An Experimental Investigation Into the Breakdown of Low Reynolds Number Pulsed Flows at a Pipe Orifice

Abstract

An experimental investigation into the behavior of pulsed vortex flows in water at a pipe orifice is outlined. An experimental apparatus is described whereby flow pulsations are generated using an electronically controlled motor-piston arrangement. Preliminary investigations are made into the unpulsed system to determine the natural vortex shedding frequency for various Reynolds numbers and orifice diameters. The downstream development of initially axisymmetric, periodically pulsed vortices shed from the orifice plate are then examined. The growth, evolution, and eventual breakdown of the initially axisymmetric vortices are investigated for a range of flow control parameters. Various flow regimes are discerned and an attempt is made to categorize them.

Wavelet analysis of the breakdown of a pulsed vortex flow

“…Figure 2b shows a sketch of the regions of behaviour in the vicinity of the orifice plate: it is with tens [40]. downstream regions 3 to 7 that the study presented here concerns itself.…”

“…The motivation for the experiment together with full details of the experimental arrangeIn order to compare Fourier power spectra with wavelet ment has been reported in full elsewhere [39,40]. For power spectra, the wavelet a scale (which is a time the purpose of this study, attention will be focused on a period) must be converted to a frequency.…”