声测井中的声压—速度有限差分方法

为了解决薄互储层的声测井问题，提出了声压—速度有限差分方法：用声压和速度矢量做为场变量，分别描述井内流体和井外弹性固体或双相介质。这样选择场变量的优点是：处理脉冲点源（或线源）与套网格技术相比简单得多；在内边界上的差分格式稳定，精度得到了改进；人为边界上的吸收效果较好。用柱坐标分别给出了井壁上流体与弹性固体、流体与双相介质的声压—速度边界条件，并用守恒积分方法处理了井壁上的边界条件。通过用声压—速度有限差分方法模拟弹性固体和双相介质地层的声场，证明了声压—速度有限差分方法的有效性。

用ANSYS模拟球面声源在流体中的声场分布

采用有限元思想,借助ANSYS软件对流体中的声压分布进行模拟,从而得到声压在流体中的分布曲线和特性规律。对一些测量环境要求较高、操作过程要求较严格、测量难度较大的声测量问题在实践操作过程中有一定的参考和指导意义。

弹性固体地层－流体井孔弹性波场的有限差分数值模拟

用有限差分数值方法研究了由分层均匀流体（地层的声波方程近似）和弹性固体地层包围的流体井孔体系声波和弹性波的传播规律．用声压描述井中流体，使奇异点源处理简单，使流体与流体、流体与弹性固体内边界连接条件的差分格式稳定．在Ｆｏｕｒｉｅｒ变换方法与半解析方法适用的简单地层条件下，将有限差分数值模拟结果与Ｆｏｕｒｉｅｒ变换及半解析方法计算结果进行比较，检验了方法的精确性．从模拟井外有薄层介质存在时的全波曲线看，层速度显示正确，并可以定性判断薄层出现的位置．

The Numerical Simulation of Collapse Pressure and Boundary of the Cavity Cloud in Venturi

The idea that the collapse proceeds from the outer boundary of the cavity cloud towards its center for the ultrasonic cavitation proposed by Hasson and Morch in 1980s is further developed for calculating the collapse pressure and boundaries of cavity cloud at the collapse stage of bubbles for hydraulic cavitation flow in Venturi in present research. The numerical simulation is carried out based on Gilmore＇s eouations of bubble dynamics, which take account of the compressibility of fluid besides the viscosity and interfacial tension. The collapse of the cavity cloud is considered to proceed layer by layer from the outer cloud towards its inner part. The simulation results indicate that thepredicted boundaries of the cavity cloudat the collapse stage agree.well with the exPerimental ones.It is also found that the maximum collapse pressure of the cavity cloud is several times as high as the collapse pressure of outside boundary, and it is located at a point in the axis, where the cavity cloud disappears completely. This means that a cavity cloud has higher collapse pressure or strength than that of a single bubble due to the interactions of the bubbles. The effects of operation and structural parameters on the collapse pressure are also analyzed in detail.

Numerical Study on Flow-induced Noise for a Steam Stop-valve Using Large Eddy Simulation

The noise induced by the fluctuant saturated steam flow under 250 °C in a stop-valve was numerically studied.The simulation was carried out using computational fluid dynamics（CFD） and ACTRAN.The acoustic field was investigated with Lighthill＇s acoustic analogy based on the properties of the flow field obtained using a large-eddy simulation that employs the LES-WALE dynamic model as the sub-grid-scale model.Firstly,the validation of mesh was well conducted,illustrating that two million elements were sufficient in this situation.Secondly,the treatment of the steam was deliberated,and conclusions indicate that when predicting the flow-induced noise of the stop-valve,the steam can be treated as incompressible gas at a low inlet velocity.Thirdly,the flow-induced noises under different inlet velocities were compared.The findings reveal it has remarkable influence on the flow-induced noises.Lastly,whether or not the heat preservation of the wall has influence on the noise was taken into account.The results show that heat preservation of the wall had little influence.

Numerical Simulation of the Supersonic Flows in the Second Throat Ejector-Diffuser Systems

The supersonic ejector-diffuser system with a second throat was simulated using CFD. A fully implicit finite volume scheme was applied to solve the axisymmetric Navier-Stokes equations and a standard k-E turbulence model was used to close the governing equations. The flow field in the supersonic ejectordiffuser system was investigated by changing the ejector throat area ratio and the secondary mass flow ratio at a fixed operating pressure ratio of 10. A convergent-divergent nozzle with a design Mach number of 2.11 was selected to give the supersonic operation of the ejector-diffuser system. For the constant area mixing tube the secondary mass flow seemed not to significantly change the flow field in the ejector-diffuser systems. It was, however, found that the flow in the ejector-diffuser systems having the second throat is strongly dependent on the secondary mass flow.

Navier-Stokes Computstions of the Supersonic Ejector Diffuser System with a Second Throat

The supersonic ejector-diffuser system with a second throat was simulated using CFD. An explicit finite volumescheme was aPPlied to solve tWo-dimensional Navier-Stokes equations with standard k - E tulbulence model. Thevacuum Performance of the supersonic ejector-diffuser system was investigated by changing the ejector throat arearatio and the operating Pressure ratio. Two convergent-divergent nozzles with design Mach nUmber of 2. 11 and 3.41were selected to give the supersonic operahon of the ejector-diffoser system. The presence of a second throat stronglyaffected the shock wave sir’UctUI’e inside the "dxing tube as well as the spreading of the under-expanded jetdischarging from the Primary nozzle. There were optimum values of the operating pressure ratio and ejector throatarea ratio for the vacuum performance of the system to maximize.

Influence of Separated Vortex on Aerodynamic Noise of an Airfoil Blade

In order to clarify the mechanism by which aerodynamic noise is generated from separated flow around an airfoil blade,the relation between the attack angle and the aerodynamic noise of the blade was analyzed using a wind tunnel experiment and a CFD code.In the case of rear surface separation,the separated vortex which has a large-scale structure in the direction of the blade chord is transformed into a structure that concentrates at the trailing edge with an increase in the attack angle.The aerodynamic noise level then becomes small according to the vortex scale in the blade chord.When the flow is separated at the leading edge,a separated vortex of low pressure is formed at the vicinity of the trailing edge.The pressure fluctuations on the blade surface at the vicinity of the trailing edge become large due to the vortex in the wake.It is considered that the aerodynamic noise level increases when the flow is separated at the leading edge because the separated vortex is causing the fluctuations due to wake vortex shedding.

Temperature Distribution on Inclined Plate Caused by Interaction withSupersonic Jet

The Phenomena of the interaction between a supersonic jet and an obstacle is a very interesting and important problem relating to the industrial engineering. This paper aims to investigate the characteristics of the two-dimensional temperature distribution on an inclined plate surface and the relation between the temperature distribution and some shock waves formed in the flow field. In this study, the measurement of temperature distribution on an inclined plate surface and the now visualization has carried out for various conditions using the thermo-sensitive liquid crystal sheet and the schlieren method. The two dimensional temperature distribution on the plate surface is clearly obtained by the thermo-sensitive liquid crystal sheet. The relation between the temperature distribution on an inclined plate surface and some shock waves reached at a plate surface is discussed. In this paper, the characteristics of the temperature distribution and the maximum temperature, and some other experimental evidences are presented.