Testing of a Multiblock Algorithm of Calculation of Nonstationary Laminar Separating Flows

Based on a comparative analysis of results of numerical and physical modeling of nonstationary laminar separating flows of an incompressible fluid, a factorized calculational algorithm on the basis of multiblock intersecting grids is verified.     

Calculation of the Pressure Pulsations in an Expansion Joint of a Pipeline Through which a Liquid is Passed

Journal of Engineering Physics and Thermophysics - The pressure pulsations in a working liquid flowing through an expansion joint of a pipeline in a power installation were calculated. The...     

Relaxation Phenomena in Nonstationary Evaporation of Liquid

Based on the phenomenological theory — the thermodynamics of irreversible processes — an analysis of a nonstationary process of liquid evaporation is carried out. It is shown that a sharp change in the heatflux magnitude causes the occurrence of processes of oscillating relaxation of vapor generation in the system.     

直角管道支化聚合物流动的数值模拟及粘弹分析

选取基于Doi-Edwards模型发展起来的XPP模型作为本构方程,采用耦合稳定化技术的同位网格有限体积法模拟了直角管道流以及嵌件直角管道流。给出了直角管道流和嵌件直角管道流中表征聚合物宏观信息量的等值线图,分析了流变参数以及嵌件对管道截面上表征聚合物宏观信息量的影响。数值结果表明,XPP模型能够合理描述聚合物溶液浓厚体系的粘弹效应,其模型中流变参数的变化能够预测聚合物溶液拉伸属性及法向应力差的基本特征。同时,流道中嵌件的放置将使得聚合物宏观属性的变化趋势在嵌件附近发生质的变化。     

Inertial Waves and Steady Flows in a Liquid Filled Librating Cylinder

The fluid flow in a non-uniformly rotating (librating) cylinder about a horizontal axis is experimentally studied. In the absence of librations the fluid performs a solid-body rotation together with the cavity. Librations lead to the appearance of steady zonal flow in the whole cylinder and the intensive steady toroidal flows near the cavity corners. If the frequency of librations is twice lower than the mean rotation rate the inertial waves are excited. The oscillating motion associated with the propagation of inertial wave in the fluid bulk leads to the appearance of an additional steady flow in the Stokes boundary layers on the cavity side wall. In this case the heavy particles of the visualizer are assembled on the side wall into ring structures. The patterns are determined by the structure of steady flow, which in turn depends on the number of reflections of inertial wave beams from the cavity side wall. For some frequencies, inertial waves experience spatial resonance, resulting in inertial modes, which are eigenmodes of the cavity geometry. The resonance of the inertial modes modifies the steady flow structure close to the boundary layer that is manifested in the direct rebuilding of patterns. It is shown that the intensity of zonal flow, as well as the intensity of steady flows excited by inertial waves, is proportional to the square of the amplitude of librations.     

Nonstationary Nonlinear Phenomena on the Charged Surface of Liquid Hydrogen

Investigations of nonlinear phenomena on the charged surface of liquid hydrogen are reviewed. It is demonstrated that excitation of the surface by a low frequency AC electric field results in the formation of capillary waves in the high-frequency domain, and that the latter exhibit turbulence. The quasi-adiabatic decay of this capillary turbulence has been studied both experimentally and theoretically. It is shown that the processes of formation and decay of the turbulence are both controlled by the same relaxation mechanisms. For spectrally narrow pumping, the application of an additional low-frequency driving force causes a decrease of wave amplitude in the high-frequency domain of the turbulent spectrum and correspondingly decreases the width of the inertial range of energy transfer.      

Analysis of Nonstationary Incompressible Flows in Differently Shaped Channels on the Basis of Symmetries

Nonstationary flows in laminar and turbulent regimes in differently shaped channels have been investigated theoretically. An approach has been used which is based on the properties of the symmetry of differential equations (Lie groups) that describe the process of an accelerated channel flow. A way in which the self-similar forms of one-dimensional and two-dimensional flow can be obtained on the basis of symmetries is shown. The self-similar equations of the process and their analytical and numerical solutions are given.     

Modeling of Nonstationary Flow in the Ramjet Channel with a Distributed Pulse-Periodic Energy Supply

A study has been made of the influence of a pulse-periodic supply of energy that is equal to the energy released in combustion of hydrogen in air on the structure of supersonic flow in a channel of variable cross section, which models the ramjet duct. The flow has been modeled based on two-dimensional nonstationary gas-dynamics equations. Different regimes of flow depending on the configuration of the zones of energy supply and the excess-air coefficient have been obtained. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 4, pp. 152–157, July–August, 2005.     

Flow Rate Limitation of Steady Convective Dominated Open Capillary Channel Flows Through a Groove

An open capillary channel is a structure that establishes a liquid flow path when the capillary pressure caused by surface tension forces dominates in comparison to the hydrostatic pressure induced by gravitational or residual accelerations. To maintain a steady flow through the channel the capillary pressure of the free surface has to balance the pressure difference between the liquid and the surrounding constant pressure gas phase. Due to convective and viscous momentum transport the pressure along the flow path of the liquid decreases and causes the free surface to bend inwards. The maximum flow rate through the channel is reached when the free surface collapses and gas ingestion occurs near the outlet. This stability limit depends on the geometry of the channel and the properties of the liquid. In this paper we present an experimental setup which is used in the low-gravity environment of the Bremen Drop Tower. Experiments with convective dominated systems have been performed where the flow rate was increased up to the maximum value. In comparison to this we present a one-dimensional theoretical model to determine important characteristics of the flow, such as the free surface shape and the limiting flow rate. Furthermore we present an explanation for the mechanism of flow rate limitation for these flow conditions which is similar to the choking problem for compressible gas flows.     

Modeling of the Nonstationary Process of Conversion of Methane to Hydrogen in a Filtration-Combustion Wave

Experimental data on incomplete oxidation of methane in air are analyzed for the stoichiometric relation = 4 using a numerical model; the data are obtained with different charges and for different flow rates of feed of a mixture. In order to explain the experimental data, it is proposed that a heterogeneous reaction that ensures the beginning of the processes of oxidation of methane at lower temperatures be introduced into the chemical model.     

Simulation of Non-Isothermal Turbulent Flows Through Circular Rings of Steel

This article is intended to examine the fluid flow patterns and heat transfer in a rectangular channel embedded with three semi-circular cylinders comprised of steel at the boundaries. Such an organization is used to generate the heat exchangers with tube and shell because of the production of more turbulence due to zigzag path which is in favor of rapid heat transformation. Because of little maintenance, the heat exchanger of such type is extensively used. Here, we generate simulation of flow and heat transfer using non-isothermal flow interface in the Comsol multiphysics 5.4 which executes the Reynolds averaged Navier stokes equation (RANS) model of the turbulent flow together with heat equation. Simulation is tested with Prandtl number (Pr = 0.7) with inlet velocity magnitude in the range from 1 to 2 m/sec which generates the Reynolds number in the range of 2.2 × 10⁵ to 4.4 × 10⁵ with turbulence kinetic energy and the dissipation rate in ranges (3.75 × 10⁻³ to 1.5 × 10⁻²) and (3.73 × 10⁻³−3 × 10⁻²) respectively. Two correlations available in the literature are used in order to check validity. The results are displayed through streamlines, surface plots, contour plots, isothermal lines, and graphs. It is concluded that by retaining such an arrangement a quick distribution of the temperature over the domain can be seen and also the velocity magnitude is increasing from 333.15% to a maximum of 514%. The temperature at the middle shows the consistency in value but declines immediately at the end. This process becomes faster with the decrease in inlet velocity magnitude.     

Vortex Flows in the Liquid Layer and Droplets on a Vibrating Flexible Plate

In certain conditions, in the layers and droplets of a liquid on a vibrating rectangular flexible plate, vortex flows are formed simultaneously with the excitation of capillary oscillations on the free surface of the liquid layers and droplets. Capillary oscillations in the form of two-dimensional standing waves form Faraday ripples on the free surface of the liquid layer. On the surface of the vibrating droplets, at the excitation of capillary oscillations a light spot reflected from a spotlight source moves along a trajectory in the form of a Lissajous figure observed with a microscope. When vortex flows visualized with graphite microparticles appear in the layer and droplets of a transparent liquid, the trajectory of the light spot on the layer and droplet surface is a two-dimensional trajectory in the form of an ellipse or a saddle. This indicates that the generation of the vortex flows in a liquid at vibrations is due to capillary oscillations in the orthogonally related directions. In the liquid layer and droplets on the surface of the flexible plate, the vibrations of which are generated by bending vibrations, the vortex flows appear due to the plate vibrations and the capillary oscillations of the surface of a layer or a droplet of the liquid. On the free surface of the liquid, the capillary waves, which are parametrically excited by the plate bending vibrations, are additionally modulated by the same bending vibrations in the transverse direction.     

Pipeline Corrosion,Modeling and Analysis

Degradation of pipelines is the result of the continuous attack by the environment of these conduits like climate change (temperature, rate moisture in the ground, etc.…) that may lead to a corrosive environment. The design and the maintenance of these conduits and pipelines is a challenge for oil industry seen the serious consequences which can occur because of several reasons, example: defects of the cracks types, rust…, etc. Which can cause escapes of the transported matter or ruptures of these conduits with all that involves like economic loss and pollution of the environment.     

Numerical Solutions for Unsteady Flows of a Magnetohydrodynamic Jeffrey Fluid Between Parallel Plates Through a Porous Medium

In the present article, the numerical solutions for three fundamental unsteady flows (namely Couette, Poiseuille, and generalized Couette flows) of an incompressible magnetohydrodynamic Jeffrey fluid between two parallel plates through a porous medium are presented using differential quadrature method. The equations governing the flow of Jeffrey fluid are modeled in Cartesian coordinate system. The resulting non-dimensional differential equations are approximated by using a new scheme that is trigonometric B-spline differential quadrature method. The scheme is based on the differential quadrature method in which the weighting coefficients are obtained by using trigonometric B-splines as a set of basis functions. This scheme reduces the equation into the system of first-order ordinary differential equation which is solved by adopting strong stability-preserving time-stepping Runge–Kutta scheme. The effects of the sundry parameters of interest on the velocity profiles are studied and the results are presented through graphs. It is observed that, the velocity increases from the horizontal channel to vertical channel. The velocity is a decreasing function of magnetic parameter. With an increase in time, the velocity increases.     

Numerical Investigation of the Wave Flows of Liquid Films Interacting with a Gas Flow

Journal of Engineering Physics and Thermophysics - The nonlinear partial differential equation, defining the state of the free surface of a viscous liquid layer (film) interacting with a backward...     

Development of Crisis Phenomena in Falling Wavy Liquid Films at Nonstationary Heat Release

This paper deals with investigation results on crisis phenomena for nonstationary heat release in falling liquid films. According to the experimental results, in the studied range of irrigation degree alteration (Re _in = 60–1,690), parameters, characterizing decay of the falling liquid film with stepped heat release (distribution of time of boiling incipience along the liquid film, velocities of movable boundaries in the boiling-up and drying fronts), depend complexly on the Reynolds number, wave characteristics and heat flux density. The time of boiling incipience at stepwise heat release was simulated numerically with consideration of intensive evaporation development from the free surface of a laminar-wave film, transportation of large wave crests at typical process times and influence of the convective component of heat transfer. It is shown that the convective component of heat transfer in the wave liquid films and film thinning because of intensive evaporation provide a significant increase in the time of boiling incipience for the given heat fluxes under the conditions of nonstationary heat release. It is also revealed that for low densities of the heat flux at decay of a laminar-wave liquid film occurs with formation of metastable regular structures with liquid rivulets and large-scale dry zones between them. When loading thermal impulses of high intensity, film decay is determined by dynamic characteristics of propagation of the self-maintained front of liquid boiling-up and the shape of structures, formed during its development.