Based on the numerical methods of volume of fluid (VOF) and piecewise parabolic method (PPM) and parallel circumstance of Message Passing Interface (MPI),a parallel multi-viscosity-fluid hydrodynamic code MVPPM (Multi...Based on the numerical methods of volume of fluid (VOF) and piecewise parabolic method (PPM) and parallel circumstance of Message Passing Interface (MPI),a parallel multi-viscosity-fluid hydrodynamic code MVPPM (Multi-Viscosity-Fluid Piecewise Parabolic Method) is developed and performed to study the hydrodynamic instability and flow mixing. Firstly,the MVPPM code is verified and validated by simulating three instability cases:The first one is a Riemann problem of viscous flow on the shock tube; the second one is the hydrodynamic instability and mixing of gaseous flows under re-shocks; the third one is a half height experiment of interfacial instability,which is conducted on the AWE's shock tube. By comparing the numerical results with experimental data,good agreement is achieved. Then the MVPPM code is applied to simulate the two cases of the interfacial instabilities of jelly models acceler-ated by explosion products of a gaseous explosive mixture (GEM),which are adopted in our experi-ments. The first is implosive dynamic interfacial instability of cylindrical symmetry and mixing. The evolving process of inner and outer interfaces,and the late distribution of mixing mass caused by Rayleigh-Taylor (RT) instability in the center of different radius are given. The second is jelly layer ex-periment which is initialized with one periodic perturbation with different amplitude and wave length. It reveals the complex processes of evolution of interface,and presents the displacement of front face of jelly layer,bubble head and top of spike relative to initial equilibrium position vs. time. The numerical results are in excellent agreement with that experimental images,and show that the amplitude of initial perturbations affects the evolvement of fluid mixing zone (FMZ) growth rate extremely,especially at late times.展开更多
The early phases of the shock interaction process on two-dimensional interfaces with different shapes are numerically investigated in this study,which are closely related to the shock refraction and reflection,vortici...The early phases of the shock interaction process on two-dimensional interfaces with different shapes are numerically investigated in this study,which are closely related to the shock refraction and reflection,vorticity production and transport.The numerical method employs an adaptive unstructured quadrilateral mesh,which can capture the wave pattern and interface evolution very well.Simulations are carried out under the conditions of an incident shock Mach number of 1.2 and the light/heavy (air/SF 6) interface.Five different shapes are considered in the simulations:rectangle,ellipse,diamond and two kinds of triangle.The results show that the interfacial shapes can influence the wave patterns particularly on the shape and evolution of refracted shock waves.The generation and the distribution of vorticity on the interfaces with five different shapes also have dissimilarities.The circulation deposition on five interfaces is quantitatively investigated and compared with theoretical model.A good agreement is found between the numerical results and the predictions by the theoretical model.Some characteristic scales of the interface are tracked.Under the influence of nonlinear-acoustic effect and vorticity effect,the interfaces present different evolution modes.展开更多
We present computational results on the evolution of the shock-accelerated heavy bubbles surrounded by nitrogen with the Atwood number At = 0.497–0.677 and the emphasis is on the jet phenomenon caused by the shock fo...We present computational results on the evolution of the shock-accelerated heavy bubbles surrounded by nitrogen with the Atwood number At = 0.497–0.677 and the emphasis is on the jet phenomenon caused by the shock focusing. The multi-fluid Eulerian equation is solved by a finite volume method based on MUSCL-Hancock approach. Based on the numerical schlieren and the distributions of density and pressure, it is found that there are three typical jet structures(outward jet, no jet, inward jet) for different combinations of gas mixture inside the bubble which determine the position of shock focusing relative to the downstream pole of the heavy bubble(upstream of the pole, at the pole, downstream the pole). Compared with the inward jet, the velocity of outward jet is obviously larger. As At increases, the moment of jet formation is postponed, and the maximal values and magnifications of pressure and density increase distinctly. Therefore, the energy convergence effects are heavily enhanced with the increase of bubble gas density.展开更多
基金Supported by the National Natural Science Foundation of China (Grant Nos. 10672151 and 10772166)the Science Foundation of China Academy of Engineering Physics (Grant No. 2008B0202011)the Fundamental Quality and Reliability of National Defence Science and Technology Industry of China (Grant No. Z112009B004)
文摘Based on the numerical methods of volume of fluid (VOF) and piecewise parabolic method (PPM) and parallel circumstance of Message Passing Interface (MPI),a parallel multi-viscosity-fluid hydrodynamic code MVPPM (Multi-Viscosity-Fluid Piecewise Parabolic Method) is developed and performed to study the hydrodynamic instability and flow mixing. Firstly,the MVPPM code is verified and validated by simulating three instability cases:The first one is a Riemann problem of viscous flow on the shock tube; the second one is the hydrodynamic instability and mixing of gaseous flows under re-shocks; the third one is a half height experiment of interfacial instability,which is conducted on the AWE's shock tube. By comparing the numerical results with experimental data,good agreement is achieved. Then the MVPPM code is applied to simulate the two cases of the interfacial instabilities of jelly models acceler-ated by explosion products of a gaseous explosive mixture (GEM),which are adopted in our experi-ments. The first is implosive dynamic interfacial instability of cylindrical symmetry and mixing. The evolving process of inner and outer interfaces,and the late distribution of mixing mass caused by Rayleigh-Taylor (RT) instability in the center of different radius are given. The second is jelly layer ex-periment which is initialized with one periodic perturbation with different amplitude and wave length. It reveals the complex processes of evolution of interface,and presents the displacement of front face of jelly layer,bubble head and top of spike relative to initial equilibrium position vs. time. The numerical results are in excellent agreement with that experimental images,and show that the amplitude of initial perturbations affects the evolvement of fluid mixing zone (FMZ) growth rate extremely,especially at late times.
基金supported by the National Natural Science Foundation of China (Grant No.10972214)the Fundamental Research Funds for the Central Universities
文摘The early phases of the shock interaction process on two-dimensional interfaces with different shapes are numerically investigated in this study,which are closely related to the shock refraction and reflection,vorticity production and transport.The numerical method employs an adaptive unstructured quadrilateral mesh,which can capture the wave pattern and interface evolution very well.Simulations are carried out under the conditions of an incident shock Mach number of 1.2 and the light/heavy (air/SF 6) interface.Five different shapes are considered in the simulations:rectangle,ellipse,diamond and two kinds of triangle.The results show that the interfacial shapes can influence the wave patterns particularly on the shape and evolution of refracted shock waves.The generation and the distribution of vorticity on the interfaces with five different shapes also have dissimilarities.The circulation deposition on five interfaces is quantitatively investigated and compared with theoretical model.A good agreement is found between the numerical results and the predictions by the theoretical model.Some characteristic scales of the interface are tracked.Under the influence of nonlinear-acoustic effect and vorticity effect,the interfaces present different evolution modes.
基金supported by the National Natural Science Foundation of China(Grant Nos.11172278,11302201,11472253 and 11202195)Science Foundation of China Academy of Engineering Physics(Grant No.2014B0201017)
文摘We present computational results on the evolution of the shock-accelerated heavy bubbles surrounded by nitrogen with the Atwood number At = 0.497–0.677 and the emphasis is on the jet phenomenon caused by the shock focusing. The multi-fluid Eulerian equation is solved by a finite volume method based on MUSCL-Hancock approach. Based on the numerical schlieren and the distributions of density and pressure, it is found that there are three typical jet structures(outward jet, no jet, inward jet) for different combinations of gas mixture inside the bubble which determine the position of shock focusing relative to the downstream pole of the heavy bubble(upstream of the pole, at the pole, downstream the pole). Compared with the inward jet, the velocity of outward jet is obviously larger. As At increases, the moment of jet formation is postponed, and the maximal values and magnifications of pressure and density increase distinctly. Therefore, the energy convergence effects are heavily enhanced with the increase of bubble gas density.
