Numerical Prediction of Cavitating Flow on a Two-Dimensional Symmetrical Hydrofoil and Comparison to Experiments

2006 ◽  
Vol 129 (3) ◽  
pp. 279-292 ◽  
Author(s):  
Olivier Coutier-Delgosha ◽  
François Deniset ◽  
Jacques André Astolfi ◽  
Jean-Baptiste Leroux
Keyword(s):  
Cavitating Flow ◽  
Physical Models ◽  
Experimental Investigations ◽  
Condensation Process ◽  
Two Dimensional ◽  
Homogeneous Fluid ◽  
Two Phase ◽  
Cloud Cavitation ◽  
Cavitation Inception ◽  
Sheet Cavitation

This paper presents comparisons between two-dimensional (2D) CFD simulations and experimental investigations of the cavitating flow around a symmetrical 2D hydrofoil. This configuration was proposed as a test case in the “Workshop on physical models and CFD tools for computation of cavitating flows” at the 5th International Symposium on cavitation, which was held in Osaka in November 2003. The calculations were carried out in the ENSTA laboratory (Palaiseau, France), and the experimental visualizations and measurements were performed in the IRENav cavitation tunnel (Brest, France). The calculations are based on a single-fluid approach of the cavitating flow: the liquid/vapor mixture is treated as a homogeneous fluid whose density is controlled by a barotropic state law. Results presented in the paper focus on cavitation inception, the shape and the general behavior of the sheet cavity, lift and drag forces without and with cavitation, wall pressure signals around the foil, and the frequency of the oscillations in the case of unsteady sheet cavitation. The ability of the numerical model to predict successively the noncavitating flow field, nearly steady sheet cavitation, unsteady cloud cavitation, and finally nearly supercavitating flow is discussed. It is shown that the unsteady features of the flow are correctly predicted by the model, while some subtle arrangements of the two-phase flow during the condensation process are not reproduced. A comparison between the peer numerical results obtained by several authors in the same flow configuration is also performed. Not only the cavitation model and the turbulence model, but also the numerical treatment of the equations, are found to have a strong influence on the results.

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.

scholarly journals Experimental Study on the Relationship Between Cavitation and Lift Fluctuations of S-Shaped Hydrofoil

2021 ◽  
Vol 9 ◽  
Author(s):  
Haiyu Liu ◽  
Pengcheng Lin ◽  
Fangping Tang ◽  
Ye Chen ◽  
Wenpeng Zhang ◽  
...  
Keyword(s):  
High Speed ◽  
Developmental Process ◽  
Angle Of Attack ◽  
Cavitation Number ◽  
High Speed Photography ◽  
Cloud Cavitation ◽  
Cavitation Inception ◽  
Sheet Cavitation ◽  
Hydraulic Machinery ◽  
Stall Angle

In order to study the energy loss of bi-directional hydraulic machinery under cavitation conditions, this paper uses high-speed photography combined with six-axis force and torque sensors to collect cavitating flow images and lift signals of S-shaped hydrofoils simultaneously in a cavitation tunnel. The experimental results show that the stall angle of attack of the S-shaped hydrofoil is at ±12° and that the lift characteristics are almost symmetrical about +1°. Choosing α = +6° and α = −4° with almost equal average lift for comparison, it was found that both cavitation inception and cloud cavitation inception were earlier at α = −4° than at α = +6°, and that the cavitation length at α = −4° grew significantly faster than at α = +6°. When α = +6°, the cavity around the S-shaped hydrofoil undergoes a typical cavitation stage as the cavitation number decreases: from incipient cavitation to sheet cavitation to cloud cavitation. However, when α = −4°, as the cavitation number decreases, the cavitation phase goes through a developmental process from incipient cavitation to sheet cavitation to cloud cavitation to sheet cavitation to cloud cavitation, mainly because the shape of the S-shaped hydrofoil at the negative angle of attack affects the flow of the cavity tails, which is not sufficient to form re-entrant jets that cuts off the sheet cavitation. The formation mechanism of cloud cavitation at the two different angles of attack (α = +6°、−4°) is the same, both being due to the movement of the re-entrant jet leading to the unstable shedding of sheet cavity. The fast Fourier analysis reveals that the fluctuations of the lift signals under cloud cavitation are significantly higher than those under non-cavitation, and the main frequencies of the lift signals under cloud cavitation were all twice the frequency of the cloud cavitation shedding.

Numerical Prediction of Cavitating MHD Flow of Electrically Conducting Magnetic Fluid in a Converging-Diverging Nozzle

2004 ◽  
Vol 71 (6) ◽  
pp. 825-838 ◽  
Author(s):  
Jun Ishimoto
Keyword(s):  
Magnetic Field ◽  
Magnetic Fluid ◽  
Mhd Flow ◽  
Cavitating Flow ◽  
Numerical Results ◽  
Nonuniform Magnetic Field ◽  
Working Fluid ◽  
Two Dimensional ◽  
Two Phase ◽  
Electrically Conducting

The fundamental characteristics of the two-dimensional cavitating MHD flow of an electrically conducting magnetic fluid in a vertical converging-diverging nozzle under a strong nonuniform magnetic field are numerically predicted to realize the further development and high performance of a two-phase liquid-metal MHD power generation system using electrically conducting magnetic fluids. First, the governing equations of the cavitating flow of a mercury-based magnetic fluid based on the unsteady thermal nonequilibrium multifluid model are presented, and several flow characteristics are numerically calculated taking into account the effect of the strong nonuniform magnetic field. Based on the numerical results, the two-dimensional structure of the cavitating flow and cavitation inception phenomena of the mercury-based magnetic fluid through a converging-diverging nozzle are shown in detail. The numerical results demonstrate that effective two-phase magnetic driving force, fluid acceleration, and high power density are obtained by the practical use of the magnetization of the working fluid. Also clarified is the precise control of the cavitating flow of magnetic fluid that is possible by effective use of the magnetic body force that acts on cavitation bubbles.

Cavitating Flow of Liquid Nitrogen in Horizontal Rectangular Nozzle

2003 ◽  
Author(s):  
Jun Ishimoto ◽  
Masahiro Onishi ◽  
Takashi Tokumasu ◽  
Kenjiro Kamijo
Keyword(s):  
Liquid Nitrogen ◽  
High Performance ◽  
Fluid Model ◽  
Flow Characteristics ◽  
Cavitating Flow ◽  
Two Phase ◽  
Cloud Cavitation ◽  
Rectangular Nozzle ◽  
Thermodynamic Effect ◽  
Two Fluid Model

The fundamental characteristics of the two-dimensional cavitating flow of liquid nitrogen through a horizontal rectangular nozzle are numerically and experimentally investigated to realize the further development and high performance of new multiphase cryogenic fluid applications. First, the governing equations of the cavitating flow of liquid nitrogen based on the unsteady thermal nonequilibrium two-fluid model are presented, and several flow characteristics are numerically calculated, taken into account the thermodynamic effect of cryogenic conditions. Next, the flow visualization measurement on unsteady cavitating flow of liquid nitrogen through a rectangular nozzle installed in a horizontal duct is carried out to clarify the basic cryogenic two-phase flow structure and fundamental characteristics of the transient growth process of cryogenic cloud cavitation.

scholarly journals Experimental Investigations of Three-Dimensional Effects on Cavitating Hydrofoils

1961 ◽  
Vol 5 (03) ◽  
pp. 22-43
Author(s):  
R. W. Kermeen
Keyword(s):  
Aspect Ratio ◽  
High Speed ◽  
Three Dimensional ◽  
Cavitating Flow ◽  
Experimental Investigations ◽  
Water Tunnel ◽  
Pitching Moment ◽  
Two Dimensional ◽  
Dimensional Effects ◽  
Aspect Ratios

An investigation in the high-speed water tunnel of the hydsrodynamic characteristics of a family of three-dimensional sharp-edged hydrofoils is described. Four rectangular plan-form, 6-deg wedge profiles with aspect ratios of 4.0, 2.0, 1.0 and 0.5 were tested over a range of cavitation numbers from noncavitating to fully cavitating flow. The effects of aspect ratio on the flow and cavity configurations and on the lift, drag and pitching moment are discussed. Where data were available the results have been compared with the two-dimensional case.

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.

A Numerical and Experimental Investigation of Wall-Pressure Fluctuations Induced by Sheet Cavitation Instabilities on Lifting Surface

2005 ◽  
Author(s):  
Jacques-Andre´ Astolfi ◽  
Jean-Baptiste Leroux ◽  
Olivier Coutier-Delgosha ◽  
Franc¸ois Deniset
Keyword(s):  
Flow Instability ◽  
Pressure Fluctuations ◽  
Homogeneous Medium ◽  
Cavitating Flow ◽  
Wall Pressure ◽  
Two Phase ◽  
Fluid Structure ◽  
Sheet Cavitation ◽  
Wall Pressure Fluctuations ◽  
Unsteady Loading

The paper is based on some previous works of the authors aimed to study the phenomenology of cavitation instabilities. In the present work, a particular attention is paid to the analysis of spatio-temporal wall-pressure fluctuations in the context of fluid structure coupling investigations. The work is based on a numerical and experimental study, whose objective was to analyze the wall-pressure fluctuations beneath an unsteady partial cavitating flow developing on an hydrofoil. Experiments were carried in a water tunnel, on a partially cavitating hydrofoil based on extended multi-point wall pressure measurements together with flow visualizations. 2D Navier-Stokes simulations solves the RANS equations combined with a physical model of cavitation The two-phase flow mixture is considered as a homogeneous medium for which the ratio of liquid and vapor is controlled by a barotropic state law. The numerical resolution is based on the SIMPLE algorithm, modified to take into account the high compressibility of the liquid/vapor mixture. The results show that various dynamics are caught by the model in agreement with the experiments. Two main unstable dynamics were observed leading to a strong variation of surface loading. The paper provides quantitative data about the severe unsteady loading that is experienced by the structure, which should very useful in a fully problem of Fluid Structure Interaction. The possibility of a structural response of the foil to the unsteady loading and how it could promote the cavitating flow instability is also discussed.

Numerical and Experimental Investigations of Cavitating Flow in a Vertical Multi-Hole Injector Nozzle

2010 ◽  
Author(s):  
Zhixia He ◽  
Jing Bai ◽  
Qian Wang ◽  
Qingmu Mu ◽  
Yunlong Huang
Keyword(s):  
Numerical Simulation ◽  
Numerical Models ◽  
Three Dimensional ◽  
Injection Pressure ◽  
Cavitating Flow ◽  
Critical Conditions ◽  
Experimental Investigations ◽  
Nozzle Flow ◽  
Cavitation Inception ◽  
Injector Nozzle

The presence of cavitation and turbulence in a diesel injector nozzle has significant effect on the subsequent spray characteristics. However, the mechanism of the cavitating flow and its effect on the subsequent spray is unclear because of the complexities of the nozzle flow, such as the cavitation phenomena and turbulence. A flow visualization experiment system with a transparent scaled-up vertical multi-hole injector nozzle tip was setup for getting the experimental data to make a comparison to validate the calculated results from the three dimensional numerical simulation of cavitating flow in the nozzle with mixture multi-phase cavitating flow model and good qualitative agreement was seen between the two sets of data. The critical conditions for cavitation inception were derived as well as the relationship between the discharge coefficient and non-dimensional cavitation parameter. After wards, the testified numerical models were used to analyze the effects of injection pressure, back pressure, cavitation parameter, Reynolds number, injector needle lift and needle eccentricity on the cavitating flow inside the nozzle. Combined with visual experimental results, numerical simulation results can clearly reveal the three-dimensional nature of the nozzle flow and the location and shape of the cavitation induced vapor distribution, which can help understand the nozzle flow better and eventually put forward the optimization ideas of diesel injectors.

scholarly journals Numerical Study on the Vibration and Noise Characteristics of a Delft Twist11 Hydrofoil

2021 ◽  
Vol 9 (2) ◽  
pp. 144
Author(s):  
Hong-Sik Hwang ◽  
Kwang-Jun Paik ◽  
Soon-Hyun Lee ◽  
Gisu Song
Keyword(s):  
Numerical Study ◽  
Marine Ecosystem ◽  
Pressure Fluctuations ◽  
Liquid Lead ◽  
Cloud Cavitation ◽  
Cavitation Inception ◽  
Radiated Noise ◽  
Sheet Cavitation ◽  
Noise Characteristics ◽  
Noise Vibration

Underwater radiated noise (URN) is greatly increasing due to an increase in commercial shipping, sonar activities, and climate change. As a result, marine life is having difficulty communicating, and marine ecosystem disturbances are occurring. The noise from the cavitation of propellers is affecting URN. Cavitation is a phenomenon in which rapid changes of pressure in a liquid lead to the formation of small vapor-filled cavities in places where the pressure is relatively low. This phenomenon results in poor efficiency of the propeller or turbine of a ship and noise, vibration, and erosion. For these reasons, this study examines the URN of sheet and cloud cavitation. A numerical analysis was done using a Delft Twist11 hydrofoil. The URN resulting from cloud cavitation and sheet cavitation was compared with the numerical results of previous studies. The results showed that URN normally increases due to pressure fluctuations when cavitation occurs. URN increased more significantly in conditions of cloud cavitation than in cavitation inception. It is also shown that a frequency begins to occur after the occurrence of the cloud cavitation, and the frequency grew as the cavitation fully developed.

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