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.

Analysis of Gaseous Flows in Minichannels by Molecular Tagging Velocimetry

2012 ◽  
Author(s):  
Feriel Samouda ◽  
Christine Barrot ◽  
Stéphane Colin ◽  
Lucien Baldas ◽  
Nicolas Laurien
Keyword(s):  
Flow Regime ◽  
Slip Flow ◽  
Velocity Slip ◽  
Velocity Profiles ◽  
Jet Flows ◽  
Gas Flows ◽  
Molecular Tagging Velocimetry ◽  
Molecular Tagging ◽  
Gaseous Flows ◽  
External Flows

The Molecular Tagging Velocimetry (MTV) technique has been widely used for analyzing velocity fields in liquid mini- and microflows. Concerning gaseous flows, only few works describe the implementation of MTV at millimetric scale, and these studies are limited to the analysis of external flows, such as jet flows. The goal of the present work is to develop this technique for the analysis of internal gas flows in minichannels. It is a first step toward the visualization of velocity profiles in rarefied conditions, and direct measurement of velocity slip at the walls. A specific experimental setup has been designed. Its features are detailed. Velocity profiles are obtained in a pressure driven steady flow of argon through a long rectangular minichannel of 1.2 × 5 mm2 cross-section and 15 cm length using acetone molecules as tracer. Experiments are carried out at atmospheric pressure, in a laminar continuum flow regime. The accuracy of the method is discussed by comparison between experimental and theoretical velocity profiles. The potential of the MTV technique for analyzing mini or micro gaseous internal flows is commented on. Perspectives of the work for discussing the validity of boundary conditions in the slip flow regime are presented.

scholarly journals Molecular tagging velocimetry for confined rarefied gas flows: Phosphorescence emission measurements at low pressure

2018 ◽  
Vol 99 ◽  
pp. 510-524 ◽  
Author(s):  
Dominique Fratantonio ◽  
Marcos Rojas-Cardenas ◽  
Hacene Si Hadj Mohand ◽  
Christine Barrot ◽  
Lucien Baldas ◽  
...  
Keyword(s):  
Rarefied Gas ◽  
Low Pressure ◽  
Gas Flows ◽  
Molecular Tagging Velocimetry ◽  
Molecular Tagging ◽  
Rarefied Gas Flows ◽  
Phosphorescence Emission

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.

Mass Flow Rate Measurements Through Metallic Microtubes in the Slip and Transition Regimes

2015 ◽  
Author(s):  
Ernane Silva ◽  
Cesar J. Deschamps ◽  
Marcos Rojas-Cárdenas
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rarefied Gas ◽  
Mean Free Path ◽  
Accommodation Coefficient ◽  
Transitional Flow ◽  
Gas Flows ◽  
Slip Regime ◽  
Non Equilibrium

The exchange of momentum and energy in gas flows through microchannels is significantly influenced by the gas-surface interaction. At this scale often the gas is rarefied and therefore non-equilibrium effects in the fluid flow can arise in a layer which extends for a distance equivalent to the mean free path from the walls. Typical examples of non-equilibrium phenomena for rarefied gas flows are slip at the wall, thermal transpiration and temperature jump at the wall. The aim of the present study is to experimentally investigate the non-equilibrium effects present in an isothermal pressure induced flow for a large range of rarefaction conditions. The isothermal slip at the wall is usually characterized by the tangential momentum accommodation coefficient (TMAC). This coefficient depends on the molecular nature of the gas and on the physical characteristics of the surface, such as material and roughness. In particular this paper explores the influence of the surface material on the TMAC through measurements of the mass flow rate in capillaries for the special case of nitrogen. Commercially available microtubes of three different metallic materials — stainless steel, copper, and brass — were considered in the analysis. Measurements were performed with a dynamic measurement technique based on the constant volume method and comprehend the transitional flow regime and most part of the slip regime. Theoretical results obtained from the solution of the Boltzmann equation via the BGK kinetic model, which is a simplified approximation for the collisional term, were compared to the experimental results.

Slip Flow in Rectangular and Annular Ducts

1965 ◽  
Vol 87 (4) ◽  
pp. 1018-1024 ◽  
Author(s):  
W. A. Ebert ◽  
E. M. Sparrow
Keyword(s):  
Pressure Drop ◽  
Rarefied Gas ◽  
Slip Flow ◽  
Velocity Slip ◽  
Density Level ◽  
Axial Pressure ◽  
Slip Regime ◽  
Rarefied Gas Flows ◽  
Axial Pressure Gradient ◽  
Viscous Shear

An analysis has been performed to determine the velocity and pressure-drop characteristics of moderately rarefied gas flows in rectangular and annular ducts. The density level is such that a velocity slip may occur at the duct walls. In general, it is found that the effect of slip is to flatten the velocity distribution relative to that for a continuum flow; furthermore, the axial pressure gradient is diminished under slip-flow conditions. The conditions characterizing the onset of the slip regime have been determined on the basis of a 2 percent reduction in friction factor relative to the continuum value. For all the geometries studied here, the onset of slip occurred at a Knudsen number of 0.003. The effect of compressibility on the axial pressure drop was also investigated. It was found that compressibility increases the pressure drop primarily through an increase in viscous shear rather than through an increase in momentum flux.

scholarly journals Role of diffusion on molecular tagging velocimetry technique for rarefied gas flow analysis

2015 ◽  
Vol 19 (6) ◽  
pp. 1335-1348 ◽  
Author(s):  
Aldo Frezzotti ◽  
Hacene Si Hadj Mohand ◽  
Christine Barrot ◽  
Stéphane Colin
Keyword(s):  
Gas Flow ◽  
Rarefied Gas ◽  
Flow Analysis ◽  
Rarefied Gas Flow ◽  
Molecular Tagging Velocimetry ◽  
Molecular Tagging

scholarly journals Effect of viscosity on slip boundary conditions in rarefied gas flows

2019 ◽  
Author(s):  
Nam T. P. Le
Keyword(s):  
Slip Velocity ◽  
Rarefied Gas ◽  
Cross Flow ◽  
Navier Stokes ◽  
Gas Flows ◽  
Gas Temperature ◽  
Slip Boundary ◽  
Rarefied Gas Flows ◽  
Viscosity Models ◽  
Simulation Results

The viscosity of gases plays an important role in the kinetic theory of gases and in the continuum-fluid modeling of the rarefied gas flows. In this paper we investigate the effect of the gas viscosity on the surface properties as surface gas temperature and slip velocity in rarefied gas simulations. Three various viscosity models in the literature such as the Maxwell, Power Law and Sutherland models are evaluated. They are implemented into OpenFOAM to work with the solver “rhoCentralFoam” that solves the Navier-Stokes-Fourier equations. Four test cases such as the pressure driven backward facing step nanochannel, lid-driven micro-cavity, hypersonic gas flows past the sharp 25-55-deg. biconic and the circular cylinder in cross-flow cases are considered for evaluating three viscosity models. The simulation results show that, whichever the first-order or second-order slip and jump conditions are adopted, the simulation results of the surface temperature and slip velocity using the Maxwell viscosity model give good agreement with DSMC data for all cases studied.

scholarly journals Modeling viscous effects on boundary layer of rarefied gas flows inside micronozzles in the slip regime condition

2018 ◽  
Vol 148 ◽  
pp. 838-845 ◽  
Author(s):  
Maria Grazia De Giorgi ◽  
Donato Fontanarosa ◽  
Antonio Ficarella
Keyword(s):  
Boundary Layer ◽  
Rarefied Gas ◽  
Gas Flows ◽  
Viscous Effects ◽  
Slip Regime ◽  
Rarefied Gas Flows

Modeling and Preliminary Experiment for Rarefied Gas Flows in Constricted Microchannels

2008 ◽  
Author(s):  
Xiaohui Guo ◽  
Chihyung Huang ◽  
Alina Alexeenko ◽  
John P. Sullivan
Keyword(s):  
Rarefied Gas ◽  
Numerical Models ◽  
Pressure Ratio ◽  
Frictional Resistance ◽  
Manufacturing Defects ◽  
Slip Regime ◽  
Rarefied Gas Flows ◽  
Mass Flowrate ◽  
Accommodation Coefficients ◽  
Slip Flows

Gaseous slip flows in 3D rectangular microchannels with constrictions have been study numerically, and the experiment using pressure-sensitive-paints (PSP) for polymer microchannel pressure measurements are proposed. Constrictions inside microchannels, either being manufacturing defects or functional design features such as micro-orifices or micro-nozzles, will change the flow pattern because of additional frictional resistance and flow separation. In current research, mass-flowrate reduction due to constrictions has been investigated numerically for air flows in the slip regime, where Knudsen number ranges from 0.003 to 0.07. The results have been compared with both straight microchannels and with 3D analytical solutions. Similar to nozzle cases at macroscale, chocked flows has been observed at the critical pressure ratio of about 1.89. A numerical model including finite inlet and outlet chambers has been used in simulations to evaluate effects of reflection waves. Slip effects have been studied for different accommodation coefficients in presence of constrictions. By implementing multi-species numerical models, thermal induced mass transport has also been studied. Preliminary experiment based on PSP measurement for polymer microchannels has able to generate high spatial resolution pressure data, which are comparable with numerical simulations. Finally, further improvement of experimental setup is discussed.

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