Research On Application Of FCT Methods In Blast Wave

With the rapid development of science and technology in our country, especially the wider application of explosion in defense and construction industry, and other aspects of life, the blast wave as an important phenomenon caused by explosion, of which the propagation law really needs studying. As early as the Nobel invented the dynamite, people began to observe a series of phenomena caused by explosive. The blast wave, as a dynamic load directly effects on the structure, will case excessive vibration and damage of the structure, even more than the ultimate bearing capacity of the structure collapsed and very serious disaster occur.Although many scholars work hard on the propagation law of the blast wave, the interactions between the explosion’s products and the blast wave in the early stage and the complicated propagation’s process of blast wave have not been satisfactorily resolved. Generally speaking, the explosion phenomena research methods basically are theoretical analysis, experimental and numerical calculation. The experiments and physical phenomena are often used to study its propagation law, however, they costs too much and are restricted by the experimental conditions, and meanwhile, the experimental date are very limited. With the development of computers and the finite element theory, it becomes possible to apply commercial finite element software to simulate the propagation of the blast wave. Many commercial software such as LS DYNA, AUTODYN and so on cost little and can get a large amount data, however, in order to make the calculation smoothly through the strong cross-section of the blast wave, the artificial viscosity techniques of the existing commercial dynamics software are widely used to handle strong discontinuity. The introduction of artificial viscosity tends to cause the pseudo-oscillation of the numerical solution which smoothes the blast wave front artificially, result in a great error in the pressure peak; therefore, the blast wave propagation cannot be truly reflected.The FCT (referred to as the flux-corrected transport method) is an advanced method of calculating, which can deal with the problem of a strong discontinuity region well without numerical oscillation by adding the method of limiting dissipation flux. Based on the study of FCT method, this thesis uses Taylor formula to analyze one-dimensional equations of dissipative and find out the keys parameters△t、△x、u with certain relationship which can improve the first-order calculation accuracy on the basis of the original FCT. By comparing the exact solution of the square wave with original second-order accuracy, the fourth-order accuracy, and the improved calculation method, the thesis verified that the newly improved method can enhance the accuracy upon the original one. Then we give a brief introduction to the simulation of four main subroutines and the boundary conditions. Finally combined with the control equation of the blast wave, the author achieves the simulation of the blast wave calculation based on the flux correct transport method.Because of the discontinuous characteristic of the blast wave, the effectiveness of the program has to be validated before calculation. The shock tube has a strong discontinuity and exact solutions. This thesis applies three different shock tube examples to verify the effectiveness of the program. According to the basic principles of the blast wave, the initial parameters of the program are briefly discussed before calculation of the blast wave. Finally, the application program to simulate the propagation of the blast wave, were analyzed from the following three aspects:(1) We simulate the air free field explosion phenomena, compared the results with LS_DYNA software and found that the pressure time curve is in good agreement, but larger pressure peak.(2) Simulated the dynamic responses of the air blast loading on structures will be compared with the experimental results, found the program to calculate the results with the experimental results agree well and prove the effectiveness of the program(3) Different distance dynamite explosion pressure peak was simulated, the calculated results were compared with the empirical formula and the LS_DYNA software and found the program to calculate the results with software value is closer to the predictive value of empirical formulaBy the above studies show that the calculation procedure can be a better simulation of the blast wave, and it has a certain value of applied research.