Modelling the Density-Driven Discharge of Sandstone Blocks

The density-driven discharge of salt-laden sandstone blocks has been studied to provide a knowledge basis for the prediction of the contaminant release of abandoned mines when they are flooded. To this end the results of a model experiment, of simplified analytical models and of numerical simulations in 1D, 2D and 3D have been analysed. Simple analytical functions have been found which approximately describe the time-dependent discharge of salt mass at complete saturation. They depend on the material parameters, the dimensions and the outflow geometry of the blocks. The discharge through the basal face is described well by an exponential behaviour. If the outflow occurs solely through the lateral block faces an algebraic function has been fitted to the simulated curves. In this case similarities to directed transport models of statistical physics have been pointed out. The results facilitate the superposition of discharge functions for single sandstone blocks to yield the discharge behaviour of the whole mine.     

Three-dimensional Composite Lattice Structures Fabricated by Electrical Discharge Machining

We present a novel method for fabricating carbon fiber composite sandwich panels with lattice core construction by means of electrical discharge machining (EDM). First, flat-top corrugated carbon fiber composite cores were fabricated by a hot press molding method. Then, two composite face sheets were bonded to each corrugated core to create precursor sandwich panels. These panels were transformed into sandwich panels with near-pyramidal truss cores by EDM plunge-cutting the corrugated core between the face sheets with a shaped cuprite electrode. The flat top corrugation permits adhesive to be applied consistently, and the selected dimensions leave a substantial bond area after cutting, resulting in a strong core-to-sheet bond. The crushing behavior of this novel construction was investigated in flatwise compression, and the results were compared to analytical expressions for strength and stiffness.     

Discharge channel structure in breakdown in an inhomogeneous field

Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 29–32, November–December, 1988.     

纯铜表面双层辉光离子渗钛合金层的摩擦磨损性能

采用双层辉光离子渗金属技术，在纯铜表面形成含钛的合金渗层；采用扫描电子显微镜观察分析磨损表面形貌，并分析了磨损机理．结果表明：纯铜表面经离子渗钛后形成了以金属问化合物Cu4Ti和含钛的α固溶体为主的合金渗层，从而使表面强度提高，磨损性能明显改善；纯铜磨损表面呈撕裂特征，而离子渗钛试样仅发生轻微擦伤．     

Discharge and energy-loss coefficients in flow through a breach in a trapezoidal dam

The paper presents experimental data on the discharge and energy-loss coefficients for two weirs of polygonal profiles with lateral contraction, which are required, in particular, in simulations of partial dam-break waves. It is shown that the values of these coefficients for a trapezoidal weir with a slope ratio of 1: 3 differ insignificantly from their values for a rectangular weir. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 1, pp. 68–73, January–February, 2008.     

孔洞放电热应力

本文研究介电材料内含空气圆孔在外加均匀电场作用下放电而引起的热应力.首先推导了圆孔放电前的临界电能,然后将复杂的放电效应简化为只存在热效应,并假设临界电能全部转化为热能且沿圆周均匀分布,计算了圆周附近的热应力.最后以聚乙烯材料作为算例,讨论了圆孔尺寸、材料常数等对热应力集中的影响,以及孔洞放电产生的径向应力和环向应力的变化规律.结果表明孔洞放电所引起的热应力集中以孔边的环向应力为主,而且材料放热系数越小,径向应力、环向应力集中程度越明显.     

水中脉冲放电的压力特性研究

同时利用高速摄影仪和压力传感器研究水中高压脉冲放电的压力特性。实验发现 ,当电容器的电容为 4 .1F ,充电电压为 10kV ,电极间隙为 7mm时 ,水中冲击波的波速为 1 5km s。通过压力传感器测得放电所产生的冲击波和气泡首次回胀时产生的冲击波在离通道 0 3m处的峰值压力分别为 1 5 5MPa和 0 5 5MPa ,模拟计算所得的峰值压力分别为 1 0MPa和 0 3 8MPa ,两者基本相符。另外 ,还根据高速摄影仪所拍摄到的等离子体通道直径的扫描照片 ,计算了在放电 3 0 s后通道内的压力为约 4 9MPa ,通道半径和壁速分别为 4mm和180m s。     

Discharge coefficients for flow through holes normal to a rotating shaft

A possible design for a more compact gas turbine engine uses contra-rotating high pressure (HP) and intermediate pressure (IP) turbine discs. Cooling air for the IP turbine stages is taken from the compressor and transferred to the turbine stage via holes in the drive shaft. The aim of this work was to investigate the discharge coefficient characteristics of the holes in this rotating shaft, and, in particular, to ascertain whether the sense of rotation of the shaft with respect to the discs affected these significantly. This paper reports mostly on experimental measurements of the discharge coefficients. Some CFD modelling of this flow was carried out and this has helped to explain the experimental work. The experimental results show the effects on the discharge coefficient of rotational speed, flow rate, and co- and contra-rotations of the shaft relative to the discs. The measured values of the discharge coefficient are compared with established experimental data for non-rotating holes in the presence of a cross-flow. For stationary shaft and discs, co-rotation of the shaft and discs and differential rotation with the disc speed less than the shaft (in the same rotational direction), the discharge coefficients are in reasonable agreement with these data. For differential rotation (including contra-rotation) with the disc speed greater than the shaft, there is a significant decrease in discharge coefficient.     

涡旋式压缩机排气系统气流脉动现象研究

研究了涡旋式空气压缩机排气系统的气流脉动现象，首次提出了排气孔口侵入现象及计算方法。由一维非定常流动理论建立了排气系统气流脉动的计算模型，利用匀熵修正理论进行了边界条件处理，并运用Ｌ－Ｗ两步计算法进行了数值计算。试验样机的实测结果与数值计算结果吻合较好。研究内容对于新型压缩机——涡旋式空气压缩机的设计具有指导意义。     

Magnetic Field Influence on the Gas Detonation Induced by Spark Discharge

The present paper describes the influence of magnetic field on the spark discharge utilized for initialization of detonation. The method of schlieren time-based scanning shows the increase of shock wave velocity in the case when magnetic field was applied to the area of electrical discharge in the air. The critical energy values are obtained for a direct initialization of detonation in hydrogen–air and hexane–air mixtures. Magnetic field has a significant influence on the deflagration–combustion transition in both mixtures at the critical energy values. Pressure and velocity of the shock front were measured by ICP pressure transducers, flame front was recorded by photo-diodes. Two cases were studied experimentally: external magnetic field is produced by inductance coils connected to capacitor; own magnetic field is induced directly by discharge current in the cables positioned in special way.     

Discharge of a supersonic jet from a nozzle with an inclined rim

The main results of a numerical study of the effect of the angle of the rim of a nozzle on the shape of the jet boundary and of the free shock and on the distribution of parameters in a three-dimensional underexpanded jet are presented. A noncentered second-order difference scheme is used to solve the gasdynamic equations for an inviscid perfect gas. Conditions are established for which the three-dimensional jet is observed to coincide partially in the radial planes and the corresponding planes of axisymmetric jets.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 105–110, July–August, 1977.In conclusion, the authors thank G. I. Petrov and his colleagues for detailed discussion of the results of the investigation reported here.     

Investigation of Physical Processes in the Gas Discharge Region Between Liquid Electrodes

Electrophysical, hydro-gas-dynamic, and thermal characteristics of a discharge arising between liquid electrodes are considered. Spatial visualization of flow patterns in the gas discharge region is performed by using the schlieren technique.