| Abstract: | The shadow flow pattern behind a horizontal cylinder uniformly towed in a stratified fluid with constant buoyancy frequency (in the imbedded vortex and turbulent wake regime) is recorded synchronously with acoustic echo sounding (basic frequency equal to 1 MHz) in a laboratory tank. Using computer processing, the illumination profiles in the schlieren pattern are constructed on scales comparable with the sounding acoustic ray width. Although the optical and acoustic profiles are not similar, nevertheless they enable the basic structural elements of the wake, including its high-gradient core to be identified, and their time variability traced. The features of the integral acoustic scattering characteristic, in particular, the volume scattering strength, allow this characteristic to be used, together with optical images of the flow pattern, to distinguish the flow regime identification criteria. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 5–17, May–June, 1998. The work was partly financed by the Russian Foundation for Basic Research (projects Nos. 96-05-64004 and 97-01-01013) and by INTAS Grant No. 93-1584. |
