197,265 research outputs found
Collective behavior of one-dimensional granular media
No full text"Modelling in Applied Sciences, A Kinetic Theory Approach" (editori N. Bellomo e M. Pulvirenti) della Birkhauser nella "Modelling and Simulation in Science, Engineering and Technology Series"
Semiclassical expansion of Wigner functions
No full textWe show that the time evolved Wigner function of a quantum particle under the action of a smooth potential can be formally expanded in powers of h, where each term of the expansion can be computed in terms of the corresponding classical flow. Moreover the solution can be approximated by the N-order truncation with an error O(h(N+1)). (c) 2006 American Institute of Physics
A stochastic particle system approximating the BGK equation
No full textWe consider a stochastic N-particle system on a torus in which each particle moving freely can instantaneously thermalize according to the particle configuration at that instant. Following [2], we show that the propagation of chaos does hold and that the one-particle distribution converges to the solution of the BGK equation. The improvement with respect to [2] consists in the fact that here, as suggested by physical considerations, the thermalizing transition is driven only by the restriction of the particle configuration in a small neighborhood of the jumping particle. In other words, the Maxwellian distribution of the outgoing particle is computed via the empirical hydrodynamical fields associated to the fraction of particles sufficiently close to the test particle and not, as in [2], via the whole particle configuration
Approach to equilibrium in a microscopic model of friction
No full textWe consider the time evolution of a disk under the action of a constant force and interacting with a free gas in the mean-field approximation. Letting V-0 > 0 be the initial velocity of the disk and V-infinity > 0 its equilibrium velocity, namely the one for which the external field is balanced by the friction force exerted by the background, we show that, if V-infinity - V-0 is positive and sufficiently small, then the disk reaches V-infinity with the power law t(-(d+2)), d = 1, 2, 3 being the dimension of the physical space. The reason for this behavior is the long tail memory due to recollisions. Any Markovian approximation (or simply neglecting the recollisions) yields an exponential approach to equilibrium
Height function interface reconstruction algorithm for the simulation of boiling flows
No full textIn this paper we present our results on numerical study of vapor bubbles growing in quiescent superheated liquid, as effect of liquid evaporation at the interface. Height Function interface reconstruction algorithm is coupled with an evaporation model based on continuum field representation of source terms. The flow solver is a finitevolume CFD code. Interface is tracked within a Volume-Of-Fluid framework. Continuum-Surface-Force method accounts for surface tension effects. Vapor bubble heat-transfer-controlled growth is simulated for three different working fluids: water, HFE-7100 and R134a. Accuracy of interface reconstruction algorithm is of maximum importance. Unbalance between pressure gradients and surface tension forces at interface leads to the growth of an unphysical velocity field which switches original only diffusive heat transfer mechanism to combined diffusive-convective one. Height Function algorithm reduces the magnitude of this unreal velocity field. Standard test cases are considered to assess the performances of implemented version, through comparison with the widely used Youngs algorithm. Keywords: volume of fluid, height function, evaporation, surface tension, bubbles. 1 Introduction Modern numerical implementation of surface tension driven flows, with phase change, begins with the work of Juric and Tryggvason [1]. Earlier methods used a Lagrangian approach with a moving mesh following the interface. The limit of these methods was that they could not manage large interface deformation. Juric and Tryggvason developed a Front Tracking algorithm where Lagrangian evolution of interface is tracked on a fixed grid. Welch and Wilson [2] and So
Dicronychus sabatinellii Platia & Pulvirenti 2020
No full text<i>Dicronychus sabatinellii</i> Platia & Pulvirenti, 2020 <p>(Fig. 11, Map 5)</p> <p> <b>Material examined</b> (HMIM, CPG). Khuzestan province: 1 ex. (HMIM): Karkheh N. P., Shush, N32°04’36.5” E48°14’15.6”, 45 m., 1.III.–10. V.2015, leg. E. Gilasian (Malaise Trap); 3 exs. (HMIM): Karkheh N. P., S Shush, ca. 5 km W Khashan vill., Karkheh ranger station, N32°04’05.1” E48°14’18.8”, 48 m., 26. V.2018, leg. H. Nasserzadeh (L. T.); 1 ex. (HMIM): Dez N. P., ca. 15 km E Haft-Tappeh, Dez ranger station, N32°03’56.6” E48°31’57.1”, 79 m., 24.IV.2018, leg. H. Nasserzadeh & M. Mozhdehi (L. T.); 1ex. (CPG): Ahvaz, 5.IV.2018, G. Sabatinelli, at light.</p> <p> <b>Climate types.</b> Arid, with mild winters and very warm summers.</p> <p> <b>Distribution in Palaearctic Region. Asia:</b> Iran (Khuzestan province) (Platia <i>et al.</i> 2020).</p>Published as part of <i>Nasserzadeh, Hiva, Platia, Giuseppe & Serri, Sayeh, 2023, Click beetles (Coleoptera: Elateridae) of Khuzestan province (Iran): with three new species, Craspedostethus izehensis sp. n., Dicronychus khuzestanicus sp. n. and Gurjevelater catei sp. n., pp. 101-130 in Zootaxa 5346 (2)</i> on page 124, DOI: 10.11646/zootaxa.5346.2.1, <a href="http://zenodo.org/record/8354558">http://zenodo.org/record/8354558</a>
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