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Numerical simulation and scaling analysis of elasticity-induced lift force in a viscoelastic fluid between confining surfaces

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Journal of Hydrodynamics 2022年第4期34卷 756-766页

作者： Xin Zhao Chao Wei The State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China Science and Technology on Vehicle Transmission Laboratory Beijing Institute of TechnologyBeijing 100081China

How to accurately characterize the lift force on the particles near the solid surfaces is an ongoing challenge in fluid mechanics and microfluidic techniques, especially in a complex system with viscoelastic fluid or/and soft surface that is commonly encountered in a biological system. The motions of the particles in vicinity of a surface can be simplified to be a rigid cylinder surrounded by the viscoelastic fluid moving along a substrate which can be rigid or soft according to different cases. In such an inertial free system with a wide range of Weissenberg number (Wi force to the viscous force), firstly we numerically evaluate the influence of the systematic parameters, including the polymer viscosity, the geometry and Wi, on the net normal force for a cylinder closely moving along a rigid substrate, and the elasticity-induced lift force in a scaled form. It is shown that a strong shear arises in the viscoelastic confinement between the moving cylinder and the rigid substrate, it leads to the asymmetry of the first normal stress distribution around the cylinder, and thus the lift force. Then, the influence of a soft substrate on the lift force is considered, and we find that the lift force induced by the viscoelastic fluid always dominates in magnitude over that induced by the soft substrate deformation. This work provides a reliable scaling that can be utilized to quantify the elasticity-induced lift force on the particles in a viscoelastic system, such as the micro- and nanofluidic systems in biological applications.

关键词： Viscoelastic fluid scaling expression computational fluid dynamics lift force

Study of the lift force Induced by An Interceptor on A High-Speed Mono-Hull:The Affecting Factors and Estimation Formula

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China Ocean Engineering 2024年第4期38卷 557-571页

作者： DENG Rui HU Yu-xiao HUANG Si-chong SONG Zhi-jie WANG Shi-gang WU Tie-cheng School of Ocean Engineering and Technology Sun Yat-sen Universityand Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)Zhuhai 519082China

To find a better way to estimate the lift force induced by an interceptor on a high-speed mono-hull ship,a series of high-speed mono-hull ship models are designed and investigated under different *** lift forces are obtained by numerical calculations and validated by a model test in a towing *** factors that influence the force are the interceptor height,velocity,draft,and deadrise *** relationship between each factor and the induced lift force is investigated and *** found that the induced lift mainly depends on the interceptor height and advancing velocity,and is proportional to the square of the interceptor height and *** results also showed that the effects of the draft and deadrise angle are relatively less important,and the relationship between the induced lift and these two factors is generally *** on the results,a formula including the combined effect of all factors used to estimate the lift force induced by the interceptor is developed based on systematic *** proposed formula could be used to estimate the lift force induced by interceptors,especially under high-speed condition.

关键词： high-speed mono-hull ship interceptor lift force formula lift force towing tank test computational fluid dynamics

A novel method of evaluating the lift force on the bluff body based on Noca's flux equation

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Chinese Physics B 2015年第8期24卷 426-430页

作者：隋相坤姜楠 State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Department of Mechanics School of Mechanical Engineering Tianjin University Tianjin Key Laboratory of Modern Engineering Mechanics

The influence of experimental error on lift force evaluated by Noca’s flux equation is studied based on adding errors into the direct numerical simulation data for flow past cylinder at Re = 100. As Noca suggested using the low-pass filter to get rid of the high-frequency noise in the evaluated lift force, we verify that his method is inapplicable for dealing with the dataset of 1% experimental error, although the precision is acceptable in practice. To overcome this defect, a novel method is proposed in this paper. The average of the lift forces calculated by using multiple control volume is taken as the evaluation before applying the low-pass filter. The method is applied to an experimental data for flow past a cylinder at approximately Re = 900 to verify its validation. The results show that it improves much better on evaluating the lift forces.

关键词： flux equation lift force experimental error

A Study of lift force and Instantaneous Velocity Field Around an Oscillating Circular Cylinder

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China Ocean Engineering 1997年第4期12卷 419-430页

作者： C.A.Greated Department of Physics and Astronomy University of Edinburgh

force measurements of oscillatory flow acting on a single circular cylinder have been carried out. The experiments were done by oscillating a circular cylinder in still water. Instantaneous forces and velocity fields around the cylinder were measured by Particle Image Velocimetry (PIV). The Keulegan-Carpenter number (KC) varied in the range from 5 to 20 and the viscous parameter beta = Re / KC was set at 500 (Re is Reynolds number). It was found that the strength and frequency of the lift force increased with KC number, the main frequency of the lift force being three times the frequency of the oscillatory flow at KC = 20. The movement and strength of the vortices around the cylinder are discussed for different KC numbers.

关键词： particle image velocimetry oscillatory polo single circular cylinder force measurement lift force velocity field vortex pattern vorticity

Kutta-Joukowski force expression for viscous flow

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Science China(Physics,Mechanics & Astronomy) 2015年第2期58卷 90-94页

作者： LI Juan XU YiZhe WU ZiNiu Department of Engineering Mechanics Tsinghua University

The Kutta Joukowski(KJ) theorem, relating the lift of an airfoil to circulation, was widely accepted for predicting the lift of viscous high Reynolds number flow without separation. However, this theorem was only proved for inviscid flow and it is thus of academic importance to see whether there is a viscous equivalent of this theorem. For lower Reynolds number flow around objects of small size, it is difficult to measure the lift force directly and it is thus convenient to measure the velocity flow field solely and then, if possible, relate the lift to the circulation in a similar way as for the inviscid KJ theorem. The purpose of this paper is to discuss the relevant conditions under which a viscous equivalent of the KJ theorem exists that reduces to the inviscid KJ theorem for high Reynolds number viscous flow and remains correct for low Reynolds number steady flow. It has been shown that if the lift is expressed as a linear function of the circulation as in the classical KJ theorem, then the freestream velocity must be corrected by a component called mean deficit velocity resulting from the wake. This correction is small only when the Reynolds number is relatively large. Moreover, the circulation, defined along a loop containing the boundary layer and a part of the wake, is generally smaller than that based on inviscid flow assumption. For unsteady viscous flow, there is an inevitable additional correction due to unsteadiness.

关键词： lift force Kutta Joukowski expression viscous flow

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几何形状对气垫升力的影响研究

哈尔滨工程大学学报（英文版） 2024年第1期23卷 74-84页

作者： Hamed Petoft Vahid Fakhari Abbas Rahi Faculty of Mechanical and Energy Engineering Shahid Beheshti UniversityTehran ***Iran

One of the crucial and challenging issues for researchers is presenting an appropriate approach to evaluate the aerodynamic characteristics of air cushion vehicles(ACVs)in terms of system design *** of these issues includes introducing a suitable approach to analyze the effect of geometric shapes on the aerodynamic characteristics of *** main novelty of this paper lies in presenting an innovative method to study the geometric shape effect on air cushion lift force,which has not been investigated thus ***,this paper introduces a new approximate mathematical formula for calculating the air cushion lift force in terms of parameters,including the air gap,lateral gaps,air inlet velocity,and scaling factor for the first ***,we calculate the aerodynamic lift force applied to nine different shapes of the air cushions used in the ACVs in the present paper through the ANSYS Fluent *** geometrical shapes studied in this paper are rectangular,square,equilateral triangle,circular,elliptic shapes,and four other combined shapes,including circle-rectangle,circle-square,hexagonal,and fillet *** showed that the cushion with a circular pattern produces the highest lift force among other geometric shapes with the same *** increase in the cushion lift force can be attributed to the fillet with a square shape and its increasing radius compared with the square shape.

关键词： lift force Air cushion vehicle Geometric shape Simulation Gap Inlet velocity Scaling factor

Effect of turbulence intensity on airfoil flow:numerical simulations and experimental measurements

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Applied Mathematics and Mechanics(English Edition) 2011年第8期32卷 1029-1038页

作者：李韵武王庶王健平米建春 Department of Mechanics and Aerospace Engineering State Key Laboratory on Turbulence and Complex Systems College of Engineering Peking University

The effect of the turbulence intensity of the oncoming stream on the aerodynamic characteristics of the NACA-0012 airfoil is investigated by a direct numerical simulation. The numerical results are found to be consistent with the experimental measurements. Based on the finite spectral QUICK scheme, the simulation gets the high accuracy results. Both the simulation and the experiment reveal that the airfoil stall does not exist for the low turbulence intensity, however, occurs when the turbulence intensity increases sufficiently. Besides, the turbulence intensity has a significant effect on both the airfoil boundary layer and the separated shear layer.

关键词： finite spectral method turbulence intensity boundary layer shear layer lift force drag force airfoil stall

Viscous Effects on Wave forces on A Submerged Horizontal Circular Cylinder

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China Ocean Engineering 2018年第3期32卷 245-255页

作者： TENG Bin MAO Hong-fei LU Lin State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology

Numerical simulations are carried out for wave action on a submerged horizontal circular cylinder by means of a viscous fluid model, and it is focused on the examination of the discrepancies between the viscous fluid results and the potential flow solutions. It is found that the lift force resulted from rotational flow on the circular cylinder is always in anti-phase with the inertia force and induces the discrepancies between the results. The influence factors on the magnitude of the lift force, especially the correlation between the stagnation-point position and the wave amplitude, and the effect of the vortex shedding are investigated by further examination on the flow fields around the cylinder. The viscous numerical calculations at different wave frequencies showed that the wave frequency has also significant influence on the wave forces. Under higher frequency and larger amplitude wave action, vortex shedding from the circular cylinder will appear and influence the wave forces on the cylinder substantially.

关键词： submerged horizontal circular cylinder wave force lift force vortex effect

Numerical simulation of low-Reynolds number flows past two tandem cylinders of different diameters

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Water Science and Engineering 2013年第4期6卷 433-445页

作者： Yong-tao WANG Zhong-min YAN Hui-min WANG College of Environmental Science and Engineering Suzhou University of Science and Technology College of Water Conservancy and Hydropower Engineering Hohai University College of Environment Hohai University

The flow past two tandem circular cylinders of different diameters was simulated using the finite volume method. The diameter of the downstream main cylinder （D） was kept constant, and the diameter of the upstream control cylinder （d） varied from 0.1D to D. The studied Reynolds numbers based on the diameter of the downstream main cylinder were 100 and 150. The gap between the control cylinder and the main cylinder （G） ranged from 0.1D to 4D. It is concluded that the gap-to-diameter ratio （G/D） and the diameter ratio between the two cylinders （d/D） have important effects on the drag and lift coefficients, pressure distributions around the cylinders, vortex shedding frequencies from the two cylinders, and flow characteristics.

关键词： two tandem cylinders vortex shedding drag force lift force numerical simulation