Compact damping models for laterally moving microstructures with gas-rarefaction effects

Veijola, Timo; Turowski, Marek

doi:10.1109/84.925777

Cited by 129 publications

(88 citation statements)

References 15 publications

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“…Veijola and Turowski [19] and Fichman and Hetsroni [20] performed theoretical analyses of the effective gas viscosity in nanospaces to illustrate that the effective viscosity of a gas in a nanospace is less than that in a large space. The MD simulation studies by Thomas et al [21] showed that the viscosity of water decreases in carbon nanotubes with diameters as small as 1.66 nm.…”

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confidence: 99%

Experimental and molecular dynamics study of gas flow characteristics in nanopores

Liu

Jiang

2012

Chin. Sci. Bull.

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Gas flow characteristics in nanopores were investigated experimentally and numerically using molecular dynamics (MD) simulations with an emphasis on the friction factor and gas viscosity. The results show that the viscosity and the friction factor in nanopores are much lower than those in macroscale channels. The actual viscosities obtained from the MD studies showed that the gas viscosity in nanopores is less than the macroscale viscosity because collisions between gas molecules are less frequent in high Knudsen number flows and there are more collisions with the wall. The MD simulations show that the velocity profile is composed of two parts, with a much steeper velocity gradient near the wall. gas flow, nanopore, friction factor, molecular dynamics simulation Citation:Liu Q X, Jiang P X, Xiang H. Experimental and molecular dynamics study of gas flow characteristics in nanopores.

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confidence: 99%

Experimental and molecular dynamics study of gas flow characteristics in nanopores

Liu

Jiang

2012

Chin. Sci. Bull.

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“…These so-called equations of state only involve the 2 Note that the term (∇v) T can alternatively be defined as (∇v) T = v ← − ∇ , where ← − ∇ is the so-called post gradient.…”

Section: Equations Of Statementioning

confidence: 99%

“…0 (−kΓr ) (4.57) where H (1) n and H (2) n are n th -order Hankel functions of the first and second kind, respectively. Applying the same strategy as for prismatic tubes to obtain an expression for volume flows in terms of pressure yields…”

Section: Circular Layersmentioning

confidence: 99%

“…• Wave propagation in in-ear hearing aids [1] • The behavior of MEMS devices with thin fluid layers [2,3,4] • The behavior of microphones, consisting of a membrane backed by a thin air layer [5,6,7,8] • The behavior of inkjet print heads, including the wave propagation in narrow ink channels [9,10] • The behavior of plates and double wall panels with a thin fluid layer for reduction of sound transmission [11,12,13,14,15,16,17] • Modeling wave propagation in the cochlea [18] • Modeling wave propagation in the vocal tract, trachea and lungs [19] Note that in many cases where the boundary-layer thicknesses are small compared to the dimensions of the domain, neglecting viscothermal effects leads to a very accurate and efficient description of the fluid behavior. Nevertheless, a second class of problems where the viscothermal effects can become significant, even if the boundary-layer thicknesses are relatively small, is in systems near resonance.…”

Section: Applications Of Viscothermal Modelsmentioning

confidence: 99%

“…LRF models for certain simple basic shapes only involve analytical solutions and are extremely time-efficient. The accuracy of such LRF models is known to be very good under most practical conditions 2 . For more complex (coupled) geometries, computational costs rise and the level of accuracy is not known a priori.…”

Section: Chapter 1 Introductionmentioning

confidence: 99%

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Viscothermal wave propagation

Nijhof¹

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SummaryIn engineering practice, the simplest, most efficient model that yields the desired level of accuracy is usually the model of choice. This is particulary true if an optimization process is involved, in which case the choice of the underlying models is often a trade-off between efficiency and accuracy. It is therefore important to know not only how efficient a model is, but also how accurate.In this work, the accuracy, efficiency and range of applicability of various (approximate) models for viscothermal wave propagation are investigated in a general setting. Models for viscothermal wave propagation describe the wave behavior of fluids including viscous and thermal effects. Cases where viscothermal effects are significant generally involve small fluid domains, low frequencies, or fluid systems near resonance. Examples of practical applications of these models are, for instance, describing the behavior of in-ear hearing aids, MEMS devices, microphones, inkjet printheads and muffler systems involving acoustic resonators.Amongst the various models for viscothermal wave propagation that are considered, a prominent role is taken by the family of approximate models known as Low Reduced Frequency (or LRF) models. These are the most efficient approximate models available and they have been used extensively to model a wide variety of problems involving viscothermal wave propagation. Nevertheless, LRF models are only available for a limited number of geometries and can become inaccurate under certain conditions. A second family of models that is considered consists of exact solutions to the equations describing viscothermal wave propagation. These models, which are less efficient than the LRF models, provide reference solutions which can be used to determine the accuracy of the LRF models. A drawback of the exact models is that they are only available for a small number of geometries. Therefore a third family of models is considered, which is based on a newly developed Finite Element (or FE) approximation of the equations for viscothermal wave propagation. The main attraction of these FE models is that they can be used to model arbitrary geometries and boundary conditions. A drawback is that obtaining a solution requires much more computing power than needed for the LRF or exact models. The vi numerical stability and convergence properties of the developed FE methods are investigated to ensure that they can yield reference solutions of a desired accuracy for cases where an exact solution is not available.Using these three families of models, a number of parameter studies are carried out that yield detailed information on accuracy of the highly efficient LRF models for a range of geometries and boundary conditions. The gathered data provides a means of estimating the accuracy of simple coupled LRF models a priori.Besides the investigation into the accuracy of LRF models, two engineering applications where viscothermal wave propagation takes a prominent role are described. The first application involves the passive si...

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2015

Nanoelectromechanical Systems

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Compact damping models for laterally moving microstructures with gas-rarefaction effects

Cited by 129 publications

References 15 publications

Experimental and molecular dynamics study of gas flow characteristics in nanopores

Experimental and molecular dynamics study of gas flow characteristics in nanopores

Viscothermal wave propagation

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