Computational investigation of the cavitation vortex dynamics in flow over a three-dimensional hydrofoil by a new transport-based model

2020 ◽  
pp. 095765092093934
Author(s):  
Feng Hong ◽  
Fan Zhang
Keyword(s):  
Vortex Dynamics ◽  
Three Dimensional ◽  
Cavitating Flow ◽  
Computational Investigation ◽  
Cavitation Model ◽  
Cloud Cavitation ◽  
Hydraulic Machinery ◽  
Variable Density Flow ◽  
Flow Past ◽  
Proposed Model

Cavitation is of significant practical interest due to its unsteady features which could induce destructive effects such as drastic drop in efficiency, noise, vibration, and corrosion for propulsion systems, rudders and other hydraulic machinery. A thorough understanding of the hydrodynamics in the cavitating flow past a three-dimensional hydrofoil makes indicators for an improved control performance of these hydraulic systems. Hence, a computational investigation of the cavitating flow over the Delft Twist-11 hydrofoil was performed with special emphasis on the cavitation vortex dynamics. A new transport-based cavitation model was proposed and compared with the conventional Schnerr–Sauer model through the predictions of cavitation characteristics, for which available experimental data were also provided. The results show that, as compared with the Schnerr–Sauer model, the proposed model can predict closer engineering parameters, including time-mean lift coefficient and vapor shedding frequency with the experiments. In addition, more reasonable structure and dynamics of the three-dimensional unsteady sheet/cloud cavitation patterns, including the cavity growth, break-off, and collapse downstream are captured by the proposed model. With the help of the vorticity transport equation in a variable density flow, further analysis of the flow field predicted by the proposed model reveals that cavitation promotes the production of vortex as well as the flow instabilities. Vorticity production in the cavitating flow is mainly induced by the terms of vortex stretching and vortex dilatation, while the baroclinic torque only contributes in the region of shedding and collapse of the cloud cavity and the contribution of the viscous diffusion term is negligible as compared with the other three terms. The main significance of this study is that it demonstrates the potential of a robust transport-based cavitation model to investigate the unsteady dynamics in the cavitating flow past a three-dimensional twisted hydrofoil and expected to make sense for other hydraulic machinery.

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.

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.

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.

Modeling Cavitating Flow in High Temperature Water

2009 ◽  
Author(s):  
Bin Ji ◽  
Xianwu Luo ◽  
Yulin Wu ◽  
Yao Zhang ◽  
Shuhong Liu ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermal Effects ◽  
Cavitating Flow ◽  
Experiment Data ◽  
Cavitation Model ◽  
High Temperature Water ◽  
Proposed Model ◽  
Thermodynamic Effect ◽  
Computational Strategy ◽  
Temperature Water

Thermal effects substantially impact the cavitation dynamics of high temperature water. This paper strives towards developing an effective computational strategy to simulate thermal cavitation. A transport equation based on mass transfer has been proposed by considering thermodynamic effect. The cavitating flow over a foil at the temperature of 293K and 373K has been calculated to evaluate the feasibility of the proposed model. The result comparison of the proposed model as well as the full cavitation model with the experiment data indicates that the proposed model is suitable for modeling cavitating flow in high temperature water.

scholarly journals Detached eddy simulation of unsteady cavitation and pressure fluctuation around 3-D NACA66 hydrofoil

2015 ◽  
Vol 19 (4) ◽  
pp. 1231-1234 ◽  
Author(s):  
De-Sheng Zhang ◽  
Hai-Yu Wang ◽  
Lin-Lin Geng ◽  
Wei-Dong Shi
Keyword(s):  
Turbulence Model ◽  
Pressure Fluctuation ◽  
Cavitating Flow ◽  
Numerical Results ◽  
Detached Eddy Simulation ◽  
Cavitation Model ◽  
Cloud Cavitation ◽  
Sheet Cavitation ◽  
Eddy Simulation ◽  
Unsteady Cavitating Flow

The unsteady cavitating flow and pressure fluctuation around the 3-D NACA66 hydrofoil were simulated and validated based on detached eddy simulation turbulence model and a homogeneous cavitation model. Numerical results show that detached eddy simulation can predict the evolution of cavity inception, sheet cavitation growth, cloud cavitation shedding, and breakup, as well as the pressure fluctuation on the surface of hydrofoil. The sheet cavitation growth, detachment, cloud cavitation shedding are responsible for the features of the pressure fluctuation.

Cavitation Characteristics of S-Blade Used in Fully Reversible Pump-Turbine

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
T. M. Premkumar ◽  
Pankaj Kumar ◽  
Dhiman Chatterjee
Keyword(s):  
Angle Of Attack ◽  
Visual Observation ◽  
Cavitating Flow ◽  
Hydrodynamic Performance ◽  
Cloud Cavitation ◽  
Cavitation Inception ◽  
Cavitation Effect ◽  
Flow Past ◽  
Turbulence Transition ◽  
Numerical Characterization

S-shaped blade profiles with double camber find use in fully reversible turbomachines that can extract power from tides. Though noncavitating characteristics of S-blades were determined in the past, yet characterizing cavitating flow was not carried out. This work, which is the first step in this direction, uses a two-pronged approach of experimental and numerical characterization of cavitating flow past these hydrofoils. Experimental results indicate that as the angle of attack increases in either positive or negative directions, cavitation inception number increases. Minimum cavitation effect is observed at 2 deg, which is zero lift angle of attack. For higher angles of attack (±6deg, ±4deg) and moderate or low cavitation number (σ/σi≤0.3), unsteady cloud cavitation was characterized through visual observation and from pressure fluctuation data. It was observed that for unsteady cavity shedding to take place is the length and thickness of the cavity should be more than 50% and 10% of the chord length, respectively. Predicting flow past this geometry is difficult and the problem may be compounded in many applications because of laminar-to-turbulence transition as well as due to the presence of cavitation. Present simulations indicate that the k-kL-ω transition model may be useful in predicting hydrodynamic performance of this type of geometry and for the range of Reynolds number considered in this paper. Hydrodynamic performance under cavitation indicates that pumping mode is more adversely affected by cavitation and, hence, a fully reversible turbomachine may not perform equally well in turbine and pump modes as expected from noncavitating results.

Numerical Study on Flow-Induced Vibration Characteristics of Three-Dimensional Hydrofoil in Cavitating Flow

2019 ◽  
Author(s):  
Chang Wang ◽  
Yuan-qing Liu ◽  
Te-zhuan Du ◽  
Yi-wei Wang
Keyword(s):  
Numerical Study ◽  
Density Ratio ◽  
Three Dimensional ◽  
Simulation Method ◽  
Cavitating Flow ◽  
Vibration Characteristics ◽  
Structural Vibration ◽  
Cavitation Flow ◽  
Flow Induced Vibration ◽  
Cloud Cavitation

Abstract With the increasing demand of higher performance and efficiencies for marine propulsion and hydropower system, structures became more flexible and were subjected to high flow rates. Cavitation-structure interaction has become one of the major issues for most engineering applications. In order to analyze the characteristics of unsteady cavitating flow induced vibration, the cloud cavitation flow over three dimensional NACA66 hydrofoil is studied by numerical simulation in this paper. The cavitating flow is modeled by large eddy simulation method and Zwart cavitation model, and the structural vibration model of three dimensional hydrofoil is established. The numerical calculation of fluid-solid coupling is realized based on ANSYS Workbench. The main dimensionless parameters of three-dimensional hydrofoil cavitation flow-induced vibration are obtained by means of dimensional analysis, including density ratio, cavitation number, Reynolds number, and the frequency ratio of flow to structure. The changes of cavity morphology during the cloud cavitation development of flexible hydrofoil and the flow-induced vibration characteristics under cloud cavitation flow of flexible hydrofoil are analyzed. The results showed that the periodic development of cavitation can be divided into three stages: the growth of attached cavity, the development of re-entrant jet and the shedding of cavity in cloud cavitaion stage. The centroid displacement of the free end of the flexible hydrofoil varies periodically with time at the stage of cloud cavitation. The hydrofoil vibration is affected by the development of cloud cavitation, and the vibration frequency corresponds to the shedding frequency of cloud cavitation.

scholarly journals Cloud Cavitating Flow Over a Submerged Axisymmetric Projectile and Comparison Between Two-Dimensional RANS and Three-Dimensional Large-Eddy Simulation Methods

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Yiwei Wang ◽  
Chenguang Huang ◽  
Xin Fang ◽  
Xianian Yu ◽  
Xiaocui Wu ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Cavitating Flow ◽  
Two Dimensional ◽  
Cloud Cavitation ◽  
Cavity Collapse ◽  
Eddy Simulation ◽  
2D Simulation ◽  
Large Eddy

For the cloud cavitation around slender axisymmetric projectiles, a two-dimensional (2D) numerical method was based on the mixture approach with Singhal cavitation model and modified renormalization-group (RNG) k–ε turbulence model, and a three-dimensional (3D) method was established with large-eddy simulation (LES) and volume of fraction (VOF) approach. The commercial computational fluid dynamic (CFD) software fluent is used for the 2D simulation, and the open source code OpenFOAM is adopted for the 3D calculation. Experimental and numerical results were presented on a typical case, in which the projectile moves with a quasi-constant axial speed. Simulation results agree well with experimental results. An analysis of the evolution of cavitating flow was performed, and the related physical mechanism was discussed. Results demonstrate that shedding cavity collapse plays an important role in the generation and acceleration of re-entry jet, which is the main reason for the instability of cloud cavitation. The 2D Reynolds-Averaged Navier–Stokes (RANS) method can represent the physical phenomena effectively. The 3D LES method can give an efficient simulation on the shedding vortices, and considerable accurate shapes of shedding cavities are captured.

Flow Past a Spinning Sphere With Surface Blowing and Heat Transfer

2005 ◽  
Vol 127 (1) ◽  
pp. 163-171 ◽  
Author(s):  
H. Niazmand ◽  
M. Renksizbulut
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Flow Regimes ◽  
Solid Sphere ◽  
Temporal Variations ◽  
Transfer Coefficients ◽  
Transfer Rates ◽  
Particle Spin ◽  
Flow Past ◽  
Angular Velocities

Computations are performed to determine the transient three-dimensional heat transfer rates and fluid forces acting on a stream-wise spinning sphere for Reynolds numbers in the range 10⩽Re⩽300 and angular velocities Ωx⩽2. In this Re range, classical flow past a solid sphere develops four different flow regimes, and the effects of particle spin are studied in each regime. Furthermore, the combined effects of particle spin and surface blowing are examined. Sphere spin increases drag in all flow regimes, while lift shows a nonmonotonic behavior. Heat transfer rates are not influenced by spin up to a certain Ωx but increase monotonically thereafter. An interesting feature associated with sphere spin is the development of a special wake regime such that the wake simply spins without temporal variations in its shape. For this flow condition, the magnitudes of the lift, drag, and heat transfer coefficients remain constant in time. Correlations are provided for drag and heat transfer.

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