EXPERIMENTAL STUDY OF FLOW NEAR A HYDROPHOBIC CYLINDER AT HIGH REYNOLDS NUMBERS

An experimental study of vortex structures in the near wake behind a circular microstructured Tefl on cylinder immersed in an oncoming water fl ow was carried out for Reynolds numbers 1.75·10⁵ –2.85·10⁵ using two-dimensional imaging (2D-PIV) of particles in a closed hydrodynamic stand. The results obtained are presented in the form of time-averaged velocity fi elds of fl ow and Reynolds stresses in it. Flow data showed changes in the geometric characteristics and Reynolds stresses of the wake fl ow depending on the Reynolds number in such a way that the studied parameters pass through a minimum in the region of Reynolds number 2.2·10⁵ with subsequent increase. This minimum of wake characteristics is likely to be associated with a crisis in the resistance of the cylinder, but earlier in comparison with a cylinder with a nonhydrophobic surface. A signifi cant increase in the velocity of water fl ow near the side surface of the hydrophobic cylinder was revealed, which at high Reynolds numbers leads to a drop in the static pressure in the fl ow below atmospheric pressure, an increase in the local gas content in it, and to a possible increase in fl ow slip on the cylinder surface.
An experimental study of vortex structures in the near wake behind a circular microstructured Tefl on cylinder immersed in an oncoming water fl ow was carried out for Reynolds numbers 1.75·10⁵ –2.85·10⁵ using two-dimensional imaging (2D-PIV) of particles in a closed hydrodynamic stand. The results obtained are presented in the form of time-averaged velocity fi elds of fl ow and Reynolds stresses in it. Flow data showed changes in the geometric characteristics and Reynolds stresses of the wake fl ow depending on the Reynolds number in such a way that the studied parameters pass through a minimum in the region of Reynolds number 2.2·10⁵ with subsequent increase. This minimum of wake characteristics is likely to be associated with a crisis in the resistance of the cylinder, but earlier in comparison with a cylinder with a nonhydrophobic surface. A signifi cant increase in the velocity of water fl ow near the side surface of the hydrophobic cylinder was revealed, which at high Reynolds numbers leads to a drop in the static pressure in the fl ow below atmospheric pressure, an increase in the local gas content in it, and to a possible increase in fl ow slip on the cylinder surface.
Author:  K. G. Dobrosel′skii
Keywords:  hydrophobic cylinder, PIV, vortex wake, Reynolds stresses
Page:  1262