Generalized Wall Functions for High-speed Separated Flows Over Adiabatic and Isothermal Walls

We present the extension of our wall-laws developed for low-speed flows to super-and hyper-sonic configurations. In particular, we are interested in flows over isothermal walls and in the modeling of heat transfer. We recall the main steps of the development:

?Obtaining generalized wall functions for low-speed fluids, valid for all y ⁺.

?Taking into account transversal effects in wall-laws.

?Accounting for the compressible feature of the flow on adiabatic walls without using information on the local boundary layer structure, for instance its thickness, but only using information available at the fictitious wall.

?Taking into account thermal effects on isothermal walls. In particular, the heat flux at the real wall is obtained by an a posteriori evaluation using information at the fictitious one.

?Only using information available on unstructured meshes and avoiding the information coming from a Cartesian hypothesis for the mesh in near-wall regions.

These ingredients are validated on hyper-sonic configurations on adiabatic and isothermal walls for expansion and compression ramps.     

基于Rough Set的油液故障诊断系统的知识发现

结合Rough Set理论和摩擦学系统的特点，讨论了油液故障诊断系统的不协调性．在包含度方法的基础上，将普通二元关系进行推广，提出了一种不协调油液故障诊断系统知识发现模型，给出具体的运算方法，并通过试验实例验证了该模型的有效性．结果表明，该模型在最大分布约简的基础上进行油液诊断知识获取，能够很好地完成不确定性问题的推理，并且可以推导出具有最大可信度的油液诊断知识规则．     

Generalized Forchheimer Equation for Two-Phase Flow Based on Hybrid Mixture Theory

In this paper, we derive a Forchheimer-type equation for two-phase flow through an isotropic porous medium using hybrid mixture theory. Hybrid mixture theory consists of classical mixture theory applied to a multiphase system with volume averaged equations. It applies to media in which the characteristic length of each phase is small relative to the extent of the mixture. The derivation of a Forchheimer equation for single phase flow has been obtained elsewhere. These results are extended to include multiphase swelling materials which have nonnegligible interfacial thermodynamic properties.     

基于微凸体接触压力分布的粗糙表面法向接触建模

提出一种考虑微凸体弹塑性接触变形影响的粗糙表面法向接触力学模型.采用有限元模拟微凸体弹塑性接触过程,分析不同塑性屈服条件对微凸体接触载荷和实际接触面积的影响.再根据微凸体接触面上压力分布的变化规律,将微凸体的接触状态分为完全弹性接触阶段、弹塑性接触阶段、完全塑性接触阶段.分析接触面压力变化规律对微凸体法向接触载荷-变形的影响,再利用GW模型的数理统计分析的方法得到粗糙表面的法向接触载荷.将论文提出的模型与完全弹性模型、CEB模型、ZMC模型、KE模型、JG模型进行对比,并且研究了塑性指数对粗糙面接触载荷-平均高度距离的影响.结果表明,论文提出的模型能够更好地描述微凸体法向接触载荷与接触变形的变化趋势,模型预测粗糙表面法向载荷与ZMC、KE模型具有较好的一致性;粗糙面接触载荷随着平均接触距离增加而减少,随着塑性指数的增加,不同模型预测的法向接触载荷差异逐渐增大.     

基于基底长度的粗糙表面分形接触模型的构建与分析

为建立更为精确的粗糙表面接触模型,根据微凸体变形特征、分形理论以及摩擦的作用,从微观角度基于基底长度建立了粗糙表面分形接触模型.通过与其他粗糙表面接触模型和实验数据的比较,验证了本文模型的正确与合理,并由数值仿真分析了分形维数、接触载荷与真实接触面积之间的相互关系.分析结果表明:特征尺度一定时,要维持一定的真实接触面积,分形维数越大,所需要的力也越大;分形维数与特征尺度一定时,随着载荷的增加,接触面积也在增加;特征尺度与接触力一定时,随着分形维数的增大,真实接触面积在减小.该模型的建立为进一步研究粗糙表面的摩擦、磨损与润滑提供了理论依据.     

A Direct Method for the Identification of the Permeability Field Based on Flux Assimilation by a Discrete Analog of Darcy's Law

Inverse models to determine the permeability are generally based on existing forward models for the pressure. The permeabilities are adapted in such a way that the calculated pressures match the specified pressures in a number of points. To assimilate a priori knowledge about the flux, we introduce the flux assimilation method, which is based on the vector potential–pressure formulation of Darcy's law. Thanks to an unconventional discretization technique – the edge-based face element method – not only the specified pressures, but also specified information about the flux density can easily be assimilated. A relatively simple, but insightful analytical example illustrates the potential of this method.     

基于RBF网络的信息融合在SAMS故障诊断中的应用

针对卫星姿态测量系统(SAMS)，将径向基函数RBF(Radial Basis Function)网络和多传感器信息融合技术相结合，并将其应用在系统的故障检测与诊断中。研究结果表明，此方法是可行有效的，可以提高系统的测量精度和性能。     

A Meshless Solution Technique for the Solution of 3D Unsaturated Zone Problems,Based on Local Hermitian Interpolation with Radial Basis Functions

Recent developments in meshless numerical methods have led to algorithms that can be used to solve arbitrarily large problems without the support of a connected mesh, and without the computational cost and numerical ill-conditioning issues usually associated with such solution techniques. This work applies the Local Hermitian Interpolation (LHI) method, based on local interpolation with Radial Basis Functions (RBFs), to the solution of 3D unsaturated porous media problems. The proposed implementation is capable of handling real soil properties, provided either as an analytical function or as a series of pointwise measurements. The technique is implemented with implicit and explicit timestepping, and is validated against two transient Richards’ equation models, of which one has a known analytical solution. In addition, a real-world infiltration problem based on a saturated–unsaturated formulation is modelled, using a realistic variation of soil properties with water-pressure.