Numerical simulation of TNT underwater explosion was carried out with AUTODYN soft-ware. Influences of artificial viscosity and mesh density on simulation results were discussed. Deto-nation waves in explosive and sho...Numerical simulation of TNT underwater explosion was carried out with AUTODYN soft-ware. Influences of artificial viscosity and mesh density on simulation results were discussed. Deto-nation waves in explosive and shock wave in water during early time of explosion are high frequency waves. Fine meshes (less than 1 mm) in explosive and water nearby, and small linear viscosity co-efficients and quadratic viscosity coefficients (0.02 and 0.1 respectively, 1/10 of default values) are needed in numerical simulation model. According to these rules, numerical computing pressure profiles can match well with those calculated by Zamyshlyayev empirical formula. Otherwise peak pressure would be smeared off and upstream relative errors would be cumulated downstream to make downstream peak pressure lower.展开更多
The inhibiting effect of AI（OH）3 and Mg（OH）2 dust on explosion of methane-air mixtures was investigated by means of explosion parameter tests in a 20-liter closed vessel. The influences of varying methane concentr...The inhibiting effect of AI（OH）3 and Mg（OH）2 dust on explosion of methane-air mixtures was investigated by means of explosion parameter tests in a 20-liter closed vessel. The influences of varying methane concentration and dust concentration on explosion parameters were characterized based on the experimental data to determine the maximum explosion pressure, maximum rate of pressure rise, lower explosion limits and upper explosion limits. The inhibiting mechanisms of these kinds of dust were analyzed as well. The investigations indicate that AI（OH）3 and Mg（OH）2 dust can be used as inhibitors to prevent meth- ane explosion, however, their inhibiting effects are less than those of inert gas such as N2 and CO2 in that their dust can weaken the methane explosion but cannot totally eliminate it. The tests show that all of the explosion parameters with dust additives are strongly dependent on methane/air ratio and dust concentration, and AI（OH）3 dust has better performance than Mg（OH）2 dust in inhibiting methane explosion. The average percentage decreases of maximum explosion pressure and maximum rate of pressure rise with AI（OH）3 dust are 11.08% and 66.15%, respectively. Experiments also showed that there is a special phe- nomenon when methane explosion is inhibited by AI（OH）3 and Mg（OH）2 dust, in which is that during the process of explosion the maximum explosion pressure value first decreases then increases as dust concentration increases. The best dust concentrations to inhibit the explosion are 250 g/m3 with methane/air ratio at 9.5%, and 200 g/m3 with methane/air ratio at 7%. It is suggested that water vapor produced by the thermal decomposition of metal hydroxides makes the particles of descending dust combine, resulting in a decrease of the real dust concentration in the vessel. Water vapor also is the major cause of another phenomenon that the LEL curve and the UEL curve never meet with the increase of gas concentration.展开更多
In recent years,with the development of simulations about supernova explosion,we have a better understanding about the density profiles and the shock waves in supernovae than before.There might be a reverse shock wave...In recent years,with the development of simulations about supernova explosion,we have a better understanding about the density profiles and the shock waves in supernovae than before.There might be a reverse shock wave,another sudden change of density except the forward shock wave,or even no shock wave,emerging in the supernova.Instead of using the expression of the crossing probability at the high resonance,PH,we have studied the matter effects on neutrino oscillations in different supernova models.In detail,we have calculated the survival probability of νe(P_s)and the conversion probability of ν_x(P_c) in the Schrodinger equation within a simplified two-flavor framework for a certain case,in which the neutrino transfers through the supernova matter from an initial flavor eigenstate located at the core of the supernova.Our calculations was based on the data of density in three different supernova models obtained from simulations.In our work,we do not steepen the density gradient around the border of the shock wave,which differs to what was done in most of the other simulations.It is found that the mass and the density distribution of the supernova do make a difference on the behavior of P_s and P_c.With the results of P_s and P_c,we can estimate the number of νe(and ν_x) remained in the beam after they go through the matter in the supernova.展开更多
文摘Numerical simulation of TNT underwater explosion was carried out with AUTODYN soft-ware. Influences of artificial viscosity and mesh density on simulation results were discussed. Deto-nation waves in explosive and shock wave in water during early time of explosion are high frequency waves. Fine meshes (less than 1 mm) in explosive and water nearby, and small linear viscosity co-efficients and quadratic viscosity coefficients (0.02 and 0.1 respectively, 1/10 of default values) are needed in numerical simulation model. According to these rules, numerical computing pressure profiles can match well with those calculated by Zamyshlyayev empirical formula. Otherwise peak pressure would be smeared off and upstream relative errors would be cumulated downstream to make downstream peak pressure lower.
基金supported by the National Natural Science Foundation of China (Grant No. 50704025)
文摘The inhibiting effect of AI（OH）3 and Mg（OH）2 dust on explosion of methane-air mixtures was investigated by means of explosion parameter tests in a 20-liter closed vessel. The influences of varying methane concentration and dust concentration on explosion parameters were characterized based on the experimental data to determine the maximum explosion pressure, maximum rate of pressure rise, lower explosion limits and upper explosion limits. The inhibiting mechanisms of these kinds of dust were analyzed as well. The investigations indicate that AI（OH）3 and Mg（OH）2 dust can be used as inhibitors to prevent meth- ane explosion, however, their inhibiting effects are less than those of inert gas such as N2 and CO2 in that their dust can weaken the methane explosion but cannot totally eliminate it. The tests show that all of the explosion parameters with dust additives are strongly dependent on methane/air ratio and dust concentration, and AI（OH）3 dust has better performance than Mg（OH）2 dust in inhibiting methane explosion. The average percentage decreases of maximum explosion pressure and maximum rate of pressure rise with AI（OH）3 dust are 11.08% and 66.15%, respectively. Experiments also showed that there is a special phe- nomenon when methane explosion is inhibited by AI（OH）3 and Mg（OH）2 dust, in which is that during the process of explosion the maximum explosion pressure value first decreases then increases as dust concentration increases. The best dust concentrations to inhibit the explosion are 250 g/m3 with methane/air ratio at 9.5%, and 200 g/m3 with methane/air ratio at 7%. It is suggested that water vapor produced by the thermal decomposition of metal hydroxides makes the particles of descending dust combine, resulting in a decrease of the real dust concentration in the vessel. Water vapor also is the major cause of another phenomenon that the LEL curve and the UEL curve never meet with the increase of gas concentration.
基金Supported by National Science Foundation of China under Grant Nos.11175020 and 11275025
文摘In recent years,with the development of simulations about supernova explosion,we have a better understanding about the density profiles and the shock waves in supernovae than before.There might be a reverse shock wave,another sudden change of density except the forward shock wave,or even no shock wave,emerging in the supernova.Instead of using the expression of the crossing probability at the high resonance,PH,we have studied the matter effects on neutrino oscillations in different supernova models.In detail,we have calculated the survival probability of νe(P_s)and the conversion probability of ν_x(P_c) in the Schrodinger equation within a simplified two-flavor framework for a certain case,in which the neutrino transfers through the supernova matter from an initial flavor eigenstate located at the core of the supernova.Our calculations was based on the data of density in three different supernova models obtained from simulations.In our work,we do not steepen the density gradient around the border of the shock wave,which differs to what was done in most of the other simulations.It is found that the mass and the density distribution of the supernova do make a difference on the behavior of P_s and P_c.With the results of P_s and P_c,we can estimate the number of νe(and ν_x) remained in the beam after they go through the matter in the supernova.
