Numerical Calculation of Internal Blade Cooling Using Porous Ribs

The study of flow and heat transfer around and through porous ribs is promising in many industrial applications that require high cooling rates, such as gas turbine blade cooling, or require noise reduction. Turbulent flow in porous media is usually investigated by using macroscopic transport equations, which are obtained by applying double (both volume and Reynolds) averaging to the Navier-Stokes equations. In this study turbulence is represented by using the Launder-Sharma low-Reynolds number k 􀀀 " turbulence model [1], which is modified via proposals by Nakayama and Kuwahara [2] and Pedras and de Lemos [3], for extra source terms in turbulent transport equations to account for the porous structure. Additional refinements are introduced to account for eects close to the porous media/clear fluid interface. In order to investigate the validity of the extended model, two types of porous channel flows have been considered, for which there is available DNS and experimental data. The first case is a fully developed turbulent porous channel flow, where the results are compared with DNS work conducted by Breugem et al. [4] and experimental work conducted by Suga et al. [5]. The second case is a turbulent porous rib channel flow to understand the behaviour of flow through and around the porous rib, which is validated against experimental work carried out by Suga et al. [6]. Cases are simulated covering a range of porous properties, such as permeability and porosity. Through the comparisons with the available data, it has been found that the extended model shows generally satisfactory accuracy, except for some predictive weaknesses in regions of either impingement or adverse pressure gradients.