首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到7条相似文献,搜索用时 15 毫秒
1.
Numerical modeling of the heat transfer and molecular mixing in an electrical furnace designed for the spectroscopic study of hydrogen/alkali-metal-vapor mixtures is described. The gases enter the furnace through three concentric tubes, the inner two of which contain the test gases while the outer contains a guard gas to protect the windows. The inner tubes terminate prior to the measurement section to allow the gases to mix. Heating is accomplished through contact with the wall of the outer tube. An implicit time-marching procedure including a preconditioning method is used to compute the coupled gas flows. The results show that optimum flow speeds occur at a Reynolds number of order ten. Higher speeds do not allow adequate heating or mixing and can become unsteady, while lower speeds allow considerable back diffusion in the concentric tubes.  相似文献   

2.
Two-dimensional incompressible laminar flow induced by a constant slip velocity on the surface of a finite flat plate is studied both analytically and numerically for large Reynolds numbers. It turned out that the thickness of the thin layer downstream of the trailing edge increases in square root of the distance from the trailing edge. Numerical integration of the boundary layer equations for the whole flow field confirmed two asymptotic natures of the flow field; near the trailing edge the analytic result is approached, and far downstream of the plate the jet flow solution is attained.  相似文献   

3.
4.
Feedback strategies of a qualitative competitive game between two players can be designed such as to influence parameters of a mechanical system to induce chaotic behavior. The purpose is to reduce the options and effects of the opponent’ s strategy. We show it on a case with dynamics specified by a nonautonomous Duffing equation with the players represented by damping and external forcing, respectively. It seems however that the conclusions can be made valid generally.  相似文献   

5.
Mean flow and turbulence properties of developing turbulent flows in a 90 degree square bend with span-wise rotation are measured by a hot-wire anemometer. A slanted wire is rotated into 6 orientations and the voltage outputs from them are combined to obtain the mean velocity and the Reynolds stress components. Combined effects of the centrifugal and Coriolis forces due to the curvature and the rotation of the bend on the mean motion and turbulence structures are investigated experimentally. Results show that the two body forces can either enhance or counteract each other depending on the flow direction in the bend.  相似文献   

6.
This paper addresses the hierarchical production planning (HPP) problem for flexible automated workshops (FAWs) with delay interaction, each with a number of flexible manufacturing systems (FMSs). The delay interaction aspect arises from taking into consideration the transfer of parts between FMSs. Any job which requires processing on more than one FMS cannot be transferred directly from one FMS to the next. Instead a semi-finished-product completed in one period must be put into shop storage until the next period at which it can be transferred to the next FMS for further processing. The objective is to decompose medium-term plans (assigned to an FAW by ERP/MRP II) into short-term plans (to be executed by FMSs in the FAW) so as to obtain the lowest production cost. The HPP problem is formulated in this paper by a nonlinear programming model whose constraints are linear but whose objective function is piecewise linear. For the convenience of solving the nonlinear programming model, it is transformed into a linear programming model. Because the model for a general workshop is too large to be solved by the simplex method on a personal computer within acceptable time, Karmarkar’s algorithm and an interaction/prediction algorithm, respectively, are used to solve the model, the former for medium- or small-scale problems and the latter for large-scale problems. With the implementations of these algorithms and with many HPP examples, Karmarkar’s algorithm, the interaction/prediction algorithm and the linear programming method in Matlab 5.0 are compared, showing that the proposed approaches are very effective.  相似文献   

7.
A 1 : 20 laboratory scale test rig of a 200 MW tangentially fired boiler is built up with completely simulated structures such as platen heaters and burners. Iso-thermal turbulent flow in the boiler is mapped by 3-D PDA (Particle Dynamic Analyzer). The 3-D numerical models for the same case are proposed based on the solution ofk-ε model closed RANS (Reynolds time-Averaged Navier-Stokes) equations, which are written in the framework of general coordinates and discretized in the corresponding body-fitted meshes. Not only are the grid lines arranged to fit the inner/outer boundaries, but also to align with the streamlines to the best possibility in order to reduce the NDE (numerical diffusion errors). Extensive comparisons of profiles of mean velocities are carried out between experiment and calculation. Predicted velocities in burner region were quantitatively similar with measured ones, while those in other area have same tendency with experimental counterpart.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号