共查询到20条相似文献,搜索用时 421 毫秒
1.
V. M. Molochnikov N. I. Mikheev A. A. Paereliy K. R. Khairnasov 《Thermophysics and Aeromechanics》2008,15(4):573-582
Visualization data and results of combined measurements of flow quantities in flow with separation past a rib at nominally
laminar regime of channel flow are reported. In the separation region, the flow is found to be essentially three-dimensional
and unsteady, exhibiting a distinct cellular structure and flow zones with transverse motion. It is shown that the rib-induced
flow separation gives rise to low-frequency fluctuations of flow velocity and initiates the turbulence transition in the channel
flow. The critical Reynolds number at which flow instability starts developing in the channel is estimated. It is shown that
at Reynolds numbers higher than the critical Reynolds number the linear integral scale of flow velocity fluctuations in the
channel is defined by the duct size. 相似文献
2.
O. Sazhin 《Journal of Experimental and Theoretical Physics》2009,109(4):700-706
A rarefied gas flow through a finite-length channel into a vacuum is studied by the direct simulation Monte Carlo method.
The mass flow rate through the channel is calculated over the wide range of gas rarefactions. The analysis of the flow field,
both within the channel and in upstream and downstream containers, is presented. 相似文献
3.
通过用分子动力学方法对颗粒物质流的计算机模拟,研究发现增大通道宽度可以使二维颗粒流从稀疏流转变为密集流状态.通过对不同通道宽度下,固定开口为9.5d的颗粒流和 漏斗口以上9.5d×8d区域记录的模拟结果分析,发现随通道宽度增大,密度变大、温 度降低.当“颗粒温度”T较低时(T/m<0.05 J/kg),颗粒流内部接触数开始超过1.2 ,同时出现较为牢固的横向链状颗粒团簇,是造成流量突变以及密集流的原因.
关键词:
颗粒物质
颗粒流
计算机模拟 相似文献
4.
Tariq Talha 《Journal of Turbulence》2013,14(11):1091-1113
The unsteady turbulent channel flow subject to the temporal acceleration is considered in this study. Large-eddy simulations were performed to study the response of the turbulent flow to the temporal acceleration. The simulations were started with the fully developed turbulent channel flow at an initial Reynolds number of Re0 = 3500 (based on the channel half-height and the bulk-mean velocity), and then a constant temporal acceleration was applied. During the acceleration, the Reynolds number of the channel flow increased linearly from the initial Reynolds number to the final Reynolds number of Re1 = 22,600. The effect of grid resolution, domain size, time step size on the simulation results was assessed in a preliminary study using simulations of the accelerating turbulent flow as well as simulations of the steady turbulent channel flow at various Reynolds numbers. Simulation parameters were carefully chosen from the preliminary study to ascertain the accuracy of the simulation. From the accelerating turbulent flow simulations, the delays in the response of various flow properties to the temporal acceleration were measured. The distinctive features of the delays responsible for turbulence production, energy redistribution, and radial propagation were identified. Detailed turbulence statistics including the wall shear stress response during the acceleration were examined. The results reveal the changes in the near-wall structures during the acceleration. A self-sustaining mechanism of turbulence is proposed to explain the response of the turbulent flow to the temporal acceleration. Although the overall flow characteristics are similar between the channel and pipe flows, some differences were observed between the two flows. 相似文献
5.
6.
The design secret of Kyokusui-no-En’s meandering channel 总被引:1,自引:0,他引:1
The purpose of this study is to investigate the characteristics of the flow through the Jonangu channel which is used for
ceremonial game called as ‘Kyokusui-no-En’ in Japanese. The geometry of the channel is measured, a visualization technique
is used to measure the actual flow characteristics, and then a numerical flow model is used to represent the flow including
unsteady flow characteristics. Numerical model of drifting cup is introduced to investigate an interaction between flow and
motion of the cup. Finally, the intention of the channel design is interpreted from the viewpoint of fluid mechanics using
observed and calculated results. 相似文献
7.
针对磷化铟(InP)复合沟道高电子迁移率晶体管(HEMT)的特点,对常规单沟道HEMT的小信号物理模型进行了修正,提出了一种新的用于复合沟道HEMT的小信号物理模型,用商用器件模拟软件ISE(integrated systems engineering)对其进行了仿真验证,对比了实测和仿真的I-V特性及转移特性曲线,重点研究了在InGaAs/InP双层沟道中考虑量子效应后的电场和电流密度随着不同栅电压的变化趋势,研究结果表明,由于在沟道中存在量子效应,在栅下靠源端低电场区域,电流主要分布在InGaAs沟道
关键词:
高电子迁移率晶体管
复合沟道
物理模型
磷化铟 相似文献
8.
This study presents a numerical investigation of the flow field in a screw pump designed to circulate biological fluid such
as blood. A simplified channel flow model is used to allow analysis using a Cartesian set of coordinates. Finite analytic
(FA) numerical simulation of the flow field inside the channel was performed to study the influence of Reynolds number and
pressure gradient on velocity distribution and shear stresses across the channel cross-section. Simulation results were used
to predict flow rates, circulatory flow and the shear stresses, which are known to be related to the level of red blood cell
damage (hemolysis) caused by the pump. The study shows that high shear levels are confined to small regions within the channel
cross-section, but the circulatory nature of the flow causes an increased percentage of blood elements to pass through the
high shear regions, and increases the likelihood of cell damage. 相似文献
9.
We have solved the problem of injection-type through electrohydrodynamic (EHD) flow in a closed channel. We have considered a model of a liquid with four types of ions. It is shown that a through EHD flow without internal vortices in the electrode gap is formed for the ratio 2 : 1 of the initial injection current from the electrodes in the channel. The structure of the flow in different parts of the channel and the integral characteristics of the flow have been analyzed. It is shown that for a quadratic function of injection at the electrodes, the current–voltage characteristic of the flow is also quadratic. 相似文献
10.
离心压气机回流器三维气动优化设计 总被引:2,自引:0,他引:2
回流器作为多级离心压气机两级间非常重要的连接部件,其内部的二次流动十分显著。回流器的设计目标是以尽可能小的损失对上一级出口气体进行整流,减小下级叶轮进口处的流场畸变。本文通过对回流器流道和整流叶栅进行参数化建模,采用多岛遗传算法对某多级离心压气机回流器进行基于N-S方程数值求解的三维气动优化设计,着力于提高变工况条件下回流器的级等熵效率以及使变工况条件下回流器的出口气流角尽可能均匀。 相似文献
11.
12.
Thadeus Schauer 《Particle & Particle Systems Characterization》1995,12(6):284-288
Measurements on paint components have been conducted with symmetrical flow field-flow fractionation (sym flow FFF) and asymmetrical flow FFF (asym flow FFF). Both methods are based on the same principle of separation, but they differ in the construction of the fractionation channel and the configuration of the channel flow and crossflow. On the basis of the good selectivity and resolution of these techniques, it was possible to determine the particle size of each individual constituent of a three-component mixture of a paint binder, pigment and filler, characterized by relatively broad and overlapping distributions, and to follow the changes on mixing them. In the case of sym flow FFF, it was possible to use thinner fractionation channels, with no system peaks and good selectivity in both the normal and steric-hyperlayer mode. The main features of asym flow FFF are the simpler construction of the fractionation channel and the possibility of focusing the sample in the channel better and of following visually the separation. This variant should be preferably used in the normal mode of operation. 相似文献
13.
I. S. Manuylovich 《Doklady Physics》2018,63(3):121-124
The results of simulation of detonation in a curved three-dimensional channel with a circular cross section of constant width blown through by a supersonic flow of a stoichiometric propane?air mixture are presented. In the bending zone, the channel wall was toroidal. The study was carried out within the framework of the one-stage combustion kinetics by the numerical method based on Godunov’s scheme in the original software package developed for multiparameter calculations and visualization of flows. The initiation of detonation occurs as a result of the formation of the shockwave configurations associated with the flow turn in the channel. Unsteady flow patterns are obtained, and their dependence on the parameters of the problem is investigated. The flow regime without detonation, the mode with the detonation wave emerging from the channel through the input cross section, and the mode with steady detonation are obtained. 相似文献
14.
S. A. Patlazhan I. V. Kravchenko R. Muller Y. Hoarau Y. Remond Al. Al. Berlin 《Doklady Physics》2017,62(3):145-148
The features of a Newtonian-fluid flow in a two-dimensional channel with sudden contraction and expansion are investigated by numerical modeling. The kinetics of the bifurcation transition from the symmetric mode to steady-state asymmetric flow on the outlet from the zone of contraction of the channel is analyzed. The linear dependence of the degree of asymmetry of flow on the Reynolds number is established. 相似文献
15.
Mark Short Stephen J. Voelkel David A. Kessler 《Proceedings of the Combustion Institute》2021,38(2):2205-2214
We study the effects of non-parallel (diverging or converging) channel walls on flame propagation and acceleration in planar and cylindrical narrow channels, closed at the ignition end and open at the other, accounting for thermal expansion in both the zero Mach number and weakly compressible flow limits. For parallel channel walls, previous work has shown that thermal expansion induces an axial flow in the channel, which can significantly increase the propagation speed and acceleration of the flame. In this study, we consider examples of diverging/converging linear walls, although our asymptotic analysis is also valid for curved walls. The slope of the channel walls is chosen so that the magnitude of the thermal-expansion induced flow through the channel obtained for parallel walls is modified at leading-order, thereby influencing the leading-order flame propagation. For zero Mach number flows, the effect of the diverging/converging channel walls is moderate. However, for weakly compressible flows, the non-parallel walls directly affect the rate at which pressure diffuses through the channel, significantly inhibiting flame acceleration for diverging walls, whereas the flame acceleration process is enhanced for converging walls. We consider several values of the compressibility factor and channel wall slopes. We also show that the effect of a cylindrical channel geometry can act to significantly enhance flame acceleration relative to planar channels. The study reveals several new physical insights on how non-parallel channel walls can influence the ability of flames to accelerate by modifying the flow and pressure distribution induced by thermal expansion. 相似文献
16.
An experimental and numerical investigation is performed in order to determine the outcome of dimple geometries on the heat transfer and friction factor in a dimple cooling channel subjected to turbulent flow. Two geometries taken into consideration are spherical and inclined teardrop. In order to have a better comparison between the two different dimple channel, the dimple depth, total wetted area of dimple, and dimple pitch have been kept constant. In case of spherical and inclined teardrop dimple channels, heat transfer augmentation, friction losses, and flow pattern have been obtained for a Reynolds Number range from 14,000 to 65,000. The investigation shows that the dimple geometry has a significant contribution to increasing the heat transfer augmentation and determining the flow pattern. The inclined teardrop dimple arrangement shows the maximum heat transfer that is 17% higher than the spherical dimple channel, whereas inclined teardrop dimple results in the rise of friction factor of about 5.93–16.14% times as compared to the spherical dimple within the specified Reynolds number. The inclined teardrop and spherical dimple channel show the heat transfer enhancement of 2.74 to 3.20 times and 2.38 to 2.68 times than that of smooth channels provided thermal boundary conditions and flow conditions are kept same. The numerical study has been performed, which provided a detailed insight into the flow structures and vortex formations in spherical and inclined teardrop dimple channel. 相似文献
17.
Subcooled flow boiling heat transfer experiments were performed with a 50/50 ethylene glycol/water mixture in a finned aluminum channel. The channel represented a hybrid electric vehicle power electronic cold plate receiving a 50/50 mixture from the radiator at 105°C and 2 atmospheres. Experiments used a range of mixture flow rates and both top- and bottom-heating situations. Boiling curves were generated, and subcooled flow boiling heat transfer coefficients were determined including the test channel fin effects. Subcooled flow boiling heat transfer coefficients showed a 25–30% increase compared to single-phase convection. 相似文献
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19.
Results of experimental investigation of a bubbly gas-liquid flow in an inclined flat channel are presented. Themeasurements were carried out in the range of superficial liquid velocities of 0.3–1.1 m/s and with different values of the volumetric gas flow rate ratio. The hydrodynamic structure wasmeasured bymeans of an electrochemical method using miniature shear stress probes. Values of average shear stress and heat transfer coefficient for different orientation of the channel were found. It is shown that in a bubbly gas-liquid flow the shear stress and heat transfer depend substantially on the channel inclination angle. 相似文献
20.
E. V. Sereshchenko R. V. Fursenko S. S. Minaev V. N. Kurdyumov 《Thermophysics and Aeromechanics》2011,18(2):293-304
The thermal-diffusive model was applied to the problem of flame propagation in a microchannel with controlled temperature
distribution in the walls; this demonstrated the possibility of formation of oscillating or rotating spatial flame structures,
which were described previously in experimental works on microcombustion. Two cases were considered: combustion in a rectangular
channel and in the clearance between two disks with radial feeding of premixture. In both cases, the typical across size of
the channel was lower than the critical diameter determined with respect to the ambient temperature. The gas flow was assigned
and described by the Poiseuille-flow velocity profile. Formation of oscillating flame in a rectangular channel and rotating
patterns in a radial channel was observed for a certain range of gas flow rate. At low flow rates beyond this range, repetitive
ignition/extinction of flame took place; at high flow rate we observed a steady flame mode. Formation of these special flame
structures is related to heat transfer between gas and hot walls of the channel, as well as to velocity maldistribution in
the microchannel. 相似文献