南京下蜀黄土的非均匀性研究

下蜀黄土分布在不同高程的多种地貌单元, 如山顶、阶地、山麓及盆地, 由黄土层和红土层两部分组成, 具有成分和结构差异, 尤其是水稳定性。它是-种非均匀性土层。当其位于地下水位以上或开放性状态时, 土层出现非饱和状态和负孔隙水压力, 产生较大的基质吸力。工程施工中, 可利用这-特性, 但必须控制各种向下净流量, 以抑制土体饱和度增大的趋势。     

圆矩形吸力式深水防波堤的循环承载力的高效计算方法

针对箱筒型基础防波堤的主要问题,提出了圆矩形新型吸力式深水防波堤。根据天津海积软土不排水循环三轴试验数据推导出了其循环强度计算公式,并将循环强度概念与承载力的破坏面理论相结合,建立了圆矩形吸力式防波堤的循环承载力的高效计算方法,得出其循环承载力的破坏包络面大小随着基础深径比的增大而逐渐扩大;随着竖向载荷的增大先扩大再收缩,在竖向载荷较小时,考虑软土循环弱化效应的承载力破坏包络面比循环前大幅缩小。

     

垂向一维均质土壤水分运动在蒸发条件下的运用

本文以新疆乌拉泊尔均衡场，新疆化肥厂试验站及昌吉地下水综合试验场资料求得的非饱和土壤水分特征曲线、水力传导度和土壤扩散率为依据，建立了适合乌鲁本齐地区非饱和土壤水分运动在蒸发条件下运用的数学模型．并用实测资料进行了验证．数值模拟结果与常观实测值有着良好的一致性，可应用于今后试验场在蒸发条件下土壤水动态的预报．     

用回归分析方法优选有杆泵抽油井的抽汲参数

姚春冬，张树江．用回归分析方法优选有杆泵抽油井的抽汲参数，数理统计与管理，１９９７，１６（１），９～１５．本文根据现场测试数据，建立了抽油机井地面效率、井下功率损失与排量系数的回归公式，以此为基础建立了以系统效率为目标函数的抽油机井抽汲参数优化设计模型，从而提出了一种优选抽油机井抽汲参数的新方法     

Application of spontaneous suction phase-dispersing (SSPD) extractors in the extraction of penicillin G

The extraction of penicillin G from an aqueous solution with butylacetate (BA) and tributyl phosphate (TBP) as extractants was carried out at pH 4 with spontaneous suction phase-dispersing (SSPD) extractors under various operating conditions. Four kinds of SSPD extractors were tested with results compared to those obtained by using an extractor with mechanical stirrers. Rotation speed and different extraction systems were found to influence the penicillin recovery and the stability of emulsion formed during extraction. The percentage of extraction under optimum conditions was 91% without formation of emulsion. The laser particle size measurement instrument combined with SSPD can be used to measure the emulsion droplet size in situ.     

Simulations of turbulent asymptotic suction boundary layers

A series of large-eddy simulations of a turbulent asymptotic suction boundary layer (TASBL) was performed in a periodic domain, on which uniform suction was applied over a flat plate. Three Reynolds numbers (defined as ratio of free-stream and suction velocity) of Re = 333, 400 and 500 and a variety of domain sizes were considered in temporal simulations in order to investigate the turbulence statistics, the importance of the computational domain size, the arising flow structures as well as temporal development length required to achieve the asymptotic state. The effect of these two important parameters was assessed in terms of their influence on integral quantities, mean velocity, Reynolds stresses, higher order statistics, amplitude modulation and spectral maps. While the near-wall region up to the buffer region appears to scale irrespective of Re and domain size, the parameters of the logarithmic law (i.e. von Kármán and additive coefficient) decrease with increasing Re, while the wake strength decreases with increasing spanwise domain size and vanishes entirely once the spanwise domain size exceeds approximately two boundary-layer thicknesses irrespective of Re. The wake strength also reduces with increasing simulation time. The asymptotic state of the TASBL is characterised by surprisingly large friction Reynolds numbers and inherits features of wall turbulence at numerically high Re. Compared to a turbulent boundary layer (TBL) or a channel flow without suction, the components of the Reynolds-stress tensor are overall reduced, but exhibit a logarithmic increase with decreasing suction rates, i.e. increasing Re. At the same time, the anisotropy is increased compared to canonical wall-bounded flows without suction. The reduced amplitudes in turbulence quantities are discussed in light of the amplitude modulation due to the weakened larger outer structures. The inner peak in the spectral maps is shifted to higher wavelength and the strength of the outer peak is much less than for TBLs. An additional spatial simulation was performed, in order to relate the simulation results to wind tunnel experiments, which – in accordance with the results from the temporal simulation – indicate that a truly TASBL is practically impossible to realise in a wind tunnel. Our unique data set agrees qualitatively with existing literature results for both numerical and experimental studies, and at the same time sheds light on the fact why the asymptotic state could not be established in a wind tunnel experiment, viz. because experimental studies resemble our simulation results from too small simulation boxes or insufficient development times.     

关于s矩阵法的剖析

本文对电力系统计算中的 s矩阵法 ,完成了相应的数学证明 ,并给出了几何解释和例子     

Flow analysis for a double suction centrifugal machine in the pump and turbine operation modes

A double suction centrifugal machine has been studied, both experimentally and numerically, operating as a pump and as a turbine. Experimentally, the static performance of the machine working as a pump was obtained. These measurements were compared with equivalent numerical results from a URANS calculation. As a second step, the numerical results have been exploited to get detailed information about the flow in both operating modes (pump and turbine). The main goals of the study are, first, the validation of the numerical procedure proposed and second, the possible turbine operation of the impeller, which could point out a wider working range for the machine. The first aspect is handled by detailed analysis in the pump mode, according to previous experience of the research group. The second objective is obtained by using the numerical model to explore the flow fields obtained, when working in an inverse mode. Therefore, the presented results join the use of a numerical methodology and the turbine mode of operation for a centrifugal impeller, providing insight into the flow characteristics. When working as a pump, the flow at the suction side is characterized by the existence of an inlet tongue, which tends to enforce a uniform flow for the nominal conditions. For the turbine mode, flow patterns in the impeller, volute and suction regions are carefully investigated. The influence of the specific geometrical arrangement is also considered for this operation mode. Copyright © 2008 John Wiley & Sons, Ltd.     

局部附面层抽吸对高负荷扩压叶栅流动特性影响

在低速条件下实验研究了局部附面层吸除对高负荷扩压叶栅内流动特性的影响。实验对叶栅壁面进行了墨迹流动显示,并采用五孔气动探针测量了叶栅出口截面参数,得到了该截面的二次流速度矢量分布。结果表明,吸力面两端附面层吸除能有效减小角区三维分离、抑制通道涡发展,而在吸力面中部抽吸不能有效抑制角区三维分离流动;在角区分离线起始位置后采用吸力面两端吸气方式时,吸气量越大流动改善的效果越好,其余方案时吸气量变化对流动影响较小。     

Suppression of vortex-induced vibration of a circular cylinder using suction-based flow control

In the present study, a flow control method is employed to mitigate vortex-induced vibration (VIV) of a circular cylinder by using a suction flow method. The VIV of a circular cylinder was first reproduced in a wind tunnel by using a spring–mass system. The time evolution of the cylinder oscillation and the time histograms of the surface pressures of 119 taps in four sections of the circular cylinder model were measured during the wind tunnel experiments. Four steady suction flow rates were used to investigate the effectiveness of the suction control method to suppress VIV of the circular cylinder. The vibration responses, the mean and fluctuating pressure coefficients, and the resultant aerodynamic force coefficients of the circular cylinder under the suction flow control are analyzed. The measurement results indicate clearly that the steady suction flow control method exhibits excellent control effectiveness and can distinctly suppress the VIV by dramatically reducing the amplitudes of cylinder vibrations, fluctuating pressure coefficients and lift coefficients of the circular cylinder model. By comparing the test cases with different suction flow rates, it is found that there exists an optimal suction flow rate for the maximum VIV control. The cases with higher suction flow rates do not necessarily behave better than those with lower suction flow rates. With the experimental setting used in the present study, the suction flow control method is found to behave better for VIV suppression when the ratio of the suction flow velocity to the oncoming flow velocity is less than one.