The influence of high temperature effects on the protrusion of Mach stem in strong shock reflection over a wedge was numerically investigated. A two-dimensional inviscid solver applies finite volume method and unstruc...The influence of high temperature effects on the protrusion of Mach stem in strong shock reflection over a wedge was numerically investigated. A two-dimensional inviscid solver applies finite volume method and unstructured quadrilateral grids were employed to simulate the flow. Theoretical analysis was also conducted to understand the phenomenon. Both numerical and theoretical results indicate a wall-jet penetrating forward is responsible for the occurrence of Mach stem protrusion. The protrusion degree seems to depend on the thermal energy buffer capacity of the testing gas. Approaches to increase the energy buffer capacity, such as vibrational relaxation, molecular dissociation, and increase of frozen heat caoacitv, all tend to escalate the orotrusion effect.展开更多
Abstract Accurate simulation of seismic wave propaga- tion in complex geological structures is of particular interest nowadays. However conventional methods may fail to simulate realistic wavefields in environments wi...Abstract Accurate simulation of seismic wave propaga- tion in complex geological structures is of particular interest nowadays. However conventional methods may fail to simulate realistic wavefields in environments with great and rapid structural changes, due for instance to the presence of shadow zones, diffractions and/or edge effects. Different methods, developed to improve seismic model- ing, are typically tested on synthetic configurations against analytical solutions for simple canonical problems or ref- erence methods, or via direct comparison with real data acquired in situ. Such approaches have limitations,especially if the propagation occurs in a complex envi- ronment with strong-contrast reflectors and surface irreg- ularities, as it can be difficult to determine the method which gives the best approximation of the ＂real＂ solution, or to interpret the results obtained without an a priori knowledge of the geologic environment. An alternative approach for seismics consists in comparing the synthetic data with high-quality data collected in laboratory experi- ments under controlled conditions for a known configuration. In contrast with numerical experiments, laboratory data possess many of the characteristics of field data, as real waves propagate through models with no numerical approximations. We thus present a comparison of laboratory-scaled measurements of 3D zero-offset wave reflection of broadband pulses from a strong topographic environment immersed in a water tank with numerical data simulated by means of a spectral-element method and a discretized Kirchhoff integral method. The results indicate a good quantitative fit in terms of time arrivals and acceptable fit in amplitudes for all datasets.展开更多
文摘The influence of high temperature effects on the protrusion of Mach stem in strong shock reflection over a wedge was numerically investigated. A two-dimensional inviscid solver applies finite volume method and unstructured quadrilateral grids were employed to simulate the flow. Theoretical analysis was also conducted to understand the phenomenon. Both numerical and theoretical results indicate a wall-jet penetrating forward is responsible for the occurrence of Mach stem protrusion. The protrusion degree seems to depend on the thermal energy buffer capacity of the testing gas. Approaches to increase the energy buffer capacity, such as vibrational relaxation, molecular dissociation, and increase of frozen heat caoacitv, all tend to escalate the orotrusion effect.
基金the INSIS Institute of the French CNRS,Aix-Marseille Universitythe Carnot Star Institute,the VISTA Projectthe Norwegian Research Council through the ROSE Project for financial support
文摘Abstract Accurate simulation of seismic wave propaga- tion in complex geological structures is of particular interest nowadays. However conventional methods may fail to simulate realistic wavefields in environments with great and rapid structural changes, due for instance to the presence of shadow zones, diffractions and/or edge effects. Different methods, developed to improve seismic model- ing, are typically tested on synthetic configurations against analytical solutions for simple canonical problems or ref- erence methods, or via direct comparison with real data acquired in situ. Such approaches have limitations,especially if the propagation occurs in a complex envi- ronment with strong-contrast reflectors and surface irreg- ularities, as it can be difficult to determine the method which gives the best approximation of the ＂real＂ solution, or to interpret the results obtained without an a priori knowledge of the geologic environment. An alternative approach for seismics consists in comparing the synthetic data with high-quality data collected in laboratory experi- ments under controlled conditions for a known configuration. In contrast with numerical experiments, laboratory data possess many of the characteristics of field data, as real waves propagate through models with no numerical approximations. We thus present a comparison of laboratory-scaled measurements of 3D zero-offset wave reflection of broadband pulses from a strong topographic environment immersed in a water tank with numerical data simulated by means of a spectral-element method and a discretized Kirchhoff integral method. The results indicate a good quantitative fit in terms of time arrivals and acceptable fit in amplitudes for all datasets.
