DSMC Simulation of Low Knudsen Micro/Nanoflows Using Small Number of Particles per Cells

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Ali Amiri-Jaghargh ◽  
Ehsan Roohi ◽  
Hamid Niazmand ◽  
Stefan Stefanov
Keyword(s):  
Direct Simulation Monte Carlo ◽  
Velocity Slip ◽  
Heat Fluxes ◽  
Dsmc Method ◽  
Suitable Alternative ◽  
Low Speed ◽  
Rarefied Flows ◽  
Dsmc Simulation ◽  
Grid Scheme ◽  
Number Of Particles

Direct simulation Monte Carlo (DSMC) method in low Knudsen rarefied flows at micro/nanoscales remains a big challenge for researchers due to large computational requirements. In this article, the application of the simplified Bernoulli-trials (SBT)/dual grid collision scheme is extended for solving low Knudsen/low speed and low Knudsen/high gradient rarefied micro/nanoflows. The main advantage of the SBT algorithm is to provide accurate calculations using much smaller number of particles per cell, i.e., 〈N〉 ≈ 2, which is quite beneficial for near continuum DSMC simulations where the requirement of fine meshes faces the simulation with serious memory restrictions. Comparing the results of the SBT/dual grid scheme with the no time counter (NTC) scheme and majorant frequency scheme (MFS), it is shown that the SBT/dual grid scheme could successfully predict the thermal pattern and hydrodynamics field as well as surface parameters such as velocity slip, temperature jump and wall heat fluxes. Therefore, we present SBT/dual grid algorithm as a suitable alternative of the standard collision schemes in the DSMC method for typical micro/nanoflows solution. Nonlinear flux-corrected transport (FCT) algorithm is also employed as a filter to extract the smooth solution from the noisy DSMC calculation for low speed/low Knudsen number DSMC calculations.

scholarly journals Development of an Efficient Particle Approach for Micro-Scale Gas Flow Simulations

2009 ◽  
Author(s):  
Quanhua Sun ◽  
Feng Li ◽  
Jing Fan ◽  
Chunpei Cai
Keyword(s):  
Cell Size ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Gas Flows ◽  
Dsmc Method ◽  
Low Speed ◽  
Micro Scale ◽  
Information Preservation ◽  
Cfd Method

The micro-scale gas flows are usually low-speed flows and exhibit rarefied gas effects. It is challenging to simulate these flows because traditional CFD method is unable to capture the rarefied gas effects and the direct simulation Monte Carlo (DSMC) method is very inefficient for low-speed flows. In this study we combine two techniques to improve the efficiency of the DSMC method. The information preservation technique is used to reduce the statistical noise and the cell-size relaxed technique is employed to increase the effective cell size. The new cell-size relaxed IP method is found capable of simulating micro-scale gas flows as shown by the 2D lid-driven cavity flows.

Various Boundary Condition Implementation to Study Microfilters Using DSMC Simulation

2010 ◽  
Author(s):  
Masoud Darbandi ◽  
Hassan Akhlaghi ◽  
Abolfazl Karchani ◽  
Soheyl Vakili
Keyword(s):  
Boundary Condition ◽  
Monte Carlo ◽  
Gas Flow ◽  
Direct Simulation Monte Carlo ◽  
Direct Simulation ◽  
Dsmc Method ◽  
Uniform Distributions ◽  
Dsmc Simulation ◽  
Flow Through ◽  
Simulation Monte Carlo

In this study, we present a vast boundary condition treatment to simulate gas flow through microfilters using direct simulation Monte Carlo (DSMC) method. We examine the effects of different boundary condition treatments on the density, pressure, and velocity distributions and suggest the best conditions to simulate gas flow through microfilters. We also refine the effects of upstream and downstream locations on the solution. The results show that uniform distributions can be achieved if we apply the inlet/outlet boundary condition at appropriate upstream and downstream distances. We also show that all the suggested boundary conditions suitably predict the pressure drop coefficient factor across the filter. To evaluate the current results they are compared with some available empirical formulations.

Coupled FVM-DSMC Simulation of Micro-Nozzle With Unstructured-Grid

2008 ◽  
Author(s):  
Zhixin Sun ◽  
Zengyao Li ◽  
Yaling He ◽  
Wenquan Tao
Keyword(s):  
Flow Field ◽  
Unstructured Grid ◽  
Direct Simulation Monte Carlo ◽  
Flow Simulation ◽  
Dsmc Method ◽  
Structured Grid ◽  
Micro Nozzle ◽  
Dsmc Simulation ◽  
Volume Method ◽  
Solid Area

The flow field and temperature distributions of free molecular micro-electro-thermal resist jet (FMMR) were studied resorting to DSMC-FVM coupled method. Direct Simulation Monte Carlo (DSMC) method is the most useful tool to simulate the flow field of FMMR and unstructured grid is suitable for the flow simulation in a complicated region with tilted wall surface. DSMC code based on unstructured grid system was developed and then the result was compared with that of structured grid and analytical solution to validate the reliability of the developed code. The DSMC method was then used to simulate the fluid flow in the micro-nozzle (Kn>0.01) and the temperature distribution in the nozzle wall was obtained by the Finite Volume Method (FVM). The Dirichlet-Neumann method was used to couple the wall heat flux and temperature between flow field and solid area. The effect of different income pressure was studied in detail and the results showed that the temperature of solid area changed drastically at different income pressure, so the commonly-adopted method of pre-setting boundary temperature before simulation was unreasonable. The results showed that the influence of boundary layer decreased as the pressure increased.

scholarly journals DSMC Simulation of Rarefied Gas Flow in a Single-sided and Double-sided Lid-Driven Cavity

2019 ◽  
Author(s):  
Jayesh Sanwal ◽  
Deepak Nabapure ◽  
Sreeram Rajesh ◽  
K Ram Chandra Murthy
Keyword(s):  
Melt Spinning ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Industrial Applications ◽  
Dsmc Method ◽  
Driven Cavity ◽  
Flow Features ◽  
Dsmc Simulation ◽  
Vortex Patterns

The present study is to investigate the behavior of a monoatomic gas enclosed in a cavity with both the top and bottom walls imparting motion to the fluid. The problem is studied for single and double-sided lid-driven flow for various wall velocities as well as parallel and anti-parallel wall motions. These types of flow have many industrial applications such as drying and melt spinning. In contrast to the single-sided flows the vortex patterns obtained in the double-sided flows are different and hence it merits a thorough examination, which is studied in this paper using the Direct Simulation Monte Carlo (DSMC) method. The DSMC method proposed by G.A. Bird is based on the kinetic theory in which the molecular motion is modeled stochastically. The computational model has been implemented in OpenFOAM software using the solver named dsmcFoam. Various flow features have been examined such as eddies and vortices.

scholarly journals Pumping Speed Measurement and Analysis for the Turbo Booster Pump

2004 ◽  
Vol 10 (1) ◽  
pp. 1-13 ◽  
Author(s):  
R. Y. Jou ◽  
S. C. Tzeng ◽  
J. H. Liou
Keyword(s):  
Rarefied Gas ◽  
High Vacuum ◽  
Direct Simulation Monte Carlo ◽  
Transitional Flow ◽  
Transition Flow ◽  
Dsmc Method ◽  
Dsmc Simulation ◽  
Computational Fluid Dynamics Cfd ◽  
Booster Pump ◽  
Cfd Method

This study applies testing apparatus and a computational approach to examine a newly designed spiral-grooved turbo booster pump (TBP), which has both volume type and momentum transfer type vacuum pump functions, and is capable of operating at optimum discharge under pressures from approximately 1000 Pa to a high vacuum. Transitional flow pumping speed is increased by a well-designed connecting element. Pumping performance is predicted and examined via two computational approaches, namely the computational fluid dynamics (CFD) method and the direct simulation Monte Carlo (DSMC) method. In CFD analysis, comparisons of measured and calculated inlet pressure in the slip and continuum flow demonstrate the accuracy of the calculation. Meanwhile, in transition flow, the continuum model of CFD is unsuitable for calculating such rarefied gas. The pumping characteristics for a full 3D model on a rotating frame in transition and molecular regimes thus are simulated using the DSMC method and then confirmed experimentally. However, when the Knudsen number is in the range 0.5 < Kn < 0.1, neither CFD computation nor DSMC simulation is suitable for analyzing the pumping speed of the turbo booster pump. In this situation, the experimental approach is the most appropriate and effective method for analyzing pumping speed. Moreover, the developed pump is tested using assessment systems constructed according to ISO and JVIS-005 standards, respectively. Comparisons are also made with other turbo pumps. The compared results show that the turbo booster pump presented here has good foreline performance.

An Efficient Hybrid DSMC/MD Algorithm for Accurate Modeling of Micro Gas Flows

2014 ◽  
Vol 15 (1) ◽  
pp. 246-264 ◽  
Author(s):  
Tengfei Liang ◽  
Wenjing Ye
Keyword(s):  
Hybrid Algorithm ◽  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Velocity Distribution Function ◽  
Gas Flows ◽  
Dsmc Method ◽  
Present Scheme ◽  
Interaction Layer ◽  
Dsmc Simulation ◽  
Wall Interaction

AbstractAiming at simulating micro gas flows with accurate boundary conditions, an efficient hybrid algorithm is developed by combining the molecular dynamics (MD) method with the direct simulation Monte Carlo (DSMC) method. The efficiency comes from the fact that the MD method is applied only within the gas-wall interaction layer, characterized by the cut-off distance of the gas-solid interaction potential, to resolve accurately the gas-wall interaction process, while the DSMC method is employed in the remaining portion of the flow field to efficiently simulate rarefied gas transport outside the gas-wall interaction layer. A unique feature about the present scheme is that the coupling between the two methods is realized by matching the molecular velocity distribution function at the DSMC/MD interface, hence there is no need for one-to-one mapping between a MD gas molecule and a DSMC simulation particle. Further improvement in efficiency is achieved by taking advantage of gas rarefaction inside the gas-wall interaction layer and by employing the “smart-wall model” proposed by Barisiket al.The developed hybrid algorithm is validated on two classical benchmarks namely 1-D Fourier thermal problem and Couette shear flow problem. Both the accuracy and efficiency of the hybrid algorithm are discussed. As an application, the hybrid algorithm is employed to simulate thermal transpiration coefficient in the free-molecule regime for a system with atomically smooth surface. Result is utilized to validate the coefficients calculated from the pure DSMC simulation with Maxwell and Cercignani-Lampis gas-wall interaction models.

DSMC Simulation of Ion Generation in Atmospheric Air

2003 ◽  
Author(s):  
W. Zhang ◽  
T. S. Fisher ◽  
D. J. Schilitz ◽  
S. V. Garimella
Keyword(s):  
Monte Carlo ◽  
Direct Simulation Monte Carlo ◽  
Direct Simulation ◽  
Dsmc Method ◽  
Atmospheric Air ◽  
Section Data ◽  
Ion Generation ◽  
The Monte Carlo Method ◽  
Dsmc Simulation ◽  
Simulation Monte Carlo

The generation of ions in air has several useful applications, such as electrohydrodynamic (EHD) pumping, air purification and isolation breakdown prevention. In this paper, ion generation processes in atmospheric air are simulated using a Direct Simulation Monte Carlo (DSMC) method. Details of the collision model are discussed. A C++ code is developed to implement the Monte Carlo method with cross-section data compiled from the literature. Self-sustaining discharge and ionization can be reproduced in the simulation under sufficient voltage bias, and the associated trends obtained are similar to those predicted by Paschen’s curve for a parallel-plate configuration.

Proper Cell Dimension and Number of Particles Per Cell for DSMC

2009 ◽  
Author(s):  
Z. X. Sun ◽  
Y. L. He ◽  
W. Q. Tao
Keyword(s):  
Flow Regime ◽  
Slip Flow ◽  
Mean Free Path ◽  
Cell Dimension ◽  
Transition Flow ◽  
Dsmc Method ◽  
Transition Flow Regime ◽  
Dsmc Simulation ◽  
Simulation Results ◽  
Number Of Particles

Different opinions still exist on some basic principles of DSMC method, such as the proper grid dimension and the proper number of particles in a cell. In this paper DSMC simulation of Poiseuille flow is made to evaluate the dependence of simulation results on cell dimension and number of particles per cell. In the simulation process a self adapting block structured grid system is employed to make sure that the number of particles per cell is constant. The simulation covers both slip flow regime and transition flow regime and each regime covers both high pressure and low pressure. Our simulation results indicate that the number of particles per cell and scaling factor exert little influence on simulation result for both slip flow and transition flow when the number of particles per cell surpasses 5, but the dimension of cell influences the accuracy of result obviously. The error caused by cell dimension decreases as the diminish of cell dimension. It is concluded that in the DSMC method it is necessary to make sure that the cell is less than 1/2 of molecular mean free path.

Particle Simulation of Detonation in Microchannel

2009 ◽  
Author(s):  
Yevgeniy A. Bondar ◽  
Mikhail S. Ivanov
Keyword(s):  
Detonation Wave ◽  
Chemical Kinetics ◽  
Numerical Study ◽  
Direct Simulation Monte Carlo ◽  
Wave Structure ◽  
Particle Simulation ◽  
Dsmc Method ◽  
Detailed Chemical Kinetics ◽  
Von Neumann ◽  
Dsmc Simulation

Direct simulation Monte Carlo (DSMC) method was applied to numerical study of detonation in an H2/O2 mixture with detailed chemical kinetics on the basis of effective DSMC molecular chemistry models. The process of homogeneous adiabatic autoignition of a stoichiometric H2/O2 mixture diluted by argon was simulated by the DSMC method. The modeling results provide a qualitatively correct description of autoingition process and are in good agreement with the numerical solution of equations of chemical kinetics. The results of the DSMC modeling of an unsteady detonation wave yield the velocity of detonation, which coincides with the Chapman-Jouguet velocity. The internal structure of the detonation wave obtained in the DSMC simulation is in good qualitative agreement with the detonation-wave structure calculated on the basis of the Zeldovich – von Neumann – Doering (ZND) theory.

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