Abstract
The objective of this study is to experimentally investigate the effects of the orbital velocity on the boundary layer flow over a rotating disk under orbital motion. The disk diameter is 300 mm, and the orbital radius is one third of the disk radius (50mm). The velocity field in the boundary layer flow is measured by the hot-wire anemometers. The effects on the transition Reynolds number from a laminar flow to a transition flow and the turbulent transition Reynolds number are shown by comparing the mean tangential velocity profiles. It is found by the frequency analysis of tangential velocity fluctuations that when the orbital velocity is more than +300 rpm, or when the ratio of the orbital velocity and the rotational velocity is 1/6 or more, in the case of coinciding rotating and orbiting direction, the generation of transient vortices is suppressed. However, in the case of the opposite direction, the transient vortices still exist even though the ratio of the orbital velocity and rotational velocity is 1/6 or more.
