共查询到20条相似文献,搜索用时 15 毫秒
1.
Unsteady convection driven by periodic horizontal displacements of a rectangular cavity heated from below is investigated numerically. The resonance effects clearly manifest themselves in the frequency dependence of the induced convection flow. These effects appear at a sufficient temperature difference (Grashof number G>104) and a considerable amplitude of the horizontal displacements of the cavity. The dependence of the parameters (resonance frequency and amplitude under resonance conditions) on the problem parameters (Grashof and Prandtl numbers and the cavity length/height ratio) and the method are found. Estimates show that the effects in question can be detected under laboratory conditions. 相似文献
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The plane problem of steady-state small oscillations of a horizontal cylinder located at the interface between two fluids of different densities and indefinite depth is considered in the linear formulation. Boundary integral equations for the surface source distribution are derived. The behavior of the distributed singularities at points of intersection of the body contour and the interface is investigated. The problem of oscillations of a circular cylinder is solved by the multipole expansion method. The apparent mass and damping coefficients of the radiation problem and the reflection coefficient of the problem of scattering of an impinging wave by a floating body are calculated. 相似文献
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On the basis of the method of matched asymptotic expansions, the problem of the outflow of a nonswirling axisymmetric laminar jet from a hole in a plane is solved for large Reynolds numbers. Since directly matching the leading terms of the asymptotic expansions for the axial boundary layer and the main flow region is impossible, the problem is solved by introducing an intermediate region. In the axial region the solution is the Schlichting solution [1] for an axisymmetric jet in the boundary-layer approximation, in the intermediate region the solution is found analytically, and in the main flow region the problem is reduced to that of viscous flow induced by a sink line in the presence of a transverse wall [2]. 相似文献
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G. L. Komissarova 《International Applied Mechanics》2002,38(1):103-112
The properties of normal axisymmetric waves propagating through a perfect compressible fluid contained in an elastic thin-walled cylinder are investigated. The problem is solved using the complete system of equations of the dynamic theory of elasticity. The effects of interaction between elastic and fluid waves are studied within a wide frequency range. The numerical results are classified on the basis of data on the properties of partial subsystems. Partial subsystems are those for which the interaction effects are insignificant. For special cases of compound waveguides, the dispersion spectra are constructed and the kinematic and energy characteristics of normal waves are analyzed. Particular attention is given to the lowest normal wave, which has specific properties and participates in the elastic–liquid interaction over a wide frequency range. 相似文献
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Alexandre Lavrov 《Transport in Porous Media》2014,105(3):559-570
Fluid flow in a single rough-walled rock fracture has been extensively studied over the last three decades. All but few of these studies, however, have been done with Newtonian fluids and unidirectional flow in rectangular fractures. Notwithstanding the importance of such setups for theoretical understanding of fundamental issues in fracture flow, practical applications in drilling and petroleum engineering often involve radial flow of a non-Newtonian fluid. An example is a borehole intersecting a natural fracture during drilling in a fractured rock. In this study, steady-state incompressible radial flow from a circular well into a self-affine rough-walled fracture was simulated numerically using the lubrication theory approximation. The fluid rheology was power law. The flow behavior index was equal to 0.6, 0.8, 1.0 (Newtonian), 1.2, or 1.4. Asperities diverted the flow from an axisymmetric radial pattern that would be observed in a smooth-walled fracture. The extent of the deviation from radial flow was found to increase as the fluid became more shear-thickening. To reveal finer details of the flow, a tracer was introduced at the borehole wall and was transported by the flow. The front of the tracer propagating into the fracture was found to become slightly smoother with a more shear-thickening fluid. In the vicinity of contacts between fracture faces a more shear-thickening fluid could deliver the tracer closer to the contact spots. 相似文献
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Laminar, single-phase, finite-volume solutions to the Navier–Stokes equations of fluid flow through a fracture within permeable
media have been obtained. The fracture geometry was acquired from computed tomography scans of a fracture in Berea sandstone,
capturing the small-scale roughness of these natural fluid conduits. First, the roughness of the two-dimensional fracture
profiles was analyzed and shown to be similar to Brownian fractal structures. The permeability and tortuosity of each fracture
profile was determined from simulations of fluid flow through these geometries with impermeable fracture walls. A surrounding
permeable medium, assumed to obey Darcy’s Law with permeabilities from 0.2 to 2,000 millidarcies, was then included in the
analysis. A series of simulations for flows in fractured permeable rocks was performed, and the results were used to develop
a relationship between the flow rate and pressure loss for fractures in porous rocks. The resulting friction-factor, which
accounts for the fracture geometric properties, is similar to the cubic law; it has the potential to be of use in discrete
fracture reservoir-scale simulations of fluid flow through highly fractured geologic formations with appreciable matrix permeability.
The observed fluid flow from the surrounding permeable medium to the fracture was significant when the resistance within the
fracture and the medium were of the same order. An increase in the volumetric flow rate within the fracture profile increased
by more than 5% was observed for flows within high permeability-fractured porous media. 相似文献
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The solutions of initial and boundary value problems of the outflow of an ideal (inviscid and non-heat-conducting) gas from cylindrical and spherical sources into a vacuum are obtained. Time is measured from the moment, when the source is turned on; at this moment the source is surrounded by a vacuum. The entropy, flow rate, and the Mach number of the gas outflowing from the source are given, together with the source radius; the Mach number can be greater of or equal to unity. If the source radius is greater than zero, then the flow domain in the “radial coordinate–time” plane consists of the stationary source flow and adjoining non-self-similar centered expansion wave consisting of C?-characteristics. The stationary flow is described by the known formulas, while the expansion wave is calculated by the method of characteristics. The calculations by this method confirm the earlier obtained laws for large values of the radial coordinate. The interface between the vacuum and the expansion wave is the straight trajectory of particles and, at the same time, a unique rectilinear C?-characteristic. For the source of zero radius (“pointwise” source) the velocity, density, and speed of sound of the outflowing gas are infinite. The gas velocity remains infinite everywhere, while the density and speed of sound become zero for any non-zero values of the radial coordinate. For the pointwise source the problem of outflow into a vacuum is self-similar. In the plane of the “self-similar” velocity and speed of sound its solution is given by three singular points of a differential equation in these variables. At one of these points the self-similar velocity is infinite, the self-similar speed of sound is zero, and the self-similar independent variable varies from zero to infinity, with the exception of the extreme values. 相似文献
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Most reservoirs in Iran are heterogeneous fractured carbonate reservoirs. Heterogeneity causes an earlier breakthrough and an unstable front which leads to a lower recovery. A series of experiments were conducted whereby the distilled water displaced n-Decane in strongly oil-wet glass micro-models containing a single fracture. Experimental data from image analysis of immiscible displacement processes are used to modify the Buckley?CLeverett and fractional flow equations by a heterogeneity factor. It is shown that the heterogeneity factor in the modified equations can be expressed as a function of fracture length and orientation. 相似文献
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I. A. Miklashevich 《Journal of Applied Mechanics and Technical Physics》2003,44(2):255-261
It is shown that fracture can be treated as a process occurring in the Finsler space. The use of the Finsler space allows one to construct a delaminated manifold whose characteristics are related to the defect structure of the medium. A method of determining the fractal dimension of fracture is developed using the concept of crack propagation along geodesics. 相似文献
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The properties of the damping coefficient and phase velocity of propagation of small-amplitude pressure waves as functions of the oscillation frequency are investigated for the turbulent flow of a weakly compressible fluid in a circular pipe. The wall friction is found by solving numerically the equation of motion and the relaxation equations for the turbulent shear stress and viscosity which provide the basis for a turbulent transfer model developed for unsteady conditions. The properties are explained in terms of an analysis of the calculated data on turbulent transfer. The results obtained are compared with experiments. 相似文献
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The paper studies the relationship between the physical characteristics of a cylinder and the properties of normal axisymmetric waves in elastic–liquid waveguides. The cylinder is made of a compliant material in which the velocity of shear waves is less than the sonic velocity in a perfect compressible liquid. The complete system of dynamic elasticity equations and the wave equation are used to describe the wave fields in the elastic cylinder and fluid, respectively. This approach allows obtaining the dispersion characteristics of coupled normal waves in compound waveguides over wide ranges of frequencies and wavelengths. The curves of real, imaginary, and complex wave numbers versus frequency are plotted for specific pairs of waveguide materials. Computations are carried out for a thick-walled cylinder filled with a fluid and immersed in either vacuum or a fluid. It is found out that compliant and rigid materials of the cylinder affect differently the wave interaction process in elastic–liquid waveguides 相似文献
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Podil'chuk Yu. N. Rubtsov Yu. K. Soroka P. N. 《International Applied Mechanics》1985,21(12):1148-1152
International Applied Mechanics - 相似文献
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A. A. Ivanova V. G. Kozlov D. V. Liubimov T. P. Liubimova S. Meragy B. Roux 《Fluid Dynamics》1998,33(5):659-666
The averaged viscous incompressible fluid flow driven by a vibrating body with a large-curvature edge is investigated experimentally and numerically. The case of an axisymmetric body immersed in fluid and performing translational vibrations along its axis is considered. Experiments carried out on fluids of various viscosity over a wide vibration frequency and amplitude range and direct numerical calculations based on the complete time-dependent equations of viscous fluid dynamics show that the global structure of the averaged flow significantly depends on the relation between the curvature radius of the body edge and the viscous skin-layer thickness. Different averaged flow regimes are detected and the flow restructuring process is investigated as a function of the vibration amplitude and frequency. 相似文献
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M. Chipot 《Archive for Rational Mechanics and Analysis》2000,155(3):237-259
The goal of this paper is to investigate a stationary model for the diffusion of a population when the diffusion coefficient
at one location depends on the population at another. This could simulate, for instance, attraction or repulsion between the
species considered.
Accepted May 29, 2000?Published online November 24, 2000 相似文献