矩形微通道Knudsen泵中的气体传输特性研究

Knudsen泵是一种基于微尺度条件下的热蠕流效应诱导气体从低温侧向高温侧流动的微型泵。为探究气体种类和分子模型对气体在Knudsen泵通道中传输特性的影响,运用直接模拟蒙特卡罗(DSMC)方法,针对经典的矩形微通道开展了研究。文中分别考虑了三种气体(Ar、N2和O2)和三种分子模型(HS、VHS和VSS)在不同工况压力下的变化情况。研究发现,不同种类气体和分子模型不会引起通道中宏观流场的明显变化。对于分子质量较轻的气体,其具有更强的热蠕流效应,且其最强热蠕流效应所对应的压力越大。对于分子模型,VHS模型的热蠕流效应最强,HS模型的热蠕流效应最弱。因此,相比于更能反映真实气体分子运动规律的VSS模型而言,当采用VHS模型时会高估泵的性能,反之,采用HS模型时会低估泵的性能。

Peristaltic flow in an asymmetric channel with convective boundary conditions and Joule heating

The peristaltic transport of viscous fluid in an asymmetric channel is concentrated. The channel walls exhibit convective boundary conditions. Both cases of hydrodynamic and magnetohydrodynamic(MHD) fluids are considered. Mathematical analysis has been presented in a wave frame of reference. The resulting problems are non-dimensionalized. Long wavelength and low Reynolds number approximations are employed. Joule heating effect on the thermal equation is retained. Analytic solutions for stream function and temperature are constructed. Numerical integration is carried out for pressure rise per wavelength. Effects of influential flow parameters have been pointed out through graphs.

Peristaltic flow with convective mass condition and thermal radiation

The primary objective of present investigation is to introduce the novel aspects of convective mass condition and thermal radiation in the peristaltic transport of fluid. Magnetohydrodynamic(MHD) fluid was considered in a symmetric channel. Heat and mass transfer characteristics were analyzed in the presence of Soret and Dufour effects, and the results were presented via two forms of thermal radiation. The temperature, concentration and pressure rise per wavelength were examined. It is observed that the velocity slip and magnetic field parameters have opposite effects on the pressure rise per wavelength. Temperature of fluid is a decreasing function of the radiation parameter. Further, the temperature of fluid decreases by increasing the heat transfer Biot number. It is notified that the heat transfer rate at the wall is a decreasing function of radiation parameter.

Peristaltic transport of MHD Williamson fluid in an inclined asymmetric channel through porous medium with heat transfer

The intention of this investigation is to study the effects of heat transfer and inclined magnetic field on the peristaltic flow of Williamson fluid in an asymmetric channel through porous medium. The governing two-dimensional equations are simplified under the assumption of long wavelength approximation. The simplified equations are solved for the stream function, temperature, and axial pressure gradient by using a regular perturbation method. The expression for pressure rise is computed numerically. The profiles of velocity, pressure gradient, temperature, heat transfer coefficient and stream function are sketched and interpreted for various embedded parameters and also the behavior of stream function for various wave forms is discussed through graphs. It is observed that the peristaltic velocity increases from porous medium to non-porous medium, the magnetic effects have increasing effect on the temperature, and the size of the trapped bolus decreases with the increasing of magnetic effects while the trend is reversed with the increasing of Darcy number. Moreover, limiting solutions of our problem are in close agreement with the corresponding results of the Newtonian fluid model.

Simultaneous effects of Hall current and thermal deposition in peristaltic transport of Eyring-Powell fluid

Peristaltic flow by a sinusoidal traveling wave in the walls of two-dimensional channel with wall properties is investigated. The channel is filled with incompressible Eyring-Powell fluid. Mathematical modeling is developed through aspects of Hall current, thermal deposition and convection. Long wavelength and low Reynolds number considerations are adopted. Perturbation solutions to the resulting problem for small material parameter of fluid are obtained. Expressions of velocity, temperature, concentration and stream function are derived. Variations of pertinent parameters on the physical quantities of interest are explored in detail. The present analysis is especially important to predict the rheological characteristics in engineering applications by peristalsis.

Effects of heat transfer on the peristaltic MHD flow of a Bingham fluid through a porous medium in a channel

In this paper, we study the effects of heat transfer on the peristaltic magneto- hydrodynamic （MHD） flow of a Bingham fluid through a porous medium in a channel. Long wavelength approximation （that is, the wavelength of the peristaltic wave is large in comparison with the radius of the channel） and low Reynolds number are used to linearize the governing equations. The velocity field for the model of interest is solved by Adomian decomposition method. The expressions for pressure rise, flow rate and frictional force are obtained. The effect of magnetic field, Darcy number, yield stress, amplitude ratio and the temperature on the axial pressure gradient, pumping charac- teristics and frictional force are discussed through graphs.

Convective heat transfer analysis for MHD peristaltic flow in an asymmetric channel

Magnetohydrodynamic peristaltic flow of Jeffery fluid in an asymmetric channel is addressed. The channel walls satisfy the convective conditions. Asymmetry here is con- sidered due to wave trains of different amplitudes and phases. Solutions for the velocity, temperature and pressure gradient are obtained using long wavelength approximation. Plots reflecting the impact of various parameters of interest are shown and examined.

Numerical Study of Mixed Convective Peristaltic Flow through Vertical Tube with Heat Generation for Moderate Reynolds and Wave Numbers

The current study focuses on the numerical investigation of the mixed convective peristaltic mechanism through a vertical tube for non-zero Reynolds and wave number. In the set of constitutional equations, energy equation contains the term representing heat generation parameter. The problem is formulated by dropping the assumption of lubrication theory that turns the model mathematically into a system of the nonlinear partial differential equations. The results of the long wavelength in a creeping flow are deduced from the present analysis. Thus, the current study explores the neglected features of peristaltic heat flow in the mixed convective model by considering moderate values of Reynolds and wave numbers. The finite element based on Galerkin's weighted residual scheme is applied to solve the governing equations. The computed solution is presented in the form of contours of streamlines and isothermal lines, velocity and temperature profiles for variation of different involved parameters. The investigation shows that the strength of circulation for stream function increases by increasing the wave number and Reynolds number. Symmetric isotherms are reported for small values of time-mean flow. Linear behavior of pressure is noticed by vanishing inertial forces while the increase in pressure is observed by amplifying the Reynolds number.

Convective heat and mass transfer analysis on peristaltic flow of Williamson fluid with Hall effects and Joule heating

This paper deals with the peristaltic flow of an incompressible and electrically conducting Williamson fluid in a symmetric planar channel with heat and mass transfer. Hall effects, viscous dissipation and Joule heating are also taken into consideration. Mathematical model is presented by using the long wavelength and low Reynolds number approximations. The differential equations governing the flow are highly nonlinear and thus perturbation solution for small Weissenberg number （0 〈 We 〈 1） is presented. Effects of the heat and mass transfer Biot numbers and Hall parameter on the longitudinal velocity, temperature, concentration and pumping characteristics are studied in detail. Main observations are presented in the concluding section, The streamlines pattern and trapping are also given due attention.

MHD peristaltic flow in an inclined channel with heat and mass transfer

This paper addresses the peristaltic flow of magnetohydrodynamic viscous fluid in an inclined compliant wall channel. Different wave amplitudes and phases ensure asymme- try in the channel flow configuration. Simultaneous effects of heat and mass transfer are also considered. Viscous dissipation effect is present. The flow and heat transfer are investigated under long wavelength and low Reynolds number assumption. The expres- sions for stream function, axial velocity, temperature and concentration are obtained. The solution expressions for physical quantities are sketched and discussed. It is found that Brinkman and Hartman numbers have reverse effect on the temperature.

Peristaltic transport of hydromagnetic Jeffrey fluid with temperature-dependent viscosity and thermal conductivity

In this paper, we investigate the effects of variable viscosity and thermal conductivity on peristaltic flow of Jeffrey fluid in an asymmetric channel. The inclined magnetic field, viscous dissipation and Joule heating are also considered. Wave frame and long wave-length approximations are made to formulate the problem. Pressure gradient, pressure drop per wavelength, velocity and temperature profiles are calculated analytically and discussed graphically. Comparison is made with the previous work for reliability.

Combined effects of rotation and thermal radiation on peristaltic transport of Jeffrey fluid

The objective of this communication is to examine the effect of rotation on the peristaltic motion of non-Newtonian fluid. Constitutive relationship of Jeffrey fluid is employed in the mathematical formulation and related analysis. The thermal radiation and Joule heating effects are also considered. An electrically conducting fluid in a channel with compliant boundaries is taken. Solution expressions are established through assumptions of large wavelength and low Reynolds number. Impact of Taylor and Hartman numbers on the axial velocity is similar in a qualitative sense. There is reverse effect of Taylor number on the secondary velocity when compared with the axial velocity. Temperature and heat transfer coefficients are increasing functions of Taylor number.

Effect of melting heat transfer on peristalsis in the presence of thermal radiation and Joule heating

Mathematical model is developed for peristaltic flow of viscous fluid through a compliant wall channel subject to melting heat transfer. Fluid is incompressible and magnetohy- drodynamic. Analysis has been performed in the presence of Joule heating and thermal radiation. Solutions for small wave number are obtained. Physical quantities of interest are examined for various parameters of interest.

The effect of heat transfer on the nonlinear peristaltic transport of a Jeffrey fluid through a finite vertical porous channel

In this paper we analyze the influence of free convection on nonlinear peristaltic transport of a Jeffrey fluid in a finite vertical porous stratum using the Brinkman model. Heat is generated within the fluid by both viscous and Darcy dissipations. The coupled nonlinear governing equations are solved analytically. The expressions for the temperature, the axial velocity, the local wall shear stress and the pressure gradient are obtained. The effects of various physical parameters such as the Jeffrey parameter λ1, the permeability parameter σ and the heat source/sink parameter β are analyzed through graphs, and the results are discussed in detail. It is observed that the velocity field increases with increasing values of the Jeffrey parameter but it decreases with increasing values of the permeability parameter. It is found that the pressure rise increases with decreasing Jeffrey parameter and increasing permeability parameter. We notice that the effect of the permeability parameter a is the strongest on the bolus trapping phenomenon. For λ1 = 0, N =0, the results of the present study reduce to the results of Tripathi [Math. Comput.Modelling 57 （2013） 1270-1283]. Further the effect of viscous and Darcy dissipations is to reduce the rate of heat transfer in the finite vertical porous channel under peristalsis.