Effect of the blockage ratio on the flow in a channel with a built-in square cylinder

The structures wakes behind a square cylinder in a laminar channel flow is conducted numerically. The Strouhal number, drag and lift coefficients were studied in a periodic flow for different blockage ratios =1/4, 1/6 and 1/8 at Reynolds number ranging from 62 to 300. The governing equations are solved by using control volume finite element method (CVFEM) adapted to the staggered grid. The SIMPLER algorithm is used for the velocity-pressure coupling. The critical Reynolds numbers corresponding to the onset of vortex shedding and its change from simple periodic to complex periodic motion are established. A discussion about the effect of the blockage ratio on the Strouhal number, the time-averaged drag coefficient and the amplitude of the lift coefficient is also presented.     

Numerical investigation on deposition of solid particles in a lid-driven square cavity with inner heated obstacles

The deposition of aerosol particles in laminar mixed-convection flow in a lid-driven cavity with two heated obstacles is investigated numerically by an Eulerian–Lagrangian method. Lagrangian particle transport calculations are carried out to track 2000 particles that initially exerted with random distribution in flow regime and also assumed that the effect of particles on the fluid is neglected. All the affecting forces on particle equation of motion, such as Brownian, thermophoresis, drag, lift and gravity are considered. The main goal is to study the effective parameter on deposition of particles such as free convection, distance and size variation of obstacles. Numerical results showed that free convection is an effective parameter that affected the deposition. As a main result, it is observed that deposition decreases with increasing in the Richardson number. Results showed that by increasing obstacles distance, deposition increases. Finally, it is revealed that the size of obstacles has a great effect on particle deposition, such that by increasing the obstacles size, the deposition increases.     

Thermophoretic deposition of particles from a boundary layer flow onto a continuously moving wavy surface

Summary A theoretical model for the coupled transport mechanisms of diffusion, convection and thermophoresis was developed to describe the particle deposition onto a continuously moving wavy surface. The numerical results reveal that the mean deposition effect of the wavy plate is greater than of a flat plate and more significant with the wavy amplitude increasing, and that the increasing rate is nearly equal to the value obtained by dividing the additional surface area of the wavy plate compared to the flat plate by 2.4 times the flat plate area.     

两并列方柱绕流相互干扰的数值研究

为了研究并列双方柱在不同间距比时气动力特性的干扰效应,采用刚性模型测压风洞试验的方法,通过改变两方柱之间的距离,得到了不同间距比下并列双方柱的风压系数、升力系数和阻力系数。结果表明：当间距比1.2≤L/D<2.5时,并列双方柱平均风压系数的干扰效应明显,且主要表现在内侧面,平均阻力系数和脉动升力系数的干扰效应表现为减小效应;当间距比L/D≥2.5时,并列双方柱的平均风压系数、平均阻力系数和脉动升力系数的干扰效应均不明显。     

Nonsteady flow of a vapor-drop flow in a heated channel

Flow of a vapor-drop mixture in a heated channel is studied under steady and non-steady conditions using a model which considers direct thermal interaction of drops with the heating surface.Translated from Inzhen-erno-Fizicheskii Zhurnal, Vol. 61, No. 6, pp. 939–946, December, 1991.     

Thermodiffusiophoretic capture of aerosol particles in a plane channel with nonuniform temperature

The article theoretically studies the process of capturing aerosol particles from a laminar stream of a binary gas mixture inhomogeneous in temperature and concentration passing through a plane channel with nonuniform temperature.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 1, pp. 47–54, July, 1981.     

Hydraulic resistance for liquid flow with boiling-up in a partially heated channel

An approximate analytic solution is obtained to the problem of calculating the hydraulic resistance. The hydraulic characteristics are analyzed and the region for static instability is determined.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 5, pp. 842–847, November, 1980.     

Calculation of developed laminar gas flow in a plane-parallel channel

A method is given for solving the Prandtl equations for adiabatic gas flow in a plane-parallel channel at Pr=1. The method is based on reduction of the Prandtl equations to an approximate system of ordinary quasilinear, first-order differential equations and can be used to solve more complicated problems.     

Similarity flow in interaction of a shock wave with an inclined heated channel

A study is made of gasdynamic flow that initiates when a shock wave propagates along a thin heated channel. Analytical conditions of the onset of an unsteady flow precursor are obtained. The flow similarity is proved experimentally; precursor characteristics vs shock wave and heated channel parameters are analyzed.Institute of Geosphere Dynamics, Russian Academy of Sciences, Moscow. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 54, No. 5, pp. 543–547, May, 1993.     

Percolation in networks of aligned SWNTs formed with laminar flow deposition

Macroscopic networks of highly aligned SWNTs have been fabricated at room temperature by laminar flow deposition from aqueous suspensions. This deposition method allows the growth of a macroscopic two dimensional SWNT network through successive deposition cycles. AFM image analysis showed that each deposition cycle puts down a reproducible density of SWNTs, with the final density being directly proportional to the number of deposition cycles for a given solution. The macroscopic electronic behavior of these networks was characterized by DC conductance measurements taken after each deposition cycle. This showed that these networks could be described by two dimensional percolation models throughout the growth process.     

Heat transfer on a flat plate immersed in a laminar flow of a heated liquid

The case of one-sided heat transfer to a flat plate immersed in a flow of heated liquid is examined. Equations are obtained for the liquid temperature distribution in the boundary layer, and for the heat flux from the liquid to the wall.     

Piston-driven laminar flow and heat transfer in a plane channel with a sudden expansion

 This paper presents a numerical study of piston-driven heat transfer and fluid flow in a plane channel containing a sudden expansion. The numerical method employed is based on a control-volume-based finite element method for incompressible flow with a staggered and moving grid and SIMPLER algorithm for pressure-velocity coupling. The numerical results show a good agreement with the experimental data reported in the literature. Results concerning time and space evolution of the thermal and flow fields are presented for different values of the expansion ratio, the initial clearance volume, and the piston velocity. Received: 20 April 2002 / Accepted: 23 January 2003     

Subcritical region of laminar adiabatic gas flow in a two-dimensional channel

It is shown that so-called developed laminar gas flow in a two-dimensional channel cannot continue beyond values of 0.74. At > > 0.74 the flow is accompanied by considerable deformation of the velocity profiles in the direction of greater fullness, while the resistance coefficient increases.     

The coagulation of aerosol particles in turbulent flow

A statistical model is given for determining the kernel of coagulation in the presence of turbulent, Brownian, gradient, and gravitational mechanisms of collisions in view of accumulation effect.     

Critical size of aerosol particles in physical and chemical deposition

Problems related to the critical size of aerosol particles, when the vapor condensation coefficient depends on the particle size, the influence of electromagnetic fields, as well as on the presence of adsorbable foreign gases in the system, are studied theoretically. The problem of the critical size of particles in chemical deposition is discussed.     

Numerical investigation of laminar separated flow through a channel with symmetric double expansion

Summary Two-dimensional Navier-Stokes equations have been solved numerically by a finite difference technique on a staggered grid for investigating the laminar flow of an incompressible viscous fluid through a channel with symmetric double expansion. A coordinate transformation has been employed to map the infinite irregular domain into a finite regular computational domain. At higher Reynolds numbers the flow becomes time-dependent and asymmetric. Such unsteadiness and asymmetry remains in the flow even up to turbulent flow conditions. The Pressure-Poisson equation has been solved and a pressure-velocity correction scheme has been invoked. Depending on the geometry and Reynolds number, secondary separation has been observed.     

Particle deposition on channel walls in a turbulent flow

The process of admixture deposition from a turbulent flow for different values of the particle reflection coefficient from the wall is analyzed. A generalizing formula is proposed for the computation of the deposition rate on a completely absorbing surface in a broad range of variation of the particle inertia.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 59, No. 5, pp. 735–742, November, 1990.