VELOCITY DISTRIBUTION AND REATTACHMENT LENGTH IN AN OSCILLATORY PIPE FLOW THROUGH A PLATE ORIFICE.

Abstract

Velocity distribution measurements in an oscillatory pipe flow through a plate orifice are made with air over Reynolds numbers 3590 to 15300 at a frequency of 1. 03 Hz. The Reynolds number is based on the amplitude of cross-sectional mean velocity and the pipe diameter. The velocity distribution in a laminar-like phase can be approximated by a laminar analytical solution presented so far, while in a turbulent phase it agrees well with that in a turbulent steady flow. A method of measuring a reattachment length, which is applicable to an unsteady flow as well, is proposed. The reattachment length in an oscillatory flow measured by this method is insensitive to acceleration and nearly constant under the present experimental conditions.