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Pu Li - One of the best experts on this subject based on the ideXlab platform.
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Analytical model of squeeze film air damping of perforated plates in the free Molecular Regime
Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems, 2019Co-Authors: Cunhao Lu, Pu Li, Yuming FangAbstract:In this paper, an analytical model of squeeze film damping (SQFD) of perforated plates in the free Molecular Regime is developed, which is based on: (1) the modification of the perforated energy transfer model (P-ETM) (Li and Hu, J Micromech Microeng 21:025006, 2011) by giving the probability of molecules entering the gap through holes; (2) the application of Sumali’s formula (J Micromech Microeng 17:2231–2240, 2007) to relate to the Monte Carlo model (MC) (Hutcherson and Ye, J Micromech Microeng 14:1726–1733, 2004) quantitatively. The analytical model can model the perforation effect on SQFD of plates of various hole sizes. Compared with experiment data and numerical models, the analytical model is proved to be accurate, easy to operate. The effect of gap distance on SQFD of perforated plate in the free Molecular Regime is discussed. Due to perforation effect, as gap distance increases, the damping constant of non-perforated plate decreases faster than that of perforated plate of the same size.
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A generalized energy transfer model for squeeze-film air damping in the free Molecular Regime
Journal of Micromechanics and Microengineering, 2018Co-Authors: Cunhao Lu, Pu Li, Yuming FangAbstract:A generalized energy transfer model (ETM) for squeeze-film air damping of micro plates in the free Molecular Regime is developed. The development of the model is based on: (1) the modification of the ETM proposed by Bao et al by using the weighted average of square traveling distance (l is the Molecular traveling distance in the gap) to replace the plain average of , (2) the incorporation of the Monte Carlo (MC) model by Hutcherson and Ye so that some assumptions in Bao's model causing the overestimation of quality factor are released, and (3) the use of Sumali's empirical formula to relate the ETM to MC model quantitatively. The generalized ETM developed in this paper features: (1) a closed form equation for predicting quality factor according to the parameters of the system, (2) without suffering from the abnormal behavior when the aspect ratio of the plate goes high, and (3) good agreement with experimental results. As a result, the ETM can find practical applications in MEMS.
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Analytical model of squeeze film air damping for circular microplates in the free Molecular Regime
2018 IEEE 3rd Advanced Information Technology Electronic and Automation Control Conference (IAEAC), 2018Co-Authors: Pu Li, Cunhao Lu, Longfei YangAbstract:Based on the generalized Energy Transfer Model (Gen-ETM) for rectangular microplates, this paper gives an analytical expression of Gen-ETM for circular microplates in the free Molecular Regime. The closed form expression of the model is very easy to use, and is validated by the FEM simulation. Quality factor of the analytical model is inversely proportional to the plate radius. Compared with FEM simulation, the model is applicable to small radius circular plate.
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a numerical Molecular dynamics approach for squeeze film damping of perforated mems structures in the free Molecular Regime
Microfluidics and Nanofluidics, 2014Co-Authors: Pu Li, Yuming Fang, Haiqiang WuAbstract:Accurate determination of the squeeze-film damping in rare air is crucial for the design of high-Q MEMS devices. In the past, for the MEMS structures with no perforations, there have been two approaches to treating the squeeze-film damping in rare air: the approach based on the continuum assumption and the approach using Molecular dynamics (MD) method. The amount of squeeze-film damping can be controlled by providing perforations in microstructures. To model perforation effects on squeeze-film damping, many methods have been proposed. However, almost all the previous methods are based on the continuum assumption. Only one paper focuses on analytical modeling of squeeze-film damping of a perforated microplate using the MD method. Hutcherson and Ye (J Micromech Microeng 14:1726–1733, 2004) developed a novel MD method to model the squeeze-film damping in free Molecular Regime. The method possesses high computational efficiency. However, their work is valid only for non-perforated rectangular microplate. This paper presents a numerical MD approach for calculating the squeeze-film damping of a perforated rectangular plate and a perforated circular plate in free Molecular Regime. In Hutcherson and Ye’s work, the microplate is non-perforated. After each collision with the non-perforated plate, all the molecules are reflected to the substrate. In this paper, the plate is perforated. For the molecules in the air gap striking the surface of the perforated microplate, some of the molecules are reflected to the substrate. The rest leave the air gap through the perforations. This paper is an extension of the work done by Hutcherson and Ye (J Micromech Microeng 14:1726–1733, 2004). The accuracy of the present numerical MD approach is verified by comparing its results with the experimental results available in the literature and the finite element method results.
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a model for squeeze film damping of perforated mems devices in the free Molecular Regime
Journal of Micromechanics and Microengineering, 2011Co-Authors: Pu Li, Rufu HuAbstract:Predicting squeeze-film damping in rare air is crucial for the design of high-Q MEMS devices. In the past, for MEMS structures with no perforations, there have been two approaches to treating the squeeze-film damping in rare air: using effective viscosity coefficient and using the Molecular dynamics method. The amount of squeeze-film damping can be controlled by providing perforations in MEMS structures. To model perforation effects on squeeze-film damping, many methods have been proposed. However, the previous methods are all based on the approach using effective viscosity coefficient. The approaches treat the gas in the gap as a continuum. This paper presents an analytical Molecular dynamics model for the squeeze-film damping of a perforated microplate in the free Molecular Regime. The quality factor is found by calculating the energy transfer from the vibrating plate to the surrounding air due to the collisions between the microplate and the molecules. This paper is an extension of the work done by Bao et al (2002 J. Micromech. Microeng. 12 341?6). Bao's work is valid only for non-perforated microplate. The accuracy of the present Molecular dynamics model is verified by comparing its results with the experimental results available in the literature. The limitations of the present Molecular dynamics model have been reported in this paper.
Yuming Fang - One of the best experts on this subject based on the ideXlab platform.
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Analytical model of squeeze film air damping of perforated plates in the free Molecular Regime
Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems, 2019Co-Authors: Cunhao Lu, Pu Li, Yuming FangAbstract:In this paper, an analytical model of squeeze film damping (SQFD) of perforated plates in the free Molecular Regime is developed, which is based on: (1) the modification of the perforated energy transfer model (P-ETM) (Li and Hu, J Micromech Microeng 21:025006, 2011) by giving the probability of molecules entering the gap through holes; (2) the application of Sumali’s formula (J Micromech Microeng 17:2231–2240, 2007) to relate to the Monte Carlo model (MC) (Hutcherson and Ye, J Micromech Microeng 14:1726–1733, 2004) quantitatively. The analytical model can model the perforation effect on SQFD of plates of various hole sizes. Compared with experiment data and numerical models, the analytical model is proved to be accurate, easy to operate. The effect of gap distance on SQFD of perforated plate in the free Molecular Regime is discussed. Due to perforation effect, as gap distance increases, the damping constant of non-perforated plate decreases faster than that of perforated plate of the same size.
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A generalized energy transfer model for squeeze-film air damping in the free Molecular Regime
Journal of Micromechanics and Microengineering, 2018Co-Authors: Cunhao Lu, Pu Li, Yuming FangAbstract:A generalized energy transfer model (ETM) for squeeze-film air damping of micro plates in the free Molecular Regime is developed. The development of the model is based on: (1) the modification of the ETM proposed by Bao et al by using the weighted average of square traveling distance (l is the Molecular traveling distance in the gap) to replace the plain average of , (2) the incorporation of the Monte Carlo (MC) model by Hutcherson and Ye so that some assumptions in Bao's model causing the overestimation of quality factor are released, and (3) the use of Sumali's empirical formula to relate the ETM to MC model quantitatively. The generalized ETM developed in this paper features: (1) a closed form equation for predicting quality factor according to the parameters of the system, (2) without suffering from the abnormal behavior when the aspect ratio of the plate goes high, and (3) good agreement with experimental results. As a result, the ETM can find practical applications in MEMS.
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a numerical Molecular dynamics approach for squeeze film damping of perforated mems structures in the free Molecular Regime
Microfluidics and Nanofluidics, 2014Co-Authors: Pu Li, Yuming Fang, Haiqiang WuAbstract:Accurate determination of the squeeze-film damping in rare air is crucial for the design of high-Q MEMS devices. In the past, for the MEMS structures with no perforations, there have been two approaches to treating the squeeze-film damping in rare air: the approach based on the continuum assumption and the approach using Molecular dynamics (MD) method. The amount of squeeze-film damping can be controlled by providing perforations in microstructures. To model perforation effects on squeeze-film damping, many methods have been proposed. However, almost all the previous methods are based on the continuum assumption. Only one paper focuses on analytical modeling of squeeze-film damping of a perforated microplate using the MD method. Hutcherson and Ye (J Micromech Microeng 14:1726–1733, 2004) developed a novel MD method to model the squeeze-film damping in free Molecular Regime. The method possesses high computational efficiency. However, their work is valid only for non-perforated rectangular microplate. This paper presents a numerical MD approach for calculating the squeeze-film damping of a perforated rectangular plate and a perforated circular plate in free Molecular Regime. In Hutcherson and Ye’s work, the microplate is non-perforated. After each collision with the non-perforated plate, all the molecules are reflected to the substrate. In this paper, the plate is perforated. For the molecules in the air gap striking the surface of the perforated microplate, some of the molecules are reflected to the substrate. The rest leave the air gap through the perforations. This paper is an extension of the work done by Hutcherson and Ye (J Micromech Microeng 14:1726–1733, 2004). The accuracy of the present numerical MD approach is verified by comparing its results with the experimental results available in the literature and the finite element method results.
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a Molecular dynamics simulation approach for the squeeze film damping of mems devices in the free Molecular Regime
Journal of Micromechanics and Microengineering, 2010Co-Authors: Pu Li, Yuming FangAbstract:Predicting squeeze-film damping in rare air is crucial for the design of high-Q MEMS devices. There have been two approaches to treating the squeeze-film damping in rare air: the approach using the effective viscosity coefficient and the approach using the Molecular dynamics method. This paper focuses on the numerical simulation of squeeze-film damping in rare air using the Molecular dynamics method. In the past, because of the heavy computational cost of simulation of a large particle system, the Molecular dynamics approach was not often used to simulate the gas damping in the MEMS area. Hutcherson and Ye (2004 J. Micromech. Microeng. 14 1726–33) developed a novel Molecular dynamics method to simulate the motion of a large number of molecules in the squeeze gas film in the free Molecular Regime. The method possesses high computational efficiency. However, in their work, the molecules entering into the interaction Regime are represented by one computational molecule. Therefore, the method is unsuitable for the torsional plate and flexible microbeam. This paper presents a Molecular dynamics approach for calculating the squeeze-film damping of the torsional microplate and flexible microbeam in the free Molecular Regime. In this approach, several computational molecules are used to represent all of the molecules interacting with the torsional microplate and flexible microbeam. The present paper is an extension of the work done by Hutcherson and Ye (2004 J. Micromech. Microeng. 14 1726–33). The accuracy of the present Molecular dynamics approaches is verified by comparing their results with the experimental results available in the literature.
O Sazhin - One of the best experts on this subject based on the ideXlab platform.
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Rarefied gas flow through a rough channel into a vacuum
Microfluidics and Nanofluidics, 2020Co-Authors: O SazhinAbstract:Rarefied gas flow through a rough channel of finite length into a vacuum was investigated using the direct simulation Monte Carlo method. The non-equilibrium effects at the input and output of the channel were considered by including certain pre-and post-channel regions into the geometry under consideration. The mass flow rate through a short and long channel was computed in a wide range of gas rarefaction from the free Molecular Regime to the hydrodynamic near. It is shown that the noticeable effect of surface roughness on flow rate is manifested in the free Molecular and transition Regimes. The analysis is provided for the flow field inside the channel as well as in the upstream and downstream regions. The results obtained are consistent with the theoretical, numerical, and experimental data available in the open literature.
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numerical analysis of gas surface scattering effect on thermal transpiration in the free Molecular Regime
Vacuum, 2007Co-Authors: O Sazhin, A Kulev, S F Borisov, S F GimelsheinAbstract:Abstract The microscopic reversibility of gas–surface collisions is discussed and analyzed using the direct simulation Monte Carlo method for different scattering kernels. A testing procedure for the reversibility analysis is described. Then, the thermal transpiration phenomenon is studied numerically for free Molecular flow through short and long capillaries using Maxwell, Cercignani–Lampis, and Epstein scattering kernels. Comparison with experimental data shows that the Cercignani–Lampis and Epstein kernels allow a more accurate description of non-isothermal internal rarefied gas flows than the commonly used Maxwell model.
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Numerical analysis of gas–surface scattering effect on thermal transpiration in the free Molecular Regime
Vacuum, 2007Co-Authors: O Sazhin, A Kulev, S F Borisov, S F GimelsheinAbstract:Abstract The microscopic reversibility of gas–surface collisions is discussed and analyzed using the direct simulation Monte Carlo method for different scattering kernels. A testing procedure for the reversibility analysis is described. Then, the thermal transpiration phenomenon is studied numerically for free Molecular flow through short and long capillaries using Maxwell, Cercignani–Lampis, and Epstein scattering kernels. Comparison with experimental data shows that the Cercignani–Lampis and Epstein kernels allow a more accurate description of non-isothermal internal rarefied gas flows than the commonly used Maxwell model.
Haiqiang Wu - One of the best experts on this subject based on the ideXlab platform.
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a numerical Molecular dynamics approach for squeeze film damping of perforated mems structures in the free Molecular Regime
Microfluidics and Nanofluidics, 2014Co-Authors: Pu Li, Yuming Fang, Haiqiang WuAbstract:Accurate determination of the squeeze-film damping in rare air is crucial for the design of high-Q MEMS devices. In the past, for the MEMS structures with no perforations, there have been two approaches to treating the squeeze-film damping in rare air: the approach based on the continuum assumption and the approach using Molecular dynamics (MD) method. The amount of squeeze-film damping can be controlled by providing perforations in microstructures. To model perforation effects on squeeze-film damping, many methods have been proposed. However, almost all the previous methods are based on the continuum assumption. Only one paper focuses on analytical modeling of squeeze-film damping of a perforated microplate using the MD method. Hutcherson and Ye (J Micromech Microeng 14:1726–1733, 2004) developed a novel MD method to model the squeeze-film damping in free Molecular Regime. The method possesses high computational efficiency. However, their work is valid only for non-perforated rectangular microplate. This paper presents a numerical MD approach for calculating the squeeze-film damping of a perforated rectangular plate and a perforated circular plate in free Molecular Regime. In Hutcherson and Ye’s work, the microplate is non-perforated. After each collision with the non-perforated plate, all the molecules are reflected to the substrate. In this paper, the plate is perforated. For the molecules in the air gap striking the surface of the perforated microplate, some of the molecules are reflected to the substrate. The rest leave the air gap through the perforations. This paper is an extension of the work done by Hutcherson and Ye (J Micromech Microeng 14:1726–1733, 2004). The accuracy of the present numerical MD approach is verified by comparing its results with the experimental results available in the literature and the finite element method results.
Y. S. Djikaev - One of the best experts on this subject based on the ideXlab platform.
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Statistico-probabilistic approach to taking account of the vapor depletion in the kinetics of homogeneous nucleation: a free-Molecular Regime of droplet growth.
Journal of Chemical Physics, 2004Co-Authors: A. P. Grinin, F. M. Kuni, Y. S. DjikaevAbstract:We propose a statistico-probabilistic approach to investigate the process of homogeneous formation of droplets in a vapor phase in the presence of an already formed and growing droplet under free-Molecular Regime of droplet growth after the instantaneous creation of initial vapor supersaturation. We find the probability density for the formation of a new, nearest (neighbor) droplet in the vicinity of an initially formed droplet. The mean distance between two neighboring droplets is also determined, as well as the average time lag for the formation of the nearest (neighbor) droplet; the latter quantity serves as an estimate for the duration of the nucleation stage. An estimate for the average number of droplets forming in unit volume by the end of the nucleation stage is also given. Our results are compared with the predictions of classical nucleation theory which assumes the density uniformity of a metastable phase. Where the proposed appoach is applicable, there is observed qualitative agreement between ...
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statistico probabilistic approach to taking account of the vapor depletion in the kinetics of homogeneous nucleation a free Molecular Regime of droplet growth
Journal of Chemical Physics, 2004Co-Authors: A. P. Grinin, F. M. Kuni, Y. S. DjikaevAbstract:We propose a statistico-probabilistic approach to investigate the process of homogeneous formation of droplets in a vapor phase in the presence of an already formed and growing droplet under free-Molecular Regime of droplet growth after the instantaneous creation of initial vapor supersaturation. We find the probability density for the formation of a new, nearest (neighbor) droplet in the vicinity of an initially formed droplet. The mean distance between two neighboring droplets is also determined, as well as the average time lag for the formation of the nearest (neighbor) droplet; the latter quantity serves as an estimate for the duration of the nucleation stage. An estimate for the average number of droplets forming in unit volume by the end of the nucleation stage is also given. Our results are compared with the predictions of classical nucleation theory which assumes the density uniformity of a metastable phase. Where the proposed appoach is applicable, there is observed qualitative agreement between the results. The underlying cause of this agreement is analyzed and the limits of applicability of the uniformity approximation are clarified.