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1.
The solvability of the problem of the flows resulting from the incidence of a discontinuous wave on a bottom step is studied using a single-layer shallow water model. Solutions in which the total energy of the flow is conserved at the step and those in which it is lost at the step are considered. Regions of double and triple hystereses in the obtained self-similar solutions are found. An analogy is drawn with the problem of single-layer flow over a bottom obstacle. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 2, pp. 8–22, March–April, 2006.  相似文献   

2.
A simple scheme is developed for treatment of vertical bed topography in shallow water flows. The effect of the vertical step on flows is modelled with the shallow water equations including local energy loss terms. The bed elevation is denoted with zb for the left and zb+ for the right values at each grid point, hence exactly representing a discontinuity in the bed topography. The surface gradient method (SGM) is generalized to reconstruct water depths at cell interfaces involving a vertical step so that the fluxes at the cell interfaces can accurately be calculated with a Riemann solver. The scheme is verified by predicting a surge crossing a step, a tidal flow over a step and dam‐break flows on wet/dry beds. The results have shown good agreements compared with analytical solutions and available experimental data. The scheme is efficient, robust, and may be used for practical flow calculations. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

3.
V.V. Shuvalov 《Shock Waves》1999,9(6):381-390
Eulerian, three-dimensional, numerical code, which conserves mass, momentum and energy simultaneously both in the Lagrangian and remap steps, is developed. The use of special form of linear viscosity provides a weaker time step restriction as compared with the Courant condition. The code is designed to investigate the multi-material problems, including dusty flows. The performance of the code is illustrated by the modeling of shock wave interaction with a dusty thermal layer. Received 15 June 1998/ Accepted 6 January 1999  相似文献   

4.
The single-layer shallow-water model is used to study flows generated by dam break over a bed level discontinuity in the form of a drop from which water flows. Emphasis is given to submerged regimes in which downstream wave processes affect the upstream flow. The paper considers solutions in which the total flow energy is conserved on the drop and solutions in which the energy is lost on the drop.  相似文献   

5.
A shear impact energy model (SIEM) of erosion suitable for both dilute and dense particle flows is proposed based on the shear impact energy of particles in discrete element method (DEM) simulations. A number of DEM simulations are performed to determine the relationship between the shear impact energy predicted by the DEM model and the theoretical erosion energy. Simulation results show that nearly one-quarter of the shear impact energy will be converted to erosion during an impingement. According to the ratio of the shear impact energy to the erosion energy, it is feasible to predict erosion from the shear impact energy, which can be accumulated at each time step for each impingement during the DEM simulation. The total erosion of the target surface can be obtained by summing the volume of material removed from each impingement. The proposed erosion model is validated against experiment and results show that the SIEM combined with DEM accurately predicts abrasive erosions.  相似文献   

6.
This paper presents computational solutions for unsteady viscous flows in channels with a downstream-facing step, followed by an oscillating floor. These solutions of the unsteady Navier–Stokes equations are obtained with a time-integration method using artificial compressibility in a fixed computational domain, which is obtained via a time-dependent coordinate transformation from the fluid domain with moving boundaries. The computational method is first validated for steady viscous flows past a downstream-facing step by comparison with previous numerical solutions and experimental results. This method is then used to obtain solutions for unsteady viscous flows with multiple separation regions over a downstream-facing step with oscillating walls, for which there are no previously known solutions. Thus, the present results may be used as benchmark solutions for the unsteady viscous flows with multiple separation regions between fixed and oscillating walls.  相似文献   

7.
竖直平板间自然对流的湍流频谱特性   总被引:2,自引:2,他引:0  
根据直接数值模拟的计算结果,对竖直平板间湍流自然对流的脉动动能、速度及温度等物理量的时间序列进行频谱分析.结果表明,流动达到充分发展状态后,小尺度到大尺度的能谱很宽,计算的分辨率足够.从能谱分布可以观察到含能区、惯性子区和耗散区的存在,文中对各区的特性进行分析.由于该流动的强各向异性,惯性子区很窄.并讨论了法向位置对脉动动能的影响以及大尺度结构的特性.  相似文献   

8.
In this study, the phenomenon of negative “loss”-coefficients reported in various studies about turbulent branched flows through combining junctions is investigated systematically. It turns out, that the “loss” for one branch of a junction and its adjacent ducts only in parts is due to devaluation of mechanical energy, which would be a real loss, so that the term energy change is more appropriate. The other part of the energy change which is not due to a loss is due to a mutual energy transfer between the two partial flows. As a consequence, non-dimensional coefficients should be called energy change coefficients rather than head loss coefficients whenever branching of flows occurs. Furthermore, a method is introduced by which losses and the energy transfer are determined directly in the flow field. The field values allow a quantification and visualization of the local loss and work transfer, while their integral values can be used to quantify the individual contributions of losses and energy transfer within the energy change of a flow through a junction.  相似文献   

9.
A numerical study of natural convection in a two-phase, two-component flow in a porous medium heated from below is presented. Interphase mass and energy transfer, latent heat and bouyancy effects are major physical features. This study extends earlier studies of natural convection based on single-phase, saturated porous medium models. The appearance of two-phase heat pipe zones in the flow has a marked effect on the fluid and heat flows as well as on the performance of the numerical methods. The numerical techniques for handling phase change, Jacobian construction and time step selection are discussed.  相似文献   

10.
Waves generated by submarine landslides are treated as three-dimensional flows of a perfect incompressible fluid. For the solution of the Cauchy-Poisson problem a time-discretization is applied which leads at each time step to a non-homogeneous free surface condition; the solution is then divided into two parts. The first part, subject to the true free surface condition, is computed in a simplified domain with constant depth. The second part involves a homogeneous free surface condition, a corrected bottom condition and the true bathymetry. In the case of constant depth, unconditional stability of the time discretization is derived. In the case of variable depth, mass and energy conservation is derived. Numerical results are presented. Comparison is made with other methods for the generation of axisymmetric waves. The transient propagation along a rectilinear coast is studied, including a comparison between two different bathymetries; trapping of energy is observed.  相似文献   

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