Developing and fully developed turbulent flow in ribbed channels

Modern turbomachines operate at combustion temperatures well beyond the incipient melting point of the turbine's metal components. Cooling channels within turbine airfoils directly affect component lifecycle in addition to influencing almost all aspects of the overall engine design. However, many aspects regarding flow structure and vortex dynamics within these cooling channels are still unknown. In this study, high fidelity Time Resolved Digital Particle Image Velocimetry (TRDPIV) was used to investigate a ribbed cooling channel. The design consisted of a square channel having square transverse ribs which were staggered on both the top and bottom walls. Rib spacing was matched to the channel height and the rib to channel height ratio was kept constant at 0.13. The Reynolds number range investigated was between 2,500 and 20,000. Flow field measurements were performed at the entrance to and within the developed rib roughened section, corresponding to the 1^st and 12^th ribs. Overall, the results indicate that large scale coherent vortical structures were generated by the presence of the front rib surface and enclosed wake region between the ribs. Higher values of vortex circulation strength were observed for Re=2,500 in addition to a more homogeneous distribution of identified coherent structures at the developed section. In addition to providing insight and feedback for a common turbine cooling design, this study also illuminates the vortex distribution for a highly turbulent and complex internal flow.