scholarly journals Numerical Modelling of Microchannel Gas Flows in the Transition Flow Regime Using the Cascaded Lattice Boltzmann Method

Entropy ◽  
2019 ◽  
Vol 22 (1) ◽  
pp. 41
Author(s):  
Qing Liu ◽  
Xiang-Bo Feng
Keyword(s):  
Flow Regime ◽  
Lattice Boltzmann ◽  
Effective Viscosity ◽  
Gas Flow ◽  
Specular Reflection ◽  
Collision Operator ◽  
Slip Boundary Condition ◽  
Gas Flows ◽  
Transition Flow ◽  
Transition Flow Regime

In this article, a lattice Boltzmann (LB) method for studying microchannel gas flows is developed in the framework of the cascaded collision operator. In the cascaded lattice Boltzmann (CLB) method, the Bosanquet-type effective viscosity is employed to capture the rarefaction effects, and the combined bounce-back/specular-reflection scheme together with the modified second-order slip boundary condition is adopted so as to match the Bosanquet-type effective viscosity. Numerical simulations of microchannel gas flow with periodic and pressure boundary conditions in the transition flow regime are carried out to validate the CLB method. The predicted results agree well with the analytical, numerical, and experimental data reported in the literature.

LATTICE BOLTZMANN METHOD FOR SIMULATING GAS FLOW IN MICROCHANNELS

2004 ◽  
Vol 15 (02) ◽  
pp. 335-347 ◽  
Author(s):  
G. H. TANG ◽  
W. Q. TAO ◽  
Y. L. HE
Keyword(s):  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Slip Velocity ◽  
Gas Flow ◽  
Specular Reflection ◽  
Gas Flows ◽  
Friction Factors ◽  
Isothermal Gas ◽  
Boltzmann Method ◽  
Good Agreement

Isothermal gas flows in microchannels is studied using the lattice Boltzmann method. A novel equation relating Knudsen number with relaxation time is derived. The slip-velocity on the solid boundaries is reasonably realized by combining the bounce-back reflection with specular reflection in a certain proportion. Predicted characteristics in a two-dimensional microchannel flow, including slip-velocity, nonlinear pressure drop, friction factors, velocity distribution along the streamwise direction and mass flow rate, are compared with available analytical and experimental results and good agreement is achieved.

Lattice-Boltzmann simulation for pressure driven microscale gas flows in transition regime

2015 ◽  
Vol 26 (04) ◽  
pp. 1550037 ◽  
Author(s):  
Xiang-Ji Yue ◽  
Ze-Huan Wu ◽  
Yao-Shuai Ba ◽  
Yan-Jun Lu ◽  
Zhi-Peng Zhu ◽  
...  
Keyword(s):  
Specular Reflection ◽  
Mean Free Path ◽  
Gas Flows ◽  
Transition Regime ◽  
Transition Flow ◽  
Transition Flow Regime ◽  
Lattice Boltzmann Simulation ◽  
Calculation Results ◽  
Bounce Back ◽  
Pressure Driven

This paper carries out numerical simulation for pressure driven microscale gas flows in transition flow regime. The relaxation time of LBM model was modified with the application of near wall effective mean free path combined with a combination of Bounce-back and Specular Reflection (BSR) boundary condition. The results in this paper are more close to those of DSCM and IP-DSCM compared with the results obtained by other LBM models. The calculation results show that in transition regime, with the increase of Knudsen number, the dimensionless slip velocity at the wall significantly increases, but the maximum linear deviation of nonlinear pressure distribution gradually decreases.

Lattice Boltzmann Simulation of Rarefied Gas Flow Along Moving Rigid Objects in Micro-Cavities

2015 ◽  
Author(s):  
Weilin Yang ◽  
Hongxia Li ◽  
TieJun Zhang ◽  
Ibrahim M. Elfadel
Keyword(s):  
Free Path ◽  
Lattice Boltzmann ◽  
Path Length ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Free Path Length ◽  
Mean Free Path ◽  
Fluid Simulation ◽  
Transition Flow ◽  
Rarefied Gas Flow

Rarefied gas flow plays an important role in the design and performance analysis of micro-electro-mechanical systems (MEMS) under high-vacuum conditions. The rarefaction can be evaluated by the Knudsen number (Kn), which is the ratio of the molecular mean free path length and the characteristic length. In micro systems, the rarefied gas flow usually stays in the slip- and transition-flow regions (10−3 < Kn < 10), and may even go into the free molecular flow region (Kn > 10). As a result, conventional design tools based on continuum Navier-Stokes equation solvers are not applicable to analyzing rarefaction phenomena in MEMS under vacuum conditions. In this paper, we investigate the rarefied gas flow by using the lattice Boltzmann method (LBM), which is suitable for mesoscopic fluid simulation. The gas pressure determines the mean free path length and Kn, which further influences the relaxation time in the collision procedure of LBM. Here, we focus on the problem of squeezed film damping caused by an oscillating rigid object in a cavity. We propose an improved LBM with an immersed boundary approach, where an adjustable force term is used to quantify the interaction between the moving object and adjacent fluid, and further determines the slip velocity. With the proposed approach, the rarefied gas flow in MEMS with squeezed film damping is characterized. Different factors that affect the damping coefficient, such as pressure of gas and frequency of oscillation, are investigated in our simulation studies.

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