A DPIV study on the effects of separation distance upon the vortical behaviour of jet–cylinder impingements

Long, Junling; New, T. H.

doi:10.1007/s00348-015-2023-6

Cited by 15 publications

(5 citation statements)

References 26 publications

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“…Figure 6(a) shows the jet half-width distributions for the SJICF at three different velocity ratios. The half-width growth of a single free jet at Re D = 2000 is included as a reference (Long and New, 2015). Though the jet exit Reynolds number of their experiments is different from the present study, it clearly illustrates the different mixing behaviours of a single free jet and a SJICF.…”

Section: A Streamwise Flow Developments Along Jet Planecontrasting

confidence: 60%

Near-field dynamics of parallel twin jets in cross-flow

Zang

New

2017

Physics of Fluids

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The present study examines the near-field flow developments and dynamics of parallel twin jets in cross-flow (TJICF) configured with jet-to-jet separation distances of 1.5 to 3 jet diameters (D) and velocity ratios of 2, 4, and 6. Both laser-induced fluorescence and particle-image velocimetry measurements were made along the streamwise and cross-stream planes in order to investigate the effects of the separation distance and velocity ratio upon the deflected jet and the formation of counterrotating vortex-pairs (CVPs) within the near-field region. Results show that each jet in the parallel TJICF configuration attains higher cross-flow entrainment and produces greater jet half-widths than a single jet in cross-flow (SJICF). Moreover, as the separation distance decreases to 1.5D, the twin jets interact closer to the jet exit such that organized leading-edge and lee-side vortices are present along the symmetry plane. Cross-stream results indicate that the pair of inner vortices associated with the two resulting CVPs is being induced to move towards each other along the symmetry plane, where their opposite-signed vorticities annihilate with each other eventually. As such, the vorticity transition from two CVPs into a resulting single CVP takes place quickly within the near-field region when the separation distance is sufficiently small. Streamwise circulation decays determined for parallel TJICF show that their circulations increase moderately when the two CVPs begin to interact with each other. Further examination into the Reynolds shear stresses indicates that there exists substantial flow shear stress as the pair of inner vortices interacts, which yields higher entrainment level of the cross-flow fluid in regions adjacent to the symmetry plane. As a result, the near-field jet trajectories for each jet in the parallel TJICF are always lower than that of the corresponding SJICF when the separation distance is small, regardless of the velocity ratios.

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Section: A Streamwise Flow Developments Along Jet Planecontrasting

confidence: 60%

Near-field dynamics of parallel twin jets in cross-flow

Zang

New

2017

Physics of Fluids

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“…Finally, the established PSO-GP model was used as the fitness evaluation plan of the PSO algorithm to optimize the hollow rectification sill of the forebay of the pump station. For the optimized rectification sill, physical model test [43,44] and DPIV measurement technology were used [33,[45][46][47] to verify the validity and engineering practicability of the PSO-GP model in optimizing the design of the hollow rectification sill of the forebay of the pump station.…”

Section: Introductionmentioning

confidence: 99%

Optimization of the Hollow Rectification Sill in the Forebay of the Pump Station Based on the PSO‐GP Collaborative Algorithm

Wang

Lü

Wang

et al. 2021

Shock and Vibration

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The layout of the pump station is easily affected by topography, site, and other factors, resulting in poor inlet flow patterns in the forebay, which seriously affect the normal operation of the pump station. To optimize its inlet flow pattern, the size of the hollow rectification sill has been continuously improved through physical model tests to meet the requirements of the required pump station inlet flow field. In this paper, particle swarm optimization (PSO) was combined with the Gaussian process (GP) to establish a particle swarm-Gaussian process (PSO-GP) model to predict the velocity uniformity of the inlet sump of pump stations with different hole-to-height ratios, hole-to-width ratios, upper-to-lower sill length ratios, and sill height-to-water table ratios. Finally, the hollow rectification sill with the optimal size was obtained and tested in the physical model to compare the rectification effect with other sizes of hollow sills. The results show that the algorithm model can help the traditional physical experiment quickly predict the velocity uniformity of the inlet sump of the pump station. Through the optimization by the PSO-GP algorithm, we can get the optimal size of the hollow rectification sill. Its hole-to-height ratio is 0.62, its hole-to-width ratio is 0.37, upper-to-lower sill length ratio is 0.63, and sill height-to-water table ratio is 0.23. It shows that this method is practical in the optimization design of the hollow rectification sill and provides a new method for the optimization of the flow field in the forebay of the pump station.

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“…Despite significant progresses made in terms of understanding impinging jet vortex dynamics through the use of DPIV technique, the majority of these investigations focused on circular jets that produce axisymmetric vortical structures along their shear layers. On the other hand, noncircular jets such as cross-shaped jet, lobed jet, slot jet and elliptic jets produce comparatively far more complex vortical structures and behaviour that potentially extend their applicability towards heat transfer applications (Rau et al, 2014;Sodjavi et al, 2015;Achari and Das, 2015;Long and New, 2015;Sodjavi et al, 2016 andTrinh et al, 2016, take for instance). Among them, elliptic jet leads to non-uniform initial momentum thicknesses along its perimeter, which further results in non-uniform self-inductions and complex threedimensional vortical motions.…”

Section: Introductionmentioning

confidence: 99%