Multi-Dimensional Two-Phase Flow Modeling Applied to Interior Ballistics

2011 ◽  
Vol 78 (5) ◽  
Author(s):  
Julien Nussbaum ◽  
Philippe Helluy ◽  
Jean-Marc Herard ◽  
Barbara Baschung
Keyword(s):  
Three Dimensional ◽  
Hyperbolic Model ◽  
Finite Volume Scheme ◽  
Step Method ◽  
Fractional Step Method ◽  
Two Phase ◽  
Decomposition Reactions ◽  
Solid Decomposition ◽  
The One ◽  
Complex Phenomena

Complex phenomena occur in a combustion chamber during a ballistic cycle. From the ignition of the black powder in the primer to the exit of the projectile through the muzzle, two-phase gas-powder mix undertakes various transfers in different forms. A detailed comprehension of these effects is fundamental to predict the behavior of the whole system, considering performances and safety. Although the ignition of the powder bed is three-dimensional due to the primer’s geometry, simulations generally only deal with one- or two-dimensional problem. In this study, we propose a method to simulate the two-phase flows in 1, 2 or 3 dimensions with the same system of partial differential equations. A one-pressure, conditionally hyperbolic model [1] was used and solved by a nonconservative finite volume scheme associated to a fractional step method, where each step is hyperbolic. We extend our study to a two-pressure, unconditionally hyperbolic model [2] in which a relaxation technique was applied in order to recover the one-pressure model by using the granular stress. The second goal of this study is also to propose an improved ignition model of the powder grains, by taking into account simplified chemical kinetics for decomposition reactions in the two phases. Here we consider a 0th-order solid decomposition and an unimolecular, 2nd-order gas reaction. Validation of the algorithm on several test cases is presented.

Numerical study of a transitional synthetic jet in quiescent external flow

2007 ◽  
Vol 581 ◽  
pp. 287-321 ◽  
Author(s):  
RUPESH B. KOTAPATI ◽  
RAJAT MITTAL ◽  
LOUIS N. CATTAFESTA III
Keyword(s):  
Numerical Study ◽  
Time Integration ◽  
Three Dimensional ◽  
Internal Flow ◽  
External Flow ◽  
Second Order ◽  
Synthetic Jet ◽  
Transition To Turbulence ◽  
Step Method ◽  
Fractional Step Method

The flow associated with a synthetic jet transitioning to turbulence in an otherwise quiescent external flow is examined using time-accurate three-dimensional numerical simulations. The incompressible Navier–Stokes solver uses a second-order accurate scheme for spatial discretization and a second-order semi-implicit fractional step method for time integration. The simulations are designed to model the experiments of C. S. Yao et al. (Proc. NASA LaRC Workshop, 2004) which have examined, in detail, the external evolution of a transitional synthetic jet in quiescent flow. Although the jet Reynolds and Stokes numbers in the simulations match with the experiment, a number of simplifications have been made in the synthetic jet actuator model adopted in the current simulations. These include a simpler representation of the cavity and slot geometry and diaphragm placement. Despite this, a reasonably good match with the experiments is obtained in the core of the jet and this indicates that for these jets, matching of these key non-dimensional parameters is sufficient to capture the critical features of the external jet flow. The computed results are analysed further to gain insight into the dynamics of the external as well as internal flow. The results indicate that near the jet exit plane, the flow field is dominated by the formation of counter-rotating spanwise vortex pairs that break down owing to the rapid growth of spanwise instabilities and transition to turbulence a short distance from the slot. Detailed analyses of the unsteady characteristics of the flow inside the jet cavity and slot provide insights that to date have not been available from experiments.

Novel Dynamic Numerical Microchannel Evaporator Model to Investigate Parallel Channel Instabilities

2015 ◽  
Author(s):  
Tom Saenen ◽  
John R. Thome
Keyword(s):  
Three Dimensional ◽  
Parallel Channel ◽  
Two Phase ◽  
One Dimensional ◽  
Pressure Losses ◽  
Initial Validation ◽  
Numerical Solver ◽  
The One ◽  
Flow Conservation ◽  
Stability Results

A novel fully dynamic model of a microchannel evaporator is presented. The aim of the model is to study the highly dynamic parallel channel instabilities that occur in these evaporators in more detail. The numerical solver for the model is custom-built and the majority of the paper is focused on detailing the various aspects of this solver. The one-dimensional homogeneous two-phase flow conservation equations are solved to simulate the flow. The full three-dimensional conduction domain of the evaporator is also dynamically resolved. This allows for the correct simulation of the complex hydraulic and thermal interactions between the microchannels that give rise to the parallel channel instabilities. The model uses state-of-the-art correlations to calculate the frictional pressure losses and heat transfer in the microchannels. In addition, a model for inlet restrictions is also included to simulate the stabilizing effect of these components. In the final part of the paper, initial validation results of the model are presented, in which stability results of the model are compared to existing experimental data from literature. Finally, some representative dynamic results are also given to demonstrate some of the unique capabilities of the model.

Chaotic Mixing in Three-Dimensional Micro Channel

2008 ◽  
Author(s):  
Thuy Hong Van-Le ◽  
Sangmo Kang ◽  
Yong Kweon Suh ◽  
Yangyang Wang
Keyword(s):  
Particle Tracking ◽  
Concentration Distribution ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Half Period ◽  
Chaotic Mixing ◽  
Micro Channel ◽  
Step Method ◽  
Fractional Step Method ◽  
Modulation Period

The quality of chaotic mixing in three-dimensional micro channel flow has been numerically studied using Fractional-step method (FSM) and particle tracking techniques such as Poincare´ section and Lyapunov exponents. The flow was driven by pressure distribution and the chaotic mixing was generated by applying alternating current to electrodes embedded on the bottom wall at a first half period and on the top wall at a second half period. The equations governing the velocity and concentration distributions were solved using FSM based on Finite Volume approach. Results showed that the mixing quality depended significantly on the modulation period. The modulation period for the best mixing performance was determined based on the mixing index for various initial conditions of concentration distribution. The optimal values of modulation period obtained by the particle tracking techniques were compared with those from the solution of concentration distribution equation using FSM and CFX software and the comparison showed their good match.

A Numerical Study on the Structure of Tip Clearance Flow in a Highly Forward-Swept Axial-Flow Fan

2002 ◽  
Author(s):  
Gong Hee Lee ◽  
Je Hyun Baek
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Axial Flow ◽  
Streamwise Velocity ◽  
Tip Clearance ◽  
Wake Flow ◽  
Axial Flow Fan ◽  
Step Method ◽  
Fractional Step Method ◽  
Tip Clearance Flow

A three-dimensional Navier-Stokes analysis was performed to investigate the tip clearance flows in a highly forward-swept axial flow fan operating at design condition. The numerical solution was based on a fractional step method, and two-layer k-ε model was used to obtain the eddy viscosity. The tip leakage vortex decayed very quickly inside the blade passage and, thus, no distinct leakage vortex appeared behind trailing edge. The main reason was the severe decrease of the streamwise velocity of the vortex. Also the interaction of the vortex with the casing boundary layer and the through-flow were other possibilities of the fast decay of the vortex. Comparison between the numerical results and LDV measurements data indicated that the complex viscous flow patterns inside the tip region as well as the wake flow could be properly predicted, but more refinement in numerical aspects are needed.

Numerical Modelling of the Thermal Process in the Aquatic Environment

2013 ◽  
Vol 787 ◽  
pp. 669-674
Author(s):  
Alibek Issakhov ◽  
Bakytzan Zhumagulov
Keyword(s):  
Aquatic Environment ◽  
Thermal Power ◽  
Three Dimensional ◽  
Fourier Method ◽  
Stratified Medium ◽  
Navier Stokes ◽  
Step Method ◽  
Fractional Step Method ◽  
Thermal Influence ◽  
The Mathematical Model

This paper presents the mathematical model of the thermal influence to the aquatic environment of thermal power plant, which is solved by the Navier-Stokes and temperature equations for an incompressible fluid in a stratified medium. Numerical algorithm based on the projection method which solved with fractional step method. Three dimensional Poisson equation solved with Fourier method with combination of tridiagonal matrix method (Thomas algorithm).

scholarly journals Development of a three dimensional circulation model based on fractional step method

2010 ◽  
Vol 2 (1) ◽  
pp. 14-23
Author(s):  
Mazen Abualtayef ◽  
Masamitsu Kuroiwa ◽  
Ahmed Khaled Sief ◽  
Yuhei Matsubara ◽  
Ahmed M. Aly ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Circulation Model ◽  
Fractional Step ◽  
Step Method ◽  
Fractional Step Method ◽  
Model Based

Large Eddy Simulation of Gas-Liquid Two-Phase Flow for a Nested Type Fixed-Cone Valve

2012 ◽  
Vol 170-173 ◽  
pp. 2458-2463
Author(s):  
Y.L. Liu ◽  
B. Lv ◽  
W.L. Wei
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Flows ◽  
Free Fluid ◽  
Step Method ◽  
Fractional Step Method ◽  
Two Phase ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Volume Method ◽  
Free Fluid Surface

large eddy simulation cooperated with a physical fractional-step method is applied to simulate steady flow around a nested type fixed-cone valve; and the equations are solved with the finite volume method. The free fluid surface is simulated by the VOF method. The pressure contours and vorticity magnitude are obtained. The modeling results conform to physical law, and show that the large eddy simulation theory has powerful capacity in simulation of microstructures of turbulent flows, and the function of the nested type fixed-cone valve for energy dissipating is good.

Dynamic Numerical Microchannel Evaporator Model to Investigate Parallel Channel Instabilities

2016 ◽  
Vol 138 (1) ◽  
Author(s):  
Tom Saenen ◽  
John R. Thome
Keyword(s):  
Three Dimensional ◽  
Solid Substrate ◽  
Parallel Channel ◽  
Two Phase ◽  
Pressure Losses ◽  
Stabilizing Effect ◽  
Substrate Properties ◽  
Numerical Solver ◽  
The Stability ◽  
The One

A fully dynamic model of a microchannel evaporator is presented. The aim of the model is to study the highly dynamic parallel channel instabilities that occur in these evaporators in more detail. The numerical solver for the model is custom-built and the majority of the paper is focused on detailing the various aspects of this solver. The one-dimensional homogeneous two-phase flow conservation equations are solved to simulate the flow. The full three-dimensional (3D) conduction domain of the evaporator is also dynamically resolved. This allows for the correct simulation of the complex hydraulic and thermal interactions between the microchannels that give rise to the parallel channel instabilities. The model uses state-of-the-art correlations to calculate the frictional pressure losses and heat transfer in the microchannels. In addition, a model for inlet restrictions is also included to simulate the stabilizing effect of these components. In the final part of the paper, validation results of the model are presented, in which the stability results of the model are compared with the existing experimental data from the literature. Next, a parametric study is performed focusing on the stabilizing effects of the solid substrate properties. It is found that increasing the thermal conductivity and thickness of the solid substrate has a strong stabilizing effect, while increasing the number of microchannels has a small destabilizing effect. Finally, representative dynamic results are also given to demonstrate some of the unique capabilities of the model.

Three-Dimensional Boundary Layers Over an Infinite Swept Bump and Free Wing

1995 ◽  
Vol 117 (4) ◽  
pp. 605-611 ◽  
Author(s):  
Xiaohua Wu ◽  
Kyle D. Squires
Keyword(s):  
Pressure Gradient ◽  
Boundary Layers ◽  
Three Dimensional ◽  
Adverse Pressure Gradient ◽  
Spanwise Direction ◽  
Step Method ◽  
Fractional Step Method ◽  
Dimensional Boundary ◽  
Single Transition ◽  
Separating Flows

Three-dimensional laminar boundary layers past an infinite swept bump and free wing were investigated numerically using the fractional step method. The objective of the work was to study the effect of surface curvature induced changes in pressure gradient and changes in the freestream flow on boundary layer skewness and growth. Simulation results demonstrate that for flows over the bump the first transition from adverse to favorable pressure gradient occurs at the front concave/convex inflexion and the second transition from favorable to adverse pressure gradient occurs at the summit. For flows past a free wing, the only transition from favorable to adverse pressure gradient occurs in front of the summit and the subsequent adverse pressure gradient is larger than the corresponding value for the bump. For both the bump and wing, the increase of initial skewing angle from 0 to 30 deg causes a 10 percent reduction in the length of the wake; the wake behind the wing is about 12 percent longer in streamwise extent than the corresponding wake behind the bump. Integral parameters in the flows over the bump display a wavy trend due to the two transitions of the pressure gradient. On the other hand, the single transition from favorable to adverse pressure gradient brings about a monotonic increase of the integral parameters for flows past the wing. Near separation and reattachment, surface-streamlines are skewed strongly in the spanwise direction. Conditions of flow detachment for the bump and wing are in good agreement with correlations for laminar separating flows with power-law velocity profiles as well as correlations for wall-curvature-induced turbulent separating flows.

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