A new set-up for Ply measurements in rotating turbulent duct flows

A novel set-up designed for flow visualizations and turbulence measurements in rotating high-aspect-ratio ducts has been described. The 8 m long duct was placed across a 13 m diameter turntable and the setup enabled stereoscopic Ply-measurements over a wide range of rotation numbers Ro 2 Omega 2H/U <= 0.80. Measurements of all three components of the instantaneous velocity vector were made in a plane spanning the channel from the pressure to the suction side. Together with the mean flow characteristics, the important turbulence statistics, such as all components of the Reynolds stress tensor and the spanwise component of the vorticity field, were obtained and compared to DNS results. The field measurements provided more details about the flow than earlier experimental studies of turbulent flows in rotating ducts. The overall observation was that the Coriolis force due to the imposed system rotation damped the turbulence level along the suction side whereas an augmentation of the turbulent agitation was found at the pressure side of the rotating channel. These findings are fully consistent with data from earlier DNS studies. The same set-up can readily be used to explore the influence of rotation on internal flows with separation bubbles provoked by massive obstructions, for instance turbulent flows over a backward-facing step or in ducts with transverse ribs of various shapes. (C) 2010 Elsevier Ltd. All rights reserved.