Large-Eddy Simulation of Pulsating Turbulent Flow in a 45-Degree Ribbed Channel

Abstract The structure of oblique ribbed channels is now widely applied in internal cooling of turbine blades, to protect turbine vanes and blades from thermal damage. Despite their ease of manufacturing and excellent performance, it is gradually difficult to adapt to the higher turbine inlet temperature of modern gas turbines. Pulsating flow presents a promising active method to further enhance flow mixing and improve convective heat transfer without increasing coolant usage. This paper presents a numerical investigation of the flow and heat transfer in a 45-degree ribbed channel under both steady and pulsating inflow conditions at a Reynolds number of Re = 12000. Large-eddy simulation, based on the open-source code OpenFOAM-8, is used to simulate turbulent flow characteristics and thermal enhancement as the forcing frequency varies. A precursor simulation method for pulsating inflow is developed to generate inflow turbulence that satisfies spatial and temporal correlations. Flow and heat transfer under steady inflow condition (StF = 0) are firstly discussed. Pulsating flow is then applied at the inlet, with the Strouhal number StF = 0.1 and amplitude A = 0.2. The development of vortices and local Nusselt number is analyzed, while the time-average Nusselt number and thermal performance factor are increased by 4.39% and 2.721% respectively compared with the steady inflow condition. Finally, The enhanced heat transfer mechanism of pulsating flow in the oblique ribbed channel is revealed that pulsating flow enhances the separation flow of each rib in the channel, resulting in an overall increase in the turbulent kinetic energy behind the rib and in the channel.