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Turbulent free convection of liquid sodium in a straight thermally insulated tube with a length equal to 20 diameters and with end heat exchangers ensuring a fixed temperature drop is investigated exper imentally. The experiments are performed for a fixed Rayleigh number Ra = 2.4 × 10 6 and various angles of inclination of the tube relative to the vertical. A strong dependence of the power transferred along the tube on the angle of inclination is revealed: the Nusselt number in the angular range under investigation changes by an order of magnitude with a maximum at the angle of 65° with the vertical. The characteristics of large scale circulation and turbulent temperature pulsations show that convective heat transfer is mainly determined by the velocity of large scale circulation of sodium. Turbulent pulsations are maximal for small angles of incli nation (α = 20°-30°) and reduce the heat flux along the channel, although in the limit of small angles (ver tical tube), there is no large scale circulation, and the convective heat flux, which is an order of magnitude larger than the molecular heat flux, is ensured only by small scale (turbulent) flow.

The energy and force characteristics of periodic internal wave beams in a viscous exponentially stratified fluid are analyzed. The exact solutions of linearized problems of generation obtained by integral transformations describe not only three-dimensional internal waves but also the associated boundary layers of two types. The solutions not containing empirical parameters are brought to a form that allows a direct comparison with experimental data for generators of various types (friction, piston, and combined) of rectangular or elliptic shape. The stress tensor and force components acting on the generator are given in quadratures. In the limiting cases, the solutions are uniformly transformed to the corresponding expressions for the problems in a two-dimensional formulation.Introduction. Internal waves, which play an important role in the dynamics of the ocean, atmosphere, and other stratified media, have been studied analytically [1], numerically, and experimentally under laboratory and natural conditions. In analytical calculations of wave fields, the real boundary conditions on the generators are simulated by sets of singular sources, whose properties are postulated [2] or borrowed from ideal fluid theory [3]. In an analysis of the perturbations induced in a fluid by a horizontal cylinder which performs rectilinear or torsional oscillations of small amplitude, the parameters of the wave beams and boundary layers are calculated separately [4,5]. The results obtained, which are used to determine the regions of applicability of asymptotic approximations, are usually given in integral form [4,5], which prevents their practical application.Accounting for all roots of the dispersion equation allows one to simultaneously calculate the parameters of two-dimensional internal waves and associated boundary layers [6]. The results of such calculations agree with experimental data [7]. The approach proposed in [6] extends the classical Stokes method [8] to inhomogeneous media. The satisfaction of the exact boundary conditions allows one to calculate both the waves and the fine structure of the boundary layers resulting from linear oscillations of segments of a flat surface in arbitrary directions. The nonlinear problem of wave generation by the boundary layers on a disk performing torsional oscillations is considered in [9].In the case of three-dimensional motion, the boundary layer on the oscillating part of the plane is more complex and includes an analog of the Stokes layer in a homogeneous fluid and a special inner boundary layer [10]. The method of constructing the solution [9] is fairly universal and suitable for calculating flows for more complex motions of the wave-generating surfaces used in experiments to increase the wave amplitude. The goal of the present study is to estimate the dynamic characteristics of beams of three-dimensional periodic internal waves generated by sources of various shapes. Governing Equations and Boundary Conditions.We study steady-state cyclic motion in a viscous incompressible exponen...