Effect of Periodic Oscillation on the Interfacial Instability of Two Superposed Fluid Layers in a Fully Saturated Porous Media

We investigate the effect of horizontal periodic oscillation on the interfacial instability of two immiscible and viscous fluids of different densities in a fully saturated porous media. A linear stability analysis of the viscous and time-dependent basic flow leads to a periodic oscillator describing the evolution of the interfacial perturbation amplitude. The horizontal oscillation leads to the occurrence of two types of instability, the Kelvin–Helmholtz’s instability and the parametric resonance. These instabilities appear at the frontier between water and petroleum and have a practical interest in oil reservoir engineering. The results show that, an increase of the oscillation frequency destabilizes the Kelvin–Helmholtz instability and displaces the parametric instability regions toward the short wavelength perturbation. Also, we examine mainly how the other physical parameters of the system affect the instabilities for various permeability and porosity values of the porous medium as well as for relative heights of the two fluid layers.

The research of the parameters of a vibration machine for composite materials compaction

Based on the analysis of the conventional methods for composite materials compaction, the authors propose a vibration machine made as a form without bottom with a horizontal oscillation vibro-exciter mounted on its end face. To determine the rational parameters of the vibration machine we researched the “vibration form – composite medium” dynamic system wherein composite medium is represented in the form of a system with distributed parameters. This system takes into account the resilient, viscous, inertia and power properties of the compacted composite material. We formulated a partial differential equation describing the variation of stresses in the compacted medium depending on the dynamic module of resilient deformation, the coefficient of dynamic viscosity, the coefficient of non-resilient resistance and the compacted medium inertia in the functional dependence on the composite material density and relative deformation. We formulated an oscillation wave equation describing the propagation of the viscous-resilient-plastic waves of deformation in the compacted composite material. The solution of the oscillation wave equation resulted in the formulation of the law of the oscillation of the form and the compacted material. We determined the stresses occurring in the composite material. We obtained the relations for the determination of the vibration machine basic parameters depending on the physical and mathematical characteristics of the compacted composite material.

Sloshing in a Hele-Shaw cell: experiments and theory

The response of the free liquid surface in a Hele-Shaw cell subjected to a horizontal oscillation is investigated. We study the low-oscillation-amplitude regime and we show, by varying the fluid viscosity, $\unicode[STIX]{x1D708}$, and the forcing frequency, $\unicode[STIX]{x1D714}$, that the ratio between the Stokes viscous length, $\sqrt{2\unicode[STIX]{x1D708}/\unicode[STIX]{x1D714}}$, and the cell thickness greatly affects the amplitude and phase lag of the gravity waves. In particular, the sloshing system undergoes an underdamped/overdamped transition for sufficiently large viscosities. A consistent theoretical model, based on a modification of Darcy’s law to include unsteadiness, is then introduced to rationalize the experimental observations. Contrary to traditional sloshing wave theory, the viscous flow dissipation comes at leading order in the analysis, rather than as a higher-order asymptotic correction to the inviscid sloshing dynamics. The analytical expression for the resonance curves agrees well with experimental results without tunable parameters.

Vertical and horizontal oscillation of three models of self-propelled boom sprayers

ABSTRACT The spray boom is one of the sprayer components that most affect the application quality and may cause phytotoxicity and overlay application problems. Therefore, this study aimed to evaluate the displacement in the vertical and horizontal movements of the spray booms in three models of self-propelled boom sprayers. The vibrations of the spray boom in the vertical direction was measured using three receivers (GNSS) with RTK differential correction. The vibration measurements in the horizontal direction were determined using a high resolution camera. At the end, the processed data were entered into a spreadsheet for the descriptive statistics. The smallest spray boom movement in the horizontal direction was obtained by the specimen 2. No statistical differences were observed between the different speeds for the spray boom vibration in the horizontal and vertical directions, in the evaluated sprayers. The largest vertical movements of the spray booms were observed for the self-propelled specimen 3. The impact/collision route type showed the highest deviations and, in undulating and gentle to undulating types, there was no significant difference in deviation values.