Effects of rotation on flow in an asymmetric rib-roughened duct: LES study

We report on large-eddy simulations (LES) of fully-developed asymmetric flow in a duct of a rectangular cross-section in which square-sectioned, equally-spaced ribs oriented perpendicular to the flow direction, were mounted on one of the walls. The configuration mimics a passage of internal cooling of a gas-turbine blade. The duct flow at a Reynolds number Re=15,000 (based on hydraulic diameter D-h, and bulk flow velocity U-0) was subjected to clock-wise (stabilising) and anti-clock-wise (destabilising) orthogonal rotation at a moderate rotational number Ro = Omega D-h/U-0 = 0.3, where Omega is the angular velocity. The LES results reproduced well the available experimental results of Coletti et al. (2011) (in the mid-plane adjacent to the ribbed wall) and provided insight into the whole duct complementing the reference Ply measurement. We analyzed the effects of stabilising and destabilising rotation on the flow, vortical structures and turbulence statistics by comparison with the non-rotating case. The analysis includes the identification of depth of penetration of the rib-effects into the bulk flow, influence of flow three-dimensionality and the role of secondary motions, all shown to be strongly affected by the rotation and its direction. (C) 2015 Elsevier Inc. All rights reserved.