Bateman variational principle for a class of problems of dynamics and stability of surface waves

A generalization is made of the Bateman-Luke principle for the problem concerning acoustic interaction with the free surface of a bounded volume of fluid. Extremal criteria are presented for the stability of capillary-sound equilibrium forms.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 9, pp. 1181–1186, September, 1991.     

A class of boundary value problems in the theory of surface waves

Boundary value problems are formulated concerning characteristic oscillations relative to capillary-sound equilibrium forms and theorems are established concerning properties of spectra of these problems; theorems are also presented concerning stability of the indicated forms of equilibrium.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 3, pp. 359–364, March, 1991.     

Variational formulations of nonlinear boundary-value problems with a free boundary in the theory of interaction of surface waves with acoustic fields

Variational problems equivalent to nonlinear evolutionary boundary-value problems with a free boundary are formulated. These problems arise in the theory of interaction of limited volumes of liquid, gas, and their interface with acoustic fields. It is proved that the principle of separation of motions can be applied to these variational problems. The problem of a capillary-acoustic equilibrium form is given in a variational formulation.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 45, No. 12, pp. 1642–1652, December, 1993.     

Two-dimensional variational vibroequilibria and Faraday’s drops

When contacting with acoustically-vibrated structures a fluid volume can take a [time-averaged] geometric shape differing from capillary equilibrium. In accordance with theorems by Beyer et al. (2001) this shape (vibroequilibrium) furnishes a local minimum of a [quasi-potential energy] functional. The variational problem contains five dimensionless parameters evaluating the fluid volume, the wave number of acoustic field in the fluid domain, the contact angle and two newly-introduced numbers (1, 2) giving relationships between (surface tension, gravitation) and Kapitsas vibrational forces/energy. The paper focuses on negligible small wave numbers (incompressible fluid) and two-dimensional flows. Although the variational problem may in some isolated cases have analytical solutions, it requires in general numerical approaches. Numerical examples simulate experiments by Wolf (1969) and Ganiyev et al. (1977) on vibroequilibria in horizontally vibrating tanks. These show that there appear at least two types of stable vibroequilibria associated with symmetric (possible non-connected) and asymmetric surface shapes. The paper represents also numerical results on flattening and vibrostabilisation of a drop hanging beneath a vibrating plate (experiments by Faraday (1831)).Received: October 17, 2002; revised: June 30, 2003     

Two-dimensional variational vibroequilibria and Faraday’s drops

When contacting with acoustically-vibrated structures a fluid volume can take a [time-averaged] geometric shape differing from capillary equilibrium. In accordance with theorems by Beyer et al. (2001) this shape (vibroequilibrium) furnishes a local minimum of a [quasi-potential energy] functional. The variational problem contains five dimensionless parameters evaluating the fluid volume, the wave number of acoustic field in the fluid domain, the contact angle and two newly-introduced numbers (1, 2) giving relationships between (surface tension, gravitation) and Kapitsas vibrational forces/energy. The paper focuses on negligible small wave numbers (incompressible fluid) and two-dimensional flows. Although the variational problem may in some isolated cases have analytical solutions, it requires in general numerical approaches. Numerical examples simulate experiments by Wolf (1969) and Ganiyev et al. (1977) on vibroequilibria in horizontally vibrating tanks. These show that there appear at least two types of stable vibroequilibria associated with symmetric (possible non-connected) and asymmetric surface shapes. The paper represents also numerical results on flattening and vibrostabilisation of a drop hanging beneath a vibrating plate (experiments by Faraday (1831)).     

Self-adjointness of a certain integrodifferential operator

The self-adjointness of an integrodifferential operator, arising in the theory of stability of capillary-sonic equilibrium forms, is proved.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 42, No. 3, pp. 421–423, March, 1990.