共查询到20条相似文献,搜索用时 15 毫秒
1.
为了说明非定常空化的流动机理,该文采用数值与实验相结合的方法对绕三维水翼片状和云状空化流动结构进行了研究.实验在高速水洞中进行,采用高速录像技术观测了片状和云状空化阶段的空穴形态.数值计算基于均相流模型,汽液混合区域密度由质量传输方程调节.利用商业软件二次开发技术引入准确描述空化流场非定常特性的FBM 湍流模型,进行绕三维水翼的数值模拟,获得了随时间变化的空穴形态、压力和速度分布等流场结构.与实验结果对比发现,数值计算结果与实验基本一致.在片状空化阶段,空穴稳定地附着在水翼表面,只有空穴尾部不断的有小空泡团沿着翼弦方向脱落.在云状空化阶段,清楚得描述了空穴的产生-发展-脱落-溃灭的准周期性变化,并准确地捕捉到空泡脱落时,附着在翼型前端的U 型空穴和翼展方向不同强度的反向射流,脱落的空泡由翼型中前部旋涡状脱落. 相似文献
2.
B. B. Rokhman 《Journal of Engineering Physics and Thermophysics》2008,81(5):880-892
A stationary isothermal model of the aerodynamics of a two-phase flow in an axisymmetric channel has been constructed with
allowance for the turbulent and pseudoturbulent mechanisms underlying the transfer of the solid phase momentum. The equations
of dispersed phase motion are closed at the level of the equations for the second moments of the pulsation velocities of particles,
whereas the equation of momentum transfer of the carrier is closed on the basis of a one-parameter model of turbulence extended
to the case of two-phase turbulent flows. The results of calculations are compared with experimental data.
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Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 5, pp. 844–855, September–October, 2008. 相似文献
3.
B. B. Rokhman 《Journal of Engineering Physics and Thermophysics》2007,80(4):742-750
A stationary isothermal system of equations defining the behavior of a two-phase rising flow in the region of steady motion
of a gas suspension in an axially symmetric channel has been developed. The equation of motion of the carrying medium is closed
using a one-parameter model of turbulence, and the equation of momentum transfer in the dispersed phase is closed with the
use of the equations for the second, third, and fourth moments of the pulsation velocities of the particles. The main mechanisms
of two-phase turbulent flows were numerically investigated.
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Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 4, pp. 99–109, July–August, 2007. 相似文献
4.
In this paper, a boundary element method (BEM) for cavitating hydrofoils moving steadily under a free surface is presented
and its performance is assessed through systematic convergence studies, comparisons with other methods, and existing measurements.
The cavitating hydrofoil part and the free surface part of the problem are solved separately, with the effects of one on the
other being accounted for in an iterative manner. Both the cavitating hydrofoil surface and the free surface are modeled by
a low-order potential based panel method using constant strength dipole and source panels. The induced potential by the cavitating
hydrofoil on the free surface and by the free surface on the hydrofoil are determined in an iterative sense and considered
on the right hand side of the discretized integral equations. The source strengths on the free surface are expressed by applying
the linearized free surface conditions. In order to prevent upstream waves the source strengths from some distance in front
of the hydrofoil to the end of the truncated upstream boundary are enforced to be equal to zero. No radiation condition is
enforced at the downstream boundary or at the transverse boundary for the three-dimensional case. First, the BEM is validated
in the case of a point vortex and some convergence studies are done. Second, the BEM is applied to 2-D hydrofoil geometry
both in fully wetted and in cavitating flow conditions and the predictions are compared to those of other methods and of the
measurements in the literature. The effects of Froude number, the cavitation number and the submergence depth of the hydrofoil
from free surface are discussed. Then, the BEM is validated in the case of a 3-D point source. The effects of grid and of
the truncated domain size on the results are investigated. Lastly, the BEM is applied to a 3-D rectangular cavitating hydrofoil
and the effect of number of iterations and the effect of Froude number on the results are discussed.
Received 6 November 2000 相似文献
5.
6.
B. B. Rokhman 《Journal of Engineering Physics and Thermophysics》2007,80(2):273-283
A chain of transfer equations for the second and third moments of dispersed-phase-velocity pulsations in the anisotropic field
of energy of random particle motion is obtained based on the computational procedure developed. The interphase and interparticle
interactions are allowed for. The turbulent characteristics of the gas are calculated on the basis of a one-parameter turbulence
model generalized to the case of two-phase turbulent flows.
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Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 2, pp. 60–70, March–April, 2007. 相似文献
7.
The fundamental characteristics of the two-dimensional cavitating flow of liquid helium through a venturi channel near the lambda point are numerically investigated to realize the further development and high performance of new multi-phase superfluid cooling systems. First, the governing equations of the cavitating flow of liquid helium based on the unsteady thermal nonequilibrium multi-fluid model with generalized curvilinear coordinates system are presented, and several flow characteristics are numerically calculated, taking into account the effect of superfluidity. Based on the numerical results, the two-dimensional structure of the cavitating flow of liquid helium though venturi channel is shown in detail, and it is also found that the generation of superfluid counterflow against normal fluid flow based on the thermomechanical effect is conspicuous in the large gas phase volume fraction region where the liquid-to-gas phase change actively occurs. Furthermore, it is clarified that the mechanism of the He I to He II phase transition caused by the temperature decrease is due to the deprivation of latent heat for vaporization from the liquid phase. 相似文献
8.
E. I. Smolyar 《Journal of Engineering Physics and Thermophysics》2005,78(4):777-785
Consideration is given to a model of turbulent flow in a roughness layer; the model is formed by the equations for turbulent
momentum and turbulence-energy density and by free boundary conditions at self-establishing boundaries of the turbulent zone
in the entire layer and in roughness cells. The model describes the interactions of the flow with the elements of roughness
and the processes in the cells of different scales. Certain calculated characteristics of turbulence in vegetation are given.
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Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 4, pp. 143–151, July–August, 2005. 相似文献
9.
《低温学》2018
Thermodynamic effects on cryogenic cavitating flow is important to the accuracy of numerical simulations mainly because cryogenic fluids are thermo-sensitive, and the vapour saturation pressure is strongly dependent on the local temperature. The present study analyses the thermal cavitating flows in liquid nitrogen around a 2D hydrofoil. Thermal effects were considered using the RNG k-ε turbulence model with a modified turbulent eddy viscosity and the mass transfer homogenous cavitation model coupled with energy equation. In the cavitation model process, the saturated vapour pressure is modified based on the Clausius-Clapron equation. The convection heat transfer approach is also considered to extend the Zwart-Gerber-Belamri model. The predicted pressure and temperature inside the cavity under cryogenic conditions show that the modified Zwart-Gerber-Belamri model is in agreement with the experimental data of Hord et al. in NASA, especially in the thermal field. The thermal effect significantly affects the cavitation dynamics during phase-change process, which could delay or suppress the occurrence and development of cavitation behaviour. Based on the modified Zwart-Gerber-Belamri model proposed in this paper, better prediction of the cryogenic cavitation is attainable. 相似文献
10.
11.
The self-similar equations for the dynamic and temperature fields of a forced free fan jet have been numerically integrated
within the framework of the standard k-ε model of turbulence. The tables of solutions obtained for the velocity, temperature,
and kinetic turbulent energy of the jet, as well as the mean square of the jet-temperature fluctuations at different turbulent
Prandtl numbers, are presented. The quantitative parameters of the evolution of the average and turbulent characteristics
of the jet flow were determined.
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Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 1, pp. 62–67, January–February, 2008. 相似文献
12.
Numerical simulation of unsteady cavitating flows using a homogenous equilibrium model 总被引:3,自引:0,他引:3
Numerical simulations of two-dimensional cavity flows around a flat plate normal to flow and flows through a 90∘ bent duct are performed to clarify unsteady behavior under various cavitation conditions. A numerical method applying a TVD-MacCormack
scheme with a cavitation model based on a homogenous equilibrium model of compressible gas-liquid two-phase media proposed
by the present authors, is applied to solve the cavitating flow. This method permits the simple treatment of the whole gas-liquid
two-phase flow field including wave propagation and large interface deformation. Numerical results including detailed observations
of unsteady cavity flows and comparisons of predicted results with experimental data are provided.
Received: 5 August 2002 / Accepted: 6 January 2003 相似文献
13.
N. A. Vladimirova 《Journal of Engineering Physics and Thermophysics》2008,81(1):196-203
A separation turbulent flow has been mathematically simulated on the basis of numerical solution of nonstationary Navier-Stokes
equations for determining the dynamics of viscous interaction of a ring vortex with a flat screen. The problem was solved
for an axisymmetric turbulent flow at Reynolds numbers falling within the range 105–107. On the basis of the calculation data obtained, the interaction of a ring vortex with a turbulent flow induced on the screen
and with the secondary ring vortices was investigated. The data obtained are in qualitative agreement with the analogous data
obtained by other authors with the use of the discrete-vortex method and the boundary-layer theory as well as with the available
experimental and calculation data obtained for a laminar flow.
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Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 1, pp. 184–190, January–February, 2008. 相似文献
14.
The results of numerical simulation of fully developed turbulent flow in a channel with the cube on the lower wall (for the
characteristic Reynolds number Re = 40,000) within the framework of the traditional approach to the solution of unsteady Reynolds-averaged Navier–Stokes equations
(URANS) in combination with the semiempirical Spalart–Allmaras turbulence model (with a correction for rotation) have been
presented. A detailed comparative analysis of the results of numerical simulation of local and integral flow characteristics
and the Martinuzzi experimental data has shown that the self-oscillating regime of flow past the cube is a superposition of
oscillations of the arms of a horseshoe vortex and the rear arched and detached vortex structures. Using fast Fourier transformation,
it has been found that the oscillations are of a bimodal character in the longitudinal and vertical directions, whereas in
the transverse direction, they are of a unimodal character. 相似文献
15.
V. A. Babenko 《Journal of Engineering Physics and Thermophysics》1997,70(3):383-393
Development of a turbulent perturbation in a homogeneous flow moving within a medium that is linearly density-stratified across
the direction of flow motion is described. The initial region of the evolution of turbulence with a large turbulent Reynolds
numberR
λ
is considered.
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 3, pp. 393–403, May–June, 1997. 相似文献
16.
The flow due to a moving extensible sheet that obeys a more general stretching law is considered. The sheet occupies the negative
x-axis and is moving continually in the positive x-direction, in an incompressible viscous and electrically conducting fluid. The sheet somehow disappears in a sink that is
located at (x, y) = (0, 0). The governing system of partial differential equations is first transformed into a system of ordinary differential
equations, and the transformed equations are solved numerically using a finite-difference scheme, namely the Keller-box method.
The features of the flow and heat-transfer characteristics for different values of the governing parameters are analyzed and
discussed. It is found that dual solutions exist for the flow near x = 0, where the velocity profiles show a reversed flow. 相似文献
17.
The numerical prediction of the acoustic pressure field induced by cavitating marine propellers is addressed. A hydrodynamic model for transient sheet cavitation on propellers in non–uniform inviscid flow is coupled with a hydroacoustic model based on the Ffowcs Williams–Hawkings equation. The proposed hydroacoustic approach, novel to marine applications, allows to split the noise signature into thickness and loading term contributions. Both hydrodynamic and hydroacoustic model equations are solved via boundary integral formulations. Numerical predictions of the propeller noise by using the Ffowcs Williams–Hawkings equation are compared to those obtained by a classical Bernoulli equation approach. The influence of cavitation on the noise waveforms is discussed by comparing non–cavitating and cavitating propeller flow results.
The authors wish to thank Prof. S.A. Kinnas for providing a detailed documentation of the experiment used as the test case in the present analysis. The present work was supported by the Ministero dei Trasporti e della Navigazione in the frame of INSEAN Research Program 2000–02. 相似文献
18.
S. T. Surzhikov 《Journal of Engineering Physics and Thermophysics》2000,73(1):175-180
Based on the system of two-dimensional axisymmetrical continuity equations, Navier-Stokes and energy equations, and the equations
of selective heat radiation transfer, a computational model is constructed and conditions of unsteady subsonic flows in a
cylindrical channel of a power unit of the laser-plasma accelerator type are investigated. The governing parameters of the
model are calculated, at which numerical solutions can be obtained to describe steady laminar gas flow in the neighborhood
of the region of heat release, nonstationary oscillatory motions, and nonstationary vortex motion.
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 1, pp. 174–179, January–February, 2000. 相似文献
19.
The fundamental two-phase flow characteristics of slush nitrogen in a pipe are numerically investigated to develop effective cooling performance for long-distance superconducting cable. First, the governing equations of two-phase slush nitrogen flow based on the unsteady thermal non-equilibrium two-fluid model are constructed and several flow characteristics are numerically calculated taking into account the effects of the slush volume fraction, the thermodynamic behavior of slush, and the duct shape. Furthermore, the numerical results are compared with previous experimental results on pressure loss measurement and visualization measurement in two-phase slush nitrogen flow along the longitudinal direction of the pipe. Results of this research show that it is possible to reduce the pressure loss by using a two-phase slush flow under the high Reynolds number condition and by applying the appropriate volume fraction of slush particles. The optimized thermal flow conditions for cryogenic two-phase slush nitrogen with practical use of latent heat for slush melting are predicted for the development of a new type of superconducting cooling system. 相似文献
20.
A two-scale model is developed for fluid flow in a deforming, unsaturated and progressively fracturing porous medium. At the
microscale, the flow in the cohesive crack is modelled using Darcy’s relation for fluid flow in a porous medium, taking into
account changes in the permeability due to the progressive damage evolution inside the cohesive zone. From the micromechanics
of the flow in the cavity, identities are derived that couple the local momentum and the mass balances to the governing equations
for an unsaturated porous medium, which are assumed to hold on the macroscopic scale. The finite element equations are derived
for this two-scale approach and integrated over time. By exploiting the partition-of-unity property of the finite element
shape functions, the position and direction of the fractures are independent from the underlying discretization. The resulting
discrete equations are nonlinear due to the cohesive crack model and the nonlinearity of the coupling terms. A consistent
linearization is given for use within a Newton–Raphson iterative procedure. Finally, examples are given to show the versatility
and the efficiency of the approach. The calculations indicate that the evolving cohesive cracks can have a significant influence
on the fluid flow and vice versa. 相似文献