The Experimental Investigation of HLFC-System Use on the Swept Wing at Subsonic Velocities

Carried out in the TsAGI T-107 subsonic wind tunnel (test section diameter dw.t. = 2.7 m.) has been the experimental investigation of subsonic flow (M = 0.2-0.74; Re = 3.3· 10⁶ -9.4· 10⁶) about a large-scale half-model (span 1.67 m, chord 0.73 m) of a swept untapered wing ( x= 35°, η= 1, c̄= 9.8%) equipped with a local boundary-layer suction system (x̄s= 0.03-0.11). Based on a measured pressure distributions, angles of attack were selected (α = -2° and -4°) to be rational from the standpoint of cross-flow disturbance's development. The extent of the laminar flow zone was determined through various methods. Based on the losses of the total pressure measured in the wake behind the mid-section of the swept portion of the model, the decrease in the section drag was estimated due to local boundary-layer suction. Several laws and suction rates as well as the chordwise extents of the suction region were tested with the aim of obtaining a maximum decrease in the section drag of the swept wing.