Session Ca - Turbulent Jets & Wakes.
ORAL session, Sunday, November 23
301, Moscone Center
(Supported by Allison Engine Company) Multiple jets in crossflow are commonly used in gas turbine film cooling applications. The various structural features such as the pair of counter-rotating ``kidney'' vortices influence the coolant jet trajectory and consequently its film cooling effectiveness. Although the canonical isolated round jet in crossflow has been studied for the past 60 years, the origin and dynamics of the complex flow structures are not yet completely understood. The problem is compounded when multiple jets interact. This study utilized a single row of five jets separated in the spanwise direction by three jet diameters, which were injected into a crossflow at 35 degree inclination. Among the parameters studied were velocity ratio (0.5 to 1.5), hole length-to-diameter ratio (1 to 3) and plenum flow characteristics. Flow visualization employing high-speed cinematography and surface streak topology were combined with hot-wire velocity measurements and computational results to investigate the various structural flow features. The flow physics of the structural features of the jet are explained and their implication for the technological problem of film cooling are discussed.