Influence of the Local Cross-Streamlined Obstacles on the Velocity and Pressure Fluctuations

Background. Developing means to enhance the effectiveness of mass and heat transfer processes on streamlined surfaces and their hydroacoustic qualities in the objects of power, aerospace and marine engineering. Objective. The purpose of the research is to determine the formation features and space-time characteristics of the velocity and wall-pressure fluctuation fields in flows above and on the streamlined surfaces with local obstacles as the cross-streamlined half-cylindrical trench on a flat surface and circular obstacle on the flexible longitudinal hydroacoustic antenna surface. Methods. The research was carried out by means of hot-wire and hydroacoustic measuring in flows on streamlined obstacles and spectral analysis of statistical characteristics of the velocity and wall-pressure fluctuations in investigating systems. Results. It has been determined experimentally the zones and conditions of vortices formation by various frequency ranges, the extremes of power spectrum densities of the velocity and wall-pressure fluctuations, vortex interaction, ejections and stalls near streamlined surfaces with local obstacles at rather wide Reynolds number ranges. Conclusions. Basing on received space-time characteristics of the velocity and wall-pressure fluctuations and discovered typical features of their spectra the hydromechanical mechanisms of heat and mass exchange and hydroacoustic processes in the investigated systems have been determined. The results of the study can be used for designing of such systems and they reveal the perspective of directed control by mentioned processes for increase of their efficiency.