Experimental study of the flow structures of 3D turbulent offset jets

Abstract

Three-dimensional turbulent offset jets were investigated using a particle image velocimetry technique. Detailed measurements were performed for offset height ratios of 0, 2 and 4. The presence of backflow influenced the distribution of the mean velocity and Reynolds stresses. A two-point correlation analysis was used to investigate the spatial distribution of large-scale structures within the inner shear layer of the flow domain. The results revealed that large-scale structures dominate the inner layer of the self-similarity region. Proper orthogonal decomposition was performed on the fluctuating velocity field within the symmetry and lateral planes using the snapshot approach. Results from the reconstructed field provided insight into the contributions of the most energetic structures to the turbulence statistics. The energetic structures contributed more to the Reynolds shear stress and streamwise turbulence intensity, while contributing less to the wall-normal turbulence intensity.

Flow characteristics of an offset jet over a surface mounted square rib

“…It is to be noted that complete collapse of U profiles was not attained within the backflow region. The streamwise extent for the onset of self-similarity of the 3D offset jets are less than x/b o ࣙ 38 for the no rib case reported by Nyantekyi-Kwakye et al [10]. …”

“…The objective of this study is therefore to investigate the effect of rib location on the flow structures of a 3D offset jet. The present experiment was performed at Reynolds number and flow condition similar to previous studies by Nyantekyi-Kwakye and co-workers [8,10]. Detailed velocity measurements were performed in the symmetry plane (where the interaction of the inner and outer shear layers can be modified in the presence of a surface mounted rib) using planar particle image velocimetry.…”

“…These structures were observed to be more dynamically dominant in the outer shear layer than in the inner shear layer of the flow. [9] In an earlier study, Nyantekyi-Kwakye et al [10] investigated the flow characteristics of 3D offset jets in the absence of a surface mounted rib in both the symmetry and lateral planes. Their results showed drastic flow variations in the symmetry plane compared to the lateral plane.…”

“…The reattached offset jet consists of an inner shear layer (which exhibits structural similarities to a turbulent boundary layer) and an outer shear layer (with characteristics similar to half of a free jet). The inner and outer shear layers are separated by a shear layer Downloaded by [University of York] at 07: 15 10 June 2016 dividing line. The inner shear layer extends from the channel bottom to y m (which is the wall-normal location of the local maximum streamwise mean velocity, U m ) while the outer shear layer extends from y m to the edge of the jet.…”

Numerical Simulation of an Offset Jet in Bounded Pool with Deflection Wall

“…Assoudi et al [8] had investigated the mean velocity and turbulence characteristics of the turbulent offset jet using PIV technique at 3 velocity ratios and 2 offset ratios; their results indicated that increasing the offset ratio gives a better distribution of the jet within the flow field, giving rise to a better dynamic mixture. Nyantekyi-Kwakye et al [9] studied experimentally the jet with different height ratios (0, 2 and 4); their work revealed that the large scale structures within the inner layer increase with wall normal distance from the pool bottom. Further, Rathore and Das [10] reported a numerical investigation for the turbulent offset jet and compared with results proposed by Launder and Sharma [11] and Yang and Shih [12].…”