Internal wave field generated by a source at rest in a moving stratified fluid

Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 58–61, July–August, 1989.     

Far fields of the surface disturbances produced by a pulsating source in an infinite-depth fluid

The problem of constructing uniform asymptotics for the far fields of surface disturbances produced by a localized pulsating source in a heavy homogeneous infinite-depth fluid is considered. The wave pattern of the excited fields is the sum of waves of two types, namely, annular and wedgeshaped. The solutions obtained describe the wave disturbances far from the pulsating source both inside and outside the Kelvin wave wedges.     

The fields of a line source of current over a stratified conductor

Summary The problem of a line source of alternating current situated over a stratified dissipative medium is theoretically investigated. Special cases of the general solution are studied in detail and several illustrative curves are given. The results have application to stratigraphic investigations of the earth's crust.     

Internal waves generated in an exponentially stratified fluid by an arbitrarily moving source

A theoretical investigation is made into the development of linear internal waves in an exponentially stratified flow of an ideal incompressible fluid in the Boussinesq approximation. The waves are generated by an arbitrarily moving point mass source. The obtained solution is used to investigate three special cases of motion: uniform motion at an angle to the horizontal, nonstationary motion during a finite interval of time, and uniform motion in a circular path. The method of solution of this problem is similar to that used by Wolfe and Lewis [1], who studied the generation of acoustic waves.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 67–74, May–June, 1980.I thank V. V. Sazonov for assistance in the calculations.     

Surface effects of internal wave generated by a moving source in a two-layer fluid of finite depth

IntroductionInternalwaves,whichcanbeexcitedbymanykindsofdisturbancesfromthesurface,bottomorinteriorofastratifiedocean ,suchasthewindstrain ,theflowoverunevenbottomsandthemovingbodyatthesurfaceorunderwater,areremarkablyobviousasthereexistsapycnoclineorathermoclineintheocean[1,2 ] .ThepropagationofgravitysurfacewaveindeepwatergeneratedbyasteadilymovingdisturbanceisrestrictedinaV_shapedregionwithahalfangleθc =19.5°,whichiswell_knownKelvinshipwave[3 ] .Thewaveinducedbyamovingunderwaterobjectisa…     

Turbulent wake in a stratified medium

The problem of determining the form of the turbulent wake being formed behind a selfpropelled body in a medium with density varying in the direction of the effect of gravity is considered. The schematic picture of wake development behind a moving object is the following: Initially, diffusion is identical in all directions, and the wake broadens symmetrically; diffusion becomes strongly anisotropic with recession from the object, it diminishes in the vertical direction under the effect of gravity, and the wake becomes flattened; turbulent mixing within the wake results in the production of a more homogeneous density distribution within the volume occupied by the wake than in the surrounding medium; such a fluid volume turns out to be removed from the equilibrium state and tends to return to the equilibrium state under the effect of gravity; collapse of the wake occurs accompanied by its further expansion in the horizontal direction and the excitation of internal waves.Translated from ZhurnalPrikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 5, pp. 68–72, September–October, 1970.     

Critical flow regime in a stratified medium

The equations for the single-point moments of second order of the velocity and temperature fields closed by means of semiempirical hypotheses are used to investigate the critical flow regime in a stratified medium.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhldkosti i Gaza, No. 2, pp. 156–159, March–April, 1979.     

Generation of internal waves by a turbulent jet in a stratified fluid

The process of generation of internal waves by an initially cylindrical, turbulent jet with a Gaussian profile of the average horizontal velocity component in a fluid with stable linear density stratification is investigated by direct numerical simulation. It is shown that on time intervals Nt < 30, where N is the buoyancy frequency, the vertical velocity pulsations collapse, which is accompanied by the generation of internal waves whose spatial period is close to the wavelength of the spiral mode of jet instability in a homogeneous fluid. The wave dynamics and kinematics can be satisfactorily described by the linear theory for a pulsed source and their parameters are in good agreement with the parameters of the “coherent” internal waves generated by a stratified wake in a laboratory experiment. At large times the wave generation ceases and the variations of the fluid density are localized in the neighborhood of the centers of large-scale vortices formed in the horizontal plane in the neighborhood of the jet.     

Characteristics of ventilating flow generated by a rotating swirler in a vortex vent

A vortex ventilation system with a rotating annular disk installed coaxially with the exhaust inlet is a very effective local ventilator. A swirling flow generated by a rotating swirler makes the ventilation flow concentrated around the axis of rotation, which can increase the ventilation depth by a factor of five compared to a conventional exhaust hood. Despite the well-documented excellent ventilation performance of such a system, detailed flow characteristics are not well understood. In this study, the swirling flow field in the vortex vent was tested, and a number of peculiar flow characteristics were observed. When the rotational speed was varied, a series of different flow patterns appeared, and the changes in the flow pattern showed rapid transition, hysteresis, and flow instability similar to the vortex. The transition of the flow pattern could be explained based on the ratio of the centrifugal force to exhaust pressure. Hysteresis of the flow transition occurred in an unstable equilibrium mode between the two forces, and an unstable flow pattern occurred when the secondary recirculating flow was located beneath the swirler. A formula for the critical rotational speed was derived, which showed satisfactory agreement with experimental observation.     

Internal waves generated by a moving sphere and its wake in a stratified fluid

The internal gravity waves and the turbulent wake of a sphere moving through stratified fluid were studied by the fluorescent dye technique. The Reynolds number Re=U·2a/v was kept nearly constant at about 3 · 10³ and the Froude number F;U/a N ranged from 0.5 to 12.5. It is observed that waves generated by the body are dominant only when F<4 and are replaced by waves generated by the large scale coherent structures of the wake when F>4.     

Self-similar implosion of a continuous stratified medium

Abstract. The subject of this paper is the non perturbed self-similar implosion of a continuous stratified medium in cylindrical and spherical geometry. The main contribution is twofold. The first one is a condition on the initial density profile which guarantees that the integral of the internal energy over a fixed volume stays finite at the collapse. The second one is the proof that the self-similar implosion model partly restitutes the dynamics of an experiment of cylindrical implosion. Numerical values of the self-similar parameter are also given for various kind of stratified media in the two geometries. Received 8 March 1999 / Accepted 9 April 2001     

Influence of a floating elastic plate on the surfaceeffects of internal waves generated by motion of a source in a non-homogeneous liquid

Perturbations of the surface of an exponentially stratified liquid of finite depth, free or covered by an elastic plate, are studied on the assumption that the perturbations are caused by internal waves generated by the steady motion of a constant -intensity source. The dependence of the spatial distribution of perturbations on the plate properties, velocity and the submersion depth of the source is considered.Sevastopol. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, pp. 118–125, March–April, 1995.