Home – Home – Jornals – Advanced Search

The paper presents the results of the experimental study of the dynamic characteristics of the laser fragmentation/laser-induced fluorescence (LF/LIF) process in nitrobenzene and para -nitrotoluene vapors under synchronized two-pulse laser irradiation. It is shown that if the values of the time delay between the pulses of fragmentation (248.4 nm) and excitation (247.87 nm) of NO-fragments are in the range 20-40 ns, the efficiency of the LF/LIF method can be increased by several times.

The goal of this study is to develop hybrid composites to experimentally and numerically assess their behavior under a ballistic impact. The Al₂O₃ ceramic/woven fabric (Kevlar or UHMWPE) reinforced epoxy/Al-alloy multi-layered armours are developed. Simulation and ballistic test results show good agreement.

The problem of thermocapillary convection in a flat bounded region filled with liquid and gas in contact along the interfacial interface is studied under weak evaporation. To study the processes of heat and mass transfer and the parameters of phase transitions under conditions of local heating, a two-sided mathematical model based on the Oberbeck-Boussinesq equations is proposed. The characteristics of mass transfer through the thermocapillary interface due to evaporation and vapor content in the gas layer are analyzed taking into account the influence of the Soret and Dufour effects. The results of a numerical study of the evolution of the interface and unsteady flows in a cell are presented. The calculation of the main characteristics of the liquid-gas system and the position of the interface at each moment of time was carried out using a specially developed numerical algorithm. The presented model makes it possible to describe the formation of characteristic thermal and concentration structures and transient modes of cellular convection with a complex configuration of flows in layers

Activities aimed at studying stabilization of a high-speed boundary layer with the use of porous coatings are reviewed. All types of coatings used in experimental research are considered. It is demonstrated that a porous coating with optimal parameters can stabilize the second mode of disturbances to a large extent and delay the laminar-turbulent transition in a high-speed boundary layer. A review of numerical investigations of porous coatings is presented, and it is shown that special boundary conditions are imposed for porous coating modeling; otherwise, the flow has to be calculated in each pore of the coating. The major part of results obtained on the basis of the linear stability theory and in direct numerical simulations agree well with experimental data. Examples of methods of porous coating optimization and of using promising metamaterials are provided.

The results of experimental studies of the process of cooling a zirconium ball in subcooled ethanol under the action of a submerged jet are presented. During the experiments, the degree of subcooling of the cooled liquid and the distance from the nozzle exit to the cooled surface varied. Thermograms of cooling are presented and the influence of the distance between the nozzle and the surface on the duration of cooling and the transition temperature from stable film boiling to intense heat transfer is revealed.

Behavior of a transversally flowing fluid in a boundary layer on a plate and a wedge is studied using the Faulkner-Scan equation in the presence and absence of suction and blowing on the body surface. Numerical methods are used to show that, under certain conditions in the boundary layer, one may observe the formation of attraction and repulsion lines (the transverse velocity along these lines is zero) and maximum transverse velocity lines. Different transverse flow regimes in the boundary layer depending on the key parameters of the problem are considered

An algorithm for controlling submerged jets has been developed to calculate the geometry of the forming device, which provides the velocity profile and (or) the required characteristics of its linear instability in the initial section of the jet. A class of forming devices is considered, the geometry of which is similar to the geometry of the device created at the Research Institute of Mechanics of the Moscow State University. The control algorithm is based on the gradient descent method to minimize the functional relating the parametrically specified shaper geometry and the selected characteristic of the corresponding initial jet velocity profile formed by it. The operation of the algorithm was tested on the example of a functional describing deviations of the jet velocity profile from the given one

The aim of the present work is to examine the flow of electrically conducting immiscible Newtonian fluids with variable viscosity through an inclined channel under the influence of a magnetic field. The flow is generated because of a constant pressure gradient. The flow in an inclined channel is governed by the Navier-Stokes equations. Analytical expressions for the velocity, flow rate, and stress are derived. The influence of various parameters of the problem on the flow characteristics is analyzed.

Using the Navier-Stokes system of equations, rotational regimes of thermocapillary fluid flows in a semi-infinite space bounded from above by a non-deformable free boundary, on which a local temperature distribution is specified, are calculated. It is shown that in the boundary layer near the free boundary, as a result of bifurcation, rotational regimes of fluid flows arise during non-uniform cooling of this boundary. Secondary rotational modes are calculated, which form two families of solutions that depend on several parameters, and two parameters are not determined by external conditions.

The theory of the complex matrix differential operator and finite amplitude analysis are used to investigate nonlinear nanofluid convection in a porous medium saturated under gravity modulation. The finite amplitude of convection for the g-jitter is derived while applying the solvability condition of the third order. To calculate the heat and mass transfer through the porous medium, the low-amplitude analysis is performed. The Nusselt numbers are calculated at the second order as a function of the finite amplitude to evaluate the heat and mass transfer. It is found that changing the gravitational field can affect the amount of heat and mass transfer effectively. It is also found that the oscillatory mode is preferable for better heat and mass transport results than the stationary mode.