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
A discontinuous Galerkin finite element method （DG-FEM） is developed for solving the axisymmetric Euler equations based on two-dimensional conservation laws. The method is used to simulate the unsteady-state underex...A discontinuous Galerkin finite element method （DG-FEM） is developed for solving the axisymmetric Euler equations based on two-dimensional conservation laws. The method is used to simulate the unsteady-state underexpanded axisymmetric jet. Several flow property distributions along the jet axis, including density, pres- sure and Mach number are obtained and the qualitative flowfield structures of interest are well captured using the proposed method, including shock waves, slipstreams, traveling vortex ring and multiple Mach disks. Two Mach disk locations agree well with computational and experimental measurement results. It indicates that the method is robust and efficient for solving the unsteady-state underexpanded axisymmetric jet.展开更多
研究了一种基于Lissajous图形的光纤分布式扰动传感器定位方法。光纤分布式扰动传感器基于Mach-Zehnder干涉仪，通过两路输出信号的时延得到扰动定位。在两路输出信号的Lissajous图形中构造拟合椭圆，基于实验数据的仿真研究表明：通过...研究了一种基于Lissajous图形的光纤分布式扰动传感器定位方法。光纤分布式扰动传感器基于Mach-Zehnder干涉仪，通过两路输出信号的时延得到扰动定位。在两路输出信号的Lissajous图形中构造拟合椭圆，基于实验数据的仿真研究表明：通过椭圆半短轴长可以得到时延，实现定位。法进行了仿真和实验研究，在无需噪声抑制的条件下定位精度较高：在信噪比为-6~7dB范围，最大定位误差为207 m 多次测量中，最大误差为94 m。研究结论可以为光纤分布式扰动传感器定位方法提供新的技术参考。展开更多
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A discontinuous Galerkin finite element method （DG-FEM） is developed for solving the axisymmetric Euler equations based on two-dimensional conservation laws. The method is used to simulate the unsteady-state underexpanded axisymmetric jet. Several flow property distributions along the jet axis, including density, pres- sure and Mach number are obtained and the qualitative flowfield structures of interest are well captured using the proposed method, including shock waves, slipstreams, traveling vortex ring and multiple Mach disks. Two Mach disk locations agree well with computational and experimental measurement results. It indicates that the method is robust and efficient for solving the unsteady-state underexpanded axisymmetric jet.
文摘研究了一种基于Lissajous图形的光纤分布式扰动传感器定位方法。光纤分布式扰动传感器基于Mach-Zehnder干涉仪，通过两路输出信号的时延得到扰动定位。在两路输出信号的Lissajous图形中构造拟合椭圆，基于实验数据的仿真研究表明：通过椭圆半短轴长可以得到时延，实现定位。法进行了仿真和实验研究，在无需噪声抑制的条件下定位精度较高：在信噪比为-6~7dB范围，最大定位误差为207 m 多次测量中，最大误差为94 m。研究结论可以为光纤分布式扰动传感器定位方法提供新的技术参考。
