The CFD numerical simulations were carried out to investigate the base drag characteristics of a projectile with base bleed unit with a central jet. Different base bleed grain types with different ...combustion temperatures were used. The goal was to find a way to effectively control the base flow for base drag reduction and optimisate the latter using an adequate CFD software. Axisymmetric, compressible, mass-averaged Navier-Stokes equations are solved using the k-? SST, transition k-kl-?, and RSM turbulence models. The various base flow characteristics are obtained by the change in the non-dimensionalized injection impulse. The results obtained through the present study show that there is an optimum bleed condition for all base bleed grains tested. That optimum is dependent on the temperature of the grain combustion products. The optimum reduces the total drag for 6,9% in the case of air injection at temperature of 300 K and reaches up to 28% in the case of propellant combustion products injection at almost 2500 K. Besides, the increasing of molecular weight has a role no less important than temperature of the combustion products in terms of base drag reduction.
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This paper considers the modeling of perforation of thin steel plates by cylindrical steel penetrators – fragment simulators. A comprehensive experimental investigation was performed and relevant ...data about the experiment setup and measuring equipment are reported. A numerical model developed in FEM based software Abaqus is described in detail. The Johnson–Cook thermo-viscoplastic constitutive law, as well as the Johnson–Cook damage model is used in the model. It has been shown that simulations correctly reproduce the main mechanisms of penetration process – indentation, bulging and plugging. Computational results are compared with experimental data in terms of the ballistic curves – diagrams that define the dependence of penetrator residual velocity on its impact velocity. The comparison of numerically obtained and measured values of deformed penetrator's diameter, plug thickness and maximum plate deflection has been also performed. Very good overall agreement is obtained between results of simulation and experimental measurements. After the validation of the numerical model, some empirical relations between perforation process parameters are derived.
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•Experimental results of perforation of thin steel plates are reported.•A FEM model is developed and simulation results are compared with experiments.•Very good overall agreement between the model and experimental results is obtained.•The empirical relation for the minimum perforation kinetic energy is suggested.
Contemporary research in the field of explosive applications implies
utilization of hydrocode simulations. Validity of these simulations strongly
depends on parameters used in the equation of state ...for high explosives
considered. A new analytical model for determination of Jones-Wilkins-Lee
(JWL) equation of state parameters based on the cylinder test is proposed.
The model relies on analysis of the metal cylinder expansion by detonation
products. Available cylinder test data for five high explosives are used for
the calculation of JWL parameters. Good agreement between results of the
model and the literature data is observed, justifying the suggested
analytical approach. Numerical finite element model of the cylinder test is
created in Abaqus in order to validate the proposed model. Using the
analytical model results as the input, it was shown that numerical simulation
of the cylinder test accurately reproduces experimental results for all
considered high explosives. Therefore, both the analytical method for
calculation of JWL equation of state parameters and numerical Abaqus model of
the cylinder test are validated.
The change of gas parameters in the cylinder of the automatic gun has a great influence on the dynamics of the gun. Many factors have an influence on the gas parameters in the gas cylinder such as ...the diameter and position of the gas port, the initial volume of the gas cylinder, the gap between the piston and the cylinder, initial temperature of the cylinder parts, etc. The analytical model was made to analyze the parameters on which depends gas piston dynamics. The numerical simulation with CFD software ANSYS Fluent was performed to analyze the change of the thermodynamic properties of the gases in the cylinder, temperature change of the cylinder parts and dynamics of the gas piston. The experiment was performed to provide pressures in the barrel and the gas cylinder and velocity of the gas piston. The comprehensive comparisons between results obtained by the analytical model, the numerical simulation and experiments have been performed and good agreements were observed.
The study of increasing range of standard 122 mm artillery projectile was done mainly by changing the base drag of standard projectile using hollow base shape and base bleed unit. The drag reduction ...in the case of the projectile with base bleed was up to 20% compared to the standard projectile, and in the case of the hollow base projectile, the drag reduction reaches 8%. Optimisation of base drag reduction was done by using the computational fluid dynamics software (CFD). CFD analyses enable complete calculation of fluid parameters behind the projectile base and determination of base bleed burning gases influence on flow field. In that way, we determine the pressure on the projectile base in the case of projectile with hollow base or with base bleed. CFD computations give us relation between base drag reduction and characteristics of base bleed grain. Using the CFD results in the modified 6-degree of freedom (6-DOF) projectile trajectory model, we calculate ranges of projectiles. The verification of estimated range increase by projectile modification was done by comparison with experimental results obtained on firing range. Comparison of measured range and results from 3-D radar show good compatibility with theoretical results from the modified 6-DOF.
The Research in this paper considered the temperatures fields as the
consequently influenced effects appeared by plastic deformation, in the
explosively forming process aimed to design Explosively ...Formed Projectiles
(henceforth EFP). As the special payloads of the missiles, used projectiles
are packaged as the metal liners, joined with explosive charges, to design
explosive propulsion effect. Their final form and velocity during shaping
depend on distributed temperatures in explosively driven plastic deformation
process. Developed simulation model consider forming process without metal
cover of explosive charge, in aim to discover liner?s dynamical correlations
of effective plastic strains and temperatures in the unconstrained detonation
environment made by payload construction. The temperature fields of the
liner?s copper material are considered in time, as the consequence of
strain/stress displacements driven by explosion environmental
thermodynamically fields of pressures and temperatures. Achieved final
velocities and mass loses as the expected EFP performances are estimated
regarding their dynamical shaping and thermal gradients behavior vs.
effective plastic strains. Performances and parameters are presented vs.
process time, numerically simulated by the Autodyne software package.
In the paper theoretical and numerical model of two-phase flow of solid granular propellant and its products of combustion in the gun barrel during interior ballistic cycle is given. Two cases are ...considered: base ignition of propellant charge and ignition by igniter. The theoretical model includes the balance equations of mass, momentum and energy for both phases, as well as necessary constitutive laws. The igniter efflux in the propellant chamber is obtained by incorporation in the model the two-phase flow model of igniter function. The convergent, unconditionally stable, numerical procedure is formed to solve the system of equations of the theoretical model. An original procedure of numerical grid adaptation to the flow field increase, caused by the projectile motion down the gun bore, is developed. The TWOPIB code for the computation of whole interior ballistic cycle of ammunition is developed. Four kinds of experimental investigations were carried out:igniter function in open air, flamespreading through propellant charge in the fibreglass tube during base ignition or during ignition by igniter, and firing of 100
mm APFSDS projectile. Verification of the theoretical–numerical approach by the comparison with experimental data is carried out. The great number of computational results is presented for the parameters that can not be measured, but which are necessary for more complete understanding of examined processes. The presented theoretical–numerical access enables, not only the complete optimisation of propellant charges, but more successful solutions of many interior ballistic problems.
Study of interaction of explosive reactive armor (ERA) with shaped charge jet is the basis for evaluation of the effectiveness of ERA. The physically based theoretical model of this interaction is ...given. It is incorporated in the NERA computer code. The influences of backward moving plate and forward moving plate thickness, explosive layer thickness, jet attack angle, and distance between ERA and main armor are investigated. The comprehensive analysis of a longitudinal point of impact effect on ERA efficiency, based on NERA code calculations, is presented. Computational results of NERA code are compared with experimental data. The computational and experimental results of penetration in the steel armour target are in good agreement. The developed code enables optimization of explosive reactive armor characteristics.
The study of increasing range of standard 122 mm artillery projectile was done mainly by changing the base drag of standard projectile using hollow base shape and base bleed unit. The drag reduction ...in the case of the projectile with base bleed was up to 20% compared to the standard projectile, and in the case of the hollow base projectile, the drag reduction reaches 8%. Optimisation of base drag reduction was done by using the computational fluid dynamics software (CFD). CFD analyses enable complete calculation of fluid parameters behind the projectile base and determination of base bleed burning gases influence on flow field. In that way, we determine the pressure on the projectile base in the case of projectile with hollow base or with base bleed. CFD computations give us relation between base drag reduction and characteristics of base bleed grain. Using the CFD results in the modified 6-degree of freedom (6-DOF) projectile trajectory model, we calculate ranges of projectiles. The verification of estimated range increase by projectile modification was done by comparison with experimental results obtained on firing range. Comparison of measured range and results from 3-D radar show good compatibility with theoretical results from the modified 6-DOF.
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