Hydrodynamic fluctuations of liquids with internal rotation inside a pore

Abstract

The correlation theory of the thermal hydrodynamic fluctuations of liquids with internal spin within a spherical cavity is developed. For the hydrodynamic fields of such a liquid, linearized equations with random thermal sources are used. For the time dependent amplitudes of the expansion of the fields in the basis functions of the vector Helmholtz equations a set of Langevin equations is obtained that allowed us, with the help of the fluctuation-dissipation theorem, to find the spectral densities of the correlation functions of the amplitudes. The spectra of the fluctuations of hydrodynamic fields are found in the form of a superposition of spectral amplitudes of the expansion with weights expressed as bilinear combinations of the proper coordinate functions and their derivatives. The correlation functions of the field of the translational velocity and internal spin of the liquid in one spatial point are analyzed. They have a sense of local coefficients of the translational and rotational diffusion coefficients of the Lagrange particle. We represent them as a series in spherical Bessel functions and roots of transcendental equations following from the boundary conditions on the sphere. The results demonstrate that the size of the pore essentially affects the character of the hydrodynamic fluctuations of the liquid.