3D-PTV measurements of the wake of a sphere

3D-PTV measurements were conducted on the wake of a sphere. The Reynolds number is 1130 with diameter d = 30 mm. The measurement system consisted of three CCD cameras, an image grabber, an Ar-ion laser and a host computer. Structural analysis was adopted for the analysis on the wake using the obtained velocity profiles. Statistical turbulent properties were quantitatively clarified using the time-consecutive instantaneous three-dimensional vectors obtained by the 3D-PTV system. The spatial velocity profiles of the sphere wake seemed to have a strong relationship with the spiral motion of the vortices that were shed from the surface of the sphere.