Drag Force on Objects in the Nearly Free Molecular Flow Regime as a Function of Speed Ratio

1974 ◽  
Author(s):  
Y. Y. Lin Wang ◽  
J. V. Sengers
Keyword(s):  
Flow Regime ◽  
Drag Force ◽  
Speed Ratio ◽  
Molecular Flow ◽  
Free Molecular Flow

scholarly journals Gas Damping in Capacitive MEMS Transducers in the Free Molecular Flow Regime

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2566
Author(s):  
Boris A. Boom ◽  
Alessandro Bertolini ◽  
Eric Hennes ◽  
Johannes F. J. van den Brand
Keyword(s):  
Flow Regime ◽  
Gas Diffusion ◽  
Diffusion Time ◽  
Molecular Flow ◽  
Free Molecular Flow ◽  
Simple Analytical Model ◽  
Gas Damping ◽  
Wide Range ◽  
Capacitive Mems ◽  
Insight Into

We present a novel analysis of gas damping in capacitive MEMS transducers that is based on a simple analytical model, assisted by Monte-Carlo simulations performed in Molflow+ to obtain an estimate for the geometry dependent gas diffusion time. This combination provides results with minimal computational expense and through freely available software, as well as insight into how the gas damping depends on the transducer geometry in the molecular flow regime. The results can be used to predict damping for arbitrary gas mixtures. The analysis was verified by experimental results for both air and helium atmospheres and matches these data to within 15% over a wide range of pressures.

Effect of reflected molecules on rotational temperature measurements with rocketborne electron beam fluorescence probes

1977 ◽  
Vol 55 (4) ◽  
pp. 370-377 ◽  
Author(s):  
A. A. Haasz
Keyword(s):  
Electron Beam ◽  
Flow Regime ◽  
Rotational Temperature ◽  
Temperature Measurements ◽  
Fluorescence Probes ◽  
Molecular Flow ◽  
Free Molecular Flow ◽  
Temperature Calibration ◽  
Black Brant ◽  
Theoretical Predictions

Theoretical predictions were obtained for the effect of reflected nitrogen molecules on rotational temperature measurements with rocketborne electron beam fluorescence probes in the free molecular flow regime. Calculations for a typical payload (Black Brant AEF-II-118 flown from Fort Churchill, Man., Canada) indicate that the effect of reflected molecules can be significant and should be considered in the derivation of the theoretical temperature calibration curves.

A New Unified Diffusion—Viscous-Flow Model Based on Pore-Level Studies of Tight Gas Formations

SPE Journal ◽  
2012 ◽  
Vol 18 (01) ◽  
pp. 38-49 ◽  
Author(s):  
Mohammad R. Rahmanian ◽  
Roberto Aguilera ◽  
Apostolos Kantzas
Keyword(s):  
Porous Media ◽  
Viscous Flow ◽  
Flow Regime ◽  
Gas Flow ◽  
Flow Model ◽  
Molecular Flow ◽  
Single Element ◽  
Free Molecular Flow ◽  
Flow Through ◽  
Tight Porous Media

Summary In this study, single-phase gas-flow simulation that considers slippage effects through a network of slots and microfractures is presented. The statistical parameters for network construction were extracted from petrographic work in tight porous media of the Nikanassin Group in the Western Canada Sedimentary Basin (WCSB). Furthermore, correlations between Klinkenberg slippage effect and absolute permeability have been developed as well as a new unified flow model in which Knudsen number acts implicitly as a flow-regime indicator. A detailed understanding of fluid flow at microscale levels in tight porous media is essential to establish and develop techniques for economic flow rate and recovery. Choosing an appropriate equation for flow through a single element of the network is crucial; this equation must include geometry and other structural features that affect the flow as well as all variation of fluid properties with pressure. Disregarding these details in a single element of porous media can easily lead to flow misinterpretation at the macroscopic scale. Because of the wide flow-path-size distribution in tight porous media, a variety of flow regimes can exist in the equivalent network. Two distinct flow regimes, viscous flow and free molecular flow, are in either side of this flow-regime spectrum. Because the nature of these two types of flow is categorically different, finding/adjusting a unified flow model is problematic. The complication stems from the fact that the viscosity concept misses its meaning as the flow regime changes from viscous to free molecular flow in which a diffusion-like mechanism dominates. For each specified flow regime, the appropriate equations for different geometries are studied. In addition, different unified flow models available in the literature are critically investigated. Simulation of gas flow through the constructed network at different mean flow pressures leads to investigating the functionality of the Klinkenberg factor with permeability of the porous media and pore-level structure.

Squeeze film damping in the free molecular flow regime with full thermal accommodation

2009 ◽  
Vol 156 (1) ◽  
pp. 171-179 ◽  
Author(s):  
M.A.G. Suijlen ◽  
J.J. Koning ◽  
M.A.J. van Gils ◽  
H.C.W. Beijerinck
Keyword(s):  
Flow Regime ◽  
Squeeze Film ◽  
Molecular Flow ◽  
Free Molecular Flow ◽  
Thermal Accommodation ◽  
Squeeze Film Damping

Anisotropic gas transport in a bilayer membrane in the free molecular flow regime

2012 ◽  
Vol 53 (3) ◽  
pp. 419-423 ◽  
Author(s):  
A. V. Kryukov ◽  
I. M. Kurchatov ◽  
N. I. Laguntsov
Keyword(s):  
Flow Regime ◽  
Gas Transport ◽  
Bilayer Membrane ◽  
Molecular Flow ◽  
Free Molecular Flow
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