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1.
A physical model of air-steam flow with homogeneous condensation, condensation on ions, mass exchange between droplets and surrounding medium, and charge exchange between droplets and ion component is presented. A kinetic equation for the droplet distribution over sizes and charges is used in the model. On the basis of this equation, the moment equations are obtained and various approximate ways of closing them are proposed. The electric self-fields produced by the ion component and the charged dispersed phase are taken into account. Modifications of the equations for the case of turbulent flow are given. A one-dimensional flow model taking into account certain special features of the condensation and electrophysical processes in real flows is realized numerically.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 67–77, January–February, 1996.  相似文献   

2.
The time-dependent process of charge accumulation on an electrically insulated sphere located in a turbulent stream with the ion component in the presence of an electric field is considered. The process is simulated numerically on the basis of the time-dependent electrodynamic equations and averaged Navier-Stokes equations (RANS approximation) using the Sekundov single-parameter turbulent viscosity model. The distributions of the ion number density, electric current, and potential are determined. Features of the obtained time dependence of the sphere potential are analyzed.  相似文献   

3.
A model of a gas mixture is studied in which one of the components can carry electric charge and undergo phase transitions. Under a number of assumptions, Boltzmann kinetic equations are written down and the form of the collision integral determined. Conservation equations for the components of the mixture are found. The conservation equations for a charged mixture of gases in the absence of phase transitions have been discussed earlier [1]. Collision integrals for a reacting gas mixture in the case of chemical reactions of bimolecular type and when the mixture is described by Boltzmann kinetic equations are derived in [2].Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No, 3, pp. 118–127, May–June, 1980.  相似文献   

4.
The macroscopic governing equations of a compressible multicomponents flow with non-uniform viscosity and with mass withdrawal (due to heterogeneous reactions) in a porous medium are developed. The method of volume averaging was used to transform local (or microscopic) governing equations into averaged (or macroscopic) governing equations. The impacts of compressibility, non-uniform viscosity, and mass withdrawal on the form of the averaged equations and on the value of the macroscopic transport coefficients were investigated. The results showed that the averaged mass conservation equation is significantly affected by mass withdrawal when a specific criterion on the size of the domain is respected. The results also showed that the form of the averaged momentum equations is not affected by mass withdrawal, by compressibility effects or by non-uniform viscosity, provided that the Reynolds number at the pore level is small. Nonetheless, the velocity field is affected by the heterogeneous reaction via the averaged mass conservation equation, and also by viscosity variations due to the presence of the volume-averaged viscosity (which value changes with position) in the averaged momentum equations. A new closure variable definition was proposed to formulate the closure problem, which avoided the need to solve an integro-differential equation in the closure problem. This formulation was used to show that the permeability tensor only depends on the geometry of the porous medium. In other words, that tensor is independent on whether the fluid is compressible/incompressible, has uniform/non-uniform viscosities, and whether mass withdrawal due to heterogeneous reactions is present/absent.  相似文献   

5.

Diffusiophoresis of a charge regulated spherical polyelectrolyte nanogel (PE) due to an externally imposed ionic concentration gradient is considered. The immobile charge density of the nanogel develops through the association/dissociation reactions of their inorganic functional groups. The nanogel is ion and fluid permeable with dielectric permittivity different from that of the surrounding electrolyte medium. This difference in dielectric permittivity creates an ion partitioning due to the difference in self energy of ions. The Nernst–Planck equation for ion transport and the Poisson equation (PNP) for the electric field are modified to take into account the ion partitioning effects. The diffusiophoresis mechanism is governed by the electrophoresis generated by the induced electric field and chemiphoresis develops due to the mitigation of counterions across the double layer of the nanogel. In addition, the convection dominated double layer polarization and the counterion condensation as well as the electroosmotic flow created by the gel immobile charge play a role in the diffusiophoresis. All these effects are incorporated through the modified PNP equations coupled with the Navier–Stokes equations. The governing equations in their full form are solved numerically through a control volume approach. Present computed solutions for the limiting cases are in good agreement with the existing solutions based on the first-order perturbation analysis. In order to illustrate the diffusiophoresis mechanism we have measured the induced electric field and effective charge density of the PE and analyzed its dependence on several electrokinetic parameters. The contribution due to chemiphoresis is low for PE compared to a rigid colloid. For a highly permeable PE the diffusiophoretic velocity increases and approaches a saturation for higher range of the PE fixed charge density. The ion partitioning effect depletes counterions in PE to manifests its diffusiophoretic velocity. The diffusiophoretic velocity of PE for pH > IEP is higher than the case for which pH < IEP.

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6.
The microfluidic system is a multi-physics interaction field that has attracted great attention. The electric double layers and electroosmosis are important flow-electricity interaction phenomena. This paper presents a thickness-averaged model to solve three-dimensional complex electroosmotic flows in a wide-shallow microchannel/chamber combined (MCC) chip based on the Navier-Stokes equations for the flow field and the Poisson equation to the electric field. Behaviors of the electroosmotic flow, the electric field, and the pressure are analyzed. The quantitative effects of the wall charge density (or the zeta potential) and the applied electric field on the electroosmotic flow rate are investigated. The two-dimensional thickness-averaged flow model greatly simplifies the three-dimensional computation of the complex electroosmotic flows, and correctly reflects the electrookinetic effects of the wall charge on the flow. The numerical results indicate that the electroosmotic flow rate of the thickness-averaged model agrees well with that of the three-dimensional slip-boundary flow model. The flow streamlines and pressure distribution of these two models are in qualitative agreement.  相似文献   

7.
An analytical study of slow modulation has been made of cylindrical interface between two inviscid streaming fluids, in the presence of a relaxation of electrical charges at the interface, and stressed by an axial electric field. A new technique based on the perturbation theory, to derive the non-linear evolution equations has been introduced. These equations are combined to yield a non-linear Ginzburg–Landau equation and a non-linear modified Schrödinger equation describing the evolution of wave packets. The linear analysis showed that the streaming has a destabilizing effect and the electric field has stabilizing influence associated with parameters condition involving the electric conductivity and permittivity of the fluids. While the non-linear approach indicated that the streaming may become unstable for sufficiently high velocities, with a new condition on the material properties, involving weak electric relaxation times in both fluids.  相似文献   

8.
The methods of the kinetics theory are used to obtain a closed system of equations describing the behavior of a multicomponent, partially ionized gaseous mixture in an electromagnetic field in which the space charge is significant. A criterion is presented that makes it possible to separate the problem of finding the magnetic field from that of finding the other defining parameters. Expressions are obtained for the viscosity stress tensors and the thermal and diffusive fluxes; the transport coefficients are calculated in the strong electric field. The relations for the friction force and the energy exchange between components during particle collisions are analyzed. The equations for a mixture consisting of neutral particles and charged particles of a single sign are discussed in detail. The dimensionless EHD criteria are written and analyzed. Possible simplifications of the system of equations are examined, and various forms of Ohm's law are discussed. Weak discontinuities in EHD are analyzed. The equations of EHD under various assumptions have also been considered in several studies* and in [1–3].  相似文献   

9.
基于Kong-Fang混凝土材料模型和LS-DYNA的多物质ALE算法,开展混凝土中爆炸波衰减规律的数值模拟研究。首先,基于已有实验数据对材料模型参数和数值算法的可靠性进行了验证,在此基础上分析球形装药在混凝土自由场中爆炸波衰减规律,利用量纲分析和数值模拟拟合了球形装药在混凝土自由场中近区爆炸波峰值应力计算公式并明确其适用范围;然后,分析装药埋深对混凝土中装药正下方不同距离处爆炸波峰值应力分布的影响,建立了耦合系数与装药埋深和测点距离之间的定量关系。结果表明:Kong-Fang混凝土材料模型可实现对混凝土中爆炸波传播衰减规律的高精度数值模拟;定义混凝土中装药质量系数和耦合常数,可定量描述装药埋深和测点距离对峰值应力耦合系数的影响;建立的混凝土中近区爆炸波峰值应力计算公式可较准确地快速预测不同装药埋深、不同测点距离和不同混凝土强度时爆炸波峰值应力。研究结果可为混凝土结构抗爆设计和爆炸毁伤评估提供参考。  相似文献   

10.
A laminar methane diffusion flame in a constant electric field whose direction is opposite to that of the velocity of the gas flow from the burner nozzle is considered. The mathematical model used includes the complete system of Navier-Stokes equations for the velocity and passive admixture concentration fields, the charge transport equation, together with the Poisson equation for the self-consistent electric field, and the chemical kinetic equations for a thin combustion zone. The calculations show that the flame shortens and its thickness increases in the root zone when an electric field is imposed. This effect is accompanied by a reduction in the nitrogen oxide emission, while is consistent with the experimental data. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 48–53, January–February, 2000. The work was supported by the Russian Foundation for Basic Research (project No. 96-01-014-50).  相似文献   

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