Home – Home – Jornals – Thermophysics and Aeromechanics 2005 number 2

An analytical review of the status and trends of development of the problem of turbulent friction reduction, which is one of the key problems in modern aero-hydrodynamics, is given. The most promising and rapidly progressing active and passive means of flow control used to reduce friction drag mainly in incompressible turbulent boundary layers are considered. Special attention is paid to evaluation of the domestic potential in this field, analysis of the most important results, and place of domestic research in the retrospective review of the worldwide trends.

The problem of nonlinear interaction of disturbances of a compressible boundary layer caused by the sound and roughness of the plate surface is reduced to a linear problem for parabolized inhomogeneous equations for the amplitude functions with inhomogeneous boundary conditions on the undisturbed wall. The numerical solution including the computation of the wave number dependence on the longitudinal coordinate is carried out by a method used for the solution of stability problem. The dependence of a parameter determining the ability to excitation of instability waves (the receptivity coefficient) on the incidence angles of the sound wave and the inclination of roughness wave front has been investigated. At a supersonic flow, the largest receptivity corresponds to the angle between the roughness wave front and the flow direction equal to the Mach angle.

The process of the drift of solid spherical particles in a closed pipe is investigated on the basis of a numerical solution of the system of equations for the motion of a viscous, compressible, and heat-conducting gas. The particles motion arises under the action of the gas column oscillations, which are excited by a flat piston moving in accordance with a harmonic law. The particles distributions typical of the first and second linear and the first nonlinear resonances are presented along the pipe axis, which are obtained under the assumption on the Stokes character of the gas flow around a particle. The drift mean velocity is shown to be determined by the asymmetry of the wave shape, and it increases near the resonances, where the oscillations are followed by the formation of shock waves.

Experimental study was performed for isothermal swirl flow behind an abrupt axisymmetric expansion resulting in development of instability in the form of precessing vortex core. LDA, high-speed video recording, and acoustic technique was used for study of instantaneous and averaged structure of unsteady flow. It was discovered that with an increase in the swirl number the flow evolved through typical stages, including the region of anomalous reduction of the precession frequency. Using the condition of helical symmetry of the flow [1], we demonstrated that this inversion in the frequency dependence occurs due to contribution from the axial movement of the helical vortex, with the helix pitch increasing with the swirl parameter.

Results of experiments with a two-tier Darrieus rotor with plain blades are presented for testing in a water channel. This design ensures an easy self-start and better power characteristics than a regular propeller-type wind turbine.

Stability of the plane-parallel flow of viscous liquid over an inclined plane was analysed using linearized Reynolds equations for a turbulent flow. Dependency of the critical Froude number and superficial velocity on Reynolds number and channel inclination angle was obtained. Value boundaries were determined for Froude numbers from 1.2 to 1.5, when the plane-parallel flow looses its stability.

Absorption of low-soluble gas in a thin film of viscous incompressible liquid, falling down a vertical surface, is considered. The film surface serves as the interface between liquid and gas. Calculations were carried out for natural and excited surface waves. Coincidence with experimental data is good. The optimal wave frequency corresponding to the modes of solitary wave and maximal mass transfer coefficient was determined for every Reynolds number. The main mass transfer modes in a liquid film were studied.

The vortex dynamics and convective heat transfer at a turbulent unsteady flow past a heated cylinder are considered in an unconfined flow and in a plane-parallel duct. The solutions of two-dimensional Reynolds and energy equations are obtained for a fixed Reynolds number 4.5^.10⁴ with the aid of a multi-block factored algorithm using the overlapping rectangular and cylindrical grids, which was implemented in the VP2/3 package. The temperature street in a body wake is analysed in detail, and a relation is established between the dynamic and thermal characteristics. Special attention is paid to the interpretation of instantaneous flow parameters, turbulence and temperature characteristics within the period of the transverse force coefficient oscillations and to the investigation of averaged and fluctuation characteristics in the near and far wake.

Results of experiments on deteriorated heat transfer mode at supercritical pressures of liquid are presented. The method for determination of this mode is suggested. Equations for determination of the wall temperature at deteriorated heat transfer and boundary value of flow enthalpy corresponding to the beginning of heat transfer deterioration are suggested.

A computational model is presented for the heat transfer processes in a non-uniform high-temperature gas flow and in the MHD channel walls. The results of modelling the processes of radiant and convective heat transfer have shown that the current layer has an unsteady and irregular structure, however, interacts with the gas flow on the whole as a local formation. The radiant fluxes onto the channel walls are computed from the parameters of the current layer structure. The temperature regime of the MHD channel walls is determined from the solution of an unsteady three-dimensional heat conduction problem. The non-uniformity and unsteadiness of radiant fluxes are shown to result in high temperature gradients in the dielectric channel wall.

The boundary-value problem of non-stationary heat transfer is considered under the modes of convection and heat conductivity for a closed area. The fields of velocity and vorticity vector are shown together with temperature distributions. Significant non-uniformity of the temperature fields obtained for the mode of convection is shown. Temperature distributions are compared under the modes of convective and conductive heat transfer. It is concluded that the solution to the boundary-value problem for the convection mode may provide more accurate temperature estimates.

Basing on a mathematical model, a tubular shape of the electric arc has been realized numerically. Some peculiarities of the gas flow and heating in the stationary tubular discharge have been analysed. The potentiality of the tubular arc applied for powder material spraying is under consideration.

26 June 2005 is the 70th anniversary of the State Prize Laureate of Russian Federation in the field of science and equipment, Doctor of Technical Sciences, the Honored Scientist of RF Anatoly P. Burdukov.