一种模拟气液两相流的格子波尔兹曼改进模型

基于格子波尔兹曼自由能模型,提出了一种模拟黏性流场中大密度比气液两相流的改进模型. 为了提高模型的精度,在原始模型的基础上计入了邻近点间粒子数密度的传递速率控制,考虑了碰撞项的差分松弛;为了避免两相间大密度比造成的数值不稳定问题,分别采用六点和九点差分格式求解?和?2. 同时,与传统格子波尔兹曼方法不同,实现了由单步碰撞操作到两步操作的转化. 通过对无重力场中气泡的模拟及与已有模型的计算结果的对比分析,表明该模型具有更高的数值精度. 成功模拟了重力作用下,单个上浮气泡的形变和尾涡形成过程,以及水平和竖直方向上两个气泡的相互作用过程,并验证了其质量守恒和体积不可压缩性.      

用鲁棒Riemann求解器和运动重叠网格计算旋翼粘性绕流

发展了一种基于鲁棒Riemann求解器和运动重叠网格技术计算直升机悬停旋翼流场的方法。基于惯性坐标系,悬停旋翼流场是非定常流场,控制方程为可压缩Reynolds平均Navier-Stoke方程,其对流项采用Roe近似Reimann求解器离散,使用改进的五阶加权基本无振荡格式进行高阶重构,非定常时间推进采用含牛顿型LUSGS子迭代的全隐式双时间步方法。为实施旋转运动和便于捕捉尾迹,计算采用运动重叠网格技术。计算得到的桨叶表面压力分布及桨尖涡涡核位置都与实验结果吻合较好。数值结果表明:所发展方法对桨尖涡具有较高的分辨率,对激波具有较好的捕捉能力,该方法可进一步推广到前飞旋翼粘性绕流的计算。     

具有粘性阻尼器的陀螺系统根轨迹特性分析

研究了含粘性阻尼器并具有陀螺效应的结构系统的根轨迹特性。结合算例着重研究了根轨迹分岔现象,指出当阻尼器位于某些点处时,随着阻尼系数的增大,系统的某两条完整的根轨迹曲线可能会越定越靠近,相遇然后又相互分离。根轨迹的这种分岔现象对于确定阻尼器的安置位置及选定阻尼系数大小有一定参考价值。     

高雷诺数流动理论、算法和应用的若干研究进展

在黏性流体力学的历史发展中,Navier-Stokes (NS)方程组的 简化理论、相应算法和应用构成了不同历史时期的学科前沿、核心内 容的应用热点。以此为线索,简要评述经典边界层、多层(三层)边界 层、干扰边界层、扩散抛物化(DP) NS方程诸理论、相应算法和应用的 若干研究进展;诸理论之间以及他们与实验的关系;简化湍流计算的 一点注释以及物理分析和数值模拟相结合的一些问题。     

A multigrid approach for steady state laminar viscous flows

In this paper, we use the laminar viscous flow in a lid‐driven cavity as an example to describe and verify a numerical scheme for non‐linear partial differential equations. The proposed scheme combines a new analytical method for strongly non‐linear problems, namely the homotopy analysis method, with the multigrid techniques. A family of formulas at different orders is given. At the lowest order, the current approach is the same as the traditional multigrid methods. However, our high‐order scheme needs a fewer number of iterations and less CPU time than the classical ones. Copyright © 2001 John Wiley & Sons, Ltd.     

Vortex structure generation on the frontal surface of a cylinder set transversely in a hypersonic flow

The problem of formation of spatially periodic structures on the frontal surface of a cylindrically blunted body set transversely in a hypersonic flow is studied. Within the framework of the model adopted, a possible mechanism of vortex structure generation on the frontal surface of the blunt body is proposed and confirmed by calculations; in this mechanism, the curved bow shock produces a vortex flow, while in its turn the vortex, which persists under weak dissipation, acts on the shock thus maintaining its curved shape. It is shown that the spatially periodic mode of hypersonic flow past a cylinder can exist in the case of a uniform incident flow and under homogeneous boundary conditions on the body surface.     

On the spectrum of natural frequencies of circular cylindrical shells completely filled with a fluid

The natural frequencies of cylindrical shells filled with a fluid and having the ends either simply supported or clamped are determined. Conditions are studied under which the natural frequencies of the shell are close or multiple __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 5, pp. 42–49, May 2006.     

Stability and nonlinear wavy regimes in downward film flows on a corrugated surface

The linear and nonlinear stability of downward viscous film flows on a corrugated surface to freesurface perturbations is analyzed theoretically. The study is performed with the use of an integral approach in ranges of parameters where the calculated results and the corresponding solutions of Navier-Stokes equations (downward wavy flow on a smooth wall and waveless flow along a corrugated surface) are in good agreement. It is demonstrated that, for moderate Reynolds numbers, there is a range of corrugation parameters (amplitude and period) where all linear perturbations of the free surface decay. For high Reynolds numbers, the waveless downward flow is unstable. Various nonlinear wavy regimes induced by varying the corrugation amplitude are determined. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 1, pp. 110–120, January–February, 2007.     

不同耗能器安装方式下的结构振动控制效果分析

在斜支撑和Ⅴ形支撑的基础上，提出了安装阻尼器的三种新型附加联动机构支撑形式；并对这三种支撑形式下的阻尼器行程和控制力的计算进行了分析，采用放大系数的形式使计算公式得以简化；以SMA耗能阻尼器为对象，利用笔者编写的计算机程序，对包括斜支撑和Ⅴ形支撑在内的五种阻尼器安装方式进行了仿真计算。结果表明：(1)不同安装方式的振动控制效果各不相同，上肢联动机构的放大作用最大；(2)SMA耗能阻尼器的控制效果受SMA丝材长度的影响较大；(3)对不同的结构和不同的阻尼器应选择不同的阻尼器安装方式，才能使整体控制效果达到最佳。