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The problem of the hydrodynamic interaction taking place between the profiled plates of a (turbine) cascade is considered. This problem has hitherto been little studied — existing papers [1, 2] consider the model of effectively steady-state flow, the flow of the liquid at any instant of time being regarded as free from eddies, while time plays the part of a parameter; however, under practical conditions the field of velocities around moving cascades changes rapidly with time, so casting doubt on the validity of the steady-flow mode. The model proposed in this paper allows for high-frequency pulsations in the flow. The approximate solution here derived determines the interference between the profiles on the basis of a limiting solution with infinitely large Strouhal numbers. A typical calculation is presented.

A system of integral equations is obtained for the tangential components of the velocities on the upper and lower surfaces of a profile which does not have a parametric singularity connected with the thickness of the airfoil. An example of the solution of these equations by the discrete vortex method is given. This shows that they are highly effective for solving problems of flow over an airfoil of any, including arbitrarily small, thickness.

Forced vibrations of an elastic wing are investigated. The main attention is devoted to the solution of the problem for Strouhal number k ~ 1. It is shown that an elastic wing makes it possible to obtain high efficiencies and high thrust coefficients in a wide range variation of the Strouhal number. The maximum of the thrust is usually achieved near resonance, while the maximum of the efficiency is achieved in a different regime, which is determined by the parameters of the vibrating system.

Sedov's equations [1], which make it possible to calculate the total hydrodynamic reactions exerted by an ideal fluid on an oscillating profile, are well known. These equations are expressed by contour integrals containing the complex potential of the unsteady flow past the profile. Certain modifications of these equations are proposed in paper [2]. In this paper, other equations are proposed for the calculation of the same quantities, based on the specification of the tangential velocity component of the fluid along the contour of the oscillating profile. In a number of cases, the application of these equations can be more useful than that of Sedov's equations.

Shock waves are formed in the channels between blades in a compressor working in the transsonic state, and the positions of these vary periodically and produce strong vibrations in the blades. The effect is extremely complex and is dependent on a large number of parameters. Here we present a simplified model for the effect, which can be examined theoretically. It is assumed that the nonstationary pulsations in the flow and the amplitudes in the oscillations of the shock waves are small, and therefore one can employ a steady-state flow whose characteristics may be taken as given, including the mean position of the shock waves.

The influence of flow nonuniformity on the aerodynamic characteristics of profiles in a cascade has been studied in [1, 2, 3]. In these studies the general problem was separated into two independent problems: first, uniform flow of a fluid about a cascade of oscillating profiles disturbed only by the cascade and second, flow of a nonuniform stream past a cascade of stationary profiles. This separation is possible within the framework of linear theory, in which the nonuniformity of the flow approaching the cascade and the profile vibration amplitudes are sufficiently small. However, the order of smallness of these two factors is different, which often leads to consideration of the influence of flow nonuniformity on the unsteady aerodynamic characteristics of the oscillating profiles. This investigation concerns that problem. In particular, certain conditions of flow nonuniformity, giving rise to parametric resonance of turbomachinery blades, are discussed.

The apparent masses of a plane lattice of plates in an incompressible fluid were determined by Gurevich (for the case of cophased translational vibrations [1]) and by Samoilovich (for cophased and antiphased translational and torsional vibrations of plates [2]). However, in a number of applications it is necessary to calculate apparent masses both for more complex forms of vibrations and also for different values of the phase shift between the vibrations of neighboring plates. In the present paper we present a calculation algorithm for the apparent masses of the lattice of plates that vibrate according to an arbitrary law with a constant phase shift between the vibrations of neighboring plates. The forms of the vibrations are approximated by trigonometric polynomials, which allows us to represent the apparent masses in the form of series in some standard coefficients. Results are given for the calculation of these coefficients over a wide range of variations of thickness, stagger, and phase shift.

The general solution for the problem of three-dimensional gas flow through a cascade of plates was obtained in [1], It is shown below that in the considered direct and inverse aerodynamic problems there may exist nontrivial solutions for uniform boundary conditions. The flow regimes for which such solutions exist may be treated as aerodynamic resonance.

The supersonic unsteady flow of a gas past a lattice of thin, slightly curved profiles has been investigated in several studies. The paper [1] is devoted to an evaluation of the effect of wind tunnel walls on the unsteady aerodynamic characteristics of a profile, and [2] investigates the effects of the boundaries of a free jet. These cases are equivalent respectively to the anti-phase and in-phase oscillations of the profiles of an unstaggered grid. In [3] consideration is given to a more general case of gas flow past a profile in a wind tunnel with perforated walls. Flow past a lattice of profiles with stagger is studied in [4], where the magnitude of the stagger angle is limited by the condition that the lattice leading edge is located in the undisturbed stream.

The transonic unsteady flow of a gas through a cascade of thin, slightly curved plates is quite complex and has received little study. The main difficulties are associated with the nonlinear dependence of the aerodynamic characteristics on the plate thickness. In [1] it is shown that, for a single thin plate performing high-frequency oscillations in a transonic gas stream, the variation of the unsteady aerodynamic characteristics with plate thickness may be neglected. For a plate cascade, the flow pattern is complicated by the aerodynamic interference between the plates, which may depend significantly on their shape. A solution of the problem of transonic flow past a cascade without account for the plate thickness has been obtained by Hamamoto [2].

A novel method to determine independent yields in proton induced fission employing ion counting after a Penning trap has been developed. A satisfactory agreement with previous measurements was found for independent yields of Cs isotopes in 50 MeV proton induced fission.

Abstract.: A novel method to determine independent yields in proton induced fission employing ion counting after a Penning trap has been developed. A satisfactory agreement with previous measurements was found for independent yields of Cs isotopes in 50 MeV proton induced fission.

A novel method to determine independent yields in proton induced fission employing ion counting after a Penning trap has been developed. A satisfactory agreement with previous measurements was found for independent yields of Cs isotopes in 50?MeV proton induced fission.