A study on the wake structure of the double vortex tubes in a ventilated supercavity

2018 ◽  
Vol 32 (4) ◽  
pp. 1601-1611
Author(s):  
Wei Wang ◽  
Cong Wang ◽  
Yingjie Wei ◽  
Wuchao Song
Keyword(s):  
Wake Structure ◽  
Ventilated Supercavity ◽  
Vortex Tubes

scholarly journals Numerical Analysis of the Effects of Periodic Gust Flow on the Wake Structure of Ventilated Supercavities

2021 ◽  
Author(s):  
Wei Wang ◽  
Zhigang Zhang ◽  
Guanghua He ◽  
Weijie Mo
Keyword(s):  
Experimental Data ◽  
Computational Model ◽  
Periodic Variation ◽  
Cavitation Number ◽  
Closed Region ◽  
Wake Structure ◽  
Vorticity Distribution ◽  
Flow Parameters ◽  
Entire Flow ◽  
Ventilated Supercavity

AbstractA computational model is established to investigate the effects of a periodic gust flow on the wake structure of ventilated supercavities. The effectiveness of the computational model is validated by comparing with available experimental data. Benefited from this numerical model, the vertical velocity characteristics in the entire flow field can be easily monitored and analyzed under the action of a gust generator; further, the unsteady evolution of the flow parameters of the closed region of the supercavity can be captured in any location. To avoid the adverse effects of mounting struts in the experiments and to obtain more realistic results, the wake structure of a ventilated supercavity without mounting struts is investigated. Unsteady changes in the wake morphology and vorticity distribution pattern of the ventilated supercavity are determined. The results demonstrate that the periodic swing of the gust generator can generate a gust flow and, therefore, generate a periodic variation of the ventilated cavitation number σ. At the peak σ, a re-entrant jet closure appears in the wake of the ventilated supercavity. At the valley σ, a twin-vortex closure appears in the wake of the ventilated supercavity. For the forward facing model, the twin vortex appears as a pair of centrally rolled-up vortices, due to the closure of vortex is affected by the structure. For the backward facing model, however, the twin vortex appears alternately as a pair of centrally rolled-up vortices and a pair of centrally rolled-down vortices, against the periodic gust flow.

On the internal flow of a ventilated supercavity

2019 ◽  
Vol 862 ◽  
pp. 1135-1165 ◽  
Author(s):  
Yue Wu ◽  
Yun Liu ◽  
Siyao Shao ◽  
Jiarong Hong
Keyword(s):  
Boundary Layer ◽  
Reverse Flow ◽  
Internal Flow ◽  
Internal Boundary Layer ◽  
Internal Boundary ◽  
Water Tunnel ◽  
Piv Measurements ◽  
Gas Leakage ◽  
Ventilated Supercavity ◽  
Vortex Tubes

This study presents an experimental investigation on the internal flow of a ventilated supercavity using fog flow visualization and particle image velocimetry (PIV) measurements. The ventilated supercavity is generated on a backward-facing cavitator and studied in the high-speed water tunnel at St. Anthony Falls Laboratory. Fog particles are introduced into the supercavity through the ventilation line, and then illuminated by a laser sheet for flow visualizations and PIV measurements. The experiments are performed on the supercavities with two closure types, i.e. the re-entrant jet (RJ) and the twin vortex (TV), under the same water tunnel flow condition but different ventilation rates. The flow visualization revealed three distinct regions within the supercavity, including the ventilation influence region near the cavitator, the extended internal boundary layer along the liquid–gas interface and the reverse flow region occupying a large centre portion of the supercavity. The streamwise and vertical extent of the ventilation influence region, the streamwise growth of the internal boundary layer and the reverse flow within the supercavity are then quantified through PIV flow measurements. Compared to the RJ case, the results indicate that the TV supercavity yields a longer vertical extent of the ventilation influence region, a thinner internal boundary layer and a stronger reverse flow. The internal flow results suggest that at the upstream of the location of the maximum cavity diameter, the gas enters the forward flow (including the internal boundary layer and the forward moving portion of the ventilation influence region) from the reverse flow, while at the downstream of that location, the gas is stripped from the internal boundary layer and enters the reverse flow due to the increasing adverse pressure gradient in the streamwise direction. The above results are combined with visualization results of the supercavity geometry and closure patterns to further explain the influence of gas leakage mechanisms on cavity growth and closure transition. Specifically, visualization of the cavity geometry change during the RJ to TV supercavity transition indicates external flow separation associated with a critical incline angle of the bottom liquid–gas interface at the closure contributes to the onset of RJ closure. The closure visualization shows the coexistence of the toroidal vortex and twin-vortex tubes for the RJ supercavity leads to two gas leakage mechanisms: one associated with the shedding of toroidal vortices ($Q_{RJ}$) and the other due to the gas entrained by the internal boundary layer and leaking from the twin-vortex tubes ($Q_{TV}$). For the RJ supercavity, with increasing ventilation input, due to the reduction of $Q_{RJ}$, the supercavity needs to elongate to increase the gas entrained by the internal boundary layer (i.e. $Q_{TV}$) to balance the ventilation increase. The elongation of the supercavity leads to reduced flow separation, and eventually a transition to the TV supercavity with ventilation above a critical value. For the TV supercavity, $Q_{RJ}$ is absent. An increase of ventilation input can be balanced by the increase of $Q_{TV}$ associated with the widening of the twin-vortex tubes, and therefore, no appreciable elongation of cavity length is observed.

PERFORMANCE MODELING OF PARALLEL-CONNECTED RANQUE-HILSCH VORTEX TUBES USING A GENERALIZABLE AND ROBUST ANN

2020 ◽  
Vol 51 (15) ◽  
pp. 1399-1415
Author(s):  
Hüseyin Kaya ◽  
Volkan Kirmaci ◽  
Hüseyin Avni Es
Keyword(s):  
Performance Modeling ◽  
Vortex Tubes

The effect of tail geometry on the slipstream and unsteady wake structure of high-speed trains

2017 ◽  
Vol 83 ◽  
pp. 215-230 ◽  
Author(s):  
J.R. Bell ◽  
D. Burton ◽  
M.C. Thompson ◽  
A.H. Herbst ◽  
J. Sheridan
Keyword(s):  
High Speed ◽  
Wake Structure ◽  
Unsteady Wake ◽  
High Speed Trains

scholarly journals Detailed Wake Structure behind an Elastic Airfoil

2009 ◽  
Vol 4 (2) ◽  
pp. 391-400 ◽  
Author(s):  
Masaki FUCHIWAKI ◽  
Tomoki KURINAMI ◽  
Kazuhiro TANAKA
Keyword(s):  
Wake Structure

Automotive Drag Reduction through Distributed Base Roughness Elements

2014 ◽  
Vol 553 ◽  
pp. 267-272
Author(s):  
Iain Robertson ◽  
Adrien Becot ◽  
Adrian Gaylard ◽  
Ben Thornber
Keyword(s):  
Drag Reduction ◽  
Reference Model ◽  
Detailed Examination ◽  
Rear Face ◽  
Cfd Simulations ◽  
Near Wake ◽  
Wake Structure ◽  
Pressure Drag ◽  
Roughness Elements ◽  
Baseline Case

This paper focuses on the effect of base roughness added to the rear of an automotive reference model, the Windsor model. This roughness addition was found to reduce both the drag and the lift of the model. RANS CFD simulations presented here replicate the experimentally observed drag reduction and enable a detailed examination of the mechanisms behind this effect. Investigations into the wake structure of the configurations with base roughness and the baseline case without base roughness showed the main changes to the wake to include a reduction in the overall size of the wake with base roughness present. Furthermore a reduction in the near wall velocities at the rear of the model caused stretching of the upper and lower vortices, a more turbulent near wake and pressure recovery over much of the rear face. This leads to reduce levels of pressure drag on the model.

On the shedding of the ventilated supercavity with velocity disturbance

2013 ◽  
Vol 57 ◽  
pp. 223-229 ◽  
Author(s):  
Wang Zou ◽  
Kai-Ping Yu ◽  
Roger E.A. Arndt ◽  
Guang Zhang ◽  
Zhen-Wang Li
Keyword(s):  
Ventilated Supercavity
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