Unsteady RANS Simulation of Turbulent Flow and Heat Transfer in Ribbed Coolant Passages of Different Aspect Ratios

Abstract The flow and heat transfer in ribbed coolant passages of aspect ratios (AR) 1:1, 4:1, and 1:4 are numerically studied through the solution of the unsteady Reynolds averaged Navier–Stokes (URANS) equations. The URANS procedure, which utilizes a two equation k – e model for the turbulent stresses, is shown to resolve large-scale bulk unsteadiness. The computations are carried out for a fixed Reynolds number of 25,000 and density ratio of 0.13, while the Rotation number is varied between 0.12 and 0.50. At higher rotation numbers (⩾0.5) at least three inter-rib modules are required to ensure periodicity in the streamwise direction. The flow exhibits unsteadiness in the Coriolis-driven secondary flow and in the separated shear layer. The average duct heat transfer is the highest for the 4:1 AR case. For this case, the secondary flow structures consist of multiple roll cells that direct flow both to the trailing and leading surfaces. The 1:4 AR duct shows flow reversal along the leading surface at high rotation numbers. For this AR, the potential for conduction-limited heat transfer along the leading surface is identified. The friction factor reveals an increase with the rotation number, and shows a significant increase at higher rotation numbers (∼ Ro  = 0.5).

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