Numerical and Experimental Investigation of the Melt Casting of Explosives

2004 ◽  
Author(s):  
Dawei Sun ◽  
Suresh V. Garimella ◽  
Sanjeev Singh ◽  
Neelam Naik
Keyword(s):  
Numerical Model ◽  
Energetic Materials ◽  
Control Volume ◽  
Simple Algorithm ◽  
Solidification Process ◽  
High Viscosity ◽  
Stress Distributions ◽  
Flow Heat ◽  
Volume Method ◽  
The Impact

Melt casting of energetic materials is investigated, and a numerical model formulated for the analysis of the coupled fluid flow, heat transfer, and stress fields involved in this phase-change process. The numerical model is based on a conservative multi-block control volume method. The SIMPLE algorithm is employed along with an enthalpy method approach to model the solidification process. Results from the model are verified against experimental data as well as published numerical results for simplified cases. In the melt casting of RDX-binder mixtures, the very high viscosity of the melt leads to the influence of melt convection being very limited. The impact of different cooling conditions on the velocity, temperature and stress distributions, as well as on the solidification time, are discussed. The model can be used to improve the quality of cast explosives, by optimizing and controlling the processing conditions.

A Thermo-Mechanical Model for a Counterflow Biomass Gasifier

2014 ◽  
Vol 354 ◽  
pp. 227-235
Author(s):  
Marcelo J.S. de Lemos
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Control Volume ◽  
Simple Algorithm ◽  
Thermal Capacity ◽  
Macroscopic Model ◽  
Algebraic Equations ◽  
Medium Permeability ◽  
Mechanical Approach ◽  
Volume Method

This article presents a thermo-mechanical approach to investigate heat transfer between solid and fluid phases in a model gasifier. A two-temperature equation approach is applied in addition to a macroscopic model for laminar flow through a porous moving bed. Transport equations are discretized using the control-volume method and the system of algebraic equations is relaxed via the SIMPLE algorithm. The effects on inter-phase heat transfer due to variation of medium permeability, thermal conductivity and thermal capacity are analyzed. Results indicate that for smaller medium permeabilities, as well as for higher solid-to-fluid thermal capacity and thermal conductivity ratios, enhancement of heat transfer between phases is observed.

Numerical Simulation of Laminar Confined Impinging Jet in a Composite Channel

2008 ◽  
Author(s):  
Marcelo J. S. de Lemos
Keyword(s):  
Porous Layer ◽  
Control Volume ◽  
Numerical Technique ◽  
Simple Algorithm ◽  
Local Distribution ◽  
Governing Equations ◽  
Stagnation Region ◽  
Volume Method ◽  
Material Porosity ◽  
Macroscopic Equations

This work shows numerical results for a jet impinging onto a flat plane covered with a layer of a porous material. Porosity of the porous layer is varied in order to analyze its effect on the local distribution of Nu. Macroscopic equations for mass and momentum ae obtained based on the volume-average concept. The numerical technique employed for discretizing the governing equations was the control volume method with a boundary-fitted non-orthogonal coordinate system. The SIMPLE algorithm was used to handle the pressure-velocity coupling. Results indicate that inclusion of a porous layer decreases the peak in Nu avoiding excessive heating or cooling near the stagnation region.

Free convective of a linear heterogeneous liquid in a square cavity at side heating

2020 ◽  
pp. 108-116
Author(s):  
K.V. Moiseev ◽  
◽  
V.S. Kuleshov ◽  
R.N. Bakhtizin ◽  
◽  
...  
Keyword(s):  
Control Volume ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Double Diffusion ◽  
Boussinesq Approximation ◽  
Square Cavity ◽  
Cell Height ◽  
Volume Method ◽  
Dimensional Statement ◽  
Stratified Liquid

In this work the problem of free convection of the Newtonian poorly stratified liquid in the cell warmed up from left and cooled from right with the heat-insulated horizontal boarders is presented. Liquid with small concentration of salt and initial linear stratification on cell height is considered. The model of double diffusion in a Boussinesq approximation is applied to model the process. The problem is solved both in two - and three-dimensional statement by means of a control volume method and a SIMPLE algorithm. It is shown that vortex structures at the layered mode of convection have quasi-two-dimensional character.

A New Approach to the Numerical Modeling of Pure Metal Solidification

2019 ◽  
Vol 22 ◽  
pp. 1-8
Author(s):  
Mariusz Ciesielski ◽  
Bohdan Mochnacki
Keyword(s):  
Source Function ◽  
Control Volume ◽  
Type Equation ◽  
Additional Term ◽  
Solidification Process ◽  
Pure Metal ◽  
Metal Solidification ◽  
New Approach ◽  
Fourier Type ◽  
Volume Method

Solidification and cooling processes proceeding in the metal domain can be described in different ways. One of them consists in the application of the Fourier-type equation in which the additional term (source function) controlling the solidification process is introduced. In this paper this type of energy equation is used, but for the phase change modeling the equation discussed is in some way transformed. Such a modification is possible if one considers the pure metal for which the solidification point is a constant value. The numerical model used at the stage of computations is based on the Control Volume Method. In the final part of the paper, examples of computations are shown.

Numerical study of the melting and resolidification of the substrate during the impact of a ceramic droplet in a plasma spraying process

2019 ◽  
Vol 88 (2) ◽  
pp. 20901 ◽  
Author(s):  
Mouloud Driouche ◽  
Tahar Rezoug ◽  
Mohammed El Ganaoui
Keyword(s):  
Numerical Model ◽  
Phase Change ◽  
Solid Phase ◽  
Numerical Study ◽  
Solid Substrate ◽  
Navier Stokes ◽  
Droplet Spreading ◽  
Substrate Melting ◽  
Volume Method ◽  
The Impact

The substrate melting can significantly improve the properties of plasma spray coatings. Indeed the adhesion of the projected particles to the substrate can be ameliorated by the substrate melting. In this article, a numerical model is developed to study the dynamics of fluids and heat transfer with liquid/solid phase change during impact of a fully melted alumina particle on an aluminum solid substrate, taking into account of the substrate melting. The model is based on solving the Navier-Stokes and energy equations with liquid / solid phase change. These equations are coupled with the fluid of volume method (VOF), to follow the free surface of the particle during its spreading and solidification. The finite volume method is used to discretize the equations in a 2D axisymmetric domain. A comparison with the published experimental results was carried out to validate this numerical model. Simulations were performed for different initial droplet diameters to study its effect on droplet spreading as well as on substrate melting. It has been observed that the substrate melting begins before the droplet spreads completely; the substrate melting reaches its maximum when the droplet is close to its total solidification. Droplet spreading and substrate melting are more important for large sizes droplets.

Turbulent Free Convection in a Composite Enclosure

2003 ◽  
Author(s):  
Marcelo J. S. de Lemos ◽  
Viviani T. Magro
Keyword(s):  
Thermal Field ◽  
Control Volume ◽  
Simple Algorithm ◽  
Flow Region ◽  
Porous Matrix ◽  
Porous Substrate ◽  
Local Flow ◽  
Vertical Walls ◽  
Energy Equations ◽  
Volume Method

This paper deals with the problem of heat transfer in square cavities partially filled with porous material. Local flow and energy equations are integrated in a representative elementary volume in order to obtain a set of equations valid in both the clear flow region and in the porous matrix. A unique set of equations is discretized with the control volume method and solved with the SIMPLE algorithm. Enhancement of convective currents within the porous substrate is detected as the Rayleigh number increases. Thin boundary layers along the cavity vertical walls and stratification of the thermal field are observed for Ra > 109.

Control Volume Simulation of Casting Directional Solidification

2014 ◽  
Vol 790-791 ◽  
pp. 146-151 ◽  
Author(s):  
Imre Budavari ◽  
Daniel Molnar
Keyword(s):  
Computer Simulation ◽  
Directional Solidification ◽  
Control Volume ◽  
Solidification Process ◽  
Control Volume Method ◽  
High Quality ◽  
Large Steel ◽  
Steel Castings ◽  
Uniform Wall ◽  
Volume Method

Quality demands of castings is elemental in recent years and becoming more stringent. Foundries are faced by the need to produce high quality castings, but nonetheless to produce them economically. To fulfill this demand, experimental castings, especially in case of individual production or small runs, are uneconomical. In these cases computer simulation can be the only economical tool for testing and approval. The modulus technique of Chvorinov is an applicable method to examine the local solidification process and to determine the application of chills, geometry modification and feeding. Numerically the control volume method is used to check the solidification process of large steel castings with non-uniform wall thicknesses.

scholarly journals Stirred tank simulation using Partially-Averaged Navier-Stokes $$k_u-\epsilon _u$$ turbulence model

2021 ◽  
Vol 3 (5) ◽  
Author(s):  
Srimanta Maji ◽  
Akshaya K. Sahu
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Power Law ◽  
Control Volume ◽  
Axial Flow ◽  
Simple Algorithm ◽  
Stirred Tank ◽  
Navier Stokes ◽  
Flow Variables ◽  
Volume Method

AbstractIn the present study, simulation of a stirred tank using axial flow impeller has been studied numerically to see the behaviour of flow variables in the entire vessel. It is assumed that the flow is steady state, two dimensional, incompressible and axisymmetric. For simulation, Partially-Averaged Navier-Stokes (PANS) $$k_u-\epsilon _u$$ k u - ϵ u turbulence model has been taken into account. For discretization, control volume method along with upwind and power-law schemes have been taken. The solutions are obtained by using the SIMPLE algorithm. The boundary conditions for impeller are given by using the experimental data. The main objective is to investigate the influence of different filters width $$f_k$$ f k of the PANS $$k_u-\epsilon _u$$ k u - ϵ u model parameter on the characteristic flow variables. The predicted results of the PANS $$k_u-\epsilon _u$$ k u - ϵ u model for different $$f_k$$ f k have been compared with the experimental data at different axial levels of the stirred tank. It has been observed that the power-law scheme gives better agreement with the experimental data. Further, near the impeller region, PANS predicted results are better for smaller $$f_k$$ f k . Also, Reynolds-Averaged Navier-Stokes Shear Stress Transport (SST) $$k-\omega $$ k - ω turbulence model has been tested for comparative study.

scholarly journals Modelling and assessment of 137-Cs and of heavy metals impact on marine ecosystems

2020 ◽  
Vol 19 ◽  
pp. 119
Author(s):  
M. Psaltaki ◽  
N. C. Markatos
Keyword(s):  
Stokes Equations ◽  
Deterministic Model ◽  
Three Dimensional ◽  
Aegean Sea ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Flow Heat ◽  
Local Ecosystem ◽  
Volume Method ◽  
The Impact

Modelling is an important and useful tool for predicting the behaviour and the impact of pollutants on the local ecosystem parameters. More specifically, simulation and computational methods can be used for estimating the environmental impact on marine ecosystems.The paper presents a three-dimensional general deterministic model, developed to simulate and study the time-dependent behaviour of 137Cs in marine environments. The model capabilities are demonstrated by applying it at the northeast region of the island of Lemnos, in the NE Aegean Sea, Greece. Full Navier-Stokes equations for transient, three-dimensional turbulent flow, heat and mass transfer are solved numerically. The solution method is the finite-volume method and the general CFD code in which the present model is implemented is Phoenics.

Window geometry impact on a room's wind comfort

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Reza Fallahtafti ◽  
Mohammadjavad Mahdavinejad
Keyword(s):  
Wind Velocity ◽  
Natural Ventilation ◽  
Control Volume ◽  
Simple Algorithm ◽  
Small Scale ◽  
Solar Absorption ◽  
Content Type ◽  
Velocity Magnitude ◽  
Architectural Element ◽  
The Impact

PurposeNatural ventilation is an environmentally friendly effective way of improving thermal comfort and the quality of indoor conditions if applied properly. This study aims to investigate the physical mechanism of the air movement and also the influence of building geometry in a cross-ventilated room through a parametric study of window geometrical characteristics using computational fluid dynamics.Design/methodology/approachMomentum and continuity equations are solved by the control volume method using a commercially available software. Standard k−ɛ turbulence model is employed to simulate the incompressible airflow and SIMPLE algorithm to solve the conservation equations. Mean air velocity magnitude is measured at three different surfaces of different heights, and the effect of incoming wind velocity inside the building is studied.FindingsThe research concluded that window hood and sill projections reduce indoor wind velocity magnitude, play a major role in incoming wind direction and thus have a crucial impact on wind circulation and indoor air quality.Social implicationsThe paper has evaluated redesigning of a both practical and ornamental architectural element named Palekaneh, which is found in many historical buildings in several hot places in the world. Its optimal design could increase indoor natural ventilation quality and decrease a space's cooling load. Therefore, a new passive cooling architectural element could be re-introduced to the regions previously enjoying such ornaments. This is economically efficient because it eventually saves a considerable amount of energy in the long run and is socially important because of the revitalization of architectural identity.Originality/valueThe role of a building envelope's physical features, although being studied for solar absorption and daylight availability, has rarely been investigated for natural ventilation, especially in a small scale, thus making the paper novel in this regard. This provides a guideline for designers to assess the impact of their design on redirecting wind-induced natural ventilation the very early stages of design.

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