Three-Dimensional Vortical Flow Simulations Using Direct Simulation Monte Carlo Methd

2003 ◽  
Author(s):  
William Liou ◽  
Yichuan Fang ◽  
Graeme Bird
Keyword(s):  
Monte Carlo ◽  
Three Dimensional ◽  
Direct Simulation Monte Carlo ◽  
Vortical Flow ◽  
Direct Simulation ◽  
Flow Simulations ◽  
Simulation Monte Carlo

Scale Effects on Rarefied Supersonic Flows in Nanochannels

2008 ◽  
Author(s):  
Nikolaos A. Gatsonis ◽  
Wael G. Al Kouz ◽  
Ryan E. Chamberlin
Keyword(s):  
Monte Carlo ◽  
Supersonic Flow ◽  
Knudsen Number ◽  
Scale Effects ◽  
Three Dimensional ◽  
Direct Simulation Monte Carlo ◽  
Supersonic Flows ◽  
Direct Simulation ◽  
Aspect Ratios ◽  
Simulation Monte Carlo

The supersonic flow of nitrogen into a nanochannel is investigated using a three dimensional unstructured Direct Simulation Monte Carlo (U3DSMC) method. The U3DSMC code is validated by comparisons with previous 2D DSMC simulations of flows in micron-scale channels. Rectangular nanochannels with heights between 100 nm to 1000 nm, and aspect ratios L/H of 1, 10, 100 are used in the U3DSMC investigation. The Mach 5.9 freestream has a pressure of 0. 1atm and Knudsen numbers of 0.481, 0.962 and 4.81. The nanochannel walls are assumed to be diffusively reflecting at the freestream temperature. The simulations show the development of a disturbance region upstream from the inlet that depends on the Knudsen number. For the L/H = 10 and L/H = 100 nanochannels considered the velocity decreases from its freestream value velocity decreases from its freestream value and becomes subsonic inside the nanochannel. The temperature shows an enhancement region near the inlet while the density shows an enhancement region inside the nanochannel.

Direct Simulation Monte Carlo Calculations of Three Dimensional Non-Continuum Gas Flows

2002 ◽  
Author(s):  
Fang Yan ◽  
Bakhtier Farouk ◽  
Jeremy Johnson
Keyword(s):  
Monte Carlo ◽  
Couette Flow ◽  
Three Dimensional ◽  
Direct Simulation Monte Carlo ◽  
Particle Removal ◽  
Direct Simulation ◽  
Transition Flow ◽  
Multiprocessor Computer ◽  
Wide Range ◽  
Simulation Monte Carlo

This paper describes the parallel implementation of a three-dimensional direct simulation Monte Carlo (DSMC) code using the OpenMP procedure on a shared memory multiprocessor computer. A dynamic domain decomposition is performed to maintain load balance among the threads. Performance tests are conducted to evaluate the effect of granularity on efficiency. It is shown that the parallel performance is dependent on the problem size. For larger-scale problems, better efficiency can be expected. Synchronization overhead due to data contention is reduced by re-arranging particle removal procedure. The parallel code is used to simulate flow through a rectangular channel with a high-speed moving wall (Couette flow). For high Knudsen (Kn) numbers, the Couette flow characteristics are found to be very different from their continuum counterparts. ‘Ultimate pressures’ are calculated for a wide range of Kn number flows. The variation of the ultimate pressure with Kn number is computed for given wall speed. Maximum compression ratio is obtained in the transition flow region.

Unsteady disturbances in micro Rayleigh-Bénard flows using direct simulation Monte Carlo method

2018 ◽  
Vol 17 (4-5) ◽  
pp. 425-437 ◽  
Author(s):  
Y Fang ◽  
WW Liou
Keyword(s):  
Heat Transfer ◽  
Monte Carlo ◽  
Monte Carlo Method ◽  
Direct Simulation Monte Carlo ◽  
Vortical Flow ◽  
Computational Domain ◽  
Dependent Manner ◽  
Direct Simulation ◽  
Simulation Monte Carlo ◽  
Rayleigh Benard

The direct simulation Monte Carlo method is applied in this paper to simulate the micro Rayleigh-Bénard convection for the Rayleigh number of 10,159 and the Knudsen number of 0.01 in a time-dependent manner. A monatomic gas is enclosed between two infinite, parallel plates with the bottom plate at a higher temperature. Cases of three different computational domain sizes in the horizontal directions are simulated. Evolutions of the convective flow unsteady disturbances patterns and the wall heat transfer are studied in detail. Three stages of distinct flow characteristics can be identified as the flows develop from an initially uniform state. In the first stage, the heat is transferred mainly by conduction. The onset of the vortical flow structures marks the beginning of the second stage. Significant differences in the flow and the heat transfer characteristics are observed in the third stage of the three simulated flows. It is found that the simulated microflows develop vortex rolls that advect along the plates at uniform speeds, which has not been reported previously.

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