Particle Image Velocimetry Measurements of Turbulent Jets Issuing From Twin Elliptic Nozzles With Various Orientations

Abstract

The effects of nozzle orientation on the mixing and turbulent characteristics of elliptical free twin jets were studied experimentally. The experiments were conducted using modified contoured nozzles with a sharp linear contraction. The centers of the nozzle pair had a separation ratio of 5.5. Two nozzle configurations were tested, twin nozzles oriented along the minor plane (Twin_Minor) and twin nozzles oriented along the major plane (Twin_Major) and the results were compared with single jet. In each case, the Reynolds number based on the maximum jet velocity and the equivalent diameter was 10,000. A planar particle image velocimetry system was used to measure the velocity field in the jet symmetry plane. It was observed that the velocity decay rate is not sensitive to nozzle orientation. However, close to the jet exit the spread rate was highest in the minor plane. In addition, contour plots of swirling strength, Reynolds shear stress and turbulent intensities revealed significant differences between the minor and major plane. Velocity profiles showed little variation close to the jet exit, while further downstream the variations between the velocity profiles were more pronounced between the major and minor planes.

The effects of spacing to diameter ratio on mixing characteristics of circular and elliptical twin jets

“…Different PC values for Single Ellipse Major and Single Ellipse Minor could result from separate simulations of elliptical jet with orientation, which could lead to a numerical discrepancy of results. Similar results for the elliptical jet with orientation are reported by Morris et al 16,30 The potential core length of the elliptical jets is 8.6% shorter than that of the single circular jet. These results agree with Mi and Nathan et al 3 for the elliptical nozzle case.…”

“…The present twin jets combined point locations correlate well with the previous investigations. 9,10,10,13,16,24 However, a slight overestimation is observed with the present CFD study compared to the experimental results. 7,9 Figures 15(a) and 16(a) show that the distances of merging and combined points from the orifice exit increase linearly with the increasing S/D e ratio, which is in good agreement with the previous literature.…”

“…Figure 16(b) presents the combined point locations of present work and compares those with literature. [9][10][11]13,16,18,24 It is understood from Figures 15 and 16 is that out of the chosen jets, the Twin Ellipse Major was found to be effective in enhancing the mixing in the merging region. This enhancement in mixing performance in the merging region is attributed to the axis-switching phenomenon.…”

“…Figure 15(b) shows the locations of merging points at different S/D e ratios from the present work and one compared with previous works. [9][10][11]13,16,18,24 It can be observed that increasing the S/D e ratio between the jets shifts the merging point further downstream. In addition, the relationship between the merging point and S/ D e ratio is linear for any given study.…”

Energy exchanges in the flow past a cylinder with a leeward control rod

“…Turbulent kinetic energy (TKE) transport in free shear flows has been the subject of numerous studies (Panchapakesan & Lumley 1993; Liu & Thomas 2004; Morris et al. 2021) using a generic TKE transport equation (for instance see Hinze (1975)). However, for a multiscale flow like the present problem, a separate TKE transport equation is required for the coherent motions present in the flow to track energy exchanges to/from the individual coherent motions (as well as the mean flow and stochastic fluctuations).…”