PCCP单管输水压力值计算方法对比分析

南水北调中线工程全线通水后,在事故情况下需将PCCP管道切换到单管运行,可能造成管道局部压力变幅大,对管道造成破坏。选取PCCP管道沿线连通井和调压池为控制断面,应用恒定总流能量方程计算,将计算压力值与现场监测数据进行对比,偏差较小,能够满足现场监测要求,可为单管运行状况下的管道压力计算提供可靠的方法。

岸壁效应对港口航道环境压力的影响

随着港口航道内船舶大型化和快速化的发展,岸壁对船舶运动的影响越来越突显。文中主要通过对直立岸壁岸吸和岸推的经验公式和实验结果的解析,提出考虑岸壁效应时港口航道环境压力的变化。

受软土侧向变形作用桩身侧压力系统分析

随着经济的不断发展,在对城市、乡村道路和桥梁进行设计和施工的过程中,应对土壤和地质结构进行系统分析和研究,进而制定科学合理的施工方案。在现阶段对软土侧向变形对桥台桩基造成的侧压力计算方式仍不明确,在实际工作中,软土对桥台桩基造成压力大小的计算与沿桩身分布的状况,属于桥台桩基内力变形以及桥台位移分析计算的核心要素。

关于螺栓扭矩计算工况及提高倍数的讨论

ASME标准中对螺栓扭矩值的计算提供了较为具体的方法,但没有明确螺栓上紧的决定工况是水压工况,且对水压工况螺栓上紧扭矩值提高的倍数没有具体的计算方法。本文提出了决定螺栓扭矩计算工况是水压工况,并对水压工况下所需要的螺栓扭矩相对设计工况螺栓扭矩提高的倍数进行了详细的推导,给实际螺栓扭矩值的计算及螺栓上紧提供了一定的指导意义。

A fast explicit finite difference method for determination of wellhead injection pressure

A fast explicit finite difference method (FEFDM),derived from the differential equations of one-dimensional steady pipe flow,was presented for calculation of wellhead injection pressure.Recalculation with a traditional numerical method of the same equations corroborates well the reliability and rate of FEFDM.Moreover,a flow rate estimate method was developed for the project whose injection rate has not been clearly determined.A wellhead pressure regime determined by this method was successfully applied to the trial injection operations in Shihezi formation of Shenhua CCS Project,which is a good practice verification of FEFDM.At last,this method was used to evaluate the effect of friction and acceleration terms on the flow equation on the wellhead pressure.The result shows that for deep wellbore,the friction term can be omitted when flow rate is low and in a wide range of velocity the acceleration term can always be deleted.It is also shown that with flow rate increasing,the friction term can no longer be neglected.

Effects of stator bending on pressure field and loss of transonic turbine stage

To study effects of the upstream flow field changing on the downstream flow field of transonic turbine, different three-dimensional bowed blades, which are the stator blades of transonic turbine stage, were designed in this paper. And then numerical calculations were carried out. The effects on downstream flow field were studied and analyzed in detail. Results show that, at the middle of stator blades, although the increasing Maeh number causes the increase of shock-wave strength and friction, the middle flow field of downstream rotors is improved obviously. It is an important change in transonic condition. This causes the loss of the rotor＇ s middle part decreased greatly. Correspondingly, efficiency of the whole transonic stage can be increased.

Crosswind stability of high-speed trains in special cuts

Analysis of the aerodynamic performance of high-speed trains in special cuts would provide references for the critical overturning velocity and complement the operation safety management under strong winds.This work was conducted to investigate the flow structure around trains under different cut depths,slope angles using computational fluid dynamics(CFD).The high-speed train was considered with bogies and inter-carriage gaps.And the accuracy of the numerical method was validated by combining with the experimental data of wind tunnel tests.Then,the variations of aerodynamic forces and surface pressure distribution of the train were mainly analyzed.The results show that the surroundings of cuts along the railway line have a great effect on the crosswind stability of trains.With the slope angle and depth of the cut increasing,the coefficients of aerodynamic forces tend to reduce.An angle of 75°is chosen as the optimum one for the follow-up research.Under different depth conditions,the reasonable cut depth for high-speed trains to run safely is 3 m lower than that of the conventional cut whose slope ratio is 1:1.5.Furthermore,the windward slope angle is more important than the leeward one for the train aerodynamic performance.Due to the shield of appropriate cuts,the train body is in a minor positive pressure environment.Thus,designing a suitable cut can contribute to improving the operation safety of high-speed trains.

Thermal Design of Power Transformers via CFD

At Siemens, an in-house CFD （computational fluid dynamics） code UniFlow is used to investigate fluid flow and heat transfer in oil-immersed and dry-type transformers, as well as transformer components like windings, cores, tank walls, and radiators. This paper outlines its physical models and numerical solution methods. Furthermore, for oil-immersed transformers, it presents an application to a HV （high voltage） winding in a traction transformer of locomotives, cooled by synthetic ester.

A parameter-free upwind scheme for all speeds' simulations

With the rapid development of the computational fluid dynamics(CFD),a parameter-free upwind scheme capable of simulating all speeds accurately and efficiently is in high demand.To achieve this goal,we present a new upwind scheme called AUSMPWM in this paper.This scheme computes the numerical mass flux as the AUSMPW+and computes the interfacial sound speed in a different way.Also,it computes the pressure flux by limiting the dissipation if the Mach number is less than 1.Series of numerical experiments show that AUSMPWM can satisfy the following attractive properties independent of any tuning coefficient:(1)Robustness against the shock anomaly and high discontinuity’s resolution;(2)high accuracy on hypersonic heating prediction and capability to give smooth reproductions of heating profiles;(3)low dissipation at low speeds;and(4)strong grid,reconstruction scheme,and Mach number independence in low speeds’simulations.These properties suggest that AUSMPWM is promising to be widely used to accurately and efficiently simulate flows of all speeds.