Elastic and inelastic collisions of interfacial solitons and integrability of two-layer fluid system subject to horizontal vibrations

We study interfacial waves in a system of two horizontal layers of immiscible inviscid fluids involved into horizontal vibrational motion. We analyze the linear and nonlinear stability properties of the solitons in the system and consider two-soliton collision scenarios. We describe the events of explosive formation of sharp peaks on the interface, which may presumably lead to the layer rapture, and find that beyond the vicinity of this peaks the system dynamics can be represented as a kinetics of a soliton gas.Comment: 6 pages, 6 figures, to appear in Europhys. Let

Physical phenomena governing the behaviour of wildfires : numerical simulation of crown fires in boreal fores

This paper presents the physical phenomena contributing to the behaviour of wildfires. The problem was formulated using a multiphase approach, including the set of balance equations governing the coupled system formed by the vegetation and the surrounding atmosphere in the vicinity of the fire front. Some numerical simulations carried out for a crown fire in boreal forest are compared to data collected during an experimental campaign conducted in the North West territories in Canada

Capture of particles of dust by convective flow

Interaction of particles of dust with vortex convective flows is under theoretical consideration. It is assumed that the volume fraction of solid phase is small, variations of density due to nonuniform distribution of particles and those caused by temperature nonisothermality of medium are comparable. Equations for the description of thermal buoyancy convection of a dusty medium are developed in the framework of the generalized Boussinesq approximation taking into account finite velocity of particle sedimentation. The capture of a cloud of dust particles by a vortex convective flow is considered, general criterion for the formation of such a cloud is obtained. The peculiarities of a steady state in the form of a dust cloud and backward influence of the solid phase on the carrier flow are studied in detail for a vertical layer heated from the sidewalls. It is shown that in the case, when this backward influence is essential, a hysteresis behavior is possible. The stability analysis of the steady state is performed. It turns out that there is a narrow range of governing parameters, in which such a steady state is stable.Comment: 14 pages, 10 figures, published in Physics of Fluid

Average flow generation by a pulsating flow near a curved interface

This paper is devoted to the study of curvature influence on the average flow generation near the fluid interface. The time averaging of a non-uniform pulsating flow often results in a nonzero average flow in the bulk. The well-known average flow occurs near a solid surface, the so-called Schlichting mechanism of the average flow generation. For flows with a free surface there is the other known mechanism of Longuet-Higgins, according to which the average flow is generated by surface waves traveling on a free surface. We found another mechanism for flow generation near a free surface. This mechanism is associated with the curvature of a free surface and does not depend on its deformations. In the present paper the influence of the curvature is studied for flow generation near the fluid interface. The investigation is carried out on an example of a liquid drop embedded in a viscous liquid. The effective boundary conditions for the tangential stress tensor and tangential velocity jumps are derived. It is shown that for comparable densities of fluids the generation mechanisms are similar to the mechanisms of Dore and Schlichting, which are determined near a flat interface. At a low density (and a low dynamic viscosity) inside the drop all of the above-mentioned mechanisms equally contribute to the average flow generation

Evaluation of tribological properties of components of polymer composite selflubricating materials

The paper presents data on the anti-wear properties of the basic components of polymer self-lubricating composite materials for heavy loaded friction units. In friction these components are released from the composite structure as a result of destructive processes or physical desorption with increasing temperature and involved in the metal plating of friction parts. Besides, it shows the wear form of a sample friction pair in comparison with I-40 base oil, often applied as a composite plasticizer, on the example of synergistic interference of unhardened epoxy-diane resin with highly dispersed mineral fillers of the serpentine group. The conducted study reveals the ability of minerals to reduce the wear rate of a sample friction pair as a result of the transferred film formation. The kinetic features of model samples wear under special conditions for testing ceramic materials are determined as well. In addition, the paper identifies the practicability to exploit layered silicates in the structure of polymer matrices as lubricating agents of heavy loaded friction units

Physical phenomena governing the behaviour of wildfires : numerical simulation of crown fires in boreal fores

Colloque avec actes et comité de lecture. Internationale.International audienceThis paper presents the physical phenomena contributing to the behaviour of wildfires. The problem was formulated using a multiphase approach, including the set of balance equations governing the coupled system formed by the vegetation and the surrounding atmosphere in the vicinity of the fire front. Some numerical simulations carried out for a crown fire in boreal forest are compared to data collected during an experimental campaign conducted in the North West territories in Canada