水力机械空化水动力学的几个基础问题研究
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摘要
空化现象是水利、船舶、交通及能源动力等工业界广泛存在的液体汽化现象,而水力机械的空化由于流道结构复杂、影响因素繁多,一直是困扰整个行业发展的关键难题。本文主要简单介绍近几年国内外以及作者课题组在空化水动力学基础研究方面的主要进展,主要内容包括:(1)三维云状空化流动结构及演变特性;以三维水翼空化云的准周期性脱落为例,阐明空化对水翼尾流区域的速度场、湍流强度以及涡量场的影响规律。(2)以扭曲水翼为对象,揭示U型云空化(马蹄形)向下游发展过程中演变规律及形成机制。(3)根据得到的空化云图和Q准则涡量图,对比扭曲水翼附着型空化绕流结构在不同攻角下的特点和演化过程。(4)基于理论分析和数值模拟,揭示了空化体积二阶导数为水力机械空化诱导低频水压脉动激振的根源,为深入理解水力机械、船舶推进器等的内部流动机理、工程中叶片区及流道表面的流动分离抑制提供了新的概念与方法。
Cavitation is a complex two-phase flow phenomenon and it is the key problem to be solved to promote the development in hydraulic machinery. In this paper, we conclude the main progress in cavitation research. The main contents are presented as:(1)time evolution of cloud cavity and the influence of cavitation on velocity, turbulence intensity and vorticity inhydrofoil wake.(2)Discussion of U-shape cloud cavity with the twisted hydrofoil.(3)Summary of the characteristics of U-shape cloud cavity with the twisted hydrofoil under different angles of attack.(4)Cavity volume acceleration is the main source of the pressure fluctuations in hydraulic machinery. These results are essential for understanding the mechanism of the cavitation excited pressure pulsations in hydraulic machinery, which will help understand the mechanism of the cavitation excited pressure pulsations and control the flow separation in engineering application.
Cavitation is a complex two-phase flow phenomenon and it is the key problem to be solved to promote the development in hydraulic machinery. In this paper, we conclude the main progress in cavitation research. The main contents are presented as:(1)time evolution of cloud cavity and the influence of cavitation on velocity, turbulence intensity and vorticity inhydrofoil wake.(2)Discussion of U-shape cloud cavity with the twisted hydrofoil.(3)Summary of the characteristics of U-shape cloud cavity with the twisted hydrofoil under different angles of attack.(4)Cavity volume acceleration is the main source of the pressure fluctuations in hydraulic machinery. These results are essential for understanding the mechanism of the cavitation excited pressure pulsations in hydraulic machinery, which will help understand the mechanism of the cavitation excited pressure pulsations and control the flow separation in engineering application.
引文
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[13]JI B,LUO XW,ARNDT REA,et al.Large eddy simulation and theoretical investigations of the transient cavitating vortical flow structure around a NACA66hydrofoil[J].International Journal of Multiphase Flow,2015.68:121-134.
[14]GOPALAN S,J KATZ.Flow structure and modeling issues in the closure region of attached cavitation[J].Physics of Fluids,2000,12(4):895-911.
[15]JI B,Luo,XW,ARNDT,REA,et al.Numerical simulation of three dimensional cavitation shedding dynamics with special emphasis on cavitation-vortex interaction[J].Ocean Engineering,2014,87:64-77.
[2]JI B,LONG Y,LONG XP,et al.Large eddy simulation of turbulent attached cavitating flow with special emphasis on large scale structures of the hydrofoil wake and turbulence-cavitation interactions[J].Journal of Hydrodynamics,2017,29(1):27-39.
[3]HUANG B,YOUNG YL,WANG GY,et al.Combined Experimental and Computational Investigation of Unsteady Structure of Sheet/Cloud Cavitation[J].Journal of Fluids Engineering-Transactions of the ASME,2013,135(7):071301.
[4]FOETH EJ.The structure of three-dimensional sheet cavitation,mechanical maritime and mat-erials engineering[J].Wageningen,the Netherlands:Delft University of Technology,2008.
[5]JI B,LUO XW,WU YL,et al.Numerical analysis of unsteady cavitating turbulent flow and shedding horse-shoe vortex structure around a twisted hydrofoil[J].International Journal of Multi-phase Flow,2013,51,33-43.
[6]PENG XX,JI B,CAO YT,et al.Combined experimental observation and numerical simulation of the cloud cavitation with U-type flow structures on hydrofoils[J].International Journal of Multiphase Flow,2016,79,10-22..
[7]KNAPP RT.Recent investigations of the mechanics of cavitation and cavitation damage[J].Transactions of the ASME 77,1955:1045-1054.
[8]KAWANAMI Y,KATO H,YAMAGUCHI H,et al.Mechanism and control of cloud cavitation[J].Journal of Fluids Engineering-Transactions of the ASME,1997,119(4):788-794..
[9]CALLENAERE M,FRANC JP,MICHEL JM,et al.The cavitation instability induced by the development of a re-entrant jet[J].Journal of Fluid Mechanics 2001,444:223-256
[10]LABERTEAUX KR,CECCIC SL.Partial cavity flows.part 2.cavities forming on test objects with spanwise variation[J].Journal of Fluid Mechanics,2001,431:43-63.
[11]GANESH H,MAKIHARJU SA,CECCIC SL.Bubbly shock propagation as a mechanism for sheet-to-cloud transition of partial cavities[J].Journal of Fluid Mechanics,2016,802:37-78.
[12]REISMAN GE,WANG YC,BRENNEN CE.Observations of shock waves in cloud cavitation[J].Journal of Fluid Mechanics,1998.355:255-283.
[13]JI B,LUO XW,ARNDT REA,et al.Large eddy simulation and theoretical investigations of the transient cavitating vortical flow structure around a NACA66hydrofoil[J].International Journal of Multiphase Flow,2015.68:121-134.
[14]GOPALAN S,J KATZ.Flow structure and modeling issues in the closure region of attached cavitation[J].Physics of Fluids,2000,12(4):895-911.
[15]JI B,Luo,XW,ARNDT,REA,et al.Numerical simulation of three dimensional cavitation shedding dynamics with special emphasis on cavitation-vortex interaction[J].Ocean Engineering,2014,87:64-77.