge of the end of the channel. The effect of each of these three parameters on the time-averaged pressure difference across the transition and the acoustic power dissipation is explored by holding two parameters fixed while varying the third. Evidence is presented that the losses due to oscillatory flow in this geometry are smaller than would be expected from commonly accepted values for steady flow in similar geometry.