TsAGI Science Journal, Issue 6, Year 2013

ON THE THEORY OF THE FLOWAROUND BODIES OF REVOLUTION AT HIGH REYNOLDS NUMBERS

Vic. V. Sychev

The steady axisymmetric flow around a body of revolution in the uniform flow of an incompressible fluid at high Reynolds numbers is considered. Based on an asymptotic analysis of the system of Reynolds equations for time-averaged functions, it is shown that the flow at the body scale is described by the solution of the problem of the flow with a free-stream surface in accordance with the Kirchhoff scheme. The flow is turbulent in the closure region of the separation zone and the wake. Outside these regions, the turbulent stresses are exponentially small. The streamwise and transverse sizes of the separation zone are rather large; in the main approximations, this zone has the form of an ellipsoid with a small relative thickness.

KEY WORDS: closure region, separation zone, mixing layer, turbulent stresses

NUMERICAL SIMULATION OF THE HYPERSONIC BOUNDARY LAYER RECEPTIVITY TO PERIODIC ENERGY SUPPLY

A. A. Ryzhov, V. G. Soudakov, & S. V. Utyuzhnikov

Numerical simulation of the receptivity of a two-dimensional boundary layer on a flat plate to the low-intensity disturbances in the form of a local periodic energy supply located above and inside the boundary layer is carried out at the free-stream Mach number M_∞ = 6. Heat spots interact with the boundary layer, which result in acoustic disturbances and generate unstable waves. It is shown that maximum amplitude of these waves is reached when the center of the energy supply is located near the upper edge of the boundary layer.

KEY WORDS: hypersonic boundary layer, receptivity, acoustics, energy supply

NUMERICAL SIMULATION OF ICING OF A CYLINDER AND AN AIRFOIL: MODEL REVIEW AND COMPUTATIONAL RESULTS

S. V. Alekseyenko & O. A. Prykhodko

General models and methods for examining the icing processes of airfoils, as well as the corresponding meteorological parameters, types of clouds, and ice, are analyzed. Techniques for estimating ice growth in typical flight conditions are considered. The model of interpenetrating media and the trajectory model (inertial model of droplets precipitation) are used to describe moisture precipitation on the streamlined surface. The results of calculating the icing of a cylinder and an airfoil in viscous compressible air-droplet flow, taking into account the form of existence of moisture on the airfoil and the mode of ice accretion, are presented.

KEY WORDS: air-droplet flow, moisture precipitation on a streamlined surface, ice accretion, airfoil icing

ABOUT THE CALCULATION OF THE SKIN FRICTION COEFFICIENT OF THE TURBULENT BOUNDARY LAYER. THE RELAMINARIZATION CRITERION FOR THE LAYER

V. V. Mikhailov & N. V. Samoilova

The formula relating the local skin friction coefficient of the two-dimensional boundary layer of an incompressible fluid to the integral layer characteristics is obtained using the modified Coles law of the wake. Because it is in agreement with the well-known Ludwieg—Tillmann formula, this relationship has a larger range of applicability. The criterion for the beginning of relaminarization in the developed turbulent flow in the boundary layer is proposed.

KEY WORDS: turbulent near-wall flow, friction coefficient, relaminarization

NUMERICAL INVESTIGATION OF VISCOUS GAS FLOWIN 3D SINGLE EXPANSION-RAMP NOZZLES

A. P. Mazurov

The results of a numerical investigation of three-dimensional (3D) viscous flow in asymmetrical plane nozzles (bounded by two parallel side walls) in the presence of an external supersonic flow are presented. The calculations were performed by an implicit difference scheme of integrating the Reynolds-averaged Navier—Stokes equations written in thin-layer approximation in generalized coordinates. A two-parameter k-e turbulence model, taking into account the influence of the wall, was used to calculate the eddy viscosity. The solution to the 3D system of difference equations is carried out using the Gauss—Seidel method of planes relaxation. A comparison of the pressure distributions calculated by the present method with appropriate experimental and computational data is carried out for an asymmetrical nozzle with a flat expansion ramp. A comparison of the two-dimensional and 3D computation results is given for the profiled contour nozzle. The parametric computation results that show the influence of the geometry parameters on the local and integral characteristics of the typical single expansion-ramp nozzle are presented.

KEY WORDS: viscous gas, single expansion-ramp nozzle, difference scheme, numerical method, nozzle thrust vector

INFLUENCE OF HEATING THE FLAT PLATE NOSE PART ON THE INTEGRAL AND STATISTICAL CHARACTERISTICS OF THE BOUNDARY LAYER

V. M. Litvinov & A. A. Uspenskii

The results of an experimental investigation on the effect of heating the nose part of a flat plate model in relation to the development of the boundary layer and the laminar-turbulent transition are presented. On the basis of processing the velocity and temperature profiles in the laminar, transitional, and turbulent flow regions, the integral and statistical characteristics of the boundary layer at different heating regimes are determined. The influence of heating on the reduction of the local and total friction coefficients is estimated. The effect of the friction coefficient reduction is determined by the laminar-to-turbulent transition delay. The experiments were carried out in the T-36I wind tunnel at TsAGI at a flow velocity of 57 m/s and a flow turbulence of 0.06%.

KEY WORDS: boundary layer, laminar-to-turbulent transition, heating of the streamlined surface, heat transfer, Tollmien—Schlichting waves, displacement thickness, momentum thickness, form parameter, intermittency factor and the frequency of intermittency of turbulence, spectra of velocity pulsations, friction drag coefficient

EXPERIMENTAL INVESTIGATIONS OF A HIGH-TEMPERATURE DUST-LADEN GAS JET IMPINGING ON AN OBSTACLE

O. K. Kudin, Yu. N. Nesterov, O. D. Tokarev, & Ya. Sh. Flaksman

The results of experimental investigations of the behavior of the supersonic high-temperature jet laden with solid particles and its action on an obstacle are presented. A gas generator with a liquid fuel combustor was used as the source of gas emission at a temperature of 1600 K. The parameters of the gas—dust jet are presented. The measurement data for a heat flux from the dusty gas to the obstacle are given. It is shown that the heat flux from the gas, which was laden with solid particles, may be three times greater than that from pure gas. The presented data concerning the cold dust-laden gas jet action on an obstacle address the possible contribution of particle kinetic energy into the heat flux to an obstacle.

KEY WORDS: dusty flow, particle-laden jet, jet—obstacle interaction, gas—dust jet generator

AEROELASTIC STABILITY RESEARCH OF A CROSS-SHAPED FLYING VEHICLE

A. G. Narizhny, V. I. Smyslov, & S. I. Sychev

Computational and experimental research to prevent self-oscillations in flight of an elastic maneuverable flying vehicle (FV) with an automatic control system (CS) is presented. The methods and means of FV ground modal (resonance) testing are presented. They are used to correct the FV dynamic model used in the calculation of flutter, to investigate experimentally the aeroelastic stability, to characterize experimentally the CS with electric drive in the frequency range of elastic oscillations, and to determine the elastic FV-CS stability margin. Some examples are presented.

KEY WORDS: aeroelastic stability, flutter, ground resonance testing, automatic control system (CS)

TORSION OF PRISMATIC BEAMS COMPOSED OF DIFFERENT MATERIALS

L. L. Teperin¤ & Tran Van Hung

A new method for the solution of the Saint-Venant torsion problem for prismatic beams using the hydrodynamic analogy is developed. The torsion stiffness of prismatic beams composed of different materials is predicted. The solution is reduced to determining the intensity of the sources and doublets distributed along the outside contour of the beam and the boundaries between the materials. Examples of the numerical results obtained using the developed method are given.

KEY WORDS: theory of elasticity, torsion of prismatic beams, hydrodynamic analogy