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The viscous strip approach to simplify the calculation of the surface acoustic wave generated streaming

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Applied Mathematics and Mechanics(English Edition) 2024年第4期45卷 711-724页

作者： f.JAZINI DORCHEH M.GHASSEMI fuel Cells and Nano Systems(fCNS)Laboratory Department of Mechanical EngineeringK.N.Toosi University of TechnologyTehran 19697Iran

In recent decades,the importance of surface acoustic waves,as a biocompatible tool to integrate with microfluidics,has been proven in various medical and biological *** numerical modeling of acoustic streaming caused by surface acoustic waves in microchannels requires the effect of viscosity to be considered in the equations which complicates the *** this paper,it is shown that the major contribution of viscosity and the horizontal component of actuation is concentrated in a narrow region alongside the actuation *** the inviscid equations are considerably easier to solve,a division into the viscous and inviscid domains would alleviate the computational load *** particles'traces calculated by this approximation are excellently alongside their counterparts from the completely viscous *** is also shown that the optimum thickness for the viscous strip is about 9-fold the acoustic boundary layer thickness for various flow patterns and amplitudes of actuation.

关键词： surface acoustic wave microfluidics numerical simulation particle tracing acoustic streaming

Monitoring spatiotemporal soil moisture changes in the subsurface of forest sites using electrical resistivity tomography (ERT)

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Journal of forestry Research 2022年第5期33卷 1649-1662页

作者： Julian fäth Julius Kunz Christof Kneisel Institute of Geography and Geology University of WürzburgAm Hubland97074 WürzburgGermany

The effects of drought on tree mortality at forest stands are not completely understood. for assessing their water supply, knowledge of the small-scale distribution of soil moisture as well as its temporal changes is a key issue in an era of climate change. However, traditional methods like taking soil samples or installing data loggers solely collect parameters of a single point or of a small soil volume. Electrical resistivity tomography (ERT) is a suitable method for monitoring soil moisture changes and has rarely been used in forests. This method was applied at two forest sites in Bavaria, Germany to obtain high-resolution data of temporal soil moisture variations. Geoelectrical measurements (2D and 3D) were conducted at both sites over several years (2015-2018/2020) and compared with soil moisture data (matric potential or volumetric water content) for the monitoring plots. The greatest variations in resistivity values that highly correlate with soil moisture data were found in the main rooting zone. Using the ERT data, temporal trends could be tracked in several dimensions, such as the interannual increase in the depth of influence from drought events and their duration, as well as rising resistivity values going along with decreasing soil moisture. The results reveal that resistivity changes are a good proxy for seasonal and interannual soil moisture variations. Therefore, 2D- and 3D-ERT are recommended as comparatively non-laborious methods for small-spatial scale monitoring of soil moisture changes in the main rooting zone and the underlying subsurface of forested sites. Higher spatial and temporal resolution allows a better understanding of the water supply for trees, especially in times of drought.

关键词： Geoelectrical monitoring forest ecology Hydrology Soil water content

Transportation of heat through Cattaneo-Christov heat flux model in non-Newtonian fluid subject to internal resistance of particles

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Applied Mathematics and Mechanics(English Edition) 2020年第8期41卷 1157-1166页

作者： M.I.KHAN f.ALZAHRANI Department of Mathematics Riphah International UniversityFaisalabad 38000Pakistan Nonlinear Analysis and Applied Mathematics(NAAM)-Research Group Department of MathematicsFaculty of SciencesKing Abdulaziz UniversityJeddah 21589Saudi Arabia

Thermal conduction which happens in all phases(liquid,solid,and gas)is the transportation of internal energy through minuscule collisions of particles and movement of electrons within a working *** colliding particles comprise electrons,molecules,and atoms,and transfer disorganized microscopic potential and kinetic energy,mutually known as the internal *** engineering sciences,heat transfer comprises the processes of convection,thermal radiation,and sometimes mass ***,more than one of these procedures may happen in a given *** use the Cattaneo-Christov(CC)heat flux model instead of the fourier law of heat conduction to discuss the behavior of heat transportation.A mathematical model is presented for the Cattaneo-Christov double diffusion(CCDD)in the flow of a non-Newtonian nanofluid(the Jeffrey fluid)towards a stretched *** magnetohydrodynamic(MHD)fluid is *** behaviors of heat and mass transportation rates are discussed with the *** models are based on fourier’s and fick’s *** convective transportation in nanofluids is discussed,subject to thermophoresis and Brownian *** nonlinear governing flow expression is first altered into ordinary differential equations via appropriate transformations,and then numerical solutions are obtained through the built-in-shooting *** impact of sundry flow parameters is discussed on the velocity,the skin friction coefficient,the temperature,and the concentration *** is reported that the velocity of material particles decreases with higher values of the Deborah number and the ratio of the relaxation to retardation time *** temperature distribution enhances when the Brownian motion and thermophoresis parameters *** concentration shows contrasting impact versus the Lewis number and the Brownian motion *** is also noticed that the skin friction coefficient decreases when the ratio of the relaxation to retarda

关键词： Cattaneo-Christov double diffusion(CCDD) non-Newtonian fluid model(Jeffrey model) viscous dissipation magnetohydrodynamic(MHD) Brownian diffusion thermophoresis diffusion

Modeling of unidirectional blood flow in microvessels with effects of shear-induced dispersion and particle migration

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Applied Mathematics and Mechanics(English Edition) 2022年第10期43卷 1585-1600页

作者： G.ROURE f.R.CUNHA Laboratory of Microhydrodynamics and Rheology Department of Mechanical EngineeringUniversity of BrasíliaBrasília70910900Brazil Department of Chemical and Biological Engineering University of Colorado BoulderBoulder803090596USA

A cell-free layer,adjacent to microvessel walls,is present in the blood flow in the microcirculation *** layer is of vital importance for the transport of oxygen-saturated red cells to unsaturated *** this work,we first discuss the physics of formation of this cell-free layer in terms of a balance between the shear-induced dispersion and particle *** this end,we use high-viscosity drops as prototypes for cells,and discuss our results in terms of physical parameters such as the viscosity ratio and the capillary *** also provide a short-time analysis of the transient drift-dispersion equation,which helps us better explain the formation process of the cell-free ***,we present models for investigating the blood flow in two different scales of *** investigating the blood flow in venules and arterioles,we consider a continuous core-flow model,where the core-flow solution is considered to be a Casson fluid,surrounded by a small annular gap of Newtonian plasma,corresponding to the cell-free *** also propose a simple model for smaller vessels,such as capillaries,whose diameters are of a few *** this lower-bound limit,we consider a periodic configuration of aligned,rigid,and axi-symmetric cells,moving in a Newtonian *** this regime,we approximate the fluid flow using the lubrication *** intrinsic viscosity of the blood is theoretically predicted,for both the lower and upper-bound regimes,as a function of the non-dimensional vessel diameter,in good agreement with the previous experimental *** compare our theoretical predictions with the experimental data,and obtain qualitatively good agreement with the well-known fåhræus-Lindqvist effect.A possible application of this work could be in illness diagnosis by evaluating changes in the intrinsic viscosity due to blood abnormalities.

关键词： theory flow dispersion

Exact Time-Dependent Wave functions of a Confined Time-Dependent Harmonic Oscillator with Two Moving Boundaries

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Communications in Theoretical Physics 2009年第11期52卷 820-824页

作者： C.f.Lo Institute of Theoretical Physics and Department of Physics The Chinese University of Hong Kong

By applying the standard analytical techniques of solving partial differential equations, we have obtained the exact solution in terms of the fourier sine series to the time-dependent Schrodinger equation describing a quantum one-dimensional harmonic oscillator of time-dependent frequency confined in an infinite square well with the two walls moving along some parametric trajectories. Based upon the orthonormal basis of quasi-stationary wave functions, the exact propagator of the system has also been analytically derived. Special eases like （i） a confined free particle, （ii） a confined time-independent harmonic oscillator, and （iii） an aging oscillator are examined, and the corresponding time- dependent wave functions are explicitly determined. Besides, the approach has been extended to solve the case of a confined generalized time-dependent harmonic oscillator for some parametric moving boundaries as well.

关键词： infinite square well harmonic oscillator moving boundaries fourier series

Determination and prediction of pavement skid resistance–connecting research and practice

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Journal of Road Engineering 2021年第1期1卷 43-62页

作者： T.f.fwa Department of Civil&Environmental Engineering National University of SingaporeSingapore 117576Singapore

Adequate pavement skid resistance is a key requirement for safe road ***,the measurement and prediction of the skid resistance property of an in-service road pavement,or pavement mixture specimens in the laboratory,is a highly challenging process from both theoretical and practical points of *** more than 60 years,owing to the lack of theoretical solutions to the complex tire-fluid-pavement interaction problem,the practice of pavement skid resistance determination and prediction has essentially been derived from experimental and field observed *** rapid development of efficient numerical computational techniques and high-power computing facilities in the last two decades made it possible for researchers to numerically solve the tire-fluidpavement interaction *** enables the numerical evaluation and prediction of high-speed wet skid resistance,and the determination of the tire-pavement kinetic friction coefficient in the evaluation of low-speed skid *** paper presents a state-of-the-art review of the research development of theoretical mechanistic approaches in the determination and prediction of pavement skid *** covers the following main aspects of the subject matter:(i)mechanisms of skid resistance generation in dry,wetted(i.e.,damp),wet and flooded pavements;(ii)theoretical evaluation of pavement skid resistance in dry,wetted,wet and flooded states;(iii)theoretical approaches in pavement skid resistance prediction;and(iv)concepts of representing the skid resistance state of *** capability of finite element simulation approach for wet skid resistance evaluation with good accuracy is *** highlighted is the practical significance of the Concept of Skid Resistance *** of practical applications of the concept,coupled with the simulation model,are *** include applications in driving safety analysis,road safety design and control,design of paving mixtures,safety mainte

关键词： Skid resistance Tire-fluid-pavement interaction Coefficient of kinetic friction Microtexture Macrotexture Pavement friction management

Predictive fatigue crack growth law of high-strength steels

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Journal of Materials Science & Technology 2022年第5期100卷 46-50页

作者： H.f.Li P.Zhang B.Wang Z.f.Zhang Laboratory of fatigue and fracture for Materials Shi-changxu Innovation Center for Advanced MaterialsChinese Academy of SciencesInstitute of Metal ResearchShenyang 110016China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuang 050043China

The fatigue resistance of metallic materials is generally attributed to both strength and ***,these properties are mutually exclusive in most *** theories like Paris’law only provide some data correlation schemes rather than a predictive capability,which cannot satisfactorily guide the anti-fatigue *** this study,for the first time,the predictive fatigue crack growth rate law is proposed by considering the effects of both strength and ***,a quantitative criterion is established for judging the fatigue crack resistance of high-strength *** predictive law would provide a unique view to the quantitative anti-fatigue design of metallic materials.

关键词： fatigue crack growth Strength and toughness Paris’law High-strength steels

Joint Distribution of Wave Periods and Rate of Change of Wave Surface Elevation

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China Ocean Engineering 1999年第2期14卷 225-229页

作者： Shi, HD Sun, f Ocean Univ Qingdao Dept Civil Engn Qingdao 266003 Peoples R China

The rate of change of wave surface elevation is of much importance in ocean engineering, especially for the determination of the limitation of wave breaking. This paper gives a kind of joint distribution of wave periods and the rate of change of wave surface elevation by means of calculation of the two-order to four-order moment of the frequency spectrum based on the linear wave theory. for the first time, the distribution density function of wave periods determined by peaks is provided, and the conclusion is drawn that the rate of change of wave surface elevation obeys the Rayleigh distribution.

关键词： rate of change wave surface elevation joint distribution wave period

RCD Large Aspect-Ratio Tokamak Equilibrium with Magnetic Islands:a Perturbed Approach

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Communications in Theoretical Physics 2013年第3期59卷 375-378页

作者： f.L.Braga Instituto de física Gleb Wataghin Departamento de Física AplicadaUniversidade Estadual de CampinasCampinasSP13083-859Brasil Instituto federal de Ci encias e Tecnologia do Esp' rito Santo Campus Santa TeresaES29600-000Brasil

Solutions of Grad-Shafranov （CS） equation with Reversed Current Density （RCD） profiles present mag- netic islands when the magnetic flux is explicitly dependent on the poloidal angle. In this work it is shown that a typical cylindrical （large aspect-ratio） RCD equilibrium configuration perturbed by the magnetic field of a circular loop （simulating a divertor） is capable of generate magnetic islands, due to the poloidal symmetry break of the GS equilibrium solution.

关键词： symmetry break magnetic islands Grad-Shafranov equation reversed current density