一种求解可压缩Navier-Stokes方程的隐式迭代时间推进方法

针对有壁面边界的可压缩流动问题,提出与基于非等距网格的高精度紧致型差分格式相结合的简化隐式迭代时间推进法,建立求解可压缩Navier-Stokes方程的直接数值模拟方法,提高了计算效率.应用该方法,直接数值模拟两种有壁面边界的二维可压缩流动问题,即可压缩平板边界层流动和可压缩槽道流动.     

多组分颗粒稠密气固两相流动的数值模拟

基于气体分子运动理论和颗粒动理学方法，建立多组分颗粒气固两相流等温流动模型。模型考虑了颗粒相各组分颗粒温度的差异、气相与颗粒相以及颗粒相各组分之间的动量和能量的传递和耗散，以及相间作用。建立颗粒相粘性系数、颗粒相压力等物性参数计算模型。模拟计算颗粒相浓度、粒径分布等参数与实测值相吻合。     

一维多介质可压缩流动数值方法

应用高精度界面追踪方法计算一般状态方程的多介质可压缩流动问题;应用LevelSet技术捕捉界面位置,在界面附近采用守恒数值离散,用双波近似求解一般状态方程Riemann问题,并采用统一高阶PPM格式进行内点和交界面点的计算.一维算例表明,该方法对于光滑区域以及多介质交界面具有二阶精度,能准确地模拟交界面的位置,交界面计算无数值振荡和数值耗散,并能处理一般状态方程的多介质可压缩流动问题.     

用于多组分同时测定的流动注射-CCD阵列探测分光光度装置研究

使用流动注射进样、多色仪分光、ＣＣＤ阵列探测器以及微机处理机等,建立了用于多组分同时测定的流动注射－ＣＣＤ阵列探测器联用分光光度装置。完成以ｍｅｓｏ－四（４－三甲铵苯基）卟啉为显色剂时铅和镉的同时测量,铅的检出限为０．０１４μｍ／ｍＬ,镉为０．０１５μｇ／ｍＬ。     

可压缩流动离散涡方法

推导了可压缩流动旋涡动力学基本方程,并分析了其基本性质。如同不可压流动,在可压缩流动中旋涡同样具有场与物质两重特征。得出了可压缩流中的旋涡诱导速度公式,对Ｂｉｏｔ－Ｓａｖａｒｔ方程进行了可压缩修正。基于Ｌａｇｒａｎｇｉａｎ框架下的粒子方法,求解可压缩流中的胀量项,从而用离散涡模型求解了非定常、不稳定、可压缩流场。数值实验验证了提议的计算方法有效性。并分析了可压缩流动中旋涡运动的特征,与不可压流动的差别。     

一种新的可计算可压缩流动的预处理方法

针对使用可压缩流动数值方法求解不可压缩流动存在的刚性问题,基于虚拟压缩法思想,构造了一种以Mach数、速度、密度、温度等变量为元素的预处理矩阵,改变了控制方程组的特征根并使其量级更接近.通过理论推导与分析,证明新方法相比Weiss, Pletcher, Dailey和Choi的方法而言,不仅能降低方程组的刚性,提高了数值求解效率,而且拥有更好的稳定性,此外还能实现低速流动和高速流动之间的光滑过渡.采用有限差分格式进行离散,对流项的Roe格式作为基本加权无振荡(WENO)格式的求解器,黏性项则使用中心型紧致差分格式来计算,与预处理矩阵相结合展开数值实验,结果表明新预处理方法可以实现对无黏和有黏不可压缩流动问题的高精度模拟,且拥有比Weiss和Pletcher等提出的方法更好的收敛性和稳定性.     

NDIR多组分气体分析的干扰修正方法研究

介绍了非分散红外(Non-Dispersive Infrared,NDIR)多组分气体分析的一种干扰修正方法.根据逐次积分气体吸收模型和方法,并考虑温度和气压对积分线强和线型的影响,选择洛伦兹展宽线型,得到了CO,CO2,NO和H2O在各个滤波通道的响应系数.利用响应系数建立了用于干扰修正的四元线性回归方程组,通过求解...     

高密度比多介质可压缩流动的PPM方法

介绍一种基于流体体积分数模型的界面捕捉方法,数值模拟高密度比及含强激波的多介质可压缩流动.将PPM方法应用到多介质体积分数形式的Euler方程组,用双波近似求解一般刚性气体状态方程Riemann问题,可方便处理界面强剪切的滑移线问题,并给出了水下激波和气泡相互作用以及多相Richtmyer Meshkov不稳定性的计算结果.     

多组分复杂体系光谱多元定量分析方法研究

为解决多元分析方法建模成本高及适用性差,严重制约其在光谱分析领域大量应用的难题,提出了一种新的多元定量分析方法。以汽油及其甲基叔丁基醚（MTBE）溶液的红外光谱为研究对象,使用五种汽油及其窄馏分建立背景光谱空间,用斜投影算法分离出混合光谱中纯MTBE光谱分量,建立纯光谱响应值与浓度之间的标准曲线,相关系数为0.995 2,截距仅为0.025,实现了多组分复杂体系中待测物的定量分析。与正交投影方法比较,新方法对五个预测样本的预测结果明显优于正交投影法。对17个实际油样的预测结果显示,新方法比PLS模型具有更好的适用性。新方法无需收集大量样本和建立复杂模型,方法简单,准确,适用性好。     

矿井风流可压缩流动规律及热风压的影响

１前言矿井通风的动力包括两部分：矿井主通风机和热风压。山区高温、深部开采和冬季寒冷地区热风压对矿井通风的影响是很大的．考虑这种影响应计入风流流动过程的可压缩性,通风机的运行工况不再是两线交点,而是系统阻力曲线、热风压变化曲线和风机性能曲线三线的相互递...     

多介质流动数值计算中的界面处理方法

 求解Riemann问题得到界面接触间断的流动状态,并以此构造带状区域的虚拟流体状态,对于多维问题设计了一种方便有效的算法。同时求解耦合的守恒形式欧拉方程组和非守恒界面捕捉方程,并用Level-Set函数捕捉界面,数值计算采用高分辨率MWENO格式。最后对可压缩多介质流动问题进行了数值模拟。     

Development and Comparative Studies of Three Non-Free Parameter Lattice Boltzmann Models for Simulation of Compressible Flows

This paper at first shows the details of finite volume-based lattice Boltzmann method (FV-LBM) for simulation of compressible flows with shock waves. In the FV-LBM, the normal convective flux at the interface of a cell is evaluated by using one-dimensional compressible lattice Boltzmann model, while the tangential flux is calculated using the same way as used in the conventional Euler solvers. The paper then presents a platform to construct one-dimensional compressible lattice Boltzmann model for its use in FV-LBM. The platform is formed from the conservation forms of moments. Under the platform, both the equilibrium distribution functions and lattice velocities can be determined, and therefore, non-free parameter model can be developed. The paper particularly presents three typical non-free parameter models, D1Q3, D1Q4 and D1Q5. The performances of these three models for simulation of compressible flows are investigated by a brief analysis and their application to solve some one-dimensional and two-dimensional test problems. Numerical results showed that D1Q3 model costs the least computation time and D1Q4 and D1Q5 models have the wider application range of Mach number. From the results, it seems that D1Q4 model could be the best choice for the FV-LBM simulation of hypersonic flows.     

Three-Dimensional Lattice Boltzmann Model for High-Speed Compressible Flows

A highly efficient three-dimensional （31）） Lattice Boltzmann （LB） model for high-speed compressible flows is proposed. This model is developed from the original one by Kataoka and Tsutahara [Phys. Rev. E 69 （2004） 056702]. The convection term is discretized by the Non-oscillatory, containing No free parameters and Dissipative （NND） scheme, which effectively damps oscillations at discontinuities. To be more consistent with the kinetic theory of viscosity and to further improve the numerical stability, an additional dissipation term is introduced. Model parameters are chosen in such a way that the von Neumann stability criterion is satisfied. The new model is validated by well-known benchmarks, （i） Riemann problems, including the problem with Lax shock tube and a newly designed shock tube problem with high Mach number; （ii） reaction of shock wave on droplet or bubble. Good agreements are obtained between LB results and exact ones or previously reported solutions. The model is capable of simulating flows from subsonic to supersonic and capturing jumps resulted from shock waves.     

Three-Dimensional Lattice Boltzmann Model for High-Speed Compressible Flows

A highly efficient three-dimensional (3D) Lattice Boltzmann (LB) model for high-speed compressible flows is proposed. This model is developed from the original one by Kataoka and Tsutahara [Phys. Rev. E 69 (2004) 056702]. The convection term is discretized by the Non-oscillatory, containing No free parameters and Dissipative (NND) scheme, which effectively damps oscillations at discontinuities. To be more consistent with the kinetic theory of viscosity and to further improve the numerical stability, an additional dissipation term is introduced. Model parameters are chosen in such a way that the von Neumann stability criterion is satisfied. The new model isvalidated by well-known benchmarks, (i) Riemann problems, including the problem with Lax shock tube and a newly designed shock tube problem with high Mach number; (ii) reaction of shock wave on droplet or bubble. Good agreements are obtained between LB results and exact ones or previously reported solutions. The model is capable of simulating flows from subsonic to supersonic and capturing jumps resulted from shock waves.     

A Switch Function-Based Gas-Kinetic Scheme for Simulation of Inviscid and Viscous Compressible Flows

In this paper, a switch function-based gas-kinetic scheme (SF-GKS) is presented for the simulation of inviscid and viscous compressible flows. With the finite volume discretization, Euler and Navier-Stokes equations are solved and the SF-GKS is applied to evaluate the inviscid flux at cell interface. The viscous flux is obtained by the conventional smooth function approximation. Unlike the traditional gas-kinetic scheme in the calculation of inviscid flux such as Kinetic Flux Vector Splitting (KFVS), the numerical dissipation is controlled with a switch function in the present scheme. That is, the numerical dissipation is only introduced in the region around strong shock waves. As a consequence, the present SF-GKS can well capture strong shock waves and thin boundary layers simultaneously. The present SF-GKS is firstly validated by its application to the inviscid flow problems, including 1-D Euler shock tube, regular shock reflection and double Mach reflection. Then, SF-GKS is extended to solve viscous transonic and hypersonic flow problems. Good agreement between the present results and those in the literature verifies the accuracy and robustness of SF-GKS.     

一种气体/液滴混合流动模型与数值计算

研究均匀液滴单态氧发生器(TUDOG)的工作机理,为Cl₂/He混合气体横向流过垂直下落的BHP(按重量25%KOH,25%H₂O₂,及50%H₂O)液滴场的化学反应流动建立模型,并对模型方程做数值求解.模型方程中考虑液滴与气体间的质量、动量交换.混合流动的二维模型方程用SIMPLEC方法求解.模拟结果与相关文献提供的实测结果对比较好.结果发现:氯气利用率、单态氧产率随入流气体速度增大而减小,随液滴速度增大而增大;在含液滴区域的上游氯气的吸收利用较显著,对TUDOG的工程设计有参考价值.     

二维可压缩流体力学Lagrange有限点方法

提出二维可压缩流体力学问题的拉格朗日有限点方法,将求解区域离散为适当的点集.在每个时间步,每个离散点与其周围适当的五个邻点组成一个基本计算单元.在每个计算单元上,利用有限点方法中的典型微分算子的五点近似公式直接离散流体力学方程中的微分算子,并在每个方程中加上一个人为拉普拉斯粘性项,达到稳定格式的目的.给出时间步长的自动选取算法.数值算例结果验证了算法的有效性,初步展示了其计算大变形流体问题的良好发展潜力.     

高压作用下不同形状气腔压缩过程的二维数值计算

 采用三阶精度的Parabolic Piecewise Method（PPM）方法和Volume of Fluid（VOF）方法相结合,运用Lagrange-Remapping算法,对高压作用下不同形状气腔压缩过程进行了二维高精度数值计算,给出了复杂形状的多流体流场之间的相互作用。此方法可以用来处理界面两边高压力比、高密度比流动以及强剪切滑移运动等问题。     

轴对称可压缩流的统一坐标系

将Hui等人提出的统一坐标系推广到轴对称欧拉方程,讨论统一坐标系下的轴对称欧拉方程的解法,并通过数值算例证明轴对称统一坐标系的优越性.