Detailed Characterization of Turbulence Intensity and Dissipation As Boundary Condition for 3D RANS Simulations

Abstract

Abstract In the present work, an Hot-Wire Anemometer and a five-hole pressure probe have been used to characterize the incoming flow of a large-scale turbine cascade. Measurements have been carried out to sample the flow in both spanwise and pitchwise directions, hence allowing a complete characterization of total pressure, mean velocity, turbulence intensity, and integral length scale, or dissipation function, of the flow. Distributions here obtained provide a fine characterization of the whole inlet plane. This kind of data will be especially important for properly setting up the boundary conditions of both low (i.e., RANS) and high-fidelity (i.e., LES or DNS) simulations aimed at solving the whole 3D flow field. To further highlight the significance of the present velocity and turbulent profiles, different RANS simulations have been carried out. The first simulation has been carried out with uniform inlet conditions while the second one with measured quantities at a flow Reynolds number equal to 400000. Two additional simulations have been conducted at a lower Reynolds number and turbulence intensity, adopting the typical assumption of uniform turbulence intensity and length scale along the span-wise direction or the more appropriate re-scaled experimental spanwise distributions. The results presented here demonstrate the improved accuracy obtained once the 3D simulations consider the proper distribution along the span, especially at low Reynolds number conditions. To further extend the present results to other simulations, the turbulence spanwise profiles have been normalized with their midspan value and their formulations are here available to the readers. CFD results obtained at the lowest Reynolds number condition show the effectiveness in adopting such re-scaled boundary conditions.