基于SPH方法的幂律流体突缩型管路流动过程仿真

应用光滑粒子流体动力学(SPH)方法进行了幂律型流体的突缩型管路流动过程仿真。推导了SPH形式的流体动力学控制方程,应用罚方法施加边界条件,应用人工应力消除拉伸不稳定现象,应用XSPH方法规范粒子秩序。提出了幂律型本构关系的SPH求解方法,推导了剪切速率及粘性项的计算公式。应用Poiseuille流算例对本文的幂律型本构求解方法进行了验证,获取了幂律型流体在突缩管中的流动特性,并与水的流动特性进行了对比分析。讨论了流动特性的成因。     

MHD simulation of magnetic field configuration above the active region NOAA 10365

The current sheet (CS) creation before a flare in the vicinity of a singular line above the active region NOAA 10365 is shown in numerical experiments. Such a way the possibility of energy accumulation for a solar flare is demonstrated. These data and results of observation confirm the electrodynamical solar flare model that explains solar flares and CME appearance during CS disruption. The model explains also all phenomena observed in flares. For correct reproduction of the real boundary conditions the magnetic flux between spots should be taken into account. The full system of 3D MHD equations are solved using the PERESVET code. For setting the boundary conditions the method of photospheric magnetic maps is used. Such a method permits to take into account all evolution of photospherical magnetic field during several days before the flare.     

基于SPH方法的射流撞击仿真

为了研究液体推进剂的撞击雾化问题,采取光滑粒子流体动力学方法 (SPH)进行了射流撞击形成液膜过程的数值模拟。修正了基于连续表面力模型的表面张力算法,推导了考虑粘性与表面张力作用的SPH形式的控制方程,对撞击雾化模型进行了合理简化,采用水作为推进剂模拟液。得到了不同撞击速度、角度下的液膜图像及液膜的形成过程图像。证明了SPH方法适于解决存在自由表面及大变形的射流撞击问题。     

离心式血液泵内非牛顿流体水力特性研究

在旋转式血液泵的研发中习惯于把血液当作牛顿流体来处理,而血液本质上是非牛顿流体.本文实验测量了0.6‰、1‰、2‰浓度的黄原胶溶液在一种离心式血泵模型内的水力特性,发现在高浓度低转速时,在相同流量下黄原胶溶液的扬程低于(或接近于)水的相应扬程,而在高转速时一定浓度的黄原胶溶液的扬程会高于水的相应扬程,最高可有7%的差值;黄原胶溶液不遵守牛顿流体相似律,一定浓度的黄原胶溶液当其雷诺数高于某一临界值后,在无量纲扬程一流量图中数据点会落在同一条曲线上,称非牛顿流体相似曲线;在高转速大流量时,非牛顿流体相似曲线位于牛顿流体相似曲线上方.     

A high-order SPH method by introducing inverse kernels

The smoothed particle hydrodynamics (SPH) method is usually expected to be an effi-cient numerical tool for calculating the fluid-structure interactions in compressors; however, an endogenetic restriction is the problem of low-order consistency. A high-order SPH method by intro-ducing inverse kernels, which is quite easy to be implemented but efficient, is proposed for solving this restriction. The basic inverse method and the special treatment near boundary are introduced with also the discussion of the combination of the Least-Square (LS) and Moving-Least-Square (MLS) methods. Then detailed analysis in spectral space is presented for people to better under-stand this method. Finally we show three test examples to verify the method behavior.     

超高速碰撞碎片散布数值分析

基于光滑粒子流体动力学(SPH)方法,对低轨卫星与某空间物体的超高速碰撞问题进行了数值模拟。通过确立航天器轨道高低判定准则及判定方法,分析了碰撞角度、碰撞速度对碰撞碎片散布的影响情况。仿真结果表明,低轨卫星与空间物体碰撞产生的大部分空间碎片所处轨道高度位于原卫星轨道周围;碰撞碎片的散布情况与碰撞方式密切相关,相比于上升式碰撞,下压式碰撞产生的下降碎片个数较多,上升碎片个数较少;低轨卫星与空间物体碰撞产生的空间碎片总数与碰撞相对速度密切相关,碰撞相对速度越大,碎片数量越多;随着碰撞相对速度的增大,上升碎片、下降碎片及双曲碎片的个数逐渐增加;在不改变碰撞总动量数量级的条件下,改变空间物体的速度大小对空间碎片散布的影响并不明显。     

‘Spectro-temporal’ characteristics and disk-jet connection of the outbursting black hole source XTE J1859+226

We re-investigated the ‘spectro-temporal’ behavior of the source XTE J1859+226 in X-rays during its outburst phase in 1999, by analysing the RXTE PCA/HEXTE data in 2–150 keV spectral band. Detailed analysis shows that the source evolves through different spectral states during its entire outburst as indicated by the variation in the spectral and temporal characteristics. Although the evolution pattern of the outburst followed the typical q-shaped profile, we observed an absence of ‘canonical’ soft state and a weak presence of ‘secondary’ emission during the decay phase of the outburst. The broad-band spectra, modeled with high energy cutoff, shows that the fold-energy increases monotonically in the hard and hard-intermediate states followed by a random variation in the soft-intermediate state. We attempted to estimate the mass of the source based on the evolution of Quasi-Periodic Oscillation (QPO) frequencies during rising phase modeled with the propagating oscillatory shock solution, and from the correlation of photon index and QPO frequency. It is also observed that during multiple ejections (observed as radio flares) the QPO frequencies are not present in the power spectra and there is an absence of lag in the soft to hard photons. The disk flux increases along with a decrease in the high energy flux, implying the soft nature of the spectrum. These results are the ‘possible’ indication that the inner part of the disk (i.e., Comptonized corona), which could be responsible for the generation of QPO and for the non-thermal Comptonized component of the spectrum, is disrupted and the matter gets evacuated in the form of jet. We attempted to explain the complex behavior of ‘spectro-temporal’ properties of the source during the entire outburst and the nature of the disk-jet connection before, during and after the ejection events in the context of two different types of accreting flow material, in presence of magnetic field.     

SPH-BASED NUMERICAL ANALYSIS FOR GRANULAR MATERIAL MODEL OF SAND AND REGOLITH

The development of an innovative drilling system makes it necessary to model the material of extra-ter- restrial soil, i.e. regolith or lunar soil. And then the drilling process is numerically simulated. Since real regolith is very scarce and costly, sand properties are investigated by means of experiments and sand model is constructed with the capability of partly reflecting these properties. With the use of smooth particle hydrodynamics （SPH） method in LS-DYNA, data analysis and modeling process are presented to reach the following achievements：（1） Develop a general model approach of sand using SPH method; （2） Compare SPH results with experimental data to validate it; （3） Adapt the sand model to lunar soil while fitting the simulation of dual-reciprocating drilling （DRD） process.     

Simulation of Wave Impact on Three-Dimensional Horizontal Plate Based on SPH Method

An improved three-dimensional incompressible smooth particle hydrodynamics （ISPH） model is developed to simulate the impact of regular wave on a horizontal plate. The improvement is the employment of a corrective function to enhance angular momentum conservation in a particle-based calculation. And a new estimation method is proposed to predict the pressure on the horizontal plate. Then, the model simulates the variation characteristics of impact pressures generated by regular wave slamming. The main features of velocity field and pressure field near the plate are presented. The present numerical model can be used to study wave impact load on the horizontal plate.     

管道内流动力学修正耗散模型

基于二维流体动力学方程组,根据管道内流动力学相关特性以及管道输入端流场边界条件,提出了修正耗散模型。相对于耗散模型,修正耗散模型考虑了管道输入端流场的影响,能够更精确地描述风洞试验中管道效应对动态压力测量的影响。FL-14风洞动态压力试验也表明:管道间接测量的动态压力结果经过修正耗散模型进行修正后,能够大幅度减少管道效应所带来的误差。在一定试验条件下,耗散模型修正结果的相对误差高达534%,而修正耗散模型修正结果的相对误差只有66%。