Flow field analysis of submerged oblique and normally impinging twin jets at varying impinging angles

Abstract

In this work, two-dimensional time-resolved particle image velocimetry (TR-PIV) measurements are carried out to study the flow structure and impinging interactions of two turbulent submerged isothermal circular impinging water jets. In this configuration, the uphill and downhill jets impinge obliquely and normally onto a flat target surface, respectively. A comprehensive parametric study is carried out for values of the jets’ exit Reynolds number of $R{e}_j=5000$ and 8000, jets’-to-surface target distances of $H/D=3$ and 5, and inclination angles of the uphill oblique jet-to-impingement surface of (${\theta }_1=$30°, 45°, 60°). For all the experiments, the jet-to-jet spacing distances were varied for each impingement angle of the oblique jet so that the impingement point of both jets coincide at the geometric intersection of the jets’ axes. Flow visualization images showing ensemble-averaged and instantaneous flow distributions and turbulent characteristics for equal and non-equal Reynolds numbers of the jets are presented. Velocity profiles and Reynolds shear stress distributions of the downhill wall jet development and its corresponding dimensionless shedding frequencies are also obtained. A proper orthogonal decomposition (POD) analysis reveals the spatial structure of the dominant fluctuation motions of the turbulent flow as well as their respective contributions to the total kinetic energy. Our results show that the jets’ exit Reynolds numbers, the oblique impingement angle of the uphill jet and the jets’-to-surface distance play a major role on the complex flow structure and dynamics, location of the stagnation point and entrainment characteristics of the turbulent flow field of the twin jets.