Euler-Euler and Euler-Lagrange approaches to cavitation modelling in marine applications (original) (raw)
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This paper presents a numerical study with pressure-based finite volume method for prediction of noncavitating and time dependent cavitating flow on hydrofoil. The phenomenon of cavitation is modeled through a mixture model. For the numerical simulation of cavitating flow, a bubble dynamics cavitation model is used to investigate the unsteady behavior of cavitating flow and describe the generation and evaporation of vapor phase. The non-cavitating study focuses on choosing mesh size and the influence of the turbulence model. Three turbulence models such as Spalart-Allmaras, Shear Stress Turbulence (SST) k-ω model and Re-Normalization Group (RNG) k-ε model with enhanced wall treatment are used to capture the turbulent boundary layer on the hydrofoil surface. The cavitating study presents an unsteady behavior of the partial cavity attached to the foil at different time steps for σ=0.8. Moreover, this study focuses on cavitation inception, the shape and general behavior of sheet cavitation, lift and drag forces for different cavitation numbers. Finally, the flow pattern and hydrodynamic characteristics are also studied at different angles of attack.
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Abstract: This paper present a study of using a proposed finite element model to predict cavitating flow motions around two dimensional hydrofoils. The proposed model solves the governing equations of momentum and mass conservation including advection, pressure and shear stress terms. To describe turbulence influences around the hydrofoil the Prandtl-Kolgomorov model is included. The cavitating conditions are modeled through a mixture model involving liquid and vapor flows. The water vapor fraction is evaluated using a transport equation with source and sink for evaporation and condensation. The finite element model uses linear spatial polynomials to approximate the variables, a characteristic scheme to approach the non-linear advection terms and non-reflecting boundary conditions for the open outlet sides of the domain. Numerical experiments are performed for cavitation numbers 0.9 and 0.5 considering the NACA 0015 hydrofoil profile. The model is able to predict the essential featu...
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In this paper a computational analysis of the dynamic vortex-cavitation flow observed on the so-called twist-11 Delft hydrofoil (Foeth 2008) is presented. Flow calculations are performed using Reynolds-Averaged Navier-Stokes (RANS) as well as Improved Delayed Detached-Eddy simulation (IDDES) models available in the commercial software STAR-CCM+. The flow-field is realized as a continuous mixture of liquid and vapor bubbles, in the context of the Eulerian Volume of Fluid (VOF) method. For predicting growth/collapse oscillations of cavitation bubbles, the multiphase VOF solver is coupled with different cavitation models based on the Rayleigh-Plesset (R-P) equation. Parametric simulations tested include the asymptotic formulation proposed by Sauer (2000) and the classical R-P equation, which also accounts for the inertia of bubbles as well as surfacetension and viscous effects (Brennen 1995). The obtained results are validated against reported experimental measurements in terms of the ...
The Analysis Of Bubble Cavitation Inception InTurbulent Flow Around A Hydrofoil
WIT transactions on engineering sciences, 1970
The paper dwells on the physical assumptions and the mathematical description of the model of the bubble cavitation inception in the flow around a hydrofoil. The objective of the model is to anticipate the risk of the cavitation inception when the flow around the hydrofoil is turbulent. The methods of the stochastic processes theory have been applied in order to determine the time evolution of the bubble radius probability distribution. The numerical application of the model is discussed. The methodology of combined experimental and theoretical research of the bubble cavitation inception in the flow around the arbitrary hydrofoil is proposed.
Experimental evaluation of numerical simulation of cavitating flow around hydrofoil
European Journal of Mechanics - B/Fluids, 2005
Cavitation in hydraulic machines causes different problems that can be related to its unsteady nature. An experimental and numerical study of developed cavitating flow was performed. Until now simulations of cavitating flow were limited to the self developed "in house" CFD codes. The goal of the work was to experimentally evaluate the capabilities of a commercial CFD code (Fluent) for simulation of a developed cavitating flow. Two simple hydrofoils that feature some 3D effects of cavitation were used for the experiments. A relatively new technique where PIV method combined with LIF technique was used to experimentally determine the instantaneous and average velocity and void ratio fields (cavity shapes) around the hydrofoils. Distribution of static pressure on the hydrofoil surface was determined. For the numerical simulation of cavitating flow a bubble dynamics cavitation model was used to describe the generation and evaporation of vapour phase. An unsteady RANS 3D simulation was performed. Comparison between numerical and experimental results shows good correlation. The distribution and size of vapour structures and the velocity fields agree well. The distribution of pressure on the hydrofoil surface is correctly predicted. The numerically predicted shedding frequencies are in fair agreement with the experimental data.
A comparative study between numerical methods in simulation of cavitating bubbles
International Journal of Multiphase Flow, 2018
In this paper, the performance of three different numerical approaches in cavitation modelling are compared by studying two benchmark test cases to understand the capabilities and limitations of each method. Two of the methods are the well established compressible thermodynamic equilibrium mixture model and the incompressible transport equation finite mass transfer mixture model, which are compared with a third method, a recently developed Lagrangian discrete bubble model. In the Lagrangian model, the continuum flow field is treated similar to the finite mass transfer approach, however the cavities are represented by individual bubbles. Further, for the Lagrangian model, different ways to consider how the fluid pressure influences bubble dynamics are studied, including a novel way by considering the local pressure effect in the Rayleigh-Plesset equation. The first case studied is the Rayleigh collapse of a single bubble, which helps to understand each model behaviour in capturing the cavity interface and the surrounding pressure variations. The special differences between the Lagrangian and finite mass transfer models in this case clarify some possible origin for some limitations of the latter method. The second investigated case is the collapse of a cluster of bubbles, where the collapse of each bubble is affected by the dynamics of surrounding bubbles. This case confirms the importance of considering local pressure in the improved form of the Rayleigh-Plesset equation and illustrates the influence of the liquid compressibility for cavity modelling and appropriate capturing of the collapse pressure.