Computational simulation of coupled nonequilibrium discharge and compressible flow phenomena in a microplasma thruster

2009 ◽  
Vol 106 (6) ◽  
pp. 063305 ◽  
Author(s):  
Thomas Deconinck ◽  
Shankar Mahadevan ◽  
Laxminarayan L. Raja
Keyword(s):  
Compressible Flow ◽  
Computational Simulation ◽  
Nonequilibrium Discharge ◽  
Flow Phenomena

scholarly journals Numerical investigation of the compressible flow past an aerofoil

2009 ◽  
Vol 643 ◽  
pp. 97-126 ◽  
Author(s):  
LI-WEI CHEN ◽  
CHANG-YUE XU ◽  
XI-YUN LU
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Turbulent Boundary Layer ◽  
Compressible Flow ◽  
Complex Flow ◽  
Dynamical Processes ◽  
Vortical Structures ◽  
Boundary Layer Interaction ◽  
Flow Phenomena ◽  
Flow Evolution

Numerical investigation of the compressible flow past an 18% thick circular-arc aerofoil was carried out using detached-eddy simulation for a free-stream Mach number M∞ = 0.76 and a Reynolds number Re = 1.1 × 107. Results have been validated carefully against experimental data. Various fundamental mechanisms dictating the intricate flow phenomena, including moving shock wave behaviours, turbulent boundary layer characteristics, kinematics of coherent structures and dynamical processes in flow evolution, have been studied systematically. A feedback model is developed to predict the self-sustained shock wave motions repeated alternately along the upper and lower surfaces of the aerofoil, which is a key issue associated with the complex flow phenomena. Based on the moving shock wave characteristics, three typical flow regimes are classified as attached boundary layer, moving shock wave/turbulent boundary layer interaction and intermittent boundary layer separation. The turbulent statistical quantities have been analysed in detail, and different behaviours are found in the three flow regimes. Some quantities, e.g. pressure-dilatation correlation and dilatational dissipation, have exhibited that the compressibility effect is enhanced because of the shock wave/boundary layer interaction. Further, the kinematics of coherent vortical structures and the dynamical processes in flow evolution are analysed. The speed of downstream-propagating pressure waves in the separated boundary layer is consistent with the convection speed of the coherent vortical structures. The multi-layer structures of the separated shear layer and the moving shock wave are reasonably captured using the instantaneous Lamb vector divergence and curl, and the underlying dynamical processes are clarified. In addition, the proper orthogonal decomposition analysis of the fluctuating pressure field illustrates that the dominated modes are associated with the moving shock waves and the separated shear layers in the trailing-edge region. The results obtained in this study provide physical insight into the understanding of the mechanisms relevant to this complex flow.

Reactor Safety Analysis Based on a Developed Two-Phase Compressible Flow Simulation

Volume 1 ◽  
2004 ◽  
Author(s):  
A. F. Nowakowski ◽  
B. V. Librovich ◽  
L. Lue
Keyword(s):  
Multiphase Flow ◽  
Compressible Flow ◽  
Fluid Model ◽  
Numerical Technique ◽  
Computational Simulation ◽  
Safety Analysis ◽  
State Equations ◽  
Pressure Relief ◽  
Two Phase ◽  
Two Phases

The direct numerical simulation of multiphase flow is a challenging research topic with various key applications. In the present work, a computational simulation of multi-phase compressible flow has been proposed for safety analysis of chemical reactors. The main objective of a pressure relief system is to prevent accidents occurring from over pressurisation of the reactor. We are particularly interested in understanding the phenomena associated with emergency pressure relief systems for batch-type reactors and storage vessels. Existence of multiphase flow is significantly influenced by the interface between the phases and the associated discontinuities across the phase. The approach, which builds on the method first introduced by Saurel and Abgrall [1], was developed for solving two-phase compressible flow problems. Each phase is separately described by conservation equations. The interactions between two phases appear in the basic equations as transfer terms across the interface. The equations are complemented by state equations for the two phases and by additional correlations for the right-hand side coupling terms. The method is able to deal with multiphase mixtures and interface problems between compressible fluids. The key difference compared to classical two-fluid model is the presence of separate pressures fields associated with phases and introduction of pressure and velocity relaxation procedures. The relaxation operators tackle the boundary conditions at the interface and consequently the model is valid for fluid mixtures, as well as for pure fluids. The numerical technique requires the system to be decomposed and involves a non-conservative hyperbolic solver, an instantaneous pressure relaxation procedure and source term operators. The solution is obtained by succession of integrators using a second-order accurate scheme. The ultimate goal of this research is to use the method for studying the venting problem in reactor systems after verifying its performance on a series of standardised test cases documented in the literature.

Temperature Evaluation of Combined Plasma Arc for High Temperature Materials Processing by Computational Simulation

2010 ◽  
Vol 148-149 ◽  
pp. 53-57
Author(s):  
Jian Bing Meng ◽  
Xiao Juan Dong ◽  
Wen Ji Xu
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Computational Simulation ◽  
Plasma Arc ◽  
Nozzle Outlet ◽  
High Temperature Materials ◽  
Flow Phenomena ◽  
Specific Calculations ◽  
Arc Current ◽  
System Operating

A mathematical model was established to describe the electromagnetic, heat flow and fluid flow phenomena within a combined plasma arc. In the development of the model allowance is made for the conservation of mass, momentum, energy and the Maxwell equations. With the ANSYS finite analysis software, specific calculations were presented for a pure argon system, operating in a laminar mode. The distributions of the current density, temperature and velocity of combined plasma arc were gotten. In addition, the influences of process parameters, including arc current, argon gas flow rate and the distance from the nozzle outlet to the anode workpiece, on the temperature distributions along the axial and radial direction were evaluated, respectively. The results shows that the temperature of combined plasma arc is much dependent on the working current, while is less sensitive to the argon flow rate and the distance from the nozzle outlet to the workpiece anode.

Velocity and Current Density Evaluation of Combined Plasma Arc for High Temperature Materials Processing by Computational Simulation

2011 ◽  
Vol 314-316 ◽  
pp. 728-732
Author(s):  
Xiao Juan Dong ◽  
Jian Bing Meng ◽  
Zhan Min Yin ◽  
Chang Ning Ma
Keyword(s):  
Flow Rate ◽  
Current Density ◽  
Gas Flow ◽  
Computational Simulation ◽  
Current Density Distribution ◽  
Axial Direction ◽  
Plasma Arc ◽  
Nozzle Outlet ◽  
Flow Phenomena ◽  
Specific Calculations

A mathematical model was established to describe the electromagnetic, heat flow and fluid flow phenomena within a combined plasma arc. In the development of the model allowance was made for the conservation of mass, momentum, energy and the Maxwell equations. With the ANSYS finite analysis software, specific calculations were presented for a pure argon system, operating in a laminar mode. The distributions of the current density and velocity of combined plasma arc were gotten. In addition, the influences of process parameters, including arc current, argon gas flow rate and the distance from the nozzle outlet to the anode workpiece, on the velocity along the axial direction and current density distribution along radial direction were evaluated, respectively. The results shows that the velocity and current density of combined plasma arc are much dependent on the working current, while are less sensitive to the argon flow rate and the distance from the nozzle outlet to the workpiece anode.

scholarly journals Effects of compressible flow phenomena on aerodynamic characteristics in Hyperloop system

2021 ◽  
pp. 106970
Author(s):  
Kyeong Sik Jang ◽  
Thi Thanh Giang Le ◽  
Jihoon Kim ◽  
Kwan-Sup Lee ◽  
Jaiyoung Ryu
Keyword(s):  
Compressible Flow ◽  
Aerodynamic Characteristics ◽  
Flow Phenomena

Computational Simulation of Heat flow phenomena in Newly Designed Heat Sinks

2004 ◽  
Vol 14 (11) ◽  
pp. 775-779
Author(s):  
Song Chul Lim ◽  
Jong Un Choi ◽  
Kae Myung Kang
Keyword(s):  
Heat Flow ◽  
Computational Simulation ◽  
Heat Sinks ◽  
Flow Phenomena

Compressible Flow in Inlet Guide Vanes With Mechanical Flaps

2004 ◽  
Author(s):  
M. Boehle ◽  
M. Cagna ◽  
Lutz Itter
Keyword(s):  
Mach Number ◽  
Compressible Flow ◽  
Classical Type ◽  
Cfd Simulations ◽  
Guide Vanes ◽  
Flow Physics ◽  
Inlet Guide Vanes ◽  
Flow Phenomena ◽  
Analytical Estimation ◽  
Stagger Angle

The classical type of inlet guide vanes consists of uncambered or slightly cambered profiles, the stagger angle of which can be varied. A more advantageous possibility of generating an angular momentum in front of the rotor of the first stage contains the application of inlet guide vanes with mechanical flaps. This configuration consists of uncambered profiles with mechanical flaps. In the present paper, flow physics is explained for this configuration and compared with the flow physics for the classical type of inlet guide vanes. The configuration with mechanical flaps is examined numerically for 20 deg. and 32 deg. flap angles. The emphasis lies on the description of the compressible flow phenomena, which become dominant if the Mach number of the incoming flow gets close to the critical Mach number. An analytical estimation for the Mach number at the exit of the guide vanes is introduced and the results are discussed together with the results of the CFD simulations.

scholarly journals Influence of grid distribution on CFD model of compressible flow inside the primary nozzle and mixing chamber used in refrigeration application

2018 ◽  
Vol 192 ◽  
pp. 02045
Author(s):  
Natthawut Ruangtrakoon ◽  
Eakarach Bumrungthaichaichan
Keyword(s):  
Experimental Data ◽  
Mach Number ◽  
Numerical Methods ◽  
Compressible Flow ◽  
Total Pressure ◽  
Cfd Model ◽  
Regular Grid ◽  
Mixing Chamber ◽  
Flow Phenomena ◽  
Near Wall

In this study, the influence of grid distribution on CFD model of the primary nozzle and mixing chamber used in refrigeration application was primarily investigated. The only one geometry of primary nozzle and mixing chamber was modeled. The two different grid distributions, fine near-wall grid and regular grid with the identical total grid number, were simulated to investigate the flow phenomena inside the considered system. The appropriate boundary conditions and numerical methods were carefully employed. The simulated entrainment ratios obtained by two different grid arrangements were validated by comparing with the reliable experimental data. The results revealed that the Mach number distributions of these models were different. Further, the outlet total pressure predicted by fine near-wall grid was about 1.3% higher than that obtained by regular grid.

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