The critical conditions for aeroelastic stability and the stability boundaries of a flexible two-dimensional heated panel subjected to an impinging oblique shock are considered using theoretical analysis and numerical...The critical conditions for aeroelastic stability and the stability boundaries of a flexible two-dimensional heated panel subjected to an impinging oblique shock are considered using theoretical analysis and numerical computations, respectively. The von-Karman large deflection theory of isotropic flat plates is used to account for the geometrical nonlinearity of the heated panel, and local first-order piston theory is employed in the region before and after shock waves to estimate the aerodynamic pressure. The coupled partial differential governing equations, according to the Hamilton principle, are established with thermal effect based on quasi-steady thermal stress theory.The Galerkin discrete method is employed to truncate the partial differential equations into a set of ordinary differential equations, which are then solved by the fourth-order Runge-Kutta numerical integration method. Lyapunov indirect method is applied to evaluate the stability of the heated panel. The results show that a new aeroelastic instability（distinct from regular panel flutter） arises from the complex interaction of the incident and reflected wave system with the panel flexural modes and thermal loads. What＇s more, stability of the panel is reduced in the presence of the oblique shock. In other words, the heated panel becomes aeroelastically unstable at relatively small flight aerodynamic pressure.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
基金supported by the National Natural Science Foundation of China (No. 11732013)
文摘The critical conditions for aeroelastic stability and the stability boundaries of a flexible two-dimensional heated panel subjected to an impinging oblique shock are considered using theoretical analysis and numerical computations, respectively. The von-Karman large deflection theory of isotropic flat plates is used to account for the geometrical nonlinearity of the heated panel, and local first-order piston theory is employed in the region before and after shock waves to estimate the aerodynamic pressure. The coupled partial differential governing equations, according to the Hamilton principle, are established with thermal effect based on quasi-steady thermal stress theory.The Galerkin discrete method is employed to truncate the partial differential equations into a set of ordinary differential equations, which are then solved by the fourth-order Runge-Kutta numerical integration method. Lyapunov indirect method is applied to evaluate the stability of the heated panel. The results show that a new aeroelastic instability（distinct from regular panel flutter） arises from the complex interaction of the incident and reflected wave system with the panel flexural modes and thermal loads. What＇s more, stability of the panel is reduced in the presence of the oblique shock. In other words, the heated panel becomes aeroelastically unstable at relatively small flight aerodynamic pressure.
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.
