The present work is part of a detailed aero-thermal investigation in a model of a rotating internal cooling channel performed in a novel facility setup which allows test conditions at high Rotation numbers (Ro). The test section is mounted on a rotating frame with all the required instrumentation, resulting in a high spatial resolution and accuracy. The channel has a cross section with an aspect ratio of 0.9 and a ribbed wall with 8 ribs perpendicular to the main flow direction. The blockage of the ribs is 10% of the channel cross section, whereas the rib pitch to height ratio is 10. In this first part of the paper, the flow over the wall region between the 6th and 7th ribs in the symmetry plane is investigated by means of two-dimensional Particle Image Velocimetry (PIV). Tests were carried out at a Reynolds number (Re) of 15000 in static and rotating conditions, with a maximum Ro of 0.77. Results are in good agreement with the data present in literature at the same Reynolds number and with Rotation numbers of 0 (static conditions) and 0.38 in a channel with the same geometry as in the present work. When Ro is increased from 0.38 to 0.77, the main velocity and turbulence fields show important changes. At a Rotation number of 0.77, although the extension of the recirculation bubble after the 6th rib on the trailing side does not vary significantly, it covers the full inter-rib area on the leading side in the stream-wise direction. The turbulence intensity on the leading side shows a low value with respect to the static case but roughly at the same level as in the lower Ro case. On the trailing side, the maximum value of the turbulence intensity slightly decreases from Ro=0.38 to Ro=0.77, the wall shear layer is re-stabilized along the second half of the pitch due to the high rotation, and the secondary flows are redistributed causing span-wise vortex compression. The observed result is the rapid decay of turbulent fluctuations in the second half of the inter-rib area.

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