Effect of Large-Amplitude Internal Waves on Towed Hydrodynamical Depressor

Abstract

The effect of intense internal waves on towed hydrodynamical depressor is considered on the basis of observations carried out at Mascarene Ridge in the Indian Ocean. Mascarene Ridge belongs to the regions of the World Ocean where internal waves of record (100 m or more) amplitudes are observed. For a few days the research vessel «Academician Nikolay Andreyev» had been carrying out comprehensive studies of internal waves in this area, which were based on towing line temperature sensors. Cross-sections of internal waves for both cases for coinciding with direction of their propagation and for opposite tacks were performed. It was revealed that due to strong orbital currents, accompanying internal waves, a towing depressor made significant vertical dislpacements synchronoused with crossing internal waves. Vertical displacements of the depressor reached as much as 3—11 m during crossing internal waves which amplitudes were in frame of 10—80 m. Examples of manifestations of this effect, as in the case of solitary waves and packets of short-period internal waves are presented. The equations of linear regression, relating the vertical displacement of the depressor with heights of internal waves causing them are obtained. This effect is important for any towed and selfmoving underwater object. At the present time, when the practice of ocean and marine research includes active using underwater unmanned and manned vehicles, it is necessary to take into account the difficulties that may arise during their meeting with the internal waves of large amplitudes.