Procedia IUTAM最新文献

The nonlinear free oscillations of a planar, initially straight Timoshenko beam are investigated by means of the asymptotic development method. Attention is focus on the difference in considering the “mechanical” vs the “geometric” curvature of the axis of the beam, which are different for extensible beams. A comparison of the results obtained by the two models is proposed, and it is shown when they are equivalent and when they give different nonlinear behaviours. A parametric analysis showing the effects of the slenderness (arbitrary, not necessarily large) and of the stiffness of the right-end axial spring is performed.

Turbulent thermal convection is a complex problem: the flow is forced at almost all scales, because of the presence of both large scale circulation and small scale plumes. Moreover the difference of density induced by temperature adds an ingredient in the basic equations of the flow, so that turbulence could be different from the case of pure mechanical forcing. Mixing is in principle different and probably increased because of the structure of the plumes. Moreover the entire flow is not homogeneous (at least at large scales) and the statistical behaviour can be influenced by the large scale flow. One way to probe all these specific effects is to use a Lagrangian point of view, measuring, for example, Lagrangian transport of velocity and temperature, or heat flux. We will show how the inhomogeneity of the mean temperature and velocity fields affect the heat flux. Then the interactions between the mean fields and the Lagrangian fluctuations will be highlighted.

In addition to hydrodynamic equations in the bulk region, proper hydrodynamic boundary conditions are essential to theoretically understanding and numerically simulating the hydrodynamics of many soft matter systems, e.g. two-phase flows on solid surfaces and viscoelastic fluids on solid surfaces. In this work, we show that Onsager's variational principle, first proposed by Lars Onsager in his seminal work in 1931, provides a convenient instrument for deriving not only hydrodynamic equations in the bulk region but also thermodynamically consistent hydrodynamic boundary conditions. To demonstrate its applications, we consider one-component liquid-vapor flows and immiscible two-phase flows on solid surfaces where moving contact line is involved.

Analytical solutions to one-dimensional electro-elastodynamic problems in functionally graded piezoelectric material thin plates subjected to impact pressure are obtained. In the case where both surfaces of the thin plate are free of electric charge, the stress oscillation is periodic when the mechanical impedance is independent of the space-variable, whereas it is complicated when the impedance depends on the space-variable. In the case where the voltage between both surfaces of the thin plate is zero, the stress oscillation is complicated whether the impedance is independent of or dependent on the space-variable. The complicated stress oscillations are found to be suppressed completely by applying specific voltages determined from the analytical solution.

The coherence resonance (CR) and stochastic resonance (SR) in a periodic potential driven by correlated additive and multiplicative noises are studied in this paper. The effects of the system parameters on the probability density function (PDF) of the response are discussed by using the Monte-Carlo simulation. The shapes of the average joint PDF are changed from two independent peaks to a crater shape as the amplitude of the periodic force increases. The output spectrum and qualify factor are introduced to measure the CR. The qualify factor shows a pronounced peak and the intrawell CR appears. The amplitude and the phase lag of the average response first increase with increasing multiplicative noise intensity, attain a maximum, and then decrease. That is, the SR happens.

In order to measure sheet flow near the bottom in the north passage of Yangtze Estuary during the typhoon, a submerged synchronous field survey system composited of Nortek AquaPro, Nortem AquaPro HR, AWAC and OBS 3+ was equipped on a pedestal based structure. The system was used to survey sheet flow field during the flooding season in 2015. The pedestal base synchronous field survey system can give reasonable estimation about stability of itself, and also capture simultaneously the wave climate as well as the current feature and the sediment concentration near the bottom. Analyzing the data collected by the system, it is found that the tidal current dominates the sedimentation concentration near the bottom in the Yangtze Estuary without waves, and the only peak value of suspended sediment concentration occurs at the fall slack time. The suspended sediment concentration above 50cm to the bottom is usually not larger than 15kg/m³, and it is not significantly correlated with the wave. When typhoon happens, the suspended sediment concentration increases significantly below 30cm to the bottom. There are two peaks of the suspended sediment concentration at the spring slack and the fall slack time respectively.

This paper considerers the principal feasibility of using cold gas dynamic spraying with laser post treatment technique to create Al-Ni composite coatings. The prepared mixture of two powders was coated on an aluminum substrate and laser annealed. As a result the AlxNy intermetallic phases were observed in the coating. Obtained laser-annealed coatings were studied by means of optical and electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffractometry and compared with as-sprayed coatings. Effects of laser processing parameters, such as scanning speed, power and beam shape on microstructural evolution of the composite coatings were discussed and optimal regimes for laser assisted CS were determined.

The contact problem of acting of the two semi-infinite Kirchhoff plates on the elastic layer is considered. The vertical static stresses acts on the plates. The problem is to study the contact stresses concentrations between the plates and the layer in this block structure. It was proved that the contact stresses concentrations in the end-walls of the plats are the same as in the end-walls of the rigid stamps acted on the layer if the distance between the end-walls of the plates is not equal to zero and is equal the square of this stresses if this distance is equal to zero. It can induce the destruction of the materials in engineering or appearance of the earthquake in seismology.

We deal with some aspects of the general (mathematical) modeling of sharp interfaces (i.e. two-dimensional surfaces within a three-dimensional body) without and with own thermodynamical activity (i.e. with interfacial densities, fluxes and supplies). Questions of regularity of the quantities involved are especially addressed. We present a classification of sharp interfaces taking their relation to the remaining body as well as their thermodynamic behavior into account. After a short look into local balances at the interface we discuss a model of a shrinking body (due to mechanical treatment, e.g.) in the framework of sharp singular interfaces.

The present study is devoted to the boundary value problem of coupled thermoelastoplasticity. The temperature depended yield criterion and Duhamel Neumann constitutive equation was used. The material subjected to uneven heat treatment under plane strain frameworks was considered. The new analytical solution of the problem of uneven heat treatment of the thermoelasticplastic hollow cylinder was constructed within of the thermal stresses and plastic flow theories. The three different yield criteria were used. The original numerical scheme for calculations of temperature stresses and plastic strains in the frameworks of the von Mises yield criterion was developed and implemented. The characteristics of the plastic flow in the heating domain according to the yield criterion selection are eliminated. Constructed solutions of the boundary value problems were compared and analyzed for yield criteia of von Mises, Tresca and Ishlinsky-Ivlev.