Heat and Mass Transfer of a Rarefied Gas in a Driven Micro-Cavity

2009 ◽  
Author(s):  
X. J. Gu ◽  
B. John ◽  
G. H. Tang ◽  
D. R. Emerson
Keyword(s):  
Gas Flow ◽  
Rarefied Gas ◽  
Transport Model ◽  
Direct Simulation Monte Carlo ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Order Moment ◽  
Moment Equations ◽  
Micro Cavity ◽  
Non Equilibrium

A high-order moment method is employed to construct the transport model for non-equilibrium gas flow in micro-scale geometries. The motion of a gas in a two-dimensional square micro-cavity is solved using the 26 moment equations for low Reynolds and Mach number flows in the early transition regime. The computed velocity and temperature fields are compared with data obtained from the direct simulation Monte Carlo method. It is found that the 26 moment equations are able to capture the non-equilibrium phenomena in a driven micro-cavity, such as counter-gradient heat transfer, which are not embedded in the Navier-Stokes-Fourier equations.

Extended Thermodynamic Approach for Non-Equilibrium Gas Flow

2013 ◽  
Vol 13 (5) ◽  
pp. 1330-1356 ◽  
Author(s):  
G. H. Tang ◽  
G. X. Zhai ◽  
W. Q. Tao ◽  
X. J. Gu ◽  
D. R. Emerson
Keyword(s):  
Heat Transfer ◽  
Equilibrium State ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Flow Characteristics ◽  
Bimodal Distribution ◽  
Thermodynamic Approach ◽  
Navier Stokes ◽  
Extended Thermodynamic ◽  
Non Equilibrium

AbstractGases in microfluidic structures or devices are often in a non-equilibrium state. The conventional thermodynamic models for fluids and heat transfer break down and the Navier-Stokes-Fourier equations are no longer accurate or valid. In this paper, the extended thermodynamic approach is employed to study the rarefied gas flow in microstructures, including the heat transfer between a parallel channel andpressure-driven Poiseuille flows through a parallel microchannel andcircular microtube. The gas flow characteristics are studied and it is shown that the heat transfer in the non-equilibrium state no longer obeys the Fourier gradient transport law. In addition, the bimodal distribution of streamwise and spanwise velocity and temperature through a long circular microtube is captured for the first time.

DSMC Simulation of Rarefied Gas Flow Over a Wall Mounted Cube

2019 ◽  
Author(s):  
Deepak Nabapure ◽  
Ram Chandra Murthy
Keyword(s):  
Gas Flow ◽  
Rarefied Gas ◽  
Flow Behavior ◽  
Direct Simulation Monte Carlo ◽  
Temperature Fields ◽  
Gas Flows ◽  
Rarefied Gas Flows ◽  
Dsmc Simulation ◽  
Recirculation Length ◽  
Velocity Pressure

Abstract The present study investigates the flow behavior of the rarefied gas over a wall-mounted cube. The problem is studied for different cube heights (h) of 9mm and 18mm in the slip and transition regimes. The Direct Simulation Monte Carlo (DSMC) method is employed to evaluate the properties such as velocity, pressure and temperature fields. The Reynolds number (Re) ranges from 403 to 807, and the Knudsen number (Kn) is in the range from 0.05 to 0.103. A typical shock wave is formed in front of the cube. The recirculation length of the vortices normalized with respect to the respective cube heights for Kn = 0.05 and Kn = 0.103 are about 1.11 and 1.95 respectively. Similarly, the center of the vortices is located at about 3.33 and 6.11 times the respective cube heights upstream, for Kn = 0.05 and Kn = 0.103. The local temperature and pressure variations observed upstream of the cube are two orders higher in magnitude and are primarily attributed to strong compressibility effects. The present study paves the way for benchmarking, and forms a basis for understanding the rarefied gas flows over complex geometries.

Capturing Nongradient Transport in Nonequilibrium Gas Flow

2008 ◽  
Author(s):  
X. J. Gu ◽  
D. R. Emerson
Keyword(s):  
Temperature Field ◽  
Couette Flow ◽  
Transport Mechanism ◽  
Gas Flow ◽  
Transport Model ◽  
Temperature Fields ◽  
Order Moment ◽  
Nonequilibrium Gas ◽  
The One ◽  
Planar Couette Flow

A higher order moment method is employed to construct the transport model for nonequilibrium gas flow in microscale geometries. The one dimensional planar Couette flow was chosen to demonstrate the significance of capturing the nongradient transport phenomena in the prediction of velocity and temperature fields. For planar Couette flow in the transition regime, the velocity profile is nonlinear and the induced temperature field is no longer parabolic. These features are attributed to the nongradient transport mechanism in a nonequilibrium gas. Furthermore, it is revealed that, for a given temperature field, the gradient transport model overestimates the heat transfer significantly. This, again, can be compensated by the nongradient transport mechanism.

Analysis for Rarefied Gas Flow in a Rotating Cylinder

2009 ◽  
Author(s):  
H. Futagami ◽  
H. Ninokata
Keyword(s):  
Gas Flow ◽  
Rarefied Gas ◽  
Isotope Separation ◽  
Direct Simulation Monte Carlo ◽  
Rotating Cylinder ◽  
Navier Stokes ◽  
Operating Pressure ◽  
Direct Simulation ◽  
Navier Stokes Equation ◽  
Simulation Monte Carlo

Behaviors inside rotating cylinders where the range of operating pressure is very wide, i.e. from subatmospheric to almost vacuum are subject of this study. The flow near the rotating axis is very rarefied. If a flow becomes rarefied, the flow cannot be treated as that of a continuum media. Therefore the flow cannot be analyzed by the method based on solving Navier-Stokes equation. One of the promising methods is considered to be DSMC (Direct Simulation Monte Carlo) method based on Boltzmann equation ([1]). In this paper, fundamental validation analyses related to isotope separation in a rotating cylinder calculations of endplate type centrifuge were performed for the parametric study, with DSMC. The results were compared with the experimental results by Groth et al ([2]). The validity of the calculations and its limit were also discussed.

scholarly journals Lattice Boltzmann accelerated direct simulation Monte Carlo for dilute gas flow simulations

2016 ◽  
Vol 374 (2080) ◽  
pp. 20160226 ◽  
Author(s):  
G. Di Staso ◽  
H. J. H. Clercx ◽  
S. Succi ◽  
F. Toschi
Keyword(s):  
Monte Carlo ◽  
Lattice Boltzmann ◽  
Gas Flow ◽  
Direct Simulation Monte Carlo ◽  
Bulk Flow ◽  
Navier Stokes ◽  
Direct Simulation ◽  
Dilute Gas ◽  
Simulation Monte Carlo ◽  
Non Equilibrium

Hybrid particle–continuum computational frameworks permit the simulation of gas flows by locally adjusting the resolution to the degree of non-equilibrium displayed by the flow in different regions of space and time. In this work, we present a new scheme that couples the direct simulation Monte Carlo (DSMC) with the lattice Boltzmann (LB) method in the limit of isothermal flows. The former handles strong non-equilibrium effects, as they typically occur in the vicinity of solid boundaries, whereas the latter is in charge of the bulk flow, where non-equilibrium can be dealt with perturbatively, i.e. according to Navier–Stokes hydrodynamics. The proposed concurrent multiscale method is applied to the dilute gas Couette flow, showing major computational gains when compared with the full DSMC scenarios. In addition, it is shown that the coupling with LB in the bulk flow can speed up the DSMC treatment of the Knudsen layer with respect to the full DSMC case. In other words, LB acts as a DSMC accelerator. This article is part of the themed issue ‘Multiscale modelling at the physics–chemistry–biology interface’.

Non-isothermal rarefied gas flow in microtube with constant wall temperature

2021 ◽  
Vol 13 (11) ◽  
pp. 168781402110651
Author(s):  
Iva Guranov ◽  
Snežana Milićev ◽  
Nevena Stevanović
Keyword(s):  
Wall Temperature ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Mean Free Path ◽  
Temperature Characteristic ◽  
Perturbation Series ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Constant Wall Temperature ◽  
Energy Equations

In this paper, pressure-driven gas flow through a microtube with constant wall temperature is considered. The ratio of the molecular mean free path and the diameter of the microtube cannot be negligible. Therefore, the gas rarefaction is taken into account. A solution is obtained for subsonic as well as slip and continuum gas flow. Velocity, pressure, and temperature fields are analytically attained by macroscopic approach, using continuity, Navier-Stokes, and energy equations, with the first order boundary conditions for velocity and temperature. Characteristic variables are expressed in the form of perturbation series. The first approximation stands for solution to the continuum flow. The second one reveals the effects of gas rarefaction, inertia, and dissipation. Solutions for compressible and incompressible gas flow are presented and compared with the available results from the literature. A good matching has been achieved. This enables using proposed method for solving other microtube gas flows, which are common in various fields of engineering, biomedicine, pharmacy, etc. The main contribution of this paper is the integral treatment of several important effects such as rarefaction, compressibility, temperature field variability, inertia, and viscous dissipation in the presented solutions. Since the solutions are analytical, they are useful and easily applicable.

Analysis of gas flow over a cylinder at all Knudsen numbers based on non-newtonian constitutive models

2020 ◽  
Vol 34 (14n16) ◽  
pp. 2040076
Author(s):  
Zhen-Yu Yuan ◽  
Zhong-Zheng Jiang ◽  
Wen-Wen Zhao ◽  
Wei-Fang Chen
Keyword(s):  
Constitutive Model ◽  
Gas Flow ◽  
Constitutive Relations ◽  
Constitutive Models ◽  
Direct Simulation Monte Carlo ◽  
Navier Stokes ◽  
Dsmc Simulation ◽  
Nonequilibrium Flows ◽  
Simulation Results ◽  
Better Than

This paper is focused on the gas properties over a cylinder from continuum to rarefied regimes based on the non-Newtonian constitutive model. This new constitutive model is first derived from Eu’s nonequilibrium ensemble method, which is intended for accurate description of nonequilibrium flows. Some assumptions and simplifications are made during the establishing progress of the new constitutive model by both Eu and Myong. To verify its accuracy, temperature contours and skin frictions around the cylinder are simulated by this new model. The inflow Mach number is equal to 10 and the Knudsen number ranges from 0.002 to 0.05. All simulation results are compared with Navier–Stokes (NS) and the direct simulation Monte Carlo (DSMC) methods in detail. The comparisons of friction around the surface show that the non-Newtonian constitutive models are better than the linear constitutive relations of NS equations for the prediction of nonequilibrium flow and much more close to DSMC simulation results.

scholarly journals The sound of a pulsating sphere in a rarefied gas: continuum breakdown at short length and time scales

2019 ◽  
Vol 871 ◽  
pp. 668-693 ◽  
Author(s):  
Y. Ben-Ami ◽  
A. Manela
Keyword(s):  
Time Scales ◽  
Rarefied Gas ◽  
Molecular Layer ◽  
Direct Simulation Monte Carlo ◽  
Acoustic Power ◽  
Navier Stokes ◽  
System Response ◽  
Low Frequencies ◽  
Continuum Breakdown ◽  
Short Time

The pressure field of a pulsating sphere is a canonical problem in classical acoustics, used to illustrate the acoustic efficiency of a monopole source at continuum conditions. We consider the counterpart vibroacoustic and thermoacoustic problems in a rarefied gas, to investigate the effect of continuum breakdown on monopole radiation. Focusing on small-amplitude normal-to-boundary mechanical and heat-flux excitations, the perturbation field is analysed in the entire range of gas rarefaction and input frequencies. Numerical calculations are carried out via the direct simulation Monte Carlo method, and are used to validate analytical predictions in the free-molecular and near-continuum regimes. In the latter, the regularized thirteen moments model (R13) is applied, to capture the system response at states where the Navier–Stokes–Fourier (NSF) description breaks down. Comparing with the continuum inviscid solution, the results quantitate the dampening effect of gas rarefaction on source point-wise strength and acoustic power. At near-continuum conditions, the acoustic field is composed of exponentially decaying ‘compression’, ‘thermal’ and ‘Knudsen-layer’ modes, reflecting thermoviscous and higher-order rarefaction effects. With reducing rarefaction, the contributions of the latter two modes vanish, and the former degenerates into the ideal-flow inverse-to-distance decaying wave. Stronger attenuation is obtained with increasing rarefaction, where boundary sphericity results in a ‘geometric reduction’ of the molecular layer affected by the source. Notably, while the R13 model at low frequencies appears valid up to moderate gas rarefaction rates, both the NSF and R13 descriptions break down at common low Knudsen numbers at higher frequencies. Further study should therefore be carried out to extend the applicability of moment models to unsteady flows with short time scales.

A hybrid Navier-Stokes/DSMC simulation for rarefied gas flow for the deposition of nano layers for OLEDs

2015 ◽  
Author(s):  
K. Farber ◽  
P. Farber ◽  
J. Gräbel ◽  
S. Krick ◽  
J. Reitz ◽  
...  
Keyword(s):  
Gas Flow ◽  
Rarefied Gas ◽  
Navier Stokes ◽  
Rarefied Gas Flow ◽  
Dsmc Simulation
Sign in / Sign up

Export Citation Format

Share Document