Effect of Coriolis and centrifugal forces on turbulence and transport at high rotation and density ratios in a rib-roughened channel

Prediction of three-dimensional flow field and heat transfer in a two pass rib-roughened square internal cooling channel of turbine blades with rounded staggered ribs rotating at high rotation and density ratios is the main focus of this study. Rotation, buoyancy, ribs, and geometry affect the flow within these channels. The full two-pass channel with bend and with rounded staggered ribs with fillets (e/Dh=0.1 and P/e=10) as tested by Wagner et al. [J.H. Wagner, B.V. Johnson, R.A. Graziani, F.C. Yeh, Heat transfer in rotating serpentine passages with trips normal to the flow, ASME J. Turbomach. 114 (1992) 847–857] is investigated. Reynolds stress model (RSM) turbulence model is used for this study. To resolve the near wall viscosity-affected region, enhanced wall treatment approach is employed. RSM model was validated against available experimental data (which are primarily at low rotation and buoyancy numbers). The model was then used for cases with higher rotational numbers (0.24, 0.475, 0.74 and 1) and higher density ratios (0.13, 0.23, and 0.3). Particular attention is given to how secondary flow, Reynolds stresses, turbulence intensity, and heat transfer are affected by Coriolis and buoyancy/centrifugal forces, caused by high levels of rotation and density ratios. A linear correlation for 4-side-average Nusselt number as a function of rotation number is derived.