Mean Flow and Turbulence Measurements in a Rotating Passage Using a Stationary Fibre Optic LDA Probe

This contribution describes the development of a data collection system in which a stationary fibre optic probe is used to provide LDA measurements for flows through rotating passages. The application of the technique is shown in the investigation of turbulent flow through a U-bend that rotates in orthogonal mode. A stationary 2-channel fibre optic probe is employed to collect instantaneous flow measurements from the rotating test section. The flow Reynolds number is 100,000, and the U-bend curvature ratio is 0.65. Three cases have been examined: flow through a stationary U-bend, flow through a U-bend rotating positively (the trailing side coinciding with the bend outer side) at a rotation number (Ro = ΩD/U _m ) of +0.2, and rotation at a rotation number of −0.2. The resulting measurements produce a detailed mapping of the mean and fluctuating flow fields, which reveal the effects of strong curvature and rotation on the development on turbulent flow.