Vortex diffraction on a swept wing

The forces acting on a swept wing in the presence of a vortex induced by a delta wing, as well as the velocity field in the vicinity of the swept wing, have been measured. By means of the “frozen,” vortex model and a specially-developed numerical panel method, the forces and moments acting on the wing are calculated from the known velocity field. Comparison of the calculated and measured force characteristics makes it possible to determine the extent to which the model fits the physical flow pattern. It is shown that for the intense vortex considered in this study the model gives results which disagree sharply with the experimental data. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 6, pp. 98–105, November–December, 1998. The study was supported by the International Scientific and Technical Center under grant No. 201.     

Inverse problem of wing aerodynamics in a supersonic flow

The inverse problem of wing aerodynamics—the determination of the lifting surface shape from a specified load—is solved within the framework of linear theory. Volterra's solution of the wave equation is used. Solutions are found in the class of bounded functions if certain conditions imposed on the governing parameters of the problem are satisfied. Solutions of inverse problems of supersonic flow are presented for an infinite-span wing, a triangular wing with completely subsonic edges, and a rectangular wing. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 3, pp. 86–91, May–June, 1998.     

Delta wing in a subsonic flow

On the basis of experimental wind tunnel research, a topological classification of possible delta wing flow regimes is given and a diagram in angle of attack-sweep angle coordinates is constructed. A regime with two pairs of symmetrically disposed whirlwind like vortices formed on the surface of the wing is detected. The effect of the V-shape of the wing is considered. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.2, pp. 161–164, March–April, 1994.     

Evolution of disturbances in a laminarized supersonic boundary layer on a swept wing

Experimental data on stability of a three-dimensional supersonic boundary layer on a swept wing are presented. The experiments are performed on a swept wing model with a lenticular profile with a 40° sweep angle of the leading edge at a zero angle of attack. The supersonic boundary layer on the swept wing was laminarized with the use of distributed roughness. A pioneering study of interaction of traveling and stationary disturbances is performed. Some specific features of this interaction are identified. The main reason for turbulence emergence in a supersonic boundary layer on a swept wing is demonstrated to be secondary crossflow instability. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 2, pp. 40–46, March–April, 2008.     

Influence of intense surface cooling on hypersonic viscous flow past a delta wing

The influence of intense surface cooling on the parameters of a laminar boundary layer flow on a thin delta wing in a hypersonic viscous perfect-gas stream is studied for the strong viscous-inviscid interaction regime. The effect of the power-law shape of the wing cross-section and the wing thickness to boundary-layer displacement thickness ratio on the local and total aerodynamic characteristics is numerically investigated. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 4, pp. 57–64, July–August, 1998.     

Analogy between a flapping wing and a wind turbine with a vertical axis of revolution

Based on an analysis of available experimental data, the hypothesis about an analogy between a flapping wing and a wind turbine of the Darrieus rotor type is justified. It is demonstrated that the torque on the shaft of the Darrieus rotor is generated by thrust forces acting on the blades in a pulsed flow. A conclusion is drawn that it is necessary to perform aerodynamic calculations of blades on the basis of the nonlinear theory of the wing in an unsteady flow with allowance for the airfoil thickness. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 2, pp. 152–155, March–April, 2009.     

Waveriders of complicated shape

The shape of a waverider formed by streamsurfaces behind oblique shocks and rarefaction waves is complicated by equipping the lifting body with a wing and fins. The joining of the wing to the body and the possibility of reducing the wave drag are considered. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 4, pp. 158–165, July–August, 1998.     

Origin of instability waves in a boundary layer with moderate free-stream turbulence

The characteristics of the transition mechanism in the boundary layer on a wing section are experimentally investigated for moderate free-stream turbulence. It is shown that the frequency and wavelength of the instability depend on the thickness of the boundary layer in the region of the point of inflection on the average velocity profile. Novosibirsk. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 49–54, January–February, 1994.     

Decrease in the wave resistance of the combination of a body of revolution with a wing in a supersonic gas stream

A method is proposed for making more accurate the results of the linear theory for the determination of the optimal shapes of wing—fuselage combinations in supersonic flight in the case when there is no lift and the shape of the wing and the base area of the fuselage are given.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 163–167, May–June, 1981.     

Solution of the problem of optimal cut in an elastic beam

The Kirchhoff model of an elastic beam with a transverse cut is considered. The nonpenetration condition proposed by A. M. Khludnev is formulated at the edges of the cut. The equilibrium model of a beam with a restriction on the cut is written in the form of a variational inequality. An analytical solution is obtained with the use of the projection operator. The problem of choosing optimal cuts is formulated for the criterion of minimum opening. Conditions for determining the extremum shapes of the beam are obtained and an example of the solution of the problem is given. Lavrent’ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 5, pp. 149–157, September–October, 1999.     

To formulating a nonlinear initial-boundary problem of an unsteady separated flow around an airfoil

A general formulation of a nonlinear initial-boundary problem of an unsteady separated flow around an airfoil by an ideal incompressible fluid is considered. The problem is formulated for a complex velocity. Conditions of shedding of vortex wakes from the airfoil are analyzed in detail. The proposed system of functional relations allows constructing algorithms for solving a wide class of problems of the wing theory. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 2, pp. 48–56, March–April, 2007.     

Aeroelastic stability of a wing with bracing struts (Keldysh problem)

The problem of the influence of bracing struts of two types on the aeroelastic stability of a wing is studied. The formulation of the problem follows that considered by M. V. Keldysh [1]. The behavior of the eigenvalues is studied in the complex plane and the stability, flutter, and divergence domains are constructed. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 151–162, January–February, 1998.     

Experimental study of laminar-turbulent transition on a swept wing with local boundary-layer suction at subsonic velocities

The effect of local suction of the boundary layer gas near the leading edge of the upper surface of a swept wing (with the sweep anglex=35°) on the extent of the laminar flow region is studied on a large half-model at subsonic velocities. Various experimental methods were used. The data are subjected to a comparative analysis. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 4, pp. 65–73, July–August, 1998.     

Thin airfoils of minimum wave drag with given chord, longitudinal section area, and lift

The problem of profiling optimal airfoils at small incidence in a supersonic stream in order to achieve the minimum wave drag coefficient for given chord, longitudinal section area, and lift coefficient is studied. It is demonstrated that a trailing flat end face plays an important role even for very thin airfoils. Moscow, Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 4, pp. 153–157, July–August, 1998. The study was carried out with the support of the Russian Foundation for Basic Research (project No. 96-01-01825).     

Effect of the density of twinning dislocations on the configuration of stress fields near a wedge twin with different shapes of the boundaries

The effect of changes in density of twinning dislocations on one boundary of the wedge twin on the configuration of the stress fields generated by the latter is considered on the basis of a macroscopic dislocation model. Specific features of violation of symmetry of the stress-field distribution near the wedge twin with different shapes of the boundaries are demonstrated for the case of different densities of twinning dislocations on the twin boundaries. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 5, pp. 199–204, September–October, 2008.     

Vortical structures on a flapping wing

A wing in the form of a rectangular flat plate is subjected to periodic flapping motion. Space–time imaging provides quantitative representations of the flow structure along the wing. Regions of spanwise flow exist along the wing surface; and depending on the location along the span, the flow is either toward or away from the tip of the wing. Onset and development of large-scale, streamwise-oriented vortical structures occur at locations inboard of the tip of the wing, and they can attain values of circulation of the order of one-half the circulation of the tip vortex. Time-shifted images indicate that these streamwise vortical structures persist over a major share of the wing chord. Space–time volume constructions define the form and duration of these structures, relative to the tip vortex.     

Determination of the aerodynamic characteristics of aircraft in the transonic velocity range

The problem of determining the integral aerodynamic characteristics of aircraft as a whole in the transonic velocity range is considered. An approximate method of their calculation is developed using the nonlinear transonic theory of small perturbations for three-dimensional flow over a body. The method of investigation consists in separating the flow region into two subregions (outer and inner), applying numerical methods of integrating the equations in those regions, and joining the solutions. The Murman-Cole method of calculating the pressure drag of an isolated wing is generalized to the case of a combination of wing and fuselage. Central Aerohydrodynamics Institute, Zhukovskii 140160. Translated from Prikladnaya Mekhanika i Tekhnicheskaya fizika, Vol. 39, No. 4, pp. 91–101, July–August, 1998.     

Rebounding of a shaped-charge jet

The phenomenon of rebounding of a shaped-charge jet from the armour surface with small angles between the jet axis and the target surface is considered. Rebounding angles as a function of jet velocity are obtained in experiments for a copper shaped-charge jet. An engineering calculation technique is developed. The results calculated with the use of this technique are in reasonable agreement with experimental data. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 5, pp. 17–20, September–October, 2007.     

On the mechanism of turbulence suppression by spanwise surface oscillations

The attenuation of turbulent pulsations in near-wall flows by means of spanwise periodic surface oscillation is examined. A direct numerical simulation of the flow in a circular pipe with imposed rotational oscillations has shown that for Re=4000 and the optimal oscillation frequency, the degree of turbulence attenuation increases with increase in the oscillation amplitude until the flow relaminarizes. The estimated optimal frequency ω⁺=0.06. The results of applying the theory of the development of near-wall coherent structures agree qualitatively with those of numerical simulation. It is concluded that the intensity of the pulsations is reduced because the spanwise movements weaken the longitudinal vortices which cause turbulent bursts in near-wall flows. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, pp. 37–44, March–April, 2000. The research was carried out with financial support from the Russian Foundation for Basic Research (project No. 99-01-01095).     

Controlling buffet through local mechanical action and heat addition near a lambda-shaped shock

Unsteady transonic flow past a two-dimensional airfoil with heat and momentum addition is numerically investigated. The flow analysis is based on the solution of the unsteady Reynolds equations closed by the k-ω SST turbulence model. The equations are integrated using the finite volume method. Several positions and shapes of the heat and momentum addition zones are considered for the purpose of determining an optimal means for controlling buffet. It is established that the most considerable variations in the buffet parameters are achieved when heat addition and mechanical action are realized on the upper wing surface. The thermal energy supply always increases the buffet frequency, while the mechanical action can both increase and reduce it.