共查询到20条相似文献,搜索用时 109 毫秒
1.
The “ion wind”, a gas-dynamic flow in the corona discharge that arises owing to transfer of the ion component momentum to
the neutral particles of an initially stationary gas, and its interaction with the external flow perpendicular to it are studied.
A physico-mathematical model of the flows considered is proposed and the corresponding equations are analyzed numerically.
The boundary conditions used for the electric quantities approximately model the conditions in the negative corona discharge
between a thin corona-forming electrode and a plane grid electrode transparent to the gas. 相似文献
2.
Gerald G. Kleinstein 《Archive for Rational Mechanics and Analysis》1988,101(2):95-105
We consider the possibility of irrotational flow in a fluid exterior to a moving rigid obstacle, or interior to a moving rigid shell. Observations show that when a rigid body is impulsively set into motion an irrotational flow may exist initially but does not persist. The breakup of this irrotational flow and the associated phenomenon of generation of vorticity at the wall are generally attributed to the condition of adherence at the fluid-solid interface. Since this condition itself is derived from observation, one can ask whether there is another explanation for the phenomenon. The purpose of this paper is to show that a persistent irrotational flow is incompatible with the second law of thermodynamics. 相似文献
3.
In the present paper, a theoretical model of corona discharge is proposed for the case when electric charge transport is implemented by means of the motion of discrete charged bunches of finite dimensions. A system of equations and boundary conditions is formulated for the study of unsteady cyclic processes in a corona discharge. The electric field induced by the space charge of bunches and the presence of an external electric circuit are taken into account. A solution of the formulated system of equations for corona discharge with spherical geometry is obtained. The integrated (current-voltage) characteristics and the amplitude-frequency characteristics of the corona discharge are found. The proposed theory is generalized to the case of a corona discharge in a moving gas. The unsteady characteristics of corona discharge with spherical geometry for gas motion in a radial direction are found.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 153–160, January–February, 1986.The authors wish to express their gratitude to V. A. Likhter and V. I. Shul'gin for their useful discussions and valuable observations. 相似文献
4.
A. B. Vatazhin D. A. Golentsov V. A. Likhter E. K. Kholshchevnikova 《Fluid Dynamics》2011,46(5):726-735
The negative corona discharge in a hot turbulent air jet is investigated experimentally and theoretically, within the framework
of a discrete dischargemodel making it possible to determine its frequency characteristics. When using the discrete dischargemodel,
in contrast to describing the discharge as a continuous electric charge motion, it is assumed that, like in the experiment,
the charge is transferred within the discharge space by separate portions. This was noted in an old monograph [1]. Some results
on this subject were presented in [2]. In [3], a discrete model of the corona discharge was developed and realized numerically
for a system of spherical electrodes in the presence of a hydrodynamic source at the center of the system. In the present
study, certain results earlier obtained are generalized. An approximate, using similarity and dimensional methods, model is
proposed for the negative corona discharge in a hot turbulent air jet and the frequency discharge characteristics under these
conditions are investigated experimentally. 相似文献
5.
V. M. Zubarev 《Fluid Dynamics》1984,19(5):723-729
A study is made of the problem of a two-dimensional turbulent boundary layer on the moving surface of a cylindrical body (a Rankine oval with a relative elongation of four) moving at constant velocity in an incompressible fluid. For the numerical simulation of the turbulent flow of the fluid, the boundary layer is divided into exterior and interior regions in accordance with a two-layer model, using different expressions for the coefficients of turbulent transfer for each region. A study was nade of the development of the boundary layer on the body at different speeds of the body surface and different Reynolds numbers. The following integral characteristics were found by numerical calculation: the work of friction as the body is displaced; the work expended on the movement of its surface; and, for a flow regime with separation, the work of the pressure force. In this case the following model of separation flow is assumed: beyond the singular point in the solution of the boundary layer equations that indicates the appearance of a region of reverse flow, the pressure and friction stress on the wall are constant and are determined by their values at the singular point.Translated from Izvestiya Akademii Nauk SSSH, Mekhanika Zhidkosti i Gaza, No. 5, pp. 61–67, September–October, 1984.Finally, the author would like to thank G. G. Chernyi and Yu. D. Shevelev for useful discussions and for their interest in this work. 相似文献
6.
Stereoscopic digital Particle Image Velocimetry (PIV) has been used to make a three-dimensional flow mapping of a volume of
approximately 0.1 × 0.1 × 0.15 m in a laboratory model electrostatic precipitator (ESP). The mapped volume covers about two
unit cells determined by the 100 mm electrode spacing in the 0.2 × 0.2 × 1.0 m ESP test section of the negative corona, barbed
wire, smooth-plate kind. The barbs act as corona fix points, yielding a three-dimensional electrostatic field. The induced
large-scale secondary gas velocity structures in the form of unsteadily undulating axial rolls have been analyzed for swirlnumber
and location of instantaneous swirl center in 11 axial planes. The flow possesses high levels of turbulence and axial vorticity.
Measured particle velocities are corrected for electrical drift to produce gas velocities. Subsequently experimental results
are compared to Large Eddy Simulation (LES) results. 相似文献
7.
Extension of the local domain-free discretization method to large eddy simulation of turbulent flows
In this work, an immersed boundary method, called the local domain-free discretization (DFD) method, is extended to large eddy simulation (LES) of turbulent flows. The discrete form of partial differential equations at an interior node may involve some nodes outside the solution domain. The flow variables at these exterior dependent nodes are evaluated via linear extrapolation along the direction normal to the wall. To alleviate the requirement of mesh resolution in the near-wall region, a wall model based on the turbulence boundary layer equations is introduced. The wall shear stress yielded by the wall model and the no-penetration condition are enforced at the immersed boundary to evaluate the velocity components at an exterior dependent node. For turbulence closure, a dynamic subgrid scale (SGS) model is adopted and the Lagrangian averaging procedure is used to compute the model coefficient. The SGS eddy viscosity at an exterior dependent node is set to be equal to that at the outer layer. To maintain the mass conservation near the immersed boundary, a mass source/sink term is added into the continuity equation. Numerical experiments on relatively coarse meshes with stationary or moving solid boundaries have been conducted to verify the ability of the present LES-DFD method. The predicted results agree well with the published experimental or numerical data. 相似文献
8.
This paper presents a local domain‐free discretization (DFD) method for the simulation of unsteady flows over moving bodies governed by the incompressible Navier–Stokes equations. The discretization strategy of DFD is that the discrete form of partial differential equations at an interior point may involve some points outside the solution domain. All the mesh points are classified as interior points, exterior dependent points and exterior independent points. The functional values at the exterior dependent points are updated at each time step by the approximate form of solution near the boundary. When the body is moving, only the status of points is changed and the mesh can stay fixed. The issue of ‘freshly cleared nodes/cells’ encountered in usual sharp interface methods does not pose any particular difficulty in the presented method. The Galerkin finite‐element approximation is used for spatial discretization, and the discrete equations are integrated in time via a dual‐time‐stepping scheme based on artificial compressibility. In order to validate the present method for moving‐boundary flow problems, two groups of flow phenomena have been simulated: (1) flows over a fixed circular cylinder, a harmonic in‐line oscillating cylinder in fluid at rest and a transversely oscillating cylinder in uniform flow; (2) flows over a pure pitching airfoil, a heaving–pitching airfoil and a deforming airfoil. The predictions show good agreement with the published numerical results or experimental data. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
9.
We present the results of a novel technique for the high-speed visualization of a flame reaction zone using a streamer-initiated
point-to-plane unipolar pulsed corona discharge. Our results show images of the flame front under conditions of natural hydrodynamic
flame instability, as well as external air flow modulation induced flame instability. This technique can potentially be used
as a high-speed 2-D flow visualization diagnostic tool to monitor flow instabilities in reacting and non-reacting fluids that
have a density gradient. We also show that this technique does not modify the flame characteristics in any measurable way,
if the high electric field region of the streamer/corona discharge is located in the downstream region. 相似文献
10.
In this paper, an immersed boundary method for simulating inviscid compressible flows governed by Euler equations is presented. All the mesh points are classified as interior computed points, immersed boundary points (interior points closest to the solid boundary), and exterior points that are blanked out of computation. The flow variables at an immersed boundary point are determined via the approximate form of solution in the direction normal to the wall boundary. The normal velocity is evaluated by applying the no‐penetration boundary condition, and therefore, the influence of solid wall in the inviscid flow is taken into account. The pressure is computed with the local simplified momentum equation, and the density and the tangential velocity are evaluated by using the constant‐entropy relation and the constant‐total‐enthalpy relation, respectively. With a local coordinate system, the present method has been extended easily to the three‐dimensional case. The present work is the first endeavor to extend the idea of hybrid Cartesian/immersed boundary approach to compressible inviscid flows. The tedious task of handling multi‐valued points can be eliminated, and the overshoot resulting from the extrapolation for the evaluation of flow variables at exterior points can also be avoided. In order to validate the present method, inviscid compressible flows over fixed and moving bodies have been simulated. All the obtained numerical results show good agreement with available data in the literature. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
11.
Seyed Reza Mahmoudi Kazimierz Adamiak Peter Castle Mehdi Ashjaee 《Experimental Thermal and Fluid Science》2010,34(5):528-537
Free convection heat transfer from an isothermal horizontal cylinder in the presence of DC positive corona discharge with a blade edge emitter electrode has been studied experimentally and numerically. A Mach–Zehnder interferometer was used to determine the local Nusselt numbers. The effect of corona discharge on heat transfer from the cylinder was investigated at Rayleigh numbers in the range between 1500 and 5000. To find the details of the flow patterns and to further verify the experimental results, numerical simulations were also performed. It was found that the numerical results are in good agreement with experimental data. By increasing the applied voltage up to 15.5 kV, the corona discharge generates a recirculation zone around the blade and below the lower stagnation point of the cylinder. The effect of the recirculation zone becomes stronger near the breakdown voltage (17 kV) and it is responsible for a local decrease in the cooling of the cylinder around the lower stagnation point. The results indicate that corona discharge has a significant effect on the average Nusselt number at lower Rayleigh numbers whereas it has smaller effect at higher Rayleigh numbers. 相似文献
12.
Tetsuya Miyaoka 《International Journal of Computational Fluid Dynamics》2013,27(10):677-686
The purpose of this article is to present a technique to optimally control river flood using a drainage basin considering a moving boundary. The main theme of this article is to obtain outflow discharge from the drainage basin that maintains the water level at a downstream point and empties the drainage basin as soon as possible. The water flow phenomenon inside the drainage basin when a river flood occurs is considered. This phenomenon can be analysed by the finite element method considering a moving boundary. The optimal control theory can be implemented to obtain the optimal control discharge. The finite element analysis with a moving boundary is introduced in the optimal control theory. A new boundary condition on the downstream side of the river is proposed. This condition is formulated by the solitary wave condition based on the basic water level being capable of representing natural water surface. As a numerical study, optimal control of shallow water flow is carried out for the Tsurumi River and its drainage basin model. 相似文献
13.
14.
This paper is concerned with the parametric investigation on the structural dynamic response of moving fuel‐storage tanks with baffles. Since the structural dynamic behaviour is strongly coupled with interior liquid motion, the design of a fuel‐storage tank securing the structural stability becomes the appropriate suppression of the flow motion, which is in turn related to the baffle design. In order to numerically investigate the parametric dynamic characteristics of moving tanks, we employ the arbitrary Lagrangian–Eulerian (ALE) finite element method that is widely being used to deal with the problems with free surface, moving boundary, large deformation and interface contact. Following the theoretical and numerical formulations of fluid‐structure interaction problems, we present parametric numerical results of a cylindrical fuel‐storage tank moving with uniform vertical acceleration, with respect to the baffle number and location, and the inner‐hole diameter. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
15.
Results of experimental investigation of the problem of active control of the charge acquired by a body (sphere) in flow with
an electrically charged component (ions) and electrically charged dispersed phase (water drops) are obtained and analyzed.
This situation is not uncommon during aircraft flight in a cloud front. Previous experimental studies have mainly considered
flows without a dispersed phase. The required flow was created by introducing in a turbulent air-steam jet a corona discharge
on whose ions “electric” condensation developed and on the growing drops that arose a charge was accumulated due to diffusion
processes and directional ion motion in the electric field. On the sphere which was introduced in the charged jet a discharger
(active compensator) with an autonomous high-voltage power source creating a potential difference between the discharger corona
needle insulated from the body and the body surface was mounted. Measurements of the size and concentration of the drops ahead
of the critical point of the sphere were performed. The electric currents to elements of the experimental electric system
and the floating potential of the body were measured for various corona charge parameters and various voltages on the active
compensator. An active control of the sphere charge, its complete removal and the recharge of the sphere, is realized. 相似文献
16.
The stability of a negative corona discharge between two spherical electrodes the inner of which is a hydrodynamic source is investigated. A continuum discharge model consisting of equations for the electrons and positive and negative ions written with allowance for electrokinetic reactions and electrodynamic equations is used. The steady-state (undisturbed) solution of this electrohydrodynamic system of equations is found using numerical methods and its stability is analyzed in the shortwave approximation for various structural zones of the corona discharge, namely, the ionization zone, the zone of attachment of electrons to neutral molecules, and the unipolar charge zone (negative ion zone). The perturbation growth rates in these zones are determined. It is shown that in the ionization zone the corona discharge considered is unstable. 相似文献
17.
18.
The effect of an electric body force on vorticity production and turbulence generation in a gas is investigated by examination of the governing electrohydrodynamic equations. The theoretical concepts are illustrated by hot-film anemometer measurements of the electrically induced turbulence in a large scale electrostatic precipitator. The results indicate dramatic increases in turbulence and diffusivity due to the corona discharge and suggest that turbulence control in this application requires a modification in electrode geometry.This paper was presented at the Ninth symposium on turbulence, University of Missouri-Rolla, October 1–3, 1984 相似文献
19.
V. N. Mikhailov 《Journal of Applied Mechanics and Technical Physics》1971,12(4):489-496
An analysis is made of the effects of certain processes in the interior of the gas and at the electrode surface on the potential drop near the electrode in a discharge in a dense, slightly ionized gas. Thermionic emission from the electrode, the Schottky effect, diffusion, and volume and surface ionization and recombination are taken into account. The analysis is carried out for a simple discharge-gap geometry: two infinite, plane-parallel electrodes. Relations are found for the potential drop near the electrode in a two-temperature plasma as a function of the discharge parameters and emission characteristics of the material. The calculated results are compared with experiment.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 3–12, July–August, 1971.The authors thank G. A. Lyubimov for interest in the study and for discussion of the results, and B. V. Parfenov for graciously furnishing the necessary experimental data from [13]. 相似文献
20.
We study the solidification and flow of a binary alloy over a horizontally moving substrate. A situation in which the solid, liquid and mushy regions are separated by the stationary two-dimensional interfaces is considered. The self-similar solutions of the governing boundary layer equations are obtained, and their parametric dependence is analysed asymptotically. The effect of the boundary layer flow on the physical characteristics is determined. It is found that the horizontal pulling and the resulting flow in the liquid enhance the formation of the mushy region. 相似文献