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UNSTEADY SUPERCAVITATING FLOW PAST CONES

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Journal of Hydrodynamics 2006年第3期18卷 262-272页

作者： HU Chao YANG Hong-lan ZHAO Cun-bao HUANG Wen-hu Institute of Aerospace Engineering and Applied mechanics Tongji Universtity Shanghai 200092 China Department of Aerospace Engineering and Mechanics Harbin Institute of Technology Harbin 150001 China Department of Aerospace Engineering and Mechanics Harbin Institute of Technology Harbin 150001 China

Based on integral equation method, the study of unsteady supercavitating flow past cones is presented. The shape and length of supercavity are calculated respectively using the finite difference time discretization method. The characteristics of the shape and length of supercavities, which vary with the cone＇s angle and cavitation number, are investigated respectively, the varied features of some supercavity scales are analyzed when the flow field is perturbed periodically. The curves relationship between cavity length and cavitation number, which are based respectively on present method and other theories, are discussed and compared. It is obviously shown that the supercavity changes have two characteristics： retardance and wave. These results obtained would be useful in the case of design and analysis of cavitator under water.

关键词： supercavitation cavitator unsteady flow,slender body theory integral equation method

UNDERWATER ACOUSTICS AND CAVITATING FLOW OF WATER ENTRY

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Acta Mechanica Sinica 2004年第4期20卷 374-382页

作者：施红辉 KUME Makoto State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100080China College of Mechanical Engineering and Automatic ControlZhejiang University of SciencesXiasha Higher Education ZoneHangzhou 310018China Department of Mechanical Engineering Nagoya Institute of TechnologyGokiso-choShowa-kuNagoya 466-8555Japan

The fluid mechanics of water entry is studied through investigating the underwater acoustics and the *** acoustic signals in water entry are extensively measured at about 30 different positions by using a PVDF needle *** the measurements we obtain (1)the primary shock wave caused by the impact of the blunt body on free surface;(2)the vapor pressure inside the cavity;(3)the secondary shock wave caused by pulling away of the cavity from free surface;and so *** supercavitation induced by the blunt body is observed by using a digital high-speed video camera as well as the single shot *** periodic and 3 dimensional motion of the supercavitation is *** experiment is carried out at room temperature.

关键词： water entry underwater acoustics supercavitation PVDF hydrophone high-speed photography

Breakup of Cavitation Bubbles within the Diesel Droplet

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Chinese Journal of Mechanical Engineering 2014年第1期27卷 198-204页

作者： L Ming NING Zhi YAN Kai FU Juan SONG Yunchao SUN Chunhua College of Mechanical and Electrical Engineering Beijing Jiaotong University

supercavitation in the diesel nozzle increases the instability of droplets in part due to the two-phase mixture, while the effect of cavitation bubbles on the instability of drops is still unclear. In order to investigate the breakup of cavitation bubbles within the diesel droplet, a new mathematical model describing the disturbance growth rate of the diesel bubble instability is developed. The new mathematical model is applied to predict the effects of fluids viscosity on the stability of cavitation bubbles. The predicted values reveal that the comprehensive effect of fluids viscosity makes cavitation bubbles more stable. Compared with the viscosities of air and cavitation bubble, the diesel droplet＇s viscosity plays a dominant role on the stability of cavitation bubbles. Furthermore, based on the modified bubble breakup criterion, the effects of bubble growth speed, sound speed, droplet viscosity, droplet density, and bubble-droplet radius ratio on the breakup time and the breakup radius of cavitation bubbles are studied respectively. It is found that a bubble with large bubble-droplet radius ratio has the initial condition for breaking easily. For a given bubble-droplet radius ratio （0.2）, as the bubble growth speed increases （from 2 m/s to 60 m/s）, the bubble breakup time decreases（from 3.59 gs to 0.17 ps） rapidly. Both the greater diesel droplet viscosity and the greater diesel droplet density result in the increase of the breakup time. With increasing initial bubble-droplet radius ratio （from 0.2 to 0.8）, the bubble breakup radius decreases （from 8.86 trn to 6.23 tm）. There is a limited breakup radius for a bubble with a certain initial bubble-droplet radius ratio. The mathematical model and the modified bubble breakup criterion are helpful to improve the study on the breakup mechanism of the secondary diesel droplet under the condition of supercavitation.

关键词： supercavitation instability diesel droplet cavitation bubbles secondary breakup

HYDRODYNAMIC BEHAVIOR OF AN UNDERWATER MOVING BODY AFTER WATER ENTRY

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Acta Mechanica Sinica 2001年第1期17卷 35-44页

作者：施红辉高见卓也 Department of Mechanical Engineering Nagoya Institute of Technology Gokiso-cho Showa-kuNagoya 466-8555 Japan Space Engineering Division Space Engineering Development Co. Ltd. Issei Build. Takezono 2-3-12 Tsukuba 305-0032 Japan

An experimental study was conducted to investigate the water entry phenomenon. A facility was designed to carry out the tests with the entry veloci- ties of around 352 m/s. Visualization, pressure ineasurement, velocity measurement and underwater impact test were performed to investigate the hydroballistic behav- ior of the underwater moving body, the underwater flow field, the supercavitation, etc.. This study shows that the motion of a high-speed underwater body is strongly three-dimensional and chaotic. Furthermore, it is found that the distribution of the trajectory deflection of the underwater projectile depends on the depth of water. It is also found by measuring the deformation on a witness plate submerged in water, that the impact energy of an underwater projectile is reduced as it penetrates deeper into water.

关键词： water entry supercavitation underwater acoustic wave underwater projectile trajectory projectile velocity

Drag reduction methods at solid‒liquid interfaces

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Friction 2022年第4期10卷 491-515页

作者： Min LIU Liran MA State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China

Friction drag is a nonnegligible matter when relative motion happens between solid and liquid phase,which brings many inconveniences in ship navigation,fluid transportation,microfluid devices,*** various methods have been developed focusing on friction drag *** this article,a review of several widely studied drag reduction methods is given,specially,their advantages and limitations in practical applications are ***,a comparison of different methods is made and the development prospect of drag reduction is concluded.

关键词： drag reduction microstructures superhydrophobic surfaces supercavitation polymer additives

Modeling of rotational supercavitating evaporator and the geometrical characteristics of supercavity within

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Science China(Physics,Mechanics & Astronomy) 2014年第3期57卷 541-554页

作者： LIKHACHEV Dmitriy S. LI FengChen Complex Flow and Heat Transfer Laboratory School of Energy Science and EngineeringHarbin Institute of Technology

In this paper,a rotational supercavitating evaporator(RSCE)was at first modeled by means of theoretical analysis *** geometrical characteristics of supercavity in the modeled RSCE were then studied through numerical *** current research objectives consist in determination of shape of the supercavitator(which in the plane of rotation generates supercavity occupying the most volume between blades),and location of the area suitable for steam extraction by revealing the inner structure of *** analysis was performed by solving empirical equations for the shape of RSCE,through which an evaluation of two-dimensional relative position of supercavity trailing edge for different shapes of the supercavitator has been *** simulation was then carried out,by numerically solving the unsteady Navier-Stokes equations in their conservation form coupled with the Rayleigh-Plesset cavitation and Shear-Stress Transport turbulence models,for verification of the results obtained from empirical *** unreliable assumption of applicability of empirical equations we have confirmed similarity of the supercavity shapes obtained by both methods for the same ***,the shape of supercavitator calculated by using empirical equations is acceptable,which provides a simple but reliable approach for design of *** inner structure of supercavity obtained by numerical simulation has indicated position and parameters for steam extraction openings for further numerical and experimental studies on the performance of *** application of steam or gas extraction is suggested for solving of some problems associated with cavitating pumping of cryogenic liquid.

关键词： supercavitation rotational supercavitating evaporator geometrical characteristics theoretical analysis computationalfluid dynamics

Motion stability and control of supercavitating vehicle with variable cavitation number

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Journal of Harbin Institute of Technology(New Series) 2011年第4期18卷 19-23页

作者：王京华于开平魏英杰王聪黄文虎吕瑞 School of Astronautics Harbin Institute of Technology

Cavitation number and speed are capable of variation during the motion of supercavitating vehicle underwater, for example, under the condition of accelerated motion stage and external disturbance. The dynamic model and control challenge associated with the longitudinal motion of supereavitating vehicle with variable cavitation number and speed have been explored. Based on the principle of cavity expansion independence the properties of cavity and the influence on planning force of body were researched. Calculation formula of efficiency of the fin was presented. Nonlinear dynamics model of variable cavitation number and speed supercavitating vehicle was established. Stabilities of the open-loop systems of different situations were analyzed. The simulations results of open-loop systems show that it is necessary to design a control method to control a supereavitating vehicle. A gain schedule controller with guaranteed H∞ performance was designed to stabilize the dive-plane dynamics of supercavitating vehicle under changing conditions.

关键词： supercavitation supereavitating vehicle variable cavitation number planing force gain schedule control

Dynamic Characteristics of Supercavitating Flow Around a Hydrofoil

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Journal of Beijing Institute of Technology 2004年第1期13卷 67-70页

作者：王国玉张美红刘淑艳 Ikohagi Toshiaki School of Mechanical and Vehicular Engineering Beijing Institute of Technology Beijing100081 China Institute of Fluid Science Tohoku University Sendai 980-8577 Japan

supercavitation dynamic characteristics around a hydrofoil are studied with both high-speed visualization and drag and lift measurements. In the supercavitation condition, the cavitation area covers the entire surface of the foil. There is a distinct interface between the main flow and the supercavitating flow regions. The cavitating region is filled with cavitation bubble and water mixture. Small fluctuations of the interface are observed, which indicates that even a relative smooth surface is formed in this state, the interface is unsteady. The minimum drag is to be obtained in the supercavitation condition.

关键词： supercavitation high-speed visualization drag coefficient

Study on the trajectory prediction curves of supercavitating vehicle

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Journal of Harbin Institute of Technology(New Series) 2009年第6期16卷 815-820页

作者：曹伟魏英杰王聪于开平黄文虎 School of Astronautics Harbin Institute of Technology

In order to understand the laws of motion for supercavitating vehicle better, simplified equations for longitudinal motion of supercavitating vehicle were derived. Then the corresponding simulation software for trajectory of supereavitating vehicle was programmed, by which the theoretical predicted trajectories of the supercavitating vehicle at different velocities were obtained. It was found that the predicted trajectories at low speed and without cavitation on the vehicle in theory agreed well with those in experiments, and the theoretical predicted trajectories at high speed and with supercavity on the vehicle correctly reflected the motion laws of the supercavitating vehicle. The influences of various parameters of eavitator and rudder on the underwater trajectory were compared and analyzed, which can provide a guide for the design of hydrodynamic distribution and gross parameters of the supereavitating weapons.

关键词： hydrodynamic forces supercavitation trajectory theoretical prediction