Multivision PIV에 의한 단순물체 후류에서의 유동특성에 관한 연구

Abstract

Time-resolved analyses of the wake characteristics of two-dimensional bluff body flows have been executed by applying the multivision PIV to square prism (angle of attacks:0。, 30。), circular cylinders (rotating speed :0 rpm, 76 rpm) and airfoils (fixed, pitching) submerged in a circulating water channel (Re=10⁴). The macroscopic shedding patterns and their dominant frequencies were discussed in terms of instantaneous velocity, vorticity and turbulent quantities such as turbulence intensity, turbulent kinetic energy and three Reynolds stresses.

In this study, more realistic animation of flow patterns has been exploited by adopting the multivision PIV with three input CCD cameras to obtain an expanded measurement wake region. Quantitative frequency analysis was also carried out with the conventional PIV with single CCD camera.

Particularly, the time-averaged distribution of turbulent intensity in all experimental cases revealed separate island-like small regions where the magnitude of turbulent intensity was always strengthened. The dominant shedding frequencies of the turbulent quantities in the wake regions were two times larger than those of the velocity and vorticity.