A Preliminary Study On The Inclination And Shape Of Jets Issuing From An Orifice In The Lateral Wall Of A Pipe

DICAAR – Dip. Ingegneria Civile, Ambientale e Architettura, University of Cagliari, via Marengo 2, 09123 Cagliari, Italy

^* Corresponding author: ferraris@unica.it

Published online: 24 October 2022

Abstract

The topic of the behaviour of jets issuing from an orifice in the lateral wall of a pipe is of interest in many engineering fields, such as sea discharges of pollutants via submerged pipes, diffusers to mix different fluids in tanks and reactors, leakage in industrial and civil pipelines, etc. Most of the previous researches focuses on the pressure loss across the orifice, without taking into account the modification of the internal flow and, most important, the direction and shape of the jet issuing from the outlet: as a matter of fact, this is usually considered perpendicular to the axis of the pipe and axisymmetric. We have investigated these issues in the laboratory via Digital Image Analysis techniques, namely LIF (Laser Induced Fluorescence) to measure concentration fields and FTV (Feature Tracking Velocimetry) to measure velocity fields, varying the ratio of the flow rate of the jet to the flow rate in the pipe before the orifice. Here we present some preliminary results, highlighting how the jet is not always perpendicular to the axis of the pipe nor axisymmetric: the inclination increases and the axisymmetry decreases when the ratio of the flow rates above described decreases.