平板混合层流动中两相脉动关联矩的大涡模拟

在气粒两相平板混合层流动中,对气相流动采用大涡模拟,对颗粒相流动采用轨道模拟,研究了两相脉动关联矩。由两相各自瞬时速度出发可以直接获得两相脉动关联矩的统计结果。模拟获得的颗粒相一阶矩、二阶矩以及两相脉动关联矩与实验结果定量符合,表明基于细观模拟是不通过模型获得和研究两相脉动关联矩的可行途径。     

开敞式蜗壳轴流式水轮机湍流计算及性能预估

本文在进行模型水轮机试验的基础上,完成了开敞式蜗壳轴流式模型水轮机的全流道三维定常湍流计算。计算程序以雷诺时均连续方程和N-S方程作为控制方程,选用标准κ-ε双方程湍流模型使方程组封闭。数值求解通过CIMPLEC算法实现速度、压力的分离求解,离散差分格式具有二阶精度。通过计算获得了各过流部件的流动细节,预估了水轮机的能量性能,并与试验结果进行了比较。     

氢气扩散火焰中辐射源项湍流脉动特征的PDF模拟

采用κ-ε湍流模型、标量联合的概率密度函数(PDF)输运方程和层流火焰面模型相结合,模拟氢气自由扩散火焰中辐射源项湍流脉动特征.给出了主燃区内辐射源项湍流脉动的频率图.辐射源项的样本点分布集中,大约95%以上的样本落在其系综的±3倍方差以内,频谱图为单峰.     

FINITE ELEMENT SIMULATIONS FOR COMPRESSIBLE MISCIBLE DISPLACEMENT WITH MOLECULAR DISPERSION IN POROUS MEDIA

Abstract. We consider a nonlinear parabolic system describing compressible miscible displacement in a porous medium [5]. Continuous time and discrete time Galerkinmethods are introduced to approximate the solution snd optimal H1 error estimatesare obtained. One contribution of this paper is a demonstration of how moleculaxdispersion can be handled.     

A pair of stream functions for three-dimensional vortex flows

Introducing a vector potential, that is based on a pair of stream functions, and a velocity potential, antisymmetric equations for the stream functions are derived with the help of a variational principle. It is found that the equations are in a suitable form to investigate flows with helical symmetry, and, for example, to connect upstream axisymmetric flows with downstream helical flows. The special case of a transition from an upstream solid-body vortex to a downstream helical flow is investigated in detail. Furthermore, the stream-function equations are particularly useful to investigate general small-amplitude inertia waves on vortex flows. Time-dependent helical flows that are time-independent in a suitably rotating frame of reference can also be discussed with the proposed method.     

Determination of shock wave velocity from photographs obtained using a polarization interferometer

A polarization shear interferometer is described in which one of the two images of the flow being studied is produced outside the interference field and serves as a shadow pattern. This image is recorded again using an additional light source — a pulsed laser. In this way one can determine the shock wave velocity and establish, on the basis of gas-dynamic relationships, the proper numeration of the interference fringes on the interferogram.     

对可压缩流体若干问题的讨论

根据气体幼力学中一维定常等熵等流的基本方程组,得出的一维定常等熵管流的速度变化与管截面变化关系式,定性一讨论了一维定常等熵管流的截面变化对气流速度的影响。     

有变高度圆柱干扰的平板表面流谱拓扑结构

采用分区方法和Roe三阶流通量差分分裂格式数值求解雷诺平均N-S方程,湍流附加粘性系数由修正的Baldwin-Lomax模型计算,数值模拟了高超声速绕变高度圆柱流动,进而根据拓扑学理论给出了有变高度圆柱干扰的平板表面流谱拓扑结构,并结合对称截面流谱进行了简要的分析与探讨,指出了需要进一步深入研究的问题。     

Dynamics of the thermocline in the equatorial region of the Pacific ocean

This paper is devoted to the subsurface current dynamics in equatorial regions, where the hallmark of a strong stratification is a sharp interface (thermocline), separating two layers of different density, and whose depth is dependent upon the strength of the winds above the ocean's surface. We give here a few monotonicity results concerning the dynamics of the thermocline in the equatorial region. The most important one asserts that the level of the thermocline decreases as the strength of the wind at ten meters above the ocean surface, denoted |U_w|, increases. Moreover, the strength of the current at the thermocline decreases as |U_w| increases.     

用统一二阶矩模型模拟强旋湍流气粒两相流动的初探

本文初步探索用统一二阶矩（USM）两相湍流模型及K-ε-kp模型预报旋流数为1.5的轴向-切向进风、轴向供粉的强旋气粒两相流动，预报结果与实验的对比表明，USM模型在预报强族流动两相时平均切向速度场上优于K-ε-Kp模型，并且能够合理地给出与实验定性一致的两相湍流脉动的各向异性．