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vortex dynamics and entropy generation in separated transitional flow over a compressor blade at various incidence angles

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Chinese Journal of Aeronautics 2022年第3期35卷 42-52页

作者： Mingyang WANG Ziliang LI Ge HAN Chengwu YANG Shengfeng ZHAO Yanfeng ZHANG Xin’gen LU Key Laboratory of Light-Duty Gas-Turbine Institute of Engineering ThermophysicsChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

The transition process within a Laminar Separation Bubble(LSB)that formed on a compressor blade surface was investigated using Large Eddy Simulations(LESs)at a Reynolds number of 1.5×10;and incidence angles of 0°,+3°,and+5°.The vortex dynamics in the separated shear layers were compared at various incidence angles and its effects on the loss generation were clarified through entropy *** showed that transition onset,which was accurately identified by the Linear Stability Theory(LST),was significantly promoted at the increased incidence *** such,the development of LSB was suppressed and the relative role of viscous instability played in the transition process was *** the incidence angle of 0°,two-dimensional spanwise vortices detached from the blade surface and roiled up periodically,which were further stretched and eventually evolved into large-scale hairpin *** time passed,the fully developed hairpin vortices broke down into small-scale ***,the flow near the wall reversely ejected into the outer separated shear layers and a sweeping process happened subsequently,forcing the separated shear layers to reattach and accelerating the generation of turbulent *** comparison,the strength of vortex rolling-up was weakened at higher incidence angles,and the vortex pairing and breakdown of large-scale vortices were less ***,the level of turbulent fluctuations that generated in the separated shear layers was *** entropy analysis showed that the turbulent dissipation effect related to the Reynolds shear stresses determined the largest amount of positive entropy generation,which declined to a lower level as the incidence angle increased from 0°to+5°.Correspondingly,the profile loss was reduced by 50.4%.

关键词： Aerodynamic performance Compressor airfoil Entropy Incidence angle Separation bubble vortex dynamics

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vortex dynamics OF THE ANISOTROPIC GINZBURG-LANDAU EQUATION

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Acta Mathematica Scientia 2010年第3期30卷 949-962页

作者：温焕尧丁时进 School of Mathematical Sciences South China Normal University

In this article, using coordinate transformation and Gronwall inequality, we study the vortex motion law of the anisotropic Cinzburg-Landau equation in a smooth bounded domain Ω （R^2,that is ,Эtuε=j,k=1∑2（ajkЭxkuε）xj＋ε^2^-b（x）（1-｜uε｜^2）uε,x∈Ω,and conclude that each vortex,bj（t）（j=1,2,…,N）satisfies dt^-dbj（t）=-（a（bj（t））^-a1k（bj（t））Эxka（bj（t））,a（aj（t））^-a2k（bj（t））Эxka（bj（t）））,where a（x）=√a11a22-a12^2. We prove that all the vortices are pinned together to the critical points of a（x）. Furthermore, we prove that these critical points can not be the maximum points.

关键词： Anisotropic Ginzburg-Landau equation Gronwall inequality vortex dynamics

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Flow Separation and vortex dynamics in Waves Propagating over A Submerged Quartercircular Breakwater

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China Ocean Engineering 2018年第5期32卷 514-523页

作者： JIANG Xue-lian YANG Tian ZOU Qing-ping GU Han-bin Tianjin Key Laboratory of Soft Soil Characteristics & Engineering Environment Tianjin Chengjian University State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin University The Lyell Centre for Earth and Marine Science and Technology Institute for Infrastructure and EnvironmentHeriot-Watt University School of Naval Architecture &Mechanical-Electrical Engineering Zhejiang Ocean University

The interactions of cnoidal waves with a submerged quartercircular breakwater are investigated by a ReynoldsAveraged Navier–Stokes(RANS) flow solver with a Volume of Fluid(VOF) surface capturing scheme(RANSVOF) model. The vertical variation of the instantaneous velocity indicates that flow separation occurs at the boundary layer near the breakwater. The temporal evolution of the velocity and vorticity fields demonstrates vortex generation and shedding around the submerged quartercircular breakwater due to the flow separation. An empirical relationship between the vortex intensity and a few hydrodynamic parameters is proposed based on parametric analysis. In addition, the instantaneous and time-averaged vorticity fields reveal a pair of vortices of opposite signs at the breakwater which are expected to have significant effect on sediment entrainment, suspension, and transportation,therefore, scour on the leeside of the breakwater.

关键词： submerged quartercircular breakwater cnoidal wave flow separation vortex dynamics scour

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Liutex-based vortex dynamics:A preliminary study

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Journal of Hydrodynamics 2020年第6期32卷 1217-1220页

作者： Hai-dong Yu Yi-qian Wang School of Aerospace Engineering Tsinghua UniversityBeijing100084China School of Mathematical Science Soochow UniversitySuzhou215006China

vortex dynamics,with the possibility of efficient flow control,is explored in this study based on the new introduced vortex definition and identification system of *** the six core elements of vortex identification,including(1)absolute strength,(2)relative strength,(3)local rotational axis,(4)global rotational axis,(5)vortex core size and(6)vortex boundary,provided by the Liutex system,it is possible to numerically devise strategies,primarily by introducing additional source terms in Navier-Stokes equations,which we call Liutex force field model here,to control the vortex *** methodologies of centripetal force model and counter-rotation force model are preliminarily investigated in a cavitating flow around two-dimensional Clark-Y *** is found that Liutex based models are capable of illustrating the vortex dynamics and possibly strengthening or weakening the vortices.

关键词： vortex dynamics Liutex vector flow control

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THE NONLINEAR INTERACTION OF vortex RINGS WITH A FREE SURFACE

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Acta Mechanica Sinica 1997年第2期13卷 120-129页

作者：叶取源 C.K.Chu Dept.of Engineering Mechanics Shanghai Jiao Tong UniversityShanghai 200030China Dept.of Applied Physics Columbia UniversityNew YorkNY 10027USA

Nonlinear interactions of vortex rings with a free surface are considered in an incompressible, ideal fluid using the vortex contour dynamics technique and the boundary integral equation method. The flow is axisymmetric and the vorticity is linearly distributed in the vortex. Effects of the gravity and the surface tension as well as the initial geometric parameter of the vortex on the interaction process are investigated in considerable detail. The interaction process may be divided into three major stages: the vortex free-traveling stage, the collision stage, and the vortex stretching and rebounding stage. Time evolutions of both the vortex and free surface under various conditions are provided and analyzed. Two kinds of waves exist on the free surface during interaction. In a special case where the gravity and surface tension are very weak or the vortex is very strong, an electric-bulb-like 'cavity' is formed an the free surface and the vortex is trapped in the 'cavity' for quite a. long time, resulting in a large amount, of fluid above the mean fluid surface.

关键词： vortex ring vortex dynamics contour dynamics nonlinear free surface

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Dynamic performance and wake structure of flapping plates with different shapes

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Acta Mechanica Sinica 2014年第6期30卷 800-808页

作者： Gao-Jin Li Nan-Sheng Liu Xi-Yun Lu Department of Modern Mechanics University of Science and Technology of China

The dynamic performance and wake structure of flapping plates with different shapes were studied using multi-block lattice Boltzman and immersed boundary *** typical regimes relevant to thrust behavior are *** is nonlinear relation between the thrust and the area moment of plate for lower area moment region and the other is linear relation for larger area moment *** tendency of the power variation with the area moment is reasonably similar to the thrust behavior and the efficiency decreases gradually as the area moment *** the mechanism of the dynamic properties is associated with the evolution of vortical structures around the plate,the formation and evolution of vortical structures are investigated and the effects of the plate shape,plate area,Strouhal number and Reynolds number on the vortical structures are *** results obtained in this study provide physical insight into the understanding of the mechanisms relevant to flapping locomotion.

关键词： dynamics of flapping plate Flapping locomotion Plate shape vortex dynamics

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Liutex-based centripetal force field model for improving the resistance and wake performances of JBC ship sailing in calm water

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Journal of Hydrodynamics 2021年第3期33卷 494-502页

作者： Xin-wang Liu Song-tao Chen Wei-wen Zhao De-cheng Wan Yi-qian Wang Computational Marine Hydrodynamics Lab(CMHL) School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China Ocean College Zhejiang UniversityZhoushan316021China School of Mathematical Science Soochow UniversitySuzhou215006China

For complex aerodynamic and hydrodynamic problems,the analysis of vortex is very *** Liutex method is an eigenvalue-based method which is local,accurate,and unique,which can give an accurate definition of vortex,so the control of vortex can be implemented and effectively *** on Liutex method,two methodologies of centripetal force model and counter-rotation force model were proposed to illustrate the vortex dynamics and possibly strengthen or weaken the *** this paper,the Liutex-based centripetal force model is applied by adding a source term to the Navier-Stokes *** order to investigate the influence of the constructed Liutex force model on the 3-dimensional flow around a slow-fat ship,the calm-water drag calculation result of JBC ship is regarded as the initial flow field,and the new resistance and wake performances of the ship are obtained after applying the centripetal force model to the flow field with different *** views of the comparisons of the new steady flow fields are shown,and the parametric study results indicate that the Liutex-based centripetal force model can effectively change the resistance and wake performances of the JBC ship,which provides a new idea and theoretical basis for the comprehensive hydrodynamic performance optimization of the ship hull.

关键词： vortex dynamics Liutex vector flow control ship resistance ship wake ship hydrodynamic optimization

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Slat cove dynamics of multi-element airfoil at low Reynolds number

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Science China(Technological Sciences) 2023年第4期66卷 1166-1179页

作者： WANG JiangSheng XU Yang WANG JinJun Fluid Mechanics Key Laboratory of Education Ministry Beijing University of Aeronautics and AstronauticsBeijing 100191China

The flow around the slat cove of a two-dimensional 30P30N multi-element airfoil is investigated with time-resolved particle image velocimetry(TR-PIV)at low Reynolds number(Rec=2.41×10^(4)and 4.61×10^(4)).The effects of angle of attack(α=8°,12°,and 16°)on the mean flow characteristics and vortex dynamics are *** size of the recirculation within the slat cove and the intensity of the shed vortices originating from the slat cusp shear layer are found to generally decrease as the angle of attack *** joint time-frequency analyses show that disturbances of different frequencies exist in the slat cusp shear layer and they trigger the different vortex shedding patterns of the slat cusp shear *** self-sustained oscillation within the slat cove,normally observed at high Reynolds number(Re_(c)~10^(6)),is proved to be responsible for the disturbances of different frequencies and the related vortex dynamics in the current study.

关键词： multi-element airfoil slat vortex dynamics time-resolved particle image velocimetry

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FORCE CHARACTERISTICS AND vortex SHEDDING OF A PITCHING FOIL IN SHEAR FLOWS

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Journal of Hydrodynamics 2005年第1期17卷 27-33页

作者： LIDan-yong LIUNan-sheng LUXi-yun YINXie-zhen DepartmentofMechanicsandMechanicalEngineering UniversityofScienceandTechnologyofChinaHefei230026China

The objective of this study is to deal with unsteady force acting on a pitching foil in shear flow and to study the relation of the force characteristics with vortex shedding near the foil. The two dimensional incompressible Navier Stokes equations in the vorticity and stream function formulation were solved with the fourth order essentially compact finite difference schemes for the space derivatives and a fourth order Runge Kutta scheme for the time advancement. The force characteristics and vortex shedding of the pitching foil in shear flows were investigated. The effects of some typical factors, including the incoming flow shear, the oscillating frequency and amplitude, on the vortex shedding and force behavior were analyzed and discussed.

关键词： vortex dynamics vortex shedding force unsteady flow locomotion biomechanics

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Liutex-based vortex control with implications for cavitation suppression

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Journal of Hydrodynamics 2021年第1期33卷 74-85页

作者： Yi-qian Wang Hai-dong Yu Wei-wen Zhao De-cheng Wan School of Mathematical Science Soochow UniversitySuzhou 215006China School of Aerospace Engineering Tsinghua UniversityBeijing 100084China Computational Marine Hydrodynamics Lab(CMHL) State Key Laboratory of Ocean EngineeringSchool of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China

Viewed as sinews and muscles of fluid motion,coherent vortical structures with their interactions are key to understanding the flow *** upon this observation,we explore the possibility of efficient flow control by directly manipulating vortices numerically inside the flow field based on the vortex definition and identification system of *** objective is twofold:(1)to study the vortex dynamics,for example,by observing the response of the flow to strengthening or weakening of certain vortices,and(2)to obtain efficient vortex-based control strategies which might lead us to practical *** the present numerical study,the manipulating of vortices is achieved by introducing additional source(force)terms to the Navier-Stokes equations,which hereafter will be collectively called Liutex force field *** including controlling the rotation strength and centripetal force of particular vortices are detailed in a flow past a cylinder with different control purposes at Reynolds number of *** examples are provided with a cavitating flow around two-dimensional Clark-Y hydrofoil,with particular interests on cavitation *** is illustrated particular vortex with cavitation encircled could be effectively suppressed.

关键词： vortex dynamics Liutex vector flow control cavitation Introduction

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