We present a theoretical basis for a direct method of determining buoyancy period (frequency) as a function of depth by registering the displacements and oscillations of the hydrodynamic wake formed in a stationary liquid by freely ascending bubbles (the density marker method). We achieve an error no greater than 5% by comparing theoretical computations of parameters for internal waves generated by a free submerged than wake having" uniform transverse density distribution in an exponentially strattfied liquid with measurements of internal waves in the liquid. We find that there is a power law for the decrease in amplitude of internal oscillations with time.The distr~ution of the buoyancy frequency (frequency of free internal oscillations) is the most important characteristic of stratified media that significantly affects the structure of hydrodynamic and hydroaconstic fields [1]. In conventional methods the profile of the buoyancy frequency is constructed from density distributions. The density of marine media is computed from measurements of temperature, specific electrical conductivity, and pressure [2], while under laboratory conditions, we measure weight or use refractometrie methods [3]. This procedure contains an uncontrollable error because of indefiniteness in the sampling horizon of the probe and errors in measurement of small density deviations.The direct method for determining the profile of velocity and frequency of buoyancy as a function of depth is based on registration of displacements and oscillations of a density marker -the hydrodynamic wake formed by a freely floating gas bubble [4]. In a quiescent liquid a bubble floats uniformly and reetilinearly if the Reynolds number Re = Vo(2R)h, < 200, i.e., R < < 0.1 em [5] (v o is the rate of rise for the bubble, R is the radius of the bubble, and p is the coefficient of kinematic viscosity). The hydrodynamic flow behind a bubble entails higher density liquid that then slowly sinks and, over an extended period, sustains small-scale internal oscillations. The method has been successfully used in liquids with either linear or arbitrary density profiles. Although it is widely used [6], the empirical data on which the method is based [4] has not yet been provided with the required theoretical basis. In particular, the limiting accuracy for the measurement of buoyancy frequency has not been estimated, nor has it been determined whether this method cart be used to determine other characteristics of the medium. In the present article we compute the parameters of free internal oscillations excited by a freely dropping fine wake with homogeneous transverse density distn'bution in exponentially stratified media, and we will combine the results with measurements of internal waves in the liquid to determine the achievable accuracy of such measurements.In accordance with the usual approach to studying internal waves, the linearized system of hydrodynamic equations in the Boussinesq are reduced to a single equation for vertical displacement ~ of the particles in the...

No abstract

No abstract

No abstract

No abstract