A NEW COMPUTATION METHOD FOR THE UNSTEADY HEAT TRANSFER COEFFICIENT IN A DEEP MINE

In mine geothermal prediction, the unsteady heat transfer coefficient is an Important parameter for heat transfer computation between country rock and mine airflow. In this paper, the rock temperature distributions in the geothermal fields have been derived in mathematics, the unsteady heat transfer coefficients that can expound the relation between its nature and influencing factors have been derived also based on this analytic formula. It is shown both by numerical simulations and through in situ measurements that the new computation method for determining the unsteady heat transfer coefficient is accurate, rapid and simple.     

一维非恒定流模型在太湖湖滨地区的应用研究

运用圣维南方程组构建一维非恒定流模型,对宜兴市河网湖泊等水利工程进行了概化模拟,重点对圩区排涝泵站、闸门调度方式、河道流域面上的调蓄作用及净雨流入等进行了探讨.计算结果表明,模拟效果较好,可为宜兴市防洪决策提供科学依据.     

卫生洁具水包内流速的应变式测试

卫生洁具的排水过程具有“带自由面”、“非恒定”、“过程时间短”的特性,且水包内的水流为一薄层水流,其水流速度能反映水流对水包壁面的冲刷作用的大小。通过对卫生洁具的水包内水流速度测试,获得了一种可针对带自由面的薄层水流速的和基于应变传感技术的测试方法,包括其测试原理、速度传感器的设计、测试系统设计、数据采集及计算机处理方法,并给出了测试的结果以及标定方法。     

Effects of injection frequency on the rotor stall margin

The stall margin of compressor could be improved effectively by rotor tip injection,and the periodic injection is commonly used in the research.The purpose of this work is to investigate the influence of injection frequency on the rotor stall margin.An unsteady CFD code was employed to simulate the flow field of the rotor with injections of different frequencies.Comparing the stall margin of the rotor with injections of different frequencies,it is shown that there is an optimal injection frequency,around wh...     

Thermal radiation effect on unsteady MHD free convection flow past a vertical plate with temperature‐dependent viscosity

This article investigates the influence of radiation and temperature‐dependent viscosity on the problem of unsteady MHD flow and heat transfer of an electrically conducting fluid past an infinite vertical porous plate taking into account the effect of viscous dissipation. The governing equations are converted into a system of nonlinear ordinary differential equations via a local similarity parameter which is taken as a function of time. The resulting system of coupled nonlinear ordinary differential equations is solved numerically using the fourth order Runge–Kutta integration scheme with the shooting method. The numerical results for the velocity and the temperature are displayed graphically showing the effects of various parameters. The results show that increasing the Eckert number and decreasing the viscosity of air leads to a rise in the velocity, while increasing in the magnetic or the radiation parameters is associated with a decrease in the velocity. Also, an increase in the Eckert number leads to an increase in the temperature, whereas an increase in radiation parameter leads to a decrease in the temperature.     

城市排洪(涝)工程设计

探讨了城区雨洪汇流与水工建筑物的相互关系,提出了城区雨洪汇流分析与排洪(涝)建筑物设计同步方法,建立了坡面—排洪工程耦合的非恒定流分析的基本方程及其求解方法,并用实例说明,可供借鉴。     

Sound Produced When a Vortex Pair is Swallowed by a Jet

An analysis is made of the sound generated during the high-Reynolds-number convection of a vortex pair in a jet of water exhausting from a large vessel through a slit aperture. The equations of motion are linearized about the classical free-streamline solution describing steady flow through the aperture. It is assumed that the vortex pair is swept through the aperture into the jet by the steady mean flow, with no account taken of the nonlinear influence on the motion of ‘images’ in the boundaries. Additional vorticity is shed from the edges of the aperture in order that the flow should remain smooth and continuous (the Kutta condition). This vorticity is convected away within a sheet of ‘bound’ vorticity on the mean free streamlines of the jet. A strong peak in the bound vorticity is established when the vortex pair enters the aperture. Both the incident and the shed vorticity generate sound, but their respective contributions to the acoustic pressure are of opposite phase. The dominant radiation in the water above the aperture is produced as the vortex enters the jet, and has the form of a pressure pulse of width ~h/M and monopole strength , where h is the width of the aperture, ρ _o the density of the water, v a typical flow velocity, and M is the jet Mach number.     

Numerical Simulation for Effect of Inlet Cooling Rate on Fluid Flow and Temperature Distribution in Tundish

 The fluid flow in tundish is a non-isothermal process and the temperature variation of stream from teeming ladle dominates the fluid flow and thermal distribution in tundish. A numerical model was established to investigate the effect of inlet cooling rate on fluid flow and temperature distribution in tundish based on a FTSC (Flexible Thin Slab Casting) tundish. The inlet cooling rate varies from 0.5 to 0.25 ℃/min. Under the present calculation conditions, the following conclusions were made. When the stream temperature from teeming ladle drops seriously (for inlet cooling rate of 0.5 ℃/min), there is a “backward flow” at the coming end of casting. The horizontal flow along the free surface turns to flow along the bottom of tundish. The bottom flow shortens the fluid flow route in tundish and deteriorates the removal effect of nonmetallic inclusions from molten steel. Nevertheless, when the inlet cooling rate decreases to 0.25 ℃/min, the horizontal flow is sustained during the whole casting period. The present research provides theoretical directions for temperature control in teeming ladle and continuous casting tundish during production of advanced steels.     

对旋轴流风机三维流场的非定常数值模拟研究

应用三维非定常数值计算方法对矿用对旋轴流风机的非定常特性进行了数值模拟研究.数值计算中将SIM-PLE算法与RNG k-ε湍流模型相结合,以风机三维全流道为计算域,获得了对旋风机不同特征面上压力特性的非定常分布.计算结果表明,对旋风机在一个旋转周期的不同时刻,其内部流场存在显著的非定常特性.