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rarefaction and Temperature Gradient Effect on the Performance of the Knudsen Pump

Chinese Journal of Mechanical Engineering 2012年第4期25卷 745-752页

作者： YE Jianjun YANG Jian ZHENG Jinyang DING Xianting WONG Ieong LI Weizhong CHEN Cong Institute of Process Equipment Zhejiang University Hangzhou 310027 China Engineering Research Center of High Pressure Process Equipment and SaJety oJ Mini'~try oJ l~ctucatton Zhejiang University Hangzhou 310027 China Department of Mechanical andAerospace Engineering University of California Los Angeles 90095 U.S.A School of Energy and Power Engineering Dalian University of Technology Dalian 116024 China

The prediction of the multiscale flow in the Knudsen pump is important for understanding its pumping ***,there is little research on such interesting multiscale phenomenon in the Knudsen *** this paper,a novel numerical analysis method combining the direct simulation Monte Carlo（DSMC） method with the smoothed particle hydrodynamics（SPH） method is presented for simulating the multiscale flow,which is often encountered in the application of the Knudsen *** and accuracy of the new method are given by comparing its results with that of the previous *** the coupled multiscale approach,the rarefaction and the temperature drive are studied,which are two main factors on the performance of the Knudsen *** investigate the effect of rarefaction on the performance of the Knudsen pump,various pump operation pressures are *** flow characteristics and pumping ability at different rarefaction are analyzed,and the phenomenon of the multiscale flow is also *** cases with different linear or nonlinear temperature gradients are set to investigate the effect of temperature gradient on the performance of the Knudsen *** flow characteristics of the Knudsen pump such as the velocity,pressure increase,and the mass flowrate are presented.A unique phenomenon,the reverse transpiration effect caused by the nonlinear temperature gradient is studied,and the reason of the significant pressure increase in the pump channel is also *** the multiscale gas flow is widely encountered in the microflow systems,the above method and its results can also be greatly beneficial and provide significant insights for the design of the MEMS devices.

关键词： thermal transpiration Knudsen pump mass flowrate rarefaction temperature gradient-driven

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Can rarefaction be used to estimate song repertoire size in birds？

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Current Zoology 2011年第3期57卷 300-306页

作者： Kathleen R. PESHEK Daniel T. BLUMSTEIN The Rocky Mountain Biological Laboratory Box 519 Crested Butte CO 81224 USA Department of Ecology and Evolutionary Biology University of California Los Angeles CA 90095-1606 USA

Song repertoire size is the number of distinct syllables, phrases, or song types produced by an individual or population. Repertoire size estimation is particularly difficult for species that produce highly variable songs and those that produce many song types. Estimating repertoire size is important for ecological and evolutionary studies of speciation, studies of sexual selection, as well as studies of how species may adapt their songs to various acoustic environments. There are several methods to estimate repertoire size, however prior studies discovered that all but a full numerical count of song types might have substantial inaccuracies associated with them. We evaluated a somewhat novel approach to estimate repertoire size--rarefaction; a technique ecologists use to measure species diversity on individual and population levels. Using the syllables within American robins＇ Turdus migratorius repertoire, we compared the most commonly used techniques of estimating repertoires to the results of a rarefaction analysis. American robins have elaborate and unique songs with few syllables shared between individuals, and there is no evidence that robins mimic their neighbors. Thus, they are an ideal system in which to compare techniques. We found that the rarefaction technique results resembled that of the numerical count, and were better than two alternative methods （behavioral accumulation curves, and capture-recapture） to estimate syllable repertoire size. Future estimates of repertoire size, particularly in vocally complex species, may benefit from using rarefaction techniques when numerical counts are unable to be performed [Current Zoology 57 （3）： 300-306, 2011].

关键词： Behavioral accumulation curve Bioacoustics Capture-recapture Numerical count rarefaction Song repertoire size

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Stability of rarefaction Wave to the 1-D Piston Problem for the Pressure-Gradient Equations

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Chinese Annals of Mathematics,Series B 2019年第2期40卷 161-186页

作者： Min DING Department of Mathematics School of Science Wuhan University of Technology

The 1-D piston problem for the pressure gradient equations arising from the flux-splitting of the compressible Euler equations is considered. When the total variations of the initial data and the velocity of the piston are both sufficiently small, the author establishes the global existence of entropy solutions including a strong rarefaction wave without restriction on the strength by employing a modified wave front tracking method.

关键词： Piston problem Pressure gradient equations rarefaction wave Wave front tracking method Interaction of waves

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ASYMPTOTIC STABILITY OF THE rarefaction WAVE FOR THE NON-VISCOUS AND HEAT-CONDUCTIVE IDEAL GAS IN HALF SPACE

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Acta Mathematica Scientia 2019年第4期39卷 1195-1212页

作者： Meichen HOU School of Mathematical Sciences University of Chinese Academy of Sciences Institute of Applied Mathematics AMSS Beijing 100190 China Academy of Mathematics and Systems Science Academia Sinica

This article is concerned with the impermeable wall problem for an ideal polytropic model of non-viscous and heat-conductive gas in one-dimensional half space. It is shown that the 3-rarefaction wave is stable under some smallness conditions. The proof is given by an elementary energy method and the key point is to do the higher order derivative estimates with respect to t because of the less dissipativity of the system and the higher order derivative boundary terms.

关键词： Non-viscous impermeable problem rarefaction wave

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Internal heat transfer coefficients in microporous media with rarefaction effects

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Science China(Technological Sciences) 2012年第10期55卷 2869-2876页

作者： XU RuiNa HUANG YuLi JIANG PeiXue WANG BuXuan Key Laboratory for Thermal Science and Power Engineering of Ministry of Education of China Beijing 100084China Beijing Key Laboratory of CO_(2)Utilization and Reduction Technology Beijing 100084China Department of Thermal Engineering Tsinghua UniversityBeijing 100084China

The internal heat transfer of different gases in microporous media was investigated experimentally and *** experimental test section had a sintered bronze porous media with average particle diameters from 11 μm to 225 μ*** Knudsen numbers at the average inlet and outlet pressures of each test section varied from 0.0006 to 0.13 with porosities from 0.16 to *** particle-to-fluid heat transfer coefficients of air,CO 2 and helium in the microporous media were determined *** results show that the Nusselt numbers for the internal heat transfer in the microporous media decrease with decreasing the particle diameter,d p,and increasing Knudsen number for the same Reynolds *** Kn>0.01,the rarefaction affects the internal heat transfer in the microporous media.A Nusselt number correlation was developed that includes the influence of *** computational fluid dynamics(CFD) numerical simulation was carried out to do the pore scale simulation of internal heat transfer in the microporous media considering the rarefaction *** scale three-dimensional numerical simulations were also used to predict the particle-to-fluid heat transfer *** numerical results without slip-flow and temperature jump effects for Knrarefaction effects,but closer to the experimental *** numerical results with rarefaction effects can accurately simulate the unsteady heat transfer in the microporous media.

关键词： internal heat transfer coefficients microporous media rarefaction Knudsen number

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How does the rarefaction of the air affect hypersonic vehicles

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Acta Mechanica Sinica 2021年第1期37卷 18-19,I0002页

作者： Youda Ye National Laboratory for Computational Fluid Dynamics Beijing100086China

The scope,physical concept,and mathematical model for describing how the rarefaction of the air affects on hypersonic flows have been discussed.A new method,namely the data improved Naive-Stroke(DiNS)model,was proposed for the computation of hypersonic shear flows around vehicles flying at altitude of 30-100 *** of the new continuum method has also been done.

关键词： hypersonic flows rarefaction

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ASYMPTOTIC STABILITY OF SOLUTION TO THE INITIAL-BOUNDARY VALUE PROBLEM FOR SCALAR VISCOUS CONSERVATION LAWS CORRESPONDING TO rarefaction WAVES

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Systems Science and Mathematical Sciences 1999年第4期12卷 366-377页

作者： LIU HongXia(Department of Mathematics, Jinan University, Guangzhou 510632, China)PAN Tao(Department of Mathematics and Information Science, Guangxi University, Nanning 530004, China) 暨南大学数学系广东广州 510632 广西大学数学和信息科学系广西南宁 530004

This paper is concerned with the asymptotic behaviors of solutions of thegeneral initial-boundary value problem to scalar viscous conservation law uxx on R+ with the conditions u（0, t） = u-（t） u-（t ）,u（x,0） = u0（x） u+（x-）, where f"（u） > 0 for all u under consideration, u- 0 admits the rarefaction wave. Ourproblem is divided into five cases depending on the signs of the characteristic speeds of the boundary state u- at t= and the far field state u+ = u（+）. Both the globalexistence of the solution and the asymptotic stability are shown in all cases.

关键词： Viscous conservation law rarefaction wave asymptotic stability boundary.

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Asymptotic Stability of Combination of Contact Discontinuity with rarefaction Waves for the One-Dimensional Viscous Micropolar Fluid Model

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Journal of Applied Mathematics and Physics 2019年第9期7卷 2089-2111页

作者： Lishuang Peng College of Science University of Shanghai for Science and Technology Shanghai China

In this paper, we consider with the large time behavior of solutions of the Cauchy problem to the one-dimensional compressible micropolar fluid model, where the far field states are prescribed. When the corresponding Riemann problem for the Euler system admits the solution consisting of contact discontinuity and rarefaction waves, it is shown that the combination wave corresponding to the contact discontinuity, with rarefaction waves is asymptotically stable provided that the strength of the combination wave and the initial perturbation are suitably small. This result is proved by using elementary L2-energy methods.

关键词： Contact Discontinuity rarefaction Waves Viscous Micropolar Fluid Model Asymptotic Stability Energy Estimates

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A prediction method for the performance of a low-recoil gun with front nozzle

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Defence Technology（防务技术） 2019年第5期15卷 703-712页

作者： Cheng Cheng Chong Wang Xiaobing Zhang School of Energy and Power Engineering Nanjing University of Science and Technology

One of the greatest challenges in the design of a gun is to balance muzzle velocity and recoil,especially for guns on aircrafts and deployable *** resolve the conflict between gun power and recoil force,a concept of rarefaction wave gun(RAVEN)was proposed to significantly reduce the weapon recoil and the heat in barrel,while minimally reducing the muzzle *** main principle of RAVEN is that the rarefaction wave will not reach the projectile base until the muzzle by delaying the venting time of an expansion nozzle at the *** on the RAVEN principle,the purpose of this paper is to provide an engineering method for predicting the performance of a low-recoil gun with front ***,a two-dimensional two-phase flow model of interior ballistic during the RAVEN firing cycle was *** simulation results were compared with the published data to validate the reliability and ***,the effects of the vent opening times and locations were investigated to determine the influence rules on the performance of the RAVEN with front *** according to the results above,simple nonlinear fitting formulas were provided to explain how the muzzle velocity and the recoil force change with the vent opening time and ***,a better vent venting opening time corresponding to the vent location was *** findings should make an important contribution to the field of engineering applications of the RAVEN.

关键词： Interior ballistic Low recoil rarefaction wave Prediction method Two-dimensional

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Supersonic flow past a concave double wedge

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Science China Mathematics 1998年第1期41卷 39-47页

作者：陈恕行 Institute of Mathematics Fudan University Shanghai China

The supersonic flow past a concave double wedge is discussed. Because of the interaction between the outer shock attached at the head of the wedge and the inner shock issued from the concave corner, there is a rarefaction wave issued from the intersection of the outer and inner shock. The rarefaction wave is reflected by the outer shock and the wedge infinitely, while the outer shock is also bent due to interaction. The global existence of the solution is proved under the assumptions that the outer shock is weak and the difference of two slopes of the double wedge is small. Meanwhile, a rigorous proof of the asymptotic behavior of the global solution is given. The property is often applied to numerical computation.

关键词： supersonic flow double wedge rarefaction wave shock reflection of waves.

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