Turbulent regime of thermogravitational convection in a closed cavity

We have performed a numerical analysis of the nonstationary turbulent natural convection in a closed region with heat-conducting walls of finite thickness and a heat source located at the cavity base under the conditions of convective-radiative heat exchange with the environment. Typical distributions of the thermohydrodynamic parameters (streamlines, temperature field, field of the kinetic energy of turbulence, and dissipation field of the kinetic energy of turbulence) in a fairly wide range of Grashof numbers 10⁷ ≤ Gr ≤ 10⁹ have been obtained. Results characterizing the scales of influence of the nonstationarity factor and the relative heat conductivity coefficient of the material of the surrounding walls on the heat transfer intensity are presented. A correlation for determining the average Nusselt number on the heat source surface has been established.     

Investigation of thermocapillary convection in a two-layer fluid

We examine the problem of thermocapillary motion in a system of two immiscible fluids with a linear temperature distribution at the bottom. To a first approximation in small Marangoni number we obtain a solution for velocity, temperature, and pressure in each layer.Translated from Inzhenerno-fizicheskii Zhurnal, Vol. 61, No. 5, pp. 732–740, November, 1991.     

Natural convection between coaxial vertical cylinders partially filled with a porous material

This paper presents laminar fully developed free convection flow between two coaxial vertical cylinders partially filled with a porous matrix when the cylinders are kept at different temperatures. The Brinkman-extended Darcy model is used to simulate momentum transfer in the porous region. The two regions are coupled by equating the velocity and by considering shear stress jump condition at the interface. The effect of Darcy number on the velocity throughout porous domain and adjustable coefficient in the stress jump condition at the interface is shown graphically. It is observed that velocity is influenced by the shear stress jump condition at the interface.     

Ring source potentials in a fluid with an inertial surface in the presence of surface tension

The velocity potential due to the presence of a horizontal circular ring of wave sources of time-dependent strength in a fluid of finite constant depth with an inertial surface composed of uniformly distributed floating particles is obtained when the effect of surface tension at the inertial surface is included.     

Oscillatory regimes of convection in a two-layer system

The complete nonlinear equations are used to study the oscillatory convective motions arising in a system of two liquids with an interface.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 46, No. 5, pp. 845–849, May, 1984.     

Approximate analysis of the steady-state temperature field of a parallelepiped with a local energy source

There is an approximate analysis of the steady-state temperature field of a parallelepiped on one of whose faces there is a local energy source. A practical calculation scheme is proposed, and its accuracy is evaluated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 28, No. 4, pp. 685–693, April, 1975.     

Oscillatory Marangoni convection in a conducting fluid layer with a deformable free surface in the presence of a vertical magnetic field

Summary. Linear stability theory is applied to the problem of the onset of oscillatory Marangoni convection in a horizontal layer of electrically conducting fluid heated from below in the presence of a vertical magnetic field. The fluid layer is bounded from below by a rigid boundary and from above by a deformable free surface. The critical Marangoni number M _c, the critical wavenumber a _c and the critical frequency _c are obtained for wide ranges of the Prandtl number #E5/E5#₁, the magnetic Prandtl number #E5/E5#₂, the crispation number C _r and the Chandrasekhar number Q. We present numerically a necessary and sufficient condition for oscillatory Marangoni convection to occur.     

Stability of thermocapillary convection and regimes of a fluid flow acted upon by a standing surface wave

It has been established that, in the case where a standing surface wave acts on a thermocapillary-convection flow in a cylindrical volume, there arises an oscillating-convection zone between the laminar and turbulent regimes of flow. It is shown that the boundary between these regimes is determined by the amplitude δ and the number of periods n of the standing wave and is practically independent of the Marangoni number and the oscillation frequency of this wave. At n = 2, in the range 0.004 < δ < 0.006, the parameters of the fluid cease to oscillate. The mechanisms by which the thermocapillary convection in closed volumes loses its stability are discussed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 5, pp. 108–115, September–October, 2007.     

Interaction between a cylindrical shell in a fluid and a pulsating bubble

The dynamic behavior of a cylindrical fluid-immersed shell in a pressure wave initiated by a pulsating vapor-gas bubble that develops as a result of the action of laser radiation on the absorbing medium (metal) is examined experimentally and theoretically. The results of the experiments suggest that the amplitude of the shock wave that develops as a result of complete or partial vaporization of the absorbing medium is appreciably smaller than the amplitude of the waves due to pulsations of the bubble that is formed. Experimental data on the pattern of structural deformation are confirmed by calculations. The effect of load simulation on the behavior of the shell is established according to computational data.Translated from Problemy Prochnosti, No. 6, pp. 116–120, June, 1990.     

Numerical solution of a micropolar fluid flow between two rotating coaxial disks

Summary Steady flow of a micropolar fluid between two rotating disks of infinite radius rotating at different/same speeds has been investigated. The lower and upper disks rotate with angular velocities and S respectively. By using similarity transformation method, the equations of motion are reduced to a set of ordinary non-linear coupled differential equations. The resulting non-linear equations are linearized by quasilinearization technique and integrated with the help of fourth order Runge-Kutta method via orthonormalization. Effects of micropolarity parameters on velocity components for different values of Reynolds numbers Re (200, 1000 etc.) andS (–1.0, 0.0, 0.5, 1.0) have been studied. Multiplicity of the solutions have been obtained for different values ofS and micropolar parameters at Re=1000. It is found that only one of the four micropolar parameters (₁) influences translation velocity components significantly. At high Re, flows similar to flows observed by Batchelor Stewartson and Holodniok etc., have been obtained. A new type of multiple solution has been obtained forS=1.0 which needs further investigation.     

Thermoelastic delamination of bodies in the presence of a heat-conducting filler of the intercontact gap

We propose a method for the solution of a system of nonlinear singular integrodifferential equations of the contact thermoelastic problem of delamination of half spaces in the presence of a heat-conducting filler in the gap formed between the half spaces. The effect of heat conduction in the medium filling the gap on the contact parameters of the analyzed structure is investigated. It is shown that the solution of the posed problem can be not unique for some values of the thermal load and the heat-conduction coefficient of the filler.     

Numerical and asymptotic solutions for the peristaltic transport of a heat-conducting fluid

Summary In this paper numerical and asymptotic results are obtained for the solution of the Oberbeck-Boussinesq (O-B) equations in a two-dimensional channel as a mathematical model for the peristaltic transport of a heat-conducting fluid in a flexible tube. Our results show the following: 1) The asymptotic solution based upon the long wave approximation agrees well with the corresponding exact solution when the Reynolds number is large. 2) The temperature term in the O-B equations affects the solution significantly and can cause trapping when the volume expansion coefficient increases. 3) The streamline contour map is very sensitive to mass flux change. 4) The temperature contour map is insensitive to Reynolds number change. 5) The relation between mass flux and pressure drop is almost linear.     

Investigation of a power divider using a coaxial probe array in a coaxial waveguide

A novel coaxial-waveguide power divider using coaxial probe array that achieved low-loss probe-to-waveguide transitions is presented. The small reflection theory of transverse electomagnetic (TEM) lines is extended to synthesise the gradual waveguide taper, and the equivalent-circuit approach is applied to analyse the coaxial probe array. The design and simulation of a single probe-to-waveguide transition have been developed. The detailed design, simulation, fabrication and measurements of a four-way coaxial power divider are discussed. The measured results agree well with the simulated results. The measured 15 dB return loss bandwidth of this waveguide power divider is demonstrated to be 8.2 GHz (fL = 7.8 GHz, fH = 16 GHz) and its 0.5 dB insertion loss bandwidth 11 GHz.     

Stability of a cylindrical shell with local weaknesses

It is shown that the Bubnov-Galerkin method can be used to determine the stability of a shell having discontinuous parameters if the approximating expressions for the deflection are based on a system of generalized functions. In that method, the stability is determined by deriving the eigenvalues for the determinant of a homogeneous equation system containing the fundamental functions. The case is considered of a circular cylindrical shell weakened by one circular hole, for which analytic expressions are derived for the critical stabilityloss force. The calculated and observed values agree well.Translated from Problemy Prochnosti, No. 12, pp. 57–60, December 1991.     

Numerical investigation of free convection from an instantaneous heat source in viscous fluid

A formulation is given, as well as results of the numerical solution, of the self-consistent problem of free convection from an instantaneous heat source in a viscous incompressible fluid.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 33, No. 4, pp. 700–704, October, 1977.     

Thermal convection in the presence of a vertical magnetic field

Summary The interaction between thermal convection and an external uniform magnetic field in the vertical is numerically simulated within a computational domain of a horizontally periodic convective box between upper and lower rigid plates. The numerical technique is based on a spectral element method developed earlier to simulate natural thermal convection. In this work, it is extended to a magnetoconvection problem. Its main features are the use of rescaled Legendre-Lagrangian polynomial interpolants in expanding the flow variables except the pressure for which a modal expansion in terms of lower order polynomials is used to avoid the complicated staggered grid approach. The technique is validated in the steady roll and oscillatory convective regimes where various experimental and numerical results are available in the literature. The effect of a vertical magnetic field in such a way to inhibit the convective motions has been demonstrated.     

Natural convection flow of a non-Newtonian fluid between two vertical flat plates

Summary The natural convection of a homogeneous incompressible fluid of grade three is investigated between two infinite parallel vertical plates. The effect of the non-Newtonian nature of fluid on the skin friction and heat transfer are studied.With 2 Figures     

Natural convection flow of a non-Newtonian fluid between two concentric vertical cylinders

Summary The natural convection of a homogeneous incompressible fluid of grade three between two infinite concentric vertical cylinders is studied. We consider the effect of the non-Newtonian nature of the fluid on the skin friction and heat transfer. Some numerical experimentation is presented to show the effect on the velocity and temperature profiles as the dimensionless parameters are varied.