LES investigation on vortex dynamics of transient sheet/cloud cavitating flow using different vortex identification methods

2020 ◽  
pp. 2150111
Author(s):  
Shuheng Qu ◽  
Jinping Li ◽  
Huaiyu Cheng ◽  
Bin Ji
Keyword(s):  
Vortex Dynamics ◽  
Cavitating Flow ◽  
Vortex Identification ◽  
Cavitation Model ◽  
Identification Methods ◽  
Vortex Interactions ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Lift And Drag ◽  
Criterion Method

The sheet/cloud cavitating flow always contains complex multiscale vortex structures generated by the cavity cloud shedding and collapsing. In this study, the transient sheet/cloud cavitating flow around a Clark-Y hydrofoil is numerically investigated using the Large Eddy Simulation (LES) method coupled with the Zwart–Gerber–Belamri (ZGB) cavitation model. The simulation accurately reproduces the unsteady cavitation evolution process, and the predicted time-averaged lift and drag coefficients, total vapor volume variation and velocity distribution agree fairly well with the experimental measurements. The cavitation vortex dynamics are studied in detail with different vortex identification methods including the vorticity method, the [Formula: see text]-criterion method, the [Formula: see text] method, the [Formula: see text] method and the Liutex method. The vortex identification ability of the different methods in the transient sheet/cloud cavitating flow is also discussed. Generally, the Liutex method combines the advantages of the other methods and can accurately identify both the vortex position and strength. Further analysis of cavitation-vortex interactions demonstrates that the cavity cloud shedding and collapsing have a pronounced influence on the vortex structure.

Numerical investigation of passive cavitation control using a slot on a three-dimensional hydrofoil

2019 ◽  
Vol 30 (7) ◽  
pp. 3585-3605 ◽  
Author(s):  
Cheng Liu ◽  
Qingdong Yan ◽  
Houston G. Wood
Keyword(s):  
Three Dimensional ◽  
Cavitating Flow ◽  
Control Technique ◽  
Cavitation Model ◽  
Content Type ◽  
Eddy Simulation ◽  
Simulation Based ◽  
Large Eddy ◽  
Flow Turbulence ◽  
Cavitation Behavior

Purpose The purpose of this paper is to study the mechanism and suppression of instabilities induced by cavitating flow around a three-dimensional hydrofoil with a particular focus on cavitation control with a slot. Design/methodology/approach The transient cavitating flow around a Clark-Y hydrofoil was investigated using a transport-equation-based cavitation model and the stress-blended eddy simulation model was used to capture the flow turbulence. A homogeneous Rayleigh–Plesset cavitation model was used to model the transient cavitation process and the results were validated with test data. A slot was applied to the hydrofoil to suppress cavitation instabilities, and various slot widths and exit locations were applied to the blade and the cavitation behavior, as well as drag/lift forces, were simulated and compared to investigate the effects of slot geometries on cavitation suppression. Findings The large eddy simulation based turbulence model was able to capture the interactions between the cavitation and turbulence. Moreover, the simulation revealed that the re-entrant jet was responsible for the periodic shedding of cavities. The results indicated that a slot was able to mitigate or even suppress cavitation-induced instabilities. A jet flow was generated at the slot exit and disturbed the re-entrant jet. If the slot geometry was properly designed, the jet could block the re-entrant jet and suppress the unsteady cavitation behavior. Originality/value This study provides unique insights into the complicated transient cavitation flows around a three-dimensional hydrofoil and introduces an effective passive cavitation control technique useful to researchers and engineers in the areas of fluid dynamics and turbomachinery.

Large eddy simulation of tip-leakage cavitating flow using a multiscale cavitation model and investigation on model parameters

2021 ◽  
Vol 33 (9) ◽  
pp. 092104
Author(s):  
Linmin Li ◽  
Yakang Huo ◽  
Zhengdong Wang ◽  
Xiaojun Li ◽  
Zuchao Zhu
Keyword(s):  
Large Eddy Simulation ◽  
Cavitating Flow ◽  
Model Parameters ◽  
Cavitation Model ◽  
Tip Leakage ◽  
Eddy Simulation ◽  
Large Eddy

Modeling of unsteady structure of sheet/cloud cavitation around a two-dimensional stationary hydrofoil

2015 ◽  
Vol 231 (3) ◽  
pp. 455-469 ◽  
Author(s):  
Feng Hong ◽  
Jianping Yuan ◽  
Banglun Zhou ◽  
Zhong Li
Keyword(s):  
Volume Fraction ◽  
Cavitating Flow ◽  
Wake Flow ◽  
Two Dimensional ◽  
Cavitating Flows ◽  
Cavitation Model ◽  
Ansys Fluent ◽  
Cloud Cavitation ◽  
Lift And Drag ◽  
Multi Phase

Compared to non-cavitating flow, cavitating flow is much complex owing to the numerical difficulties caused by cavity generation and collapse. In the present work, cavitating flow around a two-dimensional Clark-Y hydrofoil is studied numerically with particular emphasis on understanding the cavitation structures and the shedding dynamics. A cavitation model, coupled with the mixture multi-phase approach, and the modified shear stress transport k-ω turbulence model has been developed and implemented in this study to calculate the pressure, velocity, and vapor volume fraction of the hydrofoil. The cavitation model has been implemented in ANSYS FLUENT platform. The hydrofoil has a fixed angle of attack of α = 8° with a Reynolds number of Re = 7.5 × 105. Simulations have been carried out for various cavitation numbers ranging from non-cavitating flows to the cloud cavitation regime. In particular, we compared the lift and drag coefficients, the cavitation dynamics, and the time-averaged velocity with available experimental data. The comparisons between the numerical and experimental results show that the present numerical method is capable to predict the formation, breakup, shedding, and collapse of the sheet/cloud cavity. The periodical formation, shedding, and collapse of sheet/cloud cavity lead to substantial increase in turbulent velocity fluctuations in the cavitation regimes around the hydrofoil and in the wake flow.

Large eddy simulation of transient upstream/downstream vortex interactions

2019 ◽  
Vol 862 ◽  
pp. 227-260
Author(s):  
Kyle J. Forster ◽  
Sammy Diasinos ◽  
Graham Doig ◽  
Tracie J. Barber
Keyword(s):  
Near Field ◽  
Vortex Pair ◽  
Angle Of Incidence ◽  
Dependent Manner ◽  
Transient Effects ◽  
Single Plane ◽  
Vortex Interactions ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Close Proximity

Experimentally validated large eddy simulations were performed on two NACA0012 vanes at various lateral offsets to observe the transient effects of the near field interactions between two streamwise vortices. The vanes were separated in the streamwise direction, allowing the upstream vortex to impact on the downstream geometry. These vanes were evaluated at an angle of incidence of $8^{\circ }$ and a Reynolds number of 70 000, with rear vane angle reversed to create a co-rotating or counter-rotating vortex pair. The downstream vortex merged with the upstream in the co-rotating condition, driven by the suppression of one of the tip vortices of the downstream vane. At close proximity to the pressure side, the vane elongated the upstream vortex, resulting in it being the weakened and merging into the downstream vortex. This produced a transient production of bifurcated vortices in the wake region. The downstream vortex of the co-rotating pair experienced faster meandering growth, with position oscillations equalising between the vortices. The position oscillation was determined to be responsible for statistical variance in the merging location, with variation in vortex separation causing the vortices at a single plane to merge and separate in a time-dependent manner. In the counter-rotating condition position oscillations were found to be larger, with higher growth, but less uniform periodicity. It was found that the circulation transfer between the vortices was linked to the magnitude of their separation, with high separation fluctuations weakening the upstream vortex and strengthening the downstream vortex. In the case of upstream vortex impingement on the downstream vane, the upstream vortex was found to bifurcate, with a four vortex system being formed by interactions with the shear layer. This eventually resulted in a single dominant vortex, which did not magnify its oscillation amplitudes as it travelled downstream due to the destruction of the interacting vortices.

Numerical Simulation of an Oscillating Cylinder Using Large Eddy Simulation and Implicit Large Eddy Simulation

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
A. Feymark ◽  
N. Alin ◽  
R. Bensow ◽  
C. Fureby
Keyword(s):  
Large Eddy Simulation ◽  
Eddy Simulation ◽  
Force Magnitude ◽  
Subgrid Model ◽  
Large Eddy ◽  
Sinusoidal Oscillations ◽  
Flow Induced Vibrations ◽  
Lift And Drag ◽  
Implicit And Explicit ◽  
Volume Method

In this work, we use large eddy simulation (LES) to study the influence of grid and subgrid model on the lift and drag force predictions of a fixed cylinder undergoing streamwise sinusoidal oscillations in a steady flow, resulting in a varying Reynolds number, Re, within the range 405 ≤ Re ≤ 2482. This benchmark case is a first step toward studying engineering applications related to flow-induced vibrations. We examine the influence of both grid resolution and the subgrid model using implicit and explicit LES. The methodology used, LES based on a finite-volume method capable of handling moving meshes, are found to provide force predictions that agree well with experimentally measured data, with respect both to the overall flow development and force magnitude.

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