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Decomposition of mean skin friction in incident shock wave/turbulent boundary layer interaction flows at Mach 2.25

中国航空学报:英文版 2023年第9期36卷 178-194页

作者： Junyi DUAN Fulin TONG Xinliang LI Hongwei LIU LHD Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China State Key Laboratory of Aerodynamics China Aerodynamics Research and Development CenterMianyang 621000China

The evolution characteristics of the mean skin friction beneath the supersonic turbulent boundary layer that interacts with incident shock waves at Mach 2.25 are analyzed using Direct Numerical Simulation(DNS). The separated and attached boundary layers in the interaction region that respectively correspond to 33.2° and 28° incident shock angles are considered. The mean skin friction recovery rate for the separated boundary layer is much gentler and distinctly less than that for the attached case where the skin friction completes its recovery within one boundary layer thickness. The novel mean skin friction decomposition method for compressible flows proposed by the recent research is applied in the interaction region to investigate the internal evolution characteristics quantitatively. The results reveal that the three decomposition components are distinctly unequal between the two cases. The contributions of the turbulent motions at different scales to the associated term are focused on using empirical mode decomposition technology. It indicates that the outer large-scale structures dominate separation and reattachment regions, while contributions from inner small-scale structures are limited. In contrast, contributions from the outer largescale structures are dramatically reduced in the attached case, which results in the outer large-scale and inner small-scale motions being of equal importance.

关键词： Compressible flow Boundary layers Direct numerical simulation Shock waves skin friction Turbulent flow

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skin friction and heat transfer of liquid jet over a continuous moving horizontal hot plate

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Journal of University of Science and Technology Beijing 2002年第3期9卷 177-180页

作者： LiancunZheng JichengHe 等 AppliedScienceSchool UniversityofScienceandTechnologyBeijingBeijing100083China ThermalEngineeringDepartment SchoolofMaterials＆MetallurgyNortheasternUniversityShenyang110006China

The skin friction and heat transfer occurring in the laminar boundary layerwhich caused by a vertical liquid jet impinging on a continuously moving horizontal plate werestudied. Similarity solutions for shear stress and heat distribution were obtained by using thehooting technique. The results show that the skin friction decreases with an increase of velocityparameter, the evolving of thermal boundary decrease with increasing in Prandtl number, but increasewith increasing of velocity parameter.

关键词： liquid jet skin friction heat transfer similarity solutions movinghorizontal plate

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Boundary layer flow and heat transfer of a micropolar fluid near the stagnation point on a stretching vertical surface with prescribed skin friction

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International Journal of Minerals,Metallurgy and Materials 2011年第4期18卷 502-507页

作者： Kartini Ahmad Roslinda Nazar Ioan Pop Centre for Foundation Studies International Islamic University Malaysia46350 Petaling JayaSelangorMalaysia School of Mathematical Sciences Faculty of Science and TechnologyUniversiti Kebangsaan Malaysia43600 UKM BangiSelangorMalaysia Faculty of Mathematics University of ClujR-3400 ClujCP 253Romania

The steady laminar mixed convection boundary layer flow and heat transfer of a micropolar fluid near the stagnation point on a stretched vertical surface with prescribed skin friction were considered.The governing partial differential equations were transformed into a system of ordinary differential equations,which were then solved numerically using the shooting method.Results for the stretching velocity,the local Nusselt number,the temperature,and the velocity profiles are presented for various values of the mixed convection parameter λ and material parameter K when the Prandtl number is equal to 1.Both assisting（heated plate） and opposing（cooled plate） flow regions are considered.It is found that dual solutions exist for both assisting and opposing flows.

关键词： boundary layer flow dual solutions micropolar fluids mixed convection skin friction

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Investigation of turbulence and skin friction modification in particle-laden channel flow using lattice Boltzmann method

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Applied Mathematics and Mechanics(English Edition) 2018年第4期39卷 477-488页

作者： Ming PAN Qing xiang Shuai TANG Yuhong DONG Shanghai Institute of Applied Mathematics and Mechanics Shanghai UniversityShanghai 200072China Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai UniversityShanghai 200072China

Interaction between turbulence and particles is investigated in a channel flow. The fluid motion is calculated using direct numerical simulation(DNS) with a lattice Boltzmann(LB) method, and particles are tracked in a Lagrangian framework through the action of force imposed by the fluid. The particle diameter is smaller than the Kolmogorov length scale, and the point force is used to represent the feedback force of particles on the turbulence. The effects of particles on the turbulence and skin friction coefficient are examined with different particle inertias and mass loadings. Inertial particles suppress intensities of the spanwise and wall-normal components of velocity, and the Reynolds shear stress. It is also found that, relative to the reference particle-free flow,the overall mean skin-friction coefficient is reduced by particles. Changes of near wall turbulent structures such as longer and more regular streamwise low-speed streaks and less ejections and sweeps are the manifestation of drag reduction.

关键词： lattice Boltzmann(LB) equation particle channel flow turbulence modulation skin friction

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On skin friction in wall-bounded turbulence

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Acta Mechanica Sinica 2021年第4期37卷 589-598,I0002页

作者： Zhenhua Xia Peng Zhang Xiang I.A.Yang Department of Engineering Mechanics Zhejiang UniversityHangzhou 310027China Mechanical Engineering Pennsylvania State UniversityState CollegePA 16802USA

In this paper,we derive mathematical formulas for the skin friction coefficient in wall-bounded turbulence based on the Reynolds averaged streamwise momentum equation and the total stress.Specifically,with a theoretical or empirical relation of the total stress,the skin friction coefficient is expressed in terms of the mean velocity and the Reynolds shear stress in an arbitrary wall-normal region[h〇,h\].The formulas are validated using direct numerical simulation data of turbulent channel and boundary layer flows,and the results show that our formulas estimate the skin friction coefficient very accurately with an error less than 2%.The present integral formula can be used to determine the skin friction in turbulent channel and boundary layer flows at high Reynolds numbers where the near-wall statistics are very difficult to measure accurately.

关键词： Wall-bounded turbulence skin friction Integral formula

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A FINITE-ELEMENT FORMULATION OF HEATING RATE AND skin friction ON THE BASIS OF CONSERVAION LAWS

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Acta Mechanica Sinica 2000年第2期16卷 128-132页

作者：段占元童秉纲姜贵庆 Graduate School University of Science & Technology of China Beijing China 100039 Beijing Institute of Aerodynamics Beijing China 100074

In the framework of the finite element method (FEM), a prediction method for the heating rate and the skin friction on a body surface is presented by using the energy and momentum conservation equations respectively. ... 详细信息

关键词： conservation equations heating rate skin friction weighted functions

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EFFECT OF skin friction ON THE DIRECTIONAL STABILITY OF DRIVEN PILES DURING DRIVING

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Applied Mathematics and Mechanics(English Edition) 1992年第12期13卷 1143-1148页

作者：沈锡英高大钊 Geotechnical Engineering Department of Tongji University Shanghai

In this paper, the driving forces at a pile top are considered as a periodic load during driving and the Mathieu equation is derived. From the stability charts of this equation, we can obtain the critical length of th... 详细信息

关键词： pile skin friction directional stability Mathieu equation critical length

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Analytical and Observational Investigation of Colors Effects on Drag Reduction in Penguins

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Journal of Bionic Engineering 2022年第4期19卷 1036-1053页

作者： Grace Tenorio Anna Zagrai William Allen Mostafa Hassanalian Department of Mechanical Engineering New Mexico TechSocorroNM87801USA Cottonwood Valley Charter School SocorroNM87801USA Depertment of Biosciences Swansea UniversitySwanseaSA28PPUK

All 18 extant species of penguin are strongly countershaded,having dark dorsal and light ventral coloration.In this paper,the thermal effects of this body color in penguins are investigated through analytical and observational analyses.First,a thermal analysis that takes into account the environmental characteristics of penguins’habitats,fluxes,and morphology is used to analytically calculate penguin dorsal surface temperature.Next,a turbulent analytical solution for a heated boundary layer over a flat plate is applied to show that the dark color on the top of the penguins’bodies is very effective at skin drag reduction.To verify this result,a 2D model penguin is computationally analyzed at different temperatures,confirming in principle underwater skin drag reduction through color-based surface warming with efficiency savings of up to 30%.Finally,to study how color-based increases in body surface temperatures are maintained through foraging dives,thermal cameras are used to measure the surface temperature of captive penguins before and after dives.This study shows conceptually that dark dorsal coloration in penguins could have a significant influence on in-water drag.

关键词： Animal coloration Drag Energy balance Irradiation Penguin Thermal imaging skin friction

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Design of bidirectional frictional behaviour for tactile contact using ellipsoidal asperity micro-textures

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friction 2022年第5期10卷 762-771页

作者： Dmitrii SERGACHEV David MATTHEWS Emile VAN DER HEIDE Laboratory for Surface Technology and Tribology Faculty of Engineering TechnologyUniversity of TwenteOverissel 7522 LIWEnschedethe Netherlands Faculty of Engineering and Architecture Ghent UniversitEast Flanders 9000GhenBelgium

Tactile perception and friction can be modified by producing a deterministic surface topography.Change of surface feature arrangement and texture symmetry can produce an anisotropic frictional behaviour.It is generally achieved through skin hysteresis by promoting its deformation.This work investigates whether a bidirectional friction can be created with microscale ellipsoidal asperity textures,thus relying on the adhesive component of friction.For this purpose,four textured samples with various asperity dimensions were moulded with a silicone rubber having an elastic modulus comparable to that of the skin.Coefficient of friction measurements were conducted in-vivo in two sliding directions with a range of normal loads up to 4 N.Finite element method(FEM)was used to study elastic deformation effects,explain the observed friction difference,and predict surface material influence.Measurements performed perpendicular to the asperity major radii showed consistently higher friction coefficients than that during parallel sliding.For the larger asperity dimensions,a change of the sliding direction increased friction up to a factor of 2.The numerical analysis showed that this effect is mostly related to elastic asperity deflection.Bidirectional friction differences can be further controlled by asperity dimensions,spacing,and material properties.

关键词： surface texture sliding direction skin friction elastomer

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Resistance of the flow over rough surfaces

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Journal of Hydrodynamics 2021年第3期33卷 593-601页

作者： Yu Han Shi-yu Wang Jian Chen Shuqing Yang Liu-chao Qiu Nadeesha Dharmasir College of Water Resources and Civil Engineering China Agricultural UniversityBeijing100083China College of Engineering China Agricultural UniversityBeijing100083China School of Civil Mining and Environmental EngineeringUniversity of WollongongWollongongAustralia

The mechanism of the flow resistance in open channels and pipelines is of vital importance for various critical issues related to the water flow.The Nikurade’s method of calculating the friction factor is not applicable in some cases.It is necessary to consider the influence of the vortex volume surrounding the vegetation and to study the hydrodynamic characteristics of the vegetated channels.This paper analyzes the variation of the vortices created by the surface roughness of different types and different sizes and proposes new definitions of the hydraulic radius and the equivalent roughness height.With consideration of the skin friction and the form drag,on the basis of the force balance equation,a novel calculation method is used for the friction factor,and this method is verified by experimental data.The hydrodynamic mechanism of the flow resistance revealed in this study may serve as a theoretical basis for hydraulic engineers to calculate the friction factor.

关键词： Hydraulic radius skin friction form drag friction factor separation zone dead fluid volume

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