The 7th International Conference on Fluid Mechanics May 24-27,2015,Qingdao,China

正http://www.icfm7.org First Announcement and Call for PapersThe objective of International Conference on Fluid Mechanics(ICFM)is to provide a forum for researchers to exchange new ideas and recent advances in the fields of theoretical,experimental,computational Fluid Mechanics as well as interdisciplinary subjects.It was successfully convened by the Chinese Society of Theoretical and Applied Mechanics(CSTAM)in Beijing(1987,     

INFORMATION FOR CONTRIBUTORS

Contributions： The Journal, Acta Mechanica Solida Sinica, is pleased to receive papers from engineers and scientists working in various aspects of solid mechanics. All contributions are subject to critical review prior to acceptance and publication.     

基于鲁棒滤波的捷联导引头视线角速度估计方法

针对捷联导引头无法直接获取视线角速度等信息的问题,研究了鲁棒滤波在大气层外飞行器捷联导引头视线角速度估计中的应用。为了建立非线性滤波估计模型,考虑目标视线角速度的慢变特性,采用一阶马尔科夫模型建立了状态方程;推导了视线角速度的解耦模型,并建立了量测方程;考虑到实际应用中存在系统噪声统计特性失准的问题,基于Huber-Based鲁棒滤波方法,设计了视线角速度滤波器,并完成了基于Huber-Based滤波方法和扩展卡尔曼滤波方法的数学仿真。仿真结果表明Huber-Based滤波方法的视线角、视线角速度及视线角加速度估计精度分别达到0.1140'、0.1423'/s、0.0203'/s2,而扩展卡尔曼滤波方法的视线角、视线角速度及视线角加速度估计精度仅分别为0.6577'、0.6415'/s、0.0979'/s~2。仿真结果证明了该方法可以有效地估计出相对视线角速度等信息,并且在非高斯噪声的条件下,依然可获得较高的估计精度,具有一定的鲁棒性。     

Guide for authors

正Each of the sections below provides essential information for authors.We recommend that you take the time to read them before submitting a contribution to Acta Mechanica Sinica.We hope our guide to authors may help you navigate to the appropriate section.How to prepare a submission This document provides an outline of the editorial process involved in publishing a scientific paper in Acta Mechanica     

Use specification of multiscale materials for life spanned over macro-, micro-, nano-, and pico-scale

Multiscale material intends to enhance the strength and life of mechanical systems by matching the transmitted spatiotemporal energy distribution to the constituents at the different scale, say—macro, micro, nano, and pico,—, depending on the needs. Lower scale entities are, particularly, critical to small size systems. Large structures are less sensitive to microscopic effects. Scale shifting laws will be developed for relating test data from nano-, micro-, and macro-specimens. The benefit of reinforcement at the lower scale constituents needs to be justified at the macroscopic scale. Filling the void and space in regions of high energy density is considered.Material inhomogeneity interacts with specimen size. Their combined effect is non-equilibrium. Energy exchange between the environment and specimen becomes increasingly more significant as the specimen size is reduced. Perturbation of the operational conditions can further aggravate the situation. Scale transitional functions and/or f_j/j+1 are introduced to quantify these characteristics. They are represented, respectively, by , and (f_mi/ma,f_na/mi,f_pi/na). The abbreviations pi, na, mi, and ma refer to pico, nano, micro and macro.Local damage is assumed to initiate at a small scale, grows to a larger scale, and terminate at an even larger scale. The mechanism of energy absorption and dissipation will be introduced to develop a consistent book keeping system. Compaction of mass density for constituents of size 10⁻¹², 10⁻⁹, 10⁻⁶, 10⁻³ m, will be considered. Energy dissipation at all scales must be accounted for. Dissipations at the smaller scale must not only be included but they must abide by the same physical and mathematical interpretation, in order to avoid inconsistencies when making connections with those at the larger scale where dissipations are eminent.Three fundamental Problems I, II, and III are stated. They correspond to the commonly used service conditions. Reference is made to a Representative Tip (RT), the location where energy absorption and dissipation takes place. The RT can be a crack tip or a particle. At the larger size scales, RT can refer to a region. Scale shifting of results from the very small to the very large is needed to identify the benefit of using multiscale materials.     

Impact non-pénétrant sur le thorax : influence de la courbure sur la propagation des ondesNonpenetrating impact on the thorax: influence of curvature on wave propagation

Theoretical studies of the propagation of impact waves through the thorax are needed to improve the design of bulletproof jackets and blast protections (Fung in ‘Biomechanics Motions, Flow, Stress, and Growth’, Springer-Verlag, 1990; Cooper et al., J. Trauma 40 (1996) S38–S41). The influence of the weak acoustic coupling at the interface between the thoracic wall and the lung were described in (Grimal et al., C. R. Acad. Sci. IIB 329 (2001) 655–662); in this work, we study, within the frame of elastodynamics and with an approximate analytical method, the effects of the curvature of this interface. Results are given in terms of strain energy for the pressure wave, transmitted or converted. Focalisation of energy in the medium representing the lung is important for curvatures measured in humans. To cite this article: Q. Grimal et al., C. R. Mecanique 330 (2002) 569–574.     

Vérification expérimentale de la relation de réciprocité d'Onsager pour l'électro-osmose et l'électro-filtration dans une argile naturelleExperimental verification of the Onsager's reciprocal relations for electro-osmosis and electro-filtration phenomena on a saturated clay

This Note is devoted to the experimental verification of the Onsager's reciprocal relations in the particular case of electro-osmosis and electro-filtration. A special set up has been designed to carry out the measurements of both the electro-osmotic permeability and the streaming potential. This has been performed by using a natural material i.e., saturated kaolinite. To cite this article: K. Beddiar et al., C. R. Mecanique 330 (2002) 893–898.     

Tribology and Its Many Facets: From Macroscopic to Microscopic and Nano-scale Phenomena

The key features of tribology – interfacial phenomena of interacting bodies in relative motion – are as origin of friction and wear scientifically interesting and have important applications in technology and engineering. The interfacial interactions have been studied in various theoretical and experimental approaches. Depending on the scope of the investigation and the nature of the tribological solid/fluid/solid or solid/solid system under study, these approaches apply contact mechanics, hydrodynamics, and rheology as well as solid state physics and chemistry. Accordingly, also various experimental techniques have been used, ranging from Coulomb's classical tribometer to the contemporary atomic force microscope.This paper reviews by way of examples some of the basic interfacial facets of tribology – from bulk continuum to atomistic/discrete phenomena – in a macroscopic, microscopic, and nano-scale point of view. For tribo-testing it is important to characterize the tribo-system under study by an appropriate choice of a systems envelope and to consider the hierarchy of interaction levels.     

Evaluating Herschel-Bulkley fluids with the back extrusion (annular pumping) technique

A mathematical model was developed to describe the behavior of Herschel-Bulkley fluids in a back extrusion (annular pumping) device. A technique was also developed to determine the rheological properties (yield stress, flow behavior index, and consistency coefficient) of these fluids. Mathematical terms were expressed in four dimensionless terms, and graphical aids and tables were prepared to facilitate the handling of the expressions.Nomenclature a radius of the plunger, m - dv/dr shear rate, s^–1 - F force applied to the plunger, N - F _b buoyancy force, N - F _cb force corrected for buoyancy, N - F _T recorded force just before the plunger is stopped, N - F _Te recorded force after the plunger is stopped, N - g acceleration due to gravity, m/s² - H(t) momentary height between plunger and container bottom, m - K a/R, dimensionless - L length of annular region, m - L(t) depth of plunger penetration, m - n flow behavior index, dimensionless - p static pressure, Pa - P _L pressure in excess of hydrostatic pressure at the plunger base, Pa - p ₀ pressure at entrance to annulus, Pa - P pressure drop per unit of length, Pa/m - Q total volumetric flow rate through the annulus, m³/s - r radial coordinate, measured from common axis of cylinder forming annulus, m - R radius of outer cylinder of annulus, m - s reciprocal of n, dimensionless - t time, s - T dimensionless shear stress, defined in Eq. (3) - T ₀ dimensionless yield stress, defined in Eq. (4) - T _w dimensionless shear stress at the plunger wall - _p velocity of plunger, m/s - velocity, m/s - mass density of fluid, kg/m³ - Newtonian viscosity, Pa s - P p ₀ –p _L , Pa - consistency coefficient, Pa sⁿ - value of where shear stress is zero - _–, ₊ limits of the plug flow region (Fig. 1) - r/R - shear stress, Pa - _y yield stress, Pa - _w shear stress at the plunger wall, Pa - dimensionless flow rate defined in Eq. (24) - dimensionless velocity defined by Eq. (5) - _–, ₊ dimensionless velocity outside the plug flow region - _max dimensionless maximum velocity in the plug flow region - _p dimensionless velocity at the plunger wall     

Microscale 3D flow mapping with μDDPIV

Three-dimensional (3D) quantitative flow visualization by tracking microscale particles has become an invaluable tool in microfluid mechanics. Defocusing digital particle image velocimetry (DDPIV) can recover spatial coordinates by calculating the separation between defocused images generated by an aperture mask with a plurality of pinholes. In this paper, a high-speed 3D micro-DDPIV (μDDPIV) system was devised based on this technique to achieve microscale velocity field measurements. A micro-volume of 400 × 300 μm² with a depth of 150 μm has been mapped using an inverted microscope equipped with a 20× objective lens. The proposed technique was successfully applied to 3D tracking of 2-μm fluorescent particles inside an evaporating water droplet.     

Methode zum Messen des Langzeitverhaltens von Thermoplasten

Zusammenfassung Es wird eine neue berührungslose optische Dehnungsmeßeinrichtung für biaxiale Langzeit-Zug- bzw. Torsionsversuche vorgestellt. Die Ergebnisse der Versuche an kugel- und kurzglasfasergefülltem Polyamid 6 (PA6) zeigen, daß dieses System genügend genau arbeitet. Das untersuchte Material weist sowohl im Zugversuch als auch im Torsionsversuch nichtlineares Verhalten auf. Bei überlagerten Zug/Torsions-Belastungen verschieben sich die Dehnungen, verglichen mit denen bei gleicher einaxialer Last zu höheren Werten. Durch die Füllstoffzugabe ergeben sich unterschiedliche Verstärkungseffekte. Die faserverstärkten Proben sind erwartungsgemäß eher in Richtung der Rohrachse verstärkt, während das kugelgefüllte System eine höhere Verstärkungswirkung bei Torsionsbelastung erkennen läßt.

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A new optical device for strain measurement in long-term tension and torsion tests is presented. The new system has been compared with others and the results of the experiments with glass bead and short, glas-fiber-filled Polyamid 6 show that it works well. With a dead-weight loading machine used it is possible to perform combined tension/torsion creep experiments or simple tension and simple torsion tests. The materials under consideration here exhibit nonlinear behavior in tension as well as in torsion tests. Under combined loading, which is tensile stress with a superimposed torsional stress, or vice versa, the amounts of the strains compared with those of the one-dimensional stress state are increasing. The fillers produce different reinforcement effects. The bead-filled system is stiffer when subjected to a torsional load, which may be explained by different load carrying mechanism in tension and torsion. The glassfiber-filled system is stiffer in axis direction, because the fibers are aligned to a considerable extent by the flow of the melt during molding.

Vortrag gehalten auf der Jahrestagung der Deutschen Rheologischen Gesellschaft, TH Darmstadt, 19.–21. 4. 1989.     

Methode zum Messen des Langzeitverhaltens von Thermoplasten

Zusammenfassung Es wird eine neue berührungslose optische Dehnungsmeßeinrichtung für biaxiale Langzeit-Zug- bzw. Torsionsversuche vorgestellt. Die Ergebnisse der Versuche an kugel- und kurzglasfasergefülltem Polyamid 6 (PA 6) zeigen, daß dieses System genügend genau arbeitet. Das untersuchte Material weist sowohl im Zugversuch als auch im Torsionsversuch nichtlineares Verhalten auf. Bei überlagerten Zug/Torsions-Belastungen verschieben sich die Dehnungen, verglichen mit denen bei gleicher einaxialer Last zu höheren Werten. Durch die Füllstoffzugabe ergeben sich unterschiedliche Verstärkungseffekte. Die faserverstärkten Proben sind erwartungsgemäß eher in Richtung der Rohrachse verstärkt, während das kugelgefüllte System eine höhere Verstärkungswirkung bei Torsionsbelastung erkennen läßt.

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A new optical device for strain measurement in long-term tension and torsion tests is presented. The new system has been compared with others and the results of the experiments with glass bead and short, glas-fiber-filled Polyamid 6 show that it works well. With a dead-weight loading machine used it is possible to perform combined tension/torsion creep experiments or simple tension and simple torsion tests. The materials under consideration here exhibit nonlinear behavior in tension as well as in torsion tests. Under combined loading, which is tensile stress with a superimposed torsional stress, or vice versa, the amounts of the strains compared with those of the one-dimensional stress state are increasing. The fillers produce different reinforcement effects. The bead-filled system is stiffer when subjected to a torsional load, which may be explained by different load carrying mechanism in tension and torsion. The glass-fiber-filled system is stiffer in axis direction, because the fibers are aligned to a considerable extent by the flow of the melt during molding.

Vortrag gehalten auf der Jahrestagung der Deutschen Rheologischen Gesellschaft, TH Darmstadt, 19.–21. 4. 1989.     

Bimodal model of slurry viscosity with application to coal-slurries. Part 1. Theory and experiment

The rheological behavior of stable slurries is shown to be characterized by a bimodal model that represents a slurry as made up of a coarse fraction and a colloidal size fine fraction. According to the model, the two fractions behave independently of each other, and the non-Newtonian behavior of the viscosity is solely caused by the colloidal fraction, while the coarse fraction increases the viscosity level through hydrodynamic interactions. Data from experiments run with colloidal coal particles of about 2–3 µm average size dispersed in water show the viscosity of these colloidal suspensions to exhibit a highly shearrate-dependent behavior and, in the high shear limit, to match very closely the viscosity of suspensions of uniform size rigid spheres although the coal volume fraction must be determined semi-empirically. Different amounts of coarse coal particles are added to the colloidal suspension and the viscosity of the truly bimodal slurries measured as a function of shear rate. In agreement with the bimodal model, the measured shear viscosities show the coarse fraction to behave independently of the colloidal fraction and its contribution to the viscosity rise to be independent of the shear rate. It is shown that the shear rate exerted on the colloidal fraction is higher than that applied by the viscometer as a result of hydrodynamic interactions between the coarse particles, and that it is this effective higher shear rate which is necessary to apply in the correlations. For determining the coal volume fraction a relatively simple and quite accurate measurement technique is developed for determining the density and void fraction of coarse porous particles; the technique directly relates volume fraction to mass fraction.     

Pont entre les « micro » et « méso » mécaniques des composites stratifiésRelationships between ‘micro’ and ‘meso’ mechanics of laminated composites

A relatively complete bridge is built between the micromechanics of laminates for which there are numerous theoritical and experimental works and the mesomechanics of laminates introduced and developped in particular at Cachan for more than 15 years. At the ‘meso’ scale, the ply and the interface are homogeneized. To cite this article: P. Ladevèze, G. Lubineau, C. R. Mecanique 331 (2003).     

Laser-based measurements of gas-phase chemistry in non-equilibrium pulsed nanosecond discharges

Detailed experimental investigation of a non-equilibrium nanosecond pulsed discharge in premixed CH₄/air mixtures at atmospheric pressure has been carried out. The experiments demonstrated significant reductions in ignition delay and increased lean burn capability relative to conventional spark ignition. Advanced laser diagnostics have been used to identify the physical processes which lead to these improvements. The electron temperature and density properties were measured using laser Thomson scattering (LTS). Temperature measurements were performed using N₂ CARS thermometry to quantify the energy transfer in the gas mixture. Effect of the discharge on the local temperature shows the existence of the ignition of the gas mixture for equivalence ratio between 0.7 and 1.3. Fast development of a flame kernel is then observed. The experiment also shows that the flame can be sustained above the discharge due the repetitive ignition of the flame at the plasma repetition rate. Finally, OH and CH PLIF experiments were performed to confirm the large OH and CH streamer-induced production over the discharge volume. To cite this article: F. Grisch et al., C. R. Mecanique 337 (2009).     

Shrinkage effect on polyethylene based blends

An experimental study of the shrinkage effect in low density-high density polyethylene blends, high density-high density polyethylene blends and low density polyethylene-ethylene vinyl acetate copolymer blends is presented. Viscosity measurements are also included.The strain recovery is analysed as the addition of the interfacial tension effect and the elastic recoverable strain. The results are compared with those obtained for other polyolefin blends observing that in the case of compatible systems as low density-high density polyethylene and high density-high density polyethylene blends the strain recovery and the viscosity follow approximately the additive rule. In the case of more incompatible systems like polyethylene-ethylene vinyl acetate copolymer, polyethylene-polypropylene and others very large recoveries were observed. The formation of minifibres of the dispersed phase during the preparation of the samples is suggested as responsible for the obtained results.