Simulation of Rarefied Micro and Nano Gas Flows Using Improved Slip Flow Models

2007 ◽  
Author(s):  
Masoud Darbandi ◽  
F. Rikhtegar ◽  
Gerry Schneider
Keyword(s):  
Slip Flow ◽  
Gas Flows ◽  
Flow Models

Slip Flow Models for Gas Flows in Rectangular, Trapezoidal, and Hexagonal Microchannels

AIAA Journal ◽  
2020 ◽  
Vol 58 (5) ◽  
pp. 2147-2155
Author(s):  
M. M. Yovanovich ◽  
W. A. Khan
Keyword(s):  
Slip Flow ◽  
Gas Flows ◽  
Flow Models

Second Order Slip Flow Effects on Heat Transfer Performance of Microchannels

2009 ◽  
Author(s):  
Cem Dolu ◽  
Lu¨tfullah Kuddusi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Flow Model ◽  
Slip Flow ◽  
Second Order ◽  
Flow Models ◽  
Uniform Wall Temperature ◽  
Uniform Wall ◽  
Slip Flow Regime ◽  
Flow Effects

First and second order slip flow models in rectangular microchannels heated at constant and uniform wall temperature are studied. The velocity and temperature profiles for hydrodynamically and thermally developed incompressible slip flow regime available in literature are used. The average nondimensional slip velocity and temperature jump are found by using first and second order slip flow models. The average Nusselt number is also derived by using both first and second order slip flow models. The effects of Knudsen number, aspect ratio and second order slip flow model on the heat transfer characteristics of microchannel are explored.

Is the Lattice Boltzmann Method Applicable to Rarefied Gas Flows? Comprehensive Evaluation of the Higher-Order Models

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Minoru Watari
Keyword(s):  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Rarefied Gas ◽  
Slip Flow ◽  
Higher Order ◽  
Gas Flows ◽  
Rarefied Gas Flows ◽  
Slip Flow Regime ◽  
Boltzmann Method ◽  
Higher Order Models

Lattice Boltzmann method (LBM) whose equilibrium distribution function contains higher-order terms is called higher-order LBM. It is expected that nonequilibrium physics beyond the Navier–Stokes can be accurately captured using the higher-order LBM. Relationship between the level of higher-order and the simulation accuracy of rarefied gas flows is studied. Theoretical basis for constructing higher-order LBM is presented. On this basis, specific higher-order models are constructed. To confirm that the models have been correctly constructed, verification simulations are performed focusing on the continuum regime: sound wave and supersonic flow in Laval nozzle. With applications to microelectromechanical systems (MEMS) in mind, low Mach number flows are studied. Shear flow and heat conduction between parallel walls in the slip flow regime are investigated to confirm the relaxation process in the Knudsen layer. Problems between concentric cylinders are investigated from the slip flow regime to the free molecule regime to confirm the effect of boundary curvature. The accuracy is discussed comparing the simulation results with pioneers' studies. Models of the fourth-order give sufficient accuracy even for highly rarefied gas flows. Increase of the particle directions is necessary as the Knudsen number increases.

Numerical Study of Flow and Heat in Long Micro and Nano Channels

2008 ◽  
Author(s):  
Masoud Darbandi ◽  
Shidvash Vakilipour
Keyword(s):  
Boundary Condition ◽  
Numerical Study ◽  
Slip Flow ◽  
Constant Heat Flux ◽  
Gas Flows ◽  
Transfer Rates ◽  
Compressibility Effect ◽  
Momentum And Heat Transfer ◽  
Compressibility Effects ◽  
Early Transition

In this work, we extend a numerical tool capable of solving compressible and incompressible gas flows to study the momentum and heat transfer rates in micro/nano channels with high aspect ratio (L/H = 8000), where the compressibility effect is dominant. The constant heat flux thermal boundary condition is firstly applied at the wall. Next, the flow regime is extended to the early transition regime employing a high order slip velocity boundary condition based on the kinetic theory assumptions. The accuracy of the present results in the slip flow regimes is evaluated against other available theoretical and experimental results. The thermal and compressibility effects on the pressure and Knudsen number distribution are extensively studied along the channel at early transition regimes up to Kn = 0.5. Likely, this Knudsen is the highest one to be reached via applying the foregoing boundary conditions.

Study of Some Contemporary Laminar Flow Models Over a Flat Plate Using Maple

2008 ◽  
Author(s):  
Abdul Aziz
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Laminar Boundary Layer ◽  
Numerical Solutions ◽  
Nonlinear Differential Equations ◽  
Slip Flow ◽  
Moving Plate ◽  
Flow Models ◽  
Layer Flow ◽  
Energy Equations

The paper uses a modern computing tool, Maple, to study some contemporary problems in laminar boundary layer flow over a flat plate. The purpose is to demonstrate that Maple is a powerful computational tool for solving realistic contemporary problems in laminar boundary layer theory. The specific problems (all pertaining to a flat plate) chosen for this study are (1) hydrodynamic boundary layer with slip flow condition, (2) velocity boundary layer on a moving plate, (3) hydrodynamic and thermal boundary layers with a linear shear flow. Each problem is of contemporary interest and allows a similarity analysis which reduces the continuity, momentum, and energy equations into ordinary nonlinear differential equations. Numerical solutions of these equations are generated and physical interpretations of the results provided. Maple worksheets for solving each problem are available from the author upon request. It is shown that the effort required to solve these problems with Maple is modest, consisting of few lines of easily learned commands. The use of Maple facilitates and enriches the study of laminar boundary flows in general.

Numerical and Experimental Study of Gas Flows in 2D and 3D Microchannels

2007 ◽  
Author(s):  
Xiaohui Guo ◽  
Chihyung Huang ◽  
Alina A. Alexeenko ◽  
John P. Sullivan
Keyword(s):  
Stokes Equations ◽  
Rectangular Cross Section ◽  
Air Flow ◽  
Slip Flow ◽  
Temperature Drop ◽  
Apparent Temperature ◽  
Gas Flows ◽  
Infinite Length ◽  
Slip Boundary ◽  
2D And 3D

In the experiments conducted at Purdue, the air flow in rectangular cross-section microchannels was investigated using the pressure sensitive paints. The high resolution pressure measurements were obtained for inlet-to-outlet pressure ratios from 1.76 to 20 with the outlet Knudsen numbers in the range from 0.002 to 0.06 based on hydraulic diameter of 157.9 micron and the length-to-height ratio of about 50. In the slip flow regime, air flow was simulated by the 2D and 3D Navier-Stokes equations with no-slip and slip boundary conditions. For various pressure ratios, the entrance flow development, compressibility and rarefaction effects were observed in both experiments and numerical simulations. It was found that accurate modeling of gas flows infinite-length channels requires that inlet and outlet reservoirs to be included in computations. Effects of entrance geometry on the friction factor were studied for 3D cases. In both experiments and numerical modelings, significant pressure drop was found starting at the inlet chamber. The numerical modeling also predicted an apparent temperature drop especially at the channel exit.

scholarly journals Velocity Measurements in Channel Gas Flows in the Slip Regime by means of Molecular Tagging Velocimetry

Micromachines ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 374 ◽  
Author(s):  
Dominique Fratantonio ◽  
Marcos Rojas-Cárdenas ◽  
Christine Barrot ◽  
Lucien Baldas ◽  
Stéphane Colin
Keyword(s):  
Slip Velocity ◽  
Rarefied Gas ◽  
Numerical Models ◽  
Slip Flow ◽  
Diagnostic Methods ◽  
Gas Flows ◽  
Reconstruction Method ◽  
Molecular Tagging Velocimetry ◽  
Molecular Tagging ◽  
Slip Regime

Direct measurements of the slip velocity in rarefied gas flows produced by local thermodynamic non-equilibrium at the wall represent crucial information for the validation of existing theoretical and numerical models. In this work, molecular tagging velocimetry (MTV) by direct phosphorescence is applied to argon and helium flows at low pressures in a 1-mm deep channel. MTV has provided accurate measurements of the molecular displacement of the gas at average pressures of the order of 1 kPa. To the best of our knowledge, this work reports the very first flow visualizations of a gas in a confined domain and in the slip flow regime, with Knudsen numbers up to 0.014. MTV is cross-validated with mass flowrate measurements by the constant volume technique. The two diagnostic methods are applied simultaneously, and the measurements in terms of average velocity at the test section are in good agreement. Moreover, preliminary results of the slip velocity at the wall are computed from the MTV data by means of a reconstruction method.

Sign in / Sign up

Export Citation Format

Share Document