Research On High Accuracy Numerical Calculation Of The Blast Field And Load Characteristics In Confined Space

According to the statistics of battle examples and test data,the anti-ship missile has become the main threat to the naval ship's life force.The damage effect analysis and protection structure design of the naval ship under blast load in the cabin are the hot spots in the field of naval ship engineering.The accurate analysis of the blast load in the cabin is the precondition of the structural response evaluation and the load input of the protective structure design.When explosion occurs in the the naval ship cabin,the blast field environment and load forms are quite different from those in the open space.The blast load of anti-ship missile warhead in naval ship cabin is characterized by complex evolution process,long loading time and obvious afterburning effect.In addition to the initial blast wave,quasi-static overpressure and high temperature load become important damage sources.Therefore,it is of great theoretical significance and engineering application value to deeply study the blast field and its formed load(overpressure load and temperature load)in confined space to provide reliable input load for the analysis of blast damage of ships,the design of anti-explosion structure and the evaluation of impact response of shipboard equipment.For this reason,this paper focuses on the high-precision numerical calculation and load characteristic of the blast field in confined space.Based on FORTRAN platform,an in-house high accuracy three dimensional numerical calculation code for blast waves in confined space was developed in Chapter 2 of this paper.The reliability and correctness of the code were verified using some classical Riemann examples and three dimensional internal explosion overpressure load experiment.Then,the in-house code was used to conduct research on overpressure load characteristics in confined space in Chapter 3 of this paper.Formula for calculating the peak quasi-static overpressure in closed space was derived based on the principle of energy conservation.Characteristics of blast overpressure load in venting space were investigated discussing the influence of venting hole size and explosive mass on quasi-static overpressure load in venting space.A simplified calculation formula of quasi-static overpressure load in venting space was proposed.This formula is in good agreement with empirical formula based on experimental data.High temperature is one of the characteristics of internal blast loads.A numerical method for calculating transient temperature field of explosive explosion in confined space was presented,and a three-dimensional numerical code for explosion temperature field in confined space was developed in Chapter 4 of this paper.Numerical calculations of explosion temperature field in closed space were carried out using the developed code discussing the corresponding characteristics of explosion temperature load.Numerical calculations of the quasi-static temperature stationary value are in good agreement with theoretical solutions verifying the reliability of the developed code.Numerical calculations of explosion temperature field in venting space were carried out,and the influence of explosive mass and venting hole sizes on explosion temperature load were discussed.Theoretical analysis and numerical calculation were carried out to study the influence of afterburning effect on internal blast loads.The formulas for calculating quasi-static temperature,quasi-static specific heat ratio and peak quasi-static overpressure varing with mass volume ratio in closed space were derived in Chapter 5 of this paper.The difference and reliability of the calculation results from present two theoretical models were analyzed.On this basis,the theoretical model was extended and applied to the calculation of quasi-static parameters in different environment atmospheres.The influence law of oxygen content in environment atmospheres on the quasi-static parameters of internal explosion was analyzed.A simplified reaction rate model considering afterburning energy was proposed in Chapter 6 of this paper.And then an in-house high accuracy code considering the afterburning energy adding was developed.The influence of the afterburning energy and the reaction rate constant on the internal explosion overpressure load was investigated numerically using the code.The influence law of the specific heat ratio change of gas on internal explosion parameters was discussed.Finally,a numerical calculation model for the internal explosion field considering afterburning effects was proposed.This model not only takes the addition of afterbruninig energy,but also the variation of gas parameters with reaction components into consideration.The influence of afterburning effects on internal explosion parameters was discussed adopting the corresponding in-house developed high accuracy 3D numerical code.In order to further improve the calculation accuracy and resolution of internal blast field.A kind of improved third-order WENO scheme named WENO-P+3 scheme for resolution enhancement was proposed in Chapter 7 of this paper.An improved third-order WENO-Z scheme named WENO-NN3 scheme was proposed as well achieving optimal order near critical points in Chapter 8 of this paper.Some classic examples were selected such as Sod shock tube,Interacting blast waves,Rayleigh-Taylor problem and strong shock double Mach reflection to investigate the computing performance of the improved schemes.It is indicated from the results that the improved schemes not only improve the calculation precision near critical points,also reduce the dissipation giving higher resolution of complex flow field structures.Finally,the improved schemes were applied to the numerical calculation of blast load in confined space and higher accuracy and resolution results were abtained.