LES and Measurement of Heat Transfer and Flow in Rectangular Channels with Crossed Angled Ribs

Characteristics of fully developed flow and heat transfer in stationary rectangular channels with two opposite ribbed walls, adopted for internal cooling of a gas turbine blade, were investigated by using Large Eddy Simulation (LES) and measurement. Effect of aspect ratio of the channel cross section on the flow and thermal fields in the channels with crossed, 60-deg. angle ribs was studied. The thermo-flow field in the stationary rectangular channels with the crossed angled ribs has a single secondary swirl in the cross sections, which exhibits a basic pattern for convection in the channels with the angled ribs. The aspect ratio was varied from 0.5 to 2.0. The rib height-to-hydraulic diameter and the rib pitch-to-height ratio were kept at 0.075 and 11.547, respectively. Calculations were conducted for Reynolds number based on the hydraulic diameter at around 50 000 and 120 000. The present calculations showed that formation of rib induced separation vortex varies with the channel aspect ratio. The change in the vortex formation has an influence on augmentation of friction and heat transfer. Current correlations for friction and heat transfer agreed reasonably with previous experiments.