Recent years the modify ghost fluid method （MGFM） and the real ghost fluid method （RGFM） based on Riemann problem have been developed for multimedium compressible flows. According to authors, these methods have on...Recent years the modify ghost fluid method （MGFM） and the real ghost fluid method （RGFM） based on Riemann problem have been developed for multimedium compressible flows. According to authors, these methods have only been used with the level set technique to track the interface. In this paper, we combine the MCFM and the RGFM respectively with front tracking method, for which the fluid interfaces are explicitly tracked by connected points. The method is tested with some one-dimensional problems, and its applicability is also studied. Furthermore, in order to capture the interface more accurately, especially for strong shock impacting on interface, a shock monitor is proposed to determine the initial states of the Riemann problem. The present method is applied to various one- dimensional problems involving strong shock-interface interaction. An extension of the present method to two dimension is also introduced and preliminary results are given.展开更多
Considering droplet phenomena at low Mach numbers,large differences in the magnitude of the occurring characteristic waves are presented.As acoustic phenomena often play a minor role in such applications,classical exp...Considering droplet phenomena at low Mach numbers,large differences in the magnitude of the occurring characteristic waves are presented.As acoustic phenomena often play a minor role in such applications,classical explicit schemes which resolve these waves suffer from a very restrictive timestep restriction.In this work,a novel scheme based on a specific level set ghost fluid method and an implicit-explicit(IMEX)flux splitting is proposed to overcome this timestep restriction.A fully implicit narrow band around the sharp phase interface is combined with a splitting of the convective and acoustic phenomena away from the interface.In this part of the domain,the IMEX Runge-Kutta time discretization and the high order discontinuous Galerkin spectral element method are applied to achieve high accuracies in the bulk phases.It is shown that for low Mach numbers a significant gain in computational time can be achieved compared to a fully explicit method.Applica-tions to typical droplet dynamic phenomena validate the proposed method and illustrate its capabilities.展开更多
The ghost fluid method and the level set function is used to simulate the Richtmyer Meshkov instability of multi material flow interface in two dimensions. To keep the density profile from smearing out, the isobaric f...The ghost fluid method and the level set function is used to simulate the Richtmyer Meshkov instability of multi material flow interface in two dimensions. To keep the density profile from smearing out, the isobaric fix technique is used in numerical algorithms.展开更多
Accurately approximating higher order derivatives is an inherently difficult problem. It is shown that a random variable shape parameter strategy can improve the accuracy of approximating higher order derivatives with...Accurately approximating higher order derivatives is an inherently difficult problem. It is shown that a random variable shape parameter strategy can improve the accuracy of approximating higher order derivatives with Radial Basis Function methods. The method is used to solve fourth order boundary value problems. The use and location of ghost points are examined in order to enforce the extra boundary conditions that are necessary to make a fourth-order problem well posed. The use of ghost points versus solving an overdetermined linear system via least squares is studied. For a general fourth-order boundary value problem, the recommended approach is to either use one of two novel sets of ghost centers introduced here or else to use a least squares approach. When using either ghost centers or least squares, the random variable shape parameter strategy results in significantly better accuracy than when a constant shape parameter is used.展开更多
以往虚拟流法主要用于处理流体-流体界面。在虚拟流方法的基础上,提出了一种基于虚拟流的浸入式边界方法,用于研究强不间断的复杂激波-障碍物相互作用,在界面附近构造Riemann问题并采用HLLC(Harten Lax and van Leer contact)方法对其...以往虚拟流法主要用于处理流体-流体界面。在虚拟流方法的基础上,提出了一种基于虚拟流的浸入式边界方法,用于研究强不间断的复杂激波-障碍物相互作用,在界面附近构造Riemann问题并采用HLLC(Harten Lax and van Leer contact)方法对其进行求解,达到求解流体与固体相互作用的目的。文中给出了几个测试算例来验证该方法的适用性。首先将该方法用于求解超声速流绕过圆柱体和90°台阶,并与实验结果进行对比验证,然后将激波冲击三棱柱相互作用的结果与文献的实验结果进一步进行了对比,结果表明,在激波传播以及涡度发展和传输方面,文章方法与实验结果有很好的一致性,在激波冲击障碍物初期的波系演化有很好的适用性。展开更多
基金supported by National Science Foundation of China (10576015)
文摘Recent years the modify ghost fluid method （MGFM） and the real ghost fluid method （RGFM） based on Riemann problem have been developed for multimedium compressible flows. According to authors, these methods have only been used with the level set technique to track the interface. In this paper, we combine the MCFM and the RGFM respectively with front tracking method, for which the fluid interfaces are explicitly tracked by connected points. The method is tested with some one-dimensional problems, and its applicability is also studied. Furthermore, in order to capture the interface more accurately, especially for strong shock impacting on interface, a shock monitor is proposed to determine the initial states of the Riemann problem. The present method is applied to various one- dimensional problems involving strong shock-interface interaction. An extension of the present method to two dimension is also introduced and preliminary results are given.
基金support provided by the Deutsche Forschun-gsgemeinschaft(DFG,German Research Foundation)through the project GRK 2160/1“Droplet Interaction Technologies”and through the project no.457811052
文摘Considering droplet phenomena at low Mach numbers,large differences in the magnitude of the occurring characteristic waves are presented.As acoustic phenomena often play a minor role in such applications,classical explicit schemes which resolve these waves suffer from a very restrictive timestep restriction.In this work,a novel scheme based on a specific level set ghost fluid method and an implicit-explicit(IMEX)flux splitting is proposed to overcome this timestep restriction.A fully implicit narrow band around the sharp phase interface is combined with a splitting of the convective and acoustic phenomena away from the interface.In this part of the domain,the IMEX Runge-Kutta time discretization and the high order discontinuous Galerkin spectral element method are applied to achieve high accuracies in the bulk phases.It is shown that for low Mach numbers a significant gain in computational time can be achieved compared to a fully explicit method.Applica-tions to typical droplet dynamic phenomena validate the proposed method and illustrate its capabilities.
文摘The ghost fluid method and the level set function is used to simulate the Richtmyer Meshkov instability of multi material flow interface in two dimensions. To keep the density profile from smearing out, the isobaric fix technique is used in numerical algorithms.
文摘Accurately approximating higher order derivatives is an inherently difficult problem. It is shown that a random variable shape parameter strategy can improve the accuracy of approximating higher order derivatives with Radial Basis Function methods. The method is used to solve fourth order boundary value problems. The use and location of ghost points are examined in order to enforce the extra boundary conditions that are necessary to make a fourth-order problem well posed. The use of ghost points versus solving an overdetermined linear system via least squares is studied. For a general fourth-order boundary value problem, the recommended approach is to either use one of two novel sets of ghost centers introduced here or else to use a least squares approach. When using either ghost centers or least squares, the random variable shape parameter strategy results in significantly better accuracy than when a constant shape parameter is used.
文摘以往虚拟流法主要用于处理流体-流体界面。在虚拟流方法的基础上,提出了一种基于虚拟流的浸入式边界方法,用于研究强不间断的复杂激波-障碍物相互作用,在界面附近构造Riemann问题并采用HLLC(Harten Lax and van Leer contact)方法对其进行求解,达到求解流体与固体相互作用的目的。文中给出了几个测试算例来验证该方法的适用性。首先将该方法用于求解超声速流绕过圆柱体和90°台阶,并与实验结果进行对比验证,然后将激波冲击三棱柱相互作用的结果与文献的实验结果进一步进行了对比,结果表明,在激波传播以及涡度发展和传输方面,文章方法与实验结果有很好的一致性,在激波冲击障碍物初期的波系演化有很好的适用性。
