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Article
Publication date: 30 September 2019

W.G. Zhao and Guipeng Wang

The purpose of this paper is to use the NACA 0015 symmetric hydrofoil as the research subject and control cloud cavitation on hydrofoils.

Abstract

Purpose

The purpose of this paper is to use the NACA 0015 symmetric hydrofoil as the research subject and control cloud cavitation on hydrofoils.

Design/methodology/approach

Based on observed distribution of caudal fin spines on fish, a bionic structure of fin-like spines is arranged on the hydrofoil suction surface, which maintains the cavitation in a quasi-steady state stage by eliminating the cyclic shedding process of cloud cavitation. Based on the modified shear stress transport k-ω turbulence model and the Zwart–Gerber–Belamri cavitation model, this paper compares and analyzes the NACA 0015 hydrofoil and the bionic NACA 0015 hydrofoil under condition of an angle of attack of 8° and a cavitation number of 0.8.

Findings

The results show that the average drag of the hydrofoil is reduced but the lift is decreased, and the lift-drag ratio is increased after arranging the bionic structure. The bionic structure can effectively reduce the turbulent kinetic energy and make the flow more stable; it also can effectively control the hydrofoil surface side-entrant jet and the vortex shedding process of the near wall region.

Originality/value

Based on the above conclusions, the bionic structure of fin-like spines can achieve a significant passive control in the hydrofoil cloud cavitation process.

Details

Engineering Computations, vol. 37 no. 3
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 28 April 2014

Min He, Lingli Yuan, Lingjiu Zhou, Jing Yang and Zhengwei Wang

Studies of the three-dimensional flow characteristics during hydrofoil cavitation have shown that the side walls strongly affect the flow field around the hydrofoil. The…

Abstract

Purpose

Studies of the three-dimensional flow characteristics during hydrofoil cavitation have shown that the side walls strongly affect the flow field around the hydrofoil. The purpose of this paper is to analyze the side wall effect for three-dimensional non-cavitating flows around a hydrofoil.

Design/methodology/approach

A three-dimensional non-cavitating flow field around a hydrofoil is analyzed for different attack angles using the RNG turbulence model and large eddy simulations (LES). The effect of the hydrofoil span was analyzed using LES simulations for various spans.

Findings

The lift coefficient, drag coefficient and pressure coefficient on the suction side are compared with experimental values. The results from the LES model (Smagorinsky-Lilly subgrid-scale model) agree better with the experimental data than those from the RNG turbulence model.

Originality/value

This paper shows that the flow around the hydrofoil has significant three-dimensional characteristics due to the side wall. For wide hydrofoils, the wall vortex region becomes essentially stable, and the width of the span has little effect on the middle region.

Details

Engineering Computations, vol. 31 no. 3
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 8 May 2018

An Yu, Xianwu Luo, Dandan Yang and Jiajian Zhou

This paper aims to gain a clear understanding of the ventilated cavity evolution around an NACA0015 hydrofoil by using both experimental and numerical investigation.

Abstract

Purpose

This paper aims to gain a clear understanding of the ventilated cavity evolution around an NACA0015 hydrofoil by using both experimental and numerical investigation.

Design/methodology/approach

The bubble evolution around an NACA0015 hydrofoil with or without air injection was observed in a water tunnel, and the simulation was conducted using a modified turbulence model and homogeneous cavitation model.

Findings

The present simulation method can successfully predict the bubble evolutions around the NACA0015 hydrofoil with or without air injection. Air injection can alleviate the nature cavitation oscillation, and the suppression effect on nature cavitation depends on the air-entrant coefficient. It is confirmed that the air and vapor cavity have the same shedding frequency. It is seen that the air sheet closely attaches to the hydrofoil surface and is surrounded by the vapor sheet. Thus, the injected air promotes vapor growth and results in an increase in the cavity shedding frequency. Further, with a large air-entrant coefficient, the pressure fluctuation is suppressed completely.

Originality/value

The new simulation method is adopted to explore the mechanism of ventilated cavitation. The bubble evolutions with and without air injection have been comprehensively studied by experimental and numerical investigation. The effects of air injection on natural cavity oscillations and pressure fluctuations have been revealed in the present study.

Details

Engineering Computations, vol. 35 no. 3
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 13 July 2021

Włodzimierz Wróblewski, Krzysztof Bochon, Mirosław Majkut, Krzysztof Rusin and Emad Hasani Malekshah

The presence of air in the water flow over the hydrofoil is investigated. The examined hydrofoil is ClarkY 11.7% with an angle of attack of 8 deg. The flow simulations are…

Abstract

Purpose

The presence of air in the water flow over the hydrofoil is investigated. The examined hydrofoil is ClarkY 11.7% with an angle of attack of 8 deg. The flow simulations are performed with the assumption of different models. The Singhal cavitation model and the models which resolve the non-condensable gas including 2phases and 3phases are implemented in the numerical model. The calculations are performed with the uRANS model with assumption of the constant temperature of the mixture. The two-phase flow is simulated with a mixture model. The dynamics and structures of cavities are compared with literature data and experimental results.

Design/methodology/approach

The cavitation regime can be observed in some working conditions of turbomachines. The phase transition, which appears on the blades, is the source of high dynamic forces, noise and also can lead to the intensive erosion of the blade surfaces. The need to control this process and to prevent or reduce the undesirable effects can be fulfilled by the application of non-condensable gases to the liquid.

Findings

The results show that the Singhal cavitation model predicts the cavity structure and related characteristics differently with 2phases and 3phases models at low cavitation number where the cavitating flow is highly dynamic. On the other hand, the impact of dissolved air on the cloud structure and dynamic characteristic of cavitating flow is gently observable.

Originality/value

The originality of this paper is the evaluation of different numerical cavitation models for the prediction of dynamic characteristics of cavitating flow in the presence of air.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 12 November 2019

Cheng Liu, Qingdong Yan and Houston G. Wood

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…

Abstract

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.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 7
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 September 2003

Spyros A. Kinnas and Yin L. Young

Boundary element method (BEM) techniques for the prediction of cavitating or ventilated flows around hydrofoils and propeller are summarized. Classical, supercavitating…

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1563

Abstract

Boundary element method (BEM) techniques for the prediction of cavitating or ventilated flows around hydrofoils and propeller are summarized. Classical, supercavitating, and ventilated blade section geometries are considered. Recent extensions which allow for the modeling of cavities on either or both sides of the blade surface are presented. Numerical validation studies and comparisons with experimental measurements are shown.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 13 no. 6
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 June 2006

Sunil Mathew, Theo G. Keith Theo G. Keith Jr and Efstratios Nikolaidis

The purpose is to present a new approach for studying the phenomenon of traveling bubble cavitation.

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1737

Abstract

Purpose

The purpose is to present a new approach for studying the phenomenon of traveling bubble cavitation.

Design/methodology/approach

A flow around a rigid, 2D hydrofoil (NACA‐0012) with a smooth surface is analyzed computationally. The Rayleigh‐Plesset equation is numerically integrated to simulate the growth and collapse of a cavitation bubble moving in a varying pressure field. The analysis is performed for both incompressible and compressible fluid cases. Considering the initial bubble radius as a uniformly distributed random variable, the probability density function of the maximum collapse pressure is determined.

Findings

The significance of the liquid compressibility during bubble collapse is illustrated. Furthermore, it is shown that the initial size of the bubble has a significant effect on the maximum pressure generated during the bubble collapse. The maximum local pressure developed during cavitation bubble collapse is of the order of 104 atm.

Research limitations/implications

A single bubble model that does not account for the effect of neighboring bubbles is used in this analysis. A spherical bubble is assumed.

Originality/value

A new approach has been developed to simulate traveling bubble cavitation by interfacing a CFD solver for simulating a flow with a program simulating the growth and collapse of the bubble. Probabilistic analysis of the local pressure due to bubble collapse has been performed.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 16 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 7 March 2016

Yu Zhao, Guoyu Wang and Biao Huang

The purpose of this paper is to assess the predictive capability of the streamline curvature correction model (CCM) and investigate the unsteady vortex behavior of the…

Abstract

Purpose

The purpose of this paper is to assess the predictive capability of the streamline curvature correction model (CCM) and investigate the unsteady vortex behavior of the cloud cavitating flows around a hydrofoil.

Design/methodology/approach

The design of the paper is based on introducing the curvature correction method to the original k-ε model. Calculations of unsteady cloud cavitating flows around a Clark-Y hydrofoil are performed using both the CCM and the baseline model.

Findings

Compared with the baseline model, better agreements are observed between the predictions of the CCM model and experimental data, especially the cavity shedding process. Based on the computations, it is demonstrated that streamline curvature correction of the CCM model can effectively decrease predicted turbulence kinetic energy and eddy viscosity in cavity shedding region. This leads to the better prediction for the recirculation zone located downstream of the attached cavity, and dynamics of this recirculation zone contribute to the formation and development of the re-entrant jet.

Originality/value

The authors apply streamline curvature correction to the calculations of unsteady cloud cavitating flows and discuss the interactions between the cavitation unsteadiness and vortex structures to get an insight of the correction mechanics.

Details

Engineering Computations, vol. 33 no. 1
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 5 May 2015

Desheng Zhang, Weidong Shi, Dazhi Pan and Guangjian Zhang

– The purpose of this paper is to predict the unstable cavitation shedding flow around a 2D Clark-y hydrofoil.

Abstract

Purpose

The purpose of this paper is to predict the unstable cavitation shedding flow around a 2D Clark-y hydrofoil.

Design/methodology/approach

The paper studies Partially Averaged Navier-Stokes (PANS) model which was employed in the two-phase flow with a homogeneous cavitation model.

Findings

Maximum density ratio affects the mass transfer rate between the liquid and the vapor significantly. The cavitating flow predicted by PANS model can resolve more turbulent scales by decreasing the parameter fk.

Originality/value

The accuracy of numerical prediction is improved by increasing the maximum density ratio and decreasing fk.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 25 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 1 May 1968

R. Stanton‐Jones

THE rapidly growing technology of vehicles that are either totally supported or partly supported by air cushions has many branches along which future development may…

Abstract

THE rapidly growing technology of vehicles that are either totally supported or partly supported by air cushions has many branches along which future development may progress. Perhaps the most important of these, which cover most of the field, can be divided into the following six groups:—

Details

Aircraft Engineering and Aerospace Technology, vol. 40 no. 5
Type: Research Article
ISSN: 0002-2667

1 – 10 of 121