Dimensional Fluid Simulation Research Articles

Accelerated simulation of microwave breakdown in gases on Xeon Phi based cluster-application to self-organized plasma pattern formation

Modeling and simulation of high power microwave (HPM) breakdown, involving complex coupling between high frequency electromagnetic wave and plasma, is a computationally challenging and expensive problem due to the stringent numerical criteria. In this article, efficient parallelization and optimization strategies for two dimensional fluid simulation of microwave breakdown phenomena in air/gas on Intel’s Xeon Phi Many Integrated Core (MIC) data parallel architecture are being presented. The numerical model used for this study is based on Finite Difference Time Domain solutions of Maxwell Equation coupled with the plasma fluid Continuity Equation (Boeuf et al., 2010). The optimized parallel version of this algorithm using OpenMP on Xeon Phi co-processors achieves a speedup of around 5–138 times (on Knights Corner and Knights Landing for different problem sizes) compared to a serial version (on Intel i7-4790 processor) in a much more energy efficient way. Moreover, a hybrid strategy based on OpenMP and MPI, involving a three-level parallelization (instruction level within SIMD VPUs, thread-level over many cores and accelerator level across a cluster of Xeon Phi processors), achieves a speedup of around 1400 (compared to a serial version on xeon-phi 7250 processor) on an HPC cluster with 24 Xeon-Phi co-processors. Several fast and accurate numerical experiments have been performed on the Xeon-Phi based system, and the results are illustrated with the example of the formation of a self-organized fishbone like plasma structure during breakdown similar to the images obtained from high power microwave experiments in air (Hidaka et al., 2008). Numerical experiments show that a good resource utilization can be achieved by proper code design, cache optimization and good programming practices, and opens up many possibilities for HPM breakdown research which require resource intensive EM-fluid simulations as a precursor at a relatively cheap cost.

Three Dimensional Fluid Simulation and Experimental Verification of Hydrostatic Guideway for Large Rotary Worktable

Relying on the major national science and technology special project, this study used the table 12 fan-shaped oil cavity hydrostatic guideway of CKS5235 CNC vertical lathe worktable, applied FLUENT processing software GAMBIT modeling and mesh generation the flow static pressure guide film, setting boundary conditions. Used simulation software FLUENT numerical analysis the dynamic process of hydrostatic slideway oil film flow field with temperature field and the basic bearing capacity, the effectiveness of three dimensional fluid simulation method for hydrostatic guideway in engineering design is verified by experiments. According to the results of three-dimensional fluid simulation, the hydrostatic guide structure of CKS5235 CNC vertical lathe worktable has been improved, achieve the speed performance improvement of the table, complete the major special technical research and acceptance.

SF6/N2혼합기체의 DC 플라즈마 특성 분석

SF<SUB>6</SUB> gas has been used for power transformers or gas insulated switchgears, because it has the superior insulation property and the stable structure chemically. It has been, however, one of global warming gases and required to reduce the its amount. Some papers have reported that its amount could be reduced by mixing with other gases, such as N₂, CF₄, CO₂ and C₄F<SUB>8</SUB> and their mixture gases would cause the synergy effect.BR In this paper, we investigated the characteristics of DC plasmas on SF<SUB>6</SUB> mixture gases with N₂ at atmospheric pressure. N₂ gas is one of cheap gases and has been reported to show the synergy effect with mixing SF<SUB>6</SUB> gas, even though N₂ plasmas have electron-positive characteristics. 38 kinds of SF<SUB>6</SUB>/N₂ plasma particles, which consisted of an electron, two positive ions, five negative ions, 30 excitation and vibration particles, were considered in a one dimensional fluid simulation model with capacitively coupled plasma chamber.BR The results showed that the joule heating of SF<SUB>6</SUB>/N₂ plasmas was mainly caused by positive ions, on the other hand electrons acted on holding the SF<SUB>6</SUB>/N₂ plasmas stably. The joule heating was strongly generated near the electrodes, which caused the increase of neutral gas temperature within the chamber. The more N₂ mixed-ratio increased, the less joule heating was. And the power consumptions by electron and positive ions increased with the increase of N₂ mixed-ratio.

Xe 가스 첨가에 따른 방전 특성 시뮬레이션 분석

AC-PDPs have recently achieved good performance and their image quality can sufficiently compete with the LCD TV. However, it is necessary more effort to improve the luminance and luminous efficacy in the PDP technology. The gas mixture ratio plays a very important role in discharge characteristics, but the mechanism of gas discharge is complex and complicated. In this paper, we investigate the mechanism of gas discharge with Ne+Xe miture ratio through zero and two dimensional fluid simulation.

Influence of Lateral Interval on Aerodynamics Characteristics of Crossing Vehicles

The investigations about vehicle crossing process mainly use numerical simulation methods and, moreover, the relevant investigation is quite less. In this study, a three- dimensional fluid simulation model was established. By moving mesh technique, the three- dimensional transient simulation for vehicle crossing process was finished. The aerodynamics characteristics of vehicle crossing process with different lateral interval distances were analyzed. The analytical results show that the smaller the lateral interval distance, the more the transverse thrust between two vehicles during the crossing process. During the whole crossing process, the lateral force shows itself with repulsion in the beginning and attraction in the end. When the lateral interval distance of crossing is very small, the air disturbance due to crossing not only makes large affection to the lateral force but also influence obviously the positive pressure area of the front car bodywork.

Phase-shift effects on growth and transport of dust particles in VHF capacitively coupled silane discharges: Two dimensional fluid simulation

A two-dimensional (2D) self-consistent fluid model is developed to describe the formation, subsequent growth, transport, and charging mechanisms of nanoparticles in a capacitively coupled silane discharge applied by two very high frequency (VHF) sources with phase shift. In this discharge process, large anions are produced by a series of chemical reactions of anions with silane molecules, while the lower limit of the initial nanoparticles are taken as large anions (Si12H25- and Si12H24-) to directly link the coagulation module with the nucleation module. And then, by using the coagulation module, the particle number density quickly decreases over several orders of magnitude, whereas the particle size strongly increases. We investigate in particular the growth of the nanoparticles ranging in size from ∼1 to 50 nm in coagulation processes. The influences of controlled phase shifts between VHF (50 MHz) voltages on the electron density, electron temperature, nanoparticle uniformity, and deposition rate, are carefully studied. It is found from our simulation that the plasma density and nanoparticle density become center high and more uniform as the phase shift increases from 0 to 180°. Moreover, the role of phase-shift control in the silane discharge diluted with hydrogen gas is also discussed.

Equilibrium profiles for RF-plasma sources with ponderomotive forces

An analysis is given of the influence of the electron ponderomotive force on the equilibrium plasma profiles of partially ionized, radio frequency discharge sources, The ponderomotive force can be written as a gradient of a potential varying with the square of the RF field in the plasma and is largest for electrons, The impact of this electron ponderomotive force on density and electrostatic potential profiles is demonstrated using a one-dimensional analytic model with supporting numerical solutions and a two dimensional fluid simulation. For nearly collisionless plasmas the ponderomotive force is valid when /spl omega//sub ce//sup h///spl omega/ 1, the ponderomotive force, is modified by other nonlinear force terms that need to be evaluated. >