High order accurate scheme is highly desirable for Slow computation with shocks. After analysis has been made for the reason of the generation of non-physical oscillations around the shock in numerical computations, a...High order accurate scheme is highly desirable for Slow computation with shocks. After analysis has been made for the reason of the generation of non-physical oscillations around the shock in numerical computations, a third-order, upwind biased, shock capturing scheme was proposed. Also, a new shock fitting method, called pseudo shock fitting method, was suggested, which in principle can be with any order of accuracy. Test cases for one dimensional flows show that the new method is very satisfactory.展开更多
This work presents a new application for the Hierarchical Function Expansion Method for the solution of the Navier-Stokes equations for compressible fluids in two dimensions and in high velocity. This method is based ...This work presents a new application for the Hierarchical Function Expansion Method for the solution of the Navier-Stokes equations for compressible fluids in two dimensions and in high velocity. This method is based on the finite elements method using the Petrov-Galerkin formulation, know as SUPG (Streamline Upwind Petrov-Galerkin), applied with the expansion of the variables into hierarchical functions. To test and validate the numerical method proposed as well as the computational program developed simulations are performed for some cases whose theoretical solutions are known. These cases are the following: continuity test, stability and convergence test, temperature step problem, and several oblique shocks. The objective of the last cases is basically to verify the capture of the shock wave by the method developed. The results obtained in the simulations with the proposed method were good both qualitatively and quantitatively when compared with the theoretical solutions. This allows concluding that the objectives of this work are reached.展开更多
Electromagnetic(EM) field is a consequence of the plasma generation induced by shock waves generated in impacts and explosions and is an important topic of study in aerospace and geophysics. Experimental research is f...Electromagnetic(EM) field is a consequence of the plasma generation induced by shock waves generated in impacts and explosions and is an important topic of study in aerospace and geophysics. Experimental research is frequently used to investigate the plasma generation in hypervelocity impacts and the EM wave emitted in chemical explosions. However, the basic plasma generation mechanism leading to the EM emission generated by the shock waves in chemical explosions is rarely studied.Therefore, a detailed investigation is performed to determine the state of the plasmas generated by the shock waves in air blast. In addition, a multi-component ionization model was improved to evaluate the ionization state of the generated plasmas. The proposed ionization model was combined with an AUSM+-up based finite volume method(FVM) to simulate the plasmas generated in the air blast. Two typical cases of simulation were carried out to investigate the relation between the shock waves and ionization, as well as the influence of ground reflection on the ionization state. It was found that the ionization zone was close behind the shock front in the air and propagates along with the shock waves. The interaction between the original shock waves and reflected shock waves was found to have a great impact of the order of 2–3 magnitudes, on the degree of ionization of the plasmas generated by the shock waves. This phenomenon explains the observation of additional EM pulses generated by ground reflection, as explored in the reference cited in this paper.展开更多
文摘High order accurate scheme is highly desirable for Slow computation with shocks. After analysis has been made for the reason of the generation of non-physical oscillations around the shock in numerical computations, a third-order, upwind biased, shock capturing scheme was proposed. Also, a new shock fitting method, called pseudo shock fitting method, was suggested, which in principle can be with any order of accuracy. Test cases for one dimensional flows show that the new method is very satisfactory.
文摘This work presents a new application for the Hierarchical Function Expansion Method for the solution of the Navier-Stokes equations for compressible fluids in two dimensions and in high velocity. This method is based on the finite elements method using the Petrov-Galerkin formulation, know as SUPG (Streamline Upwind Petrov-Galerkin), applied with the expansion of the variables into hierarchical functions. To test and validate the numerical method proposed as well as the computational program developed simulations are performed for some cases whose theoretical solutions are known. These cases are the following: continuity test, stability and convergence test, temperature step problem, and several oblique shocks. The objective of the last cases is basically to verify the capture of the shock wave by the method developed. The results obtained in the simulations with the proposed method were good both qualitatively and quantitatively when compared with the theoretical solutions. This allows concluding that the objectives of this work are reached.
基金supported by the National Natural Science Foundation of China(Grant Nos.11472036,11702026)
文摘Electromagnetic(EM) field is a consequence of the plasma generation induced by shock waves generated in impacts and explosions and is an important topic of study in aerospace and geophysics. Experimental research is frequently used to investigate the plasma generation in hypervelocity impacts and the EM wave emitted in chemical explosions. However, the basic plasma generation mechanism leading to the EM emission generated by the shock waves in chemical explosions is rarely studied.Therefore, a detailed investigation is performed to determine the state of the plasmas generated by the shock waves in air blast. In addition, a multi-component ionization model was improved to evaluate the ionization state of the generated plasmas. The proposed ionization model was combined with an AUSM+-up based finite volume method(FVM) to simulate the plasmas generated in the air blast. Two typical cases of simulation were carried out to investigate the relation between the shock waves and ionization, as well as the influence of ground reflection on the ionization state. It was found that the ionization zone was close behind the shock front in the air and propagates along with the shock waves. The interaction between the original shock waves and reflected shock waves was found to have a great impact of the order of 2–3 magnitudes, on the degree of ionization of the plasmas generated by the shock waves. This phenomenon explains the observation of additional EM pulses generated by ground reflection, as explored in the reference cited in this paper.
