Turbulent Flow and Heat Transfer in Rotating Non-Circular Ducts with Nonlinear k-e Model

The turbulent flow through non-circular ducts is complicated by its nature due to the presence of the secondary flow originated at the corners of the duct. Actual operating conditions usually add more complexity to the problem. These non-circular ducts usually have a rectangular cross-section with different aspect ratios. For turbomachinery applications, the flow inside the cooling passages is subjected to Coriolis forces due to rotation. Manufacturing and environmental effects may lead to operation with rough surfaces. The present work is an attempt to numerically investigate the complex flow resulting from rotation, effect of aspect ratio, and wall roughness. Details of the thermal field that is produced in these flows are presented for the first time. Fully developed turbulent flow through rectangular straight cooling passages, stationary and rotating in an orthogonal mode is studied using a nonlinear K-e model. The normal Reynolds stresses are found by the nonlinear model developed by Speziale (1987). Whereas the closure of the energy equation is presented at the two-equation level of turbulence modeling as developed by Nagano and kim (1988). With any buoyancy effect neglected, temperature was considered as a passive scalar. The obtained results contained time-mean velocity, wall shear stresses, time-mean temperature distribution, turbulent heat fluxes and Nusselt numbers. Very good agreement is obtained between the present results and the recently published data (lacovides & Launder, 1991, and Knight et al., 1988).