Experimental Investigation of the Confluent Boundary Layer of a High-Lift System

A fundamental experimental investigation is described of the structure and streamwise development of a confluent boundary layer generated by the interaction of a leading-edge slat wake with the turbulent boundary layer on the main element of a multi-element airfoil model. The slat and airfoil model geometry are both fully two dimensional. The research is performed in an attempt to investigate the flow physics of confluent boundary layers and to build an archival database on the interaction of the slat wake and the main element wall layer. In addition, an attempt is made to identify clearly the role that slat wake/airfoil boundary-layer confluence has on lift production and how this occurs. Although complete laser Doppler velocimetry flow surveys were performed for a variety of slat gap and overhang settings, the focus is on two cases representing both strong and weak wake boundary-layer confluence. For those interested in performing numerical simulations, the full database is available from the authors.