Computation of turbulent flow and heat transfer in rotating Non-Circular ducts

Turbulence modcling and large eddy simulation (LES) have been utilized in the cornpu-t.at.ioll of t.lIn~(~-c1ill1el1siol1al Iu lly developed turbulent flow and heat transfer through a ductof lion-circular cross section. This type of How is charaterized by the presence of turbulence-driven secondary motions ill the plane perpendicular to the streamwise direction. Thesemotion» Sii!:l1ificitlltly modify tho i!:ross Ioaturcs of the main flow.1\. nonliuear K-E model, which is based all nonlinear stress-strain relationships, has beenused as a modcling tool to solve the flow field. This model is capable of predicting theturbulence-driven secondary motions and their effect on main flow field in a considerablyeasier and ”lore ecouom ic way than other models (e.g. algebraic or differential models)which arc of limited practical value due La their need to high computer storage and CPUtime.The closure of the energy equation is presented at the two-equation level of turbulencenioduling. The use of this method has two advantages. First, it has a similar structure asLhe standanl K-( models. Second, 11 value for the turbulent Prandtl number (Prt} need notbe postulated as it is calculated locally during computation.Large eddy simulation (LES) is based on dividing the flow field into two-scales. Thelarge-scale filed is obtained hy the solution of the filtered Navier-Stokcs equations, whereas,I.Iw sll1>-i!:rid scal(~s (SC:S) which are smaller than the grid size arc morlolcd by the dynamiceddy viscosity model.Predictions cover the following cases (for incompressible steady flow):1- Stationary ducts of rectangular cross section for various aspect ratios with and withoutheat. transfer.2- Rotating ducts around an axis perpendicular to the main flow direction for various aspect