Study of Shield Design for Shock Mitigation

2006 ◽  
Author(s):  
Wing Cheng ◽  
Kazuyuki Hokamoto ◽  
Shigeru Itoh
Keyword(s):  
High Explosive ◽  
Numerical Study ◽  
Computer Code ◽  
Layered Materials ◽  
Pressure Level ◽  
Shock Mitigation ◽  
Mechanical Shocks ◽  
Layer Structures ◽  
Shield Design ◽  
Canister Wall

Detonation of high explosive due to impact of fragments and flyer plates was modeled using hydrodynamic computer code. Included in the model were the warhead consisting of casing and high explosive (which is H-6 in this case). An 80-gram fragment simulated projectile (FSP) was used as the projectile. Flyer plates considered are single- and multi-layer structures. A reactive flow model which is able to capture the initiation, propagation and complete detonation or deflagration of detonation was used to predict the occurrence of complete detonation. Analyses were performed with several impact velocities to obtain the velocity beyond which complete detonation would occur. Shields have been used to mitigate mechanical shocks. It has been well established that shields with multi-layered materials with impedance mismatch would reduce shock levels significantly. A numerical study was conducted to derive an optimum shield design with this concept. The model used encompasses a warhead-canister system. It was assumed that one of the two adjacent warheads would detonate. The canister wall was made of multi-layered materials consisting of layers of materials made of metal and lucite. This material combination represents a medium degree of mismatch while still exhibiting certain amount of strength. The model determines the pressure level at explosive in the neighboring warhead. The pressure level was used to determine if detonation would occur, and provided a measure of effectiveness on the shields for shock mitigation.

Numerical Study of Mass Dispersion in Laminar and Turbulent Flows Through a Pipeline

2002 ◽  
Author(s):  
Horacio Antonio Flo´rez Guzma´n
Keyword(s):  
Turbulent Flows ◽  
Molecular Diffusion ◽  
Numerical Study ◽  
Computer Code ◽  
Finite Difference Schemes ◽  
Entire Volume ◽  
Two Fluids ◽  
Mass Dispersion ◽  
Miscible Fluid ◽  
Domain Discretization

A computer code for solving the equations of mass diffusion has been developed and applied to study the molecular-level mixing between two fluids inside a pipe. First, one fluid occupies the entire volume within the pipe, and then a second miscible fluid is forced into the pipe, developing a mixing process through the interface between the fluids. This phenomenon occurs as the combination of molecular diffusion, variation of velocity over the cross-section and turbulence. The code developed for this study is based on the finite element method for domain discretization and standard finite difference schemes for temporal discretization. Comparison with experimental data shows that the code is able to reproduce the physical trends and gives good predictions for engineering applications. A grid independence analysis is presented for all computations.

Numerical Study of Detonation Propagation in an Insensitive High Explosive Arc with Confinement Materials

2020 ◽  
pp. 2050117
Author(s):  
Yupei Qin ◽  
Kuibang Huang ◽  
Huan Zheng ◽  
Yousheng Zhang ◽  
Xin Yu
Keyword(s):  
Stainless Steel ◽  
Steady State ◽  
Detonation Wave ◽  
High Explosive ◽  
Numerical Study ◽  
Detonation Front ◽  
Outer Boundary ◽  
Outer Part ◽  
Transition Phase ◽  
Detonation Propagation

Detonation propagation in a confined circular arc configuration of an insensitive high explosive PBX9502 is investigated via numerical simulation in this paper. We introduce a steady detonation wave entering the explosive arc with confinements of stainless steel, and then it undergoes a transition phase and reaches a new steady state with a constant angular speed eventually. The influences of the inner and the outer confinements on the propagating detonation wave as well as the characteristics of the detonation driving zone (DDZ) in the steady state are discussed, respectively. Ignition and Growth (I&G) reaction rate and Jones–Wilkins–Lee (JWL) equations of state for the reactants and the products of PBX9502 are employed in the numerical simulations on the basis of a two-dimensional Eulerian code. The equation of state for stainless steel is in the Grüneisen form with a linear shock speed–particle speed Hugoniot relationship. Our results show that the inner confinement dominates the evolution of the detonation wave and the outer confinement only takes effect in a local region near the outer boundary within a limited initial stage during the transition phase. As for the steady state, the existence of the inner confinement makes the DDZ possess a certain width on the inner boundary. While as to the outer part of the detonation wave, the width of the DDZ decreases until the sonic locus intersects with the detonation front shock, which results in the detachment of the DDZ from the outer boundary and makes the detonation propagation fully independent of the outer confinement.

scholarly journals Parallel Numerical Simulation of the Magnetic Moment Reversal within the φ0-Josephson Junction Spintronic Model

2020 ◽  
Vol 226 ◽  
pp. 02018
Author(s):  
Stefani Panayotova ◽  
Maxim Bashashin ◽  
Elena Zemlyanaya ◽  
Pavlina Atanasova ◽  
Yury Shukrinov ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Magnetic Moment ◽  
Information Technologies ◽  
Parallel Implementation ◽  
Numerical Study ◽  
Nonlinear Differential Equations ◽  
Computer Code ◽  
Computer Time ◽  
Physical Parameters ◽  
Wide Range

The φ0-Josephson Dushanbe, Tajikistanjunction model with a coupling between the magnetic moment and the Josephson current in the “superconductor–ferromagnet–superconductor” system has been investigated. Numerical solution of the respective system of nonlinear differential equations is based on the two-stage Gauss–Legendre algorithm. For numerical simulation in a wide range of parameters which requires a significant computer time, a parallel MPI=C++ computer code has been developed. Results of numerical study of the magnetization effect depending on physical parameters, as well as results of methodological calculations demonstrating the efficiency of the parallel implementation, are presented. Calculations have been carried out at the Heterogeneous Platform “HybriLIT” and on the supercomputer “Govorun” of the Multifunctional Information and Computing Complex of the Laboratory of Information Technologies, JINR (Dubna).

Smoke and Heat Propagation Modeling in Transportation Interchange Stations Using LES and RANS Methods

2013 ◽  
Author(s):  
Claudio Zanzi ◽  
Alberto Mozas ◽  
Julio Hernández ◽  
Antonio García-Hortelano ◽  
Javier Aldecoa
Keyword(s):  
Boundary Conditions ◽  
Turbulence Modeling ◽  
Numerical Study ◽  
Combustion Process ◽  
Chemical Species ◽  
Computer Code ◽  
Heat Propagation ◽  
Safety Level ◽  
Cpu Time ◽  
Bus Station

A numerical study of smoke and heat transport from fires occurring in a large interchange bus station is presented. The ultimate goal of this type of study is to increase the fire safety level of the station by improving the design of fire protection systems and evacuation procedures. The phenomena involved in the fire are highly transient and three dimensional, and their modeling requires large computational resources. In the present work, we introduce several simplifications in the numerical model, mainly related to turbulence modeling and the boundary conditions used to reproduce the effects of the combustion process, which allow us capturing the essential features of the fire while keeping the memory requirements and the CPU time at a reasonable level. In particular, we are interested in describing in a realistic way the spread of smoke and heat in a typical fire scenario in the lobby of an interchange bus station. The numerical analysis is carried out with the aid of a general-purpose computer code, using two different approaches for turbulence modeling (RANS and LES) and several discretization schemes. The fire effects are reproduced in a simple way, describing the fire focus as a source of mass, heat and chemical species. Boundary conditions are imposed at the fire focus, by setting the inlet velocity, temperature and gas composition (combustion products) at a section of appropriate area. The values of these quantities are chosen to be consistent with the prescribed heat release rate, type of fuel (heptane) and fire spread area. A comparison of the results obtained with the different methods, along with the CPU time consumption and dependence on the computational mesh, is presented. The capabilities and limitations of unsteady RANS and LES methods to reproduce the main features of the smoke and heat propagation patterns are analyzed.

A Numerical Study of the Thermal Behaviour of Calibrators for Polymer Extrusion

2006 ◽  
Author(s):  
P. A. M. Lobarinhas ◽  
J. C. F. Teixeira ◽  
S. F. C. F. Teixeira
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Thermal Behavior ◽  
Numerical Study ◽  
Thermal Contact ◽  
Computer Code ◽  
Polymer Processing ◽  
Relevant Variables ◽  
Transient Case ◽  
Great Relevance

In polymer processing by extrusion, the thermal behavior of the components downstream of the extruder dye is of great relevance to the final characteristics of the product. In fact, the process productivity, the product dimensional quality and the physical/mechanical properties are strongly dependent upon the cooling process. In the present work, a numerical model adequate to describe the thermal behavior of the calibrator and the polymer profile is developed and implemented as a computer code. The model is fully 3D, transient and includes a formulation for the polymer movement inside the calibrator based upon the VOF method [1]. Although for practical purposes, a steady solution is desired, the model was implemented as a transient case, to enable its accurate validation with experimental data. The interface between the extrudate and the calibrator is described through a coefficient for the thermal contact resistance. The equations were discretized in a finite volume formulation [2] and the code implemented in Fortran. The good agreement between the model and the experimental data has vindicated the accuracy of the computer model and its subsequent application in the analysis and optimization of complete calibration units. A parametric analysis for the most relevant variables, such as polymer velocity and calibrator length, demonstrated the consistency of the numerical model.

A Numerical Study on Hydrodynamic Interactions Between Large Numbers of Multiple Floating Bodies

2003 ◽  
Author(s):  
Yoshiyuki Inoue ◽  
Mir Tareque Ali
Keyword(s):  
Numerical Study ◽  
Computer Code ◽  
Hydrodynamic Forces ◽  
Hydrodynamic Interactions ◽  
Physical Aspect ◽  
Floating Bodies ◽  
Coupled Equations ◽  
Large Numbers ◽  
Exciting Forces ◽  
Multi Body

This paper investigates the hydrodynamic interactions between large numbers of multiple bodies floating in each other’s close vicinity. The physical aspect of hydrodynamic interaction is rather complicated and numerically sound scheme is highly recommended to study this complex phenomenon. In the present study, the 3D sink-source method has been adopted to determine the hydrodynamic forces by taking into account the effect of hydrodynamic interactions among the different floating bodies, and the coupled equations of motions are solved directly. The validation of the computer code developed for this purpose has been justified by comparing the present results with that of the published ones for simple geometrical shaped floating bodies. The numerical computations have been carried out for different numbers of various freely floating multi-body systems and the hydrodynamic interactions between the floating bodies have been studied by calculating the hydrodynamic forces, first order wave exciting forces and motion responses. Finally some conclusions have been drawn on the basis of the present analysis.

Numerical Study of a Vertical Solidification Process under Magnetic Field in Unsteady State

2010 ◽  
Vol 297-301 ◽  
pp. 254-262
Author(s):  
Sabrina Nouri ◽  
Mouhamed Benzeghiba ◽  
Ahmed Benzaoui
Keyword(s):  
Magnetic Field ◽  
Binary Alloy ◽  
Numerical Study ◽  
Magnetic Field Effect ◽  
Solidification Process ◽  
Computer Code ◽  
Thermosolutal Convection ◽  
Unsteady State ◽  
Vertical Solidification ◽  
The Magnetic Field

Numerical computation is achieved in an axisymmetric configuration to analyze the magnetic field effect on thermosolutal convection during vertical solidification of a binary alloy. The bath is exposed to a uniform temperature profile in unsteady state. During the growth three regions appear: liquid, mushy and solid zones. The mushy zone is assimilated to porous medium. A mathematical model of heat, momentum and solute transfer has been developed in primitive variables (pressure-velocity). A single domain approach (enthalpy method) is used to build the equations system. In this context, a computer code has been developed and validated with previous studies. The results in term of stream function and solute concentration show the strong effect of the magnetic field on the fluid flow and on the solutal stratification. The effects of magnetic field and melt convection intensity were demonstrated. The main results show that the quality of highly doped binary alloy crystals can be improved when the growth process occurs at low pulling rates and under a magnetic field.

A Parametric Study of Conjugate Heat Transfer of Solar Chimney

2009 ◽  
Author(s):  
J. Arce ◽  
J. P. Xaman ◽  
G. Alvarez ◽  
M. J. Jime´nez ◽  
M. R. Heras
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Parametric Study ◽  
Solar Irradiance ◽  
Natural Ventilation ◽  
Numerical Study ◽  
Ambient Air ◽  
Computer Code ◽  
Solar Chimney ◽  
Conservation Equations

Recently, new buildings are being designed considering natural sources such as natural ventilation as a passive technique. Solar chimneys are among those techniques of passive ventilation systems in buildings, to enhance the air quality and some times the thermal comfort. In this work, a numerical study of a solar chimney for forced ventilation is carried out. Also a parametric study varying the ambient air temperature, the solar irradiance and Reynolds number is considered. The dimensions of the solar chimney are 4.0 m high, and 0.35 m deep, the absorber surface of the solar chimney was 0.15 m thick of reinforced concrete. The conservation equations of mass, momentum, energy and two turbulence equations are solved under some simplifications such as: 2-D, incompressible, steady state turbulent air flow and conjugated heat transfer (conduction, forced convection and radiation). k-ω turbulent model was implemented and finite volume technique was applied to solve the conservation equations. In order to guarantee the right performance of the computer code, it was reduced to cases reported in the literature and verified; also, it was validated with an experiment. The variation of ambient temperature, solar irradiance and Reynolds number are analyzed in the parametric study. The heat transfer correlations for total Nusselt number (convective plus radiative) are introduced. From the results, it was found that the heat transfer increases as the Reynolds number increases for the hot surface of the solar chimney.

scholarly journals Influence of Grains Shape Irregularity in Porous Ceramics—Numerical Study

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1944
Author(s):  
Danuta Miedzińska
Keyword(s):  
Finite Element ◽  
Numerical Study ◽  
Computer Code ◽  
Porous Ceramics ◽  
Ceramic Foam ◽  
Fe Model ◽  
Strength Behavior ◽  
Absorbing Material ◽  
Shape Irregularity ◽  
Energy Absorbing

The presented study deals with the analysis of the stochastic geometry of grains on ceramic foam strength behavior. A microstructural finite element (FE) model of a grainy structure of such a material was developed and stochastic changes to the grain geometry (initially of a regular cubic shape) were introduced. The numerical compression test of a series of finite element models was carried out with the use of LS Dyna computer code. To consider the ceramic specific behavior, the Johnson Holmquist constitutive model was implemented with parameters for alumina. The influence of the stochastic irregularities on the ceramic foam strength was observed—the geometry changes caused an increase in the maximum stress, which could be the basis for the indication that the production of the energy absorbing material should be based on mostly irregular grains.

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