STUDY OF WINGTIP VORTEX CHARACTERISTICS IN THE FAR-FIELD OF A NACA 0015 AIRFOIL

A study of wingtip vortices is currently underway in Utah State University's 4-ft. x 4-ft. subsonic wind tunnel on a NACA 0015 rectangular wing section. The purpose of this study is to investigate the characteristics of the flow field, which govern the size, the structure, and the oscillatory motion of the vortex core. These characteristics can be obtained by collecting and analyzing accurate velocity measurements at several locations downstream of the wingtip for different Reynolds numbers and angles-of-attack. One triple-sensor and two single-sensor hot wire probes are used to collect the data. The axial velocity profiles generated from the data will help determine how the Reynolds number and angle-of-attack modifies the structure of the vortex core and the conditions that cause it to transition from a "wake-liken to a "jet-like " profile. In addition, the tangential velocity profiles will help determine the effects Reynolds number and angle-of-attack have on the size and strength of the vortex core. In addition, a database of vortex characteristics for varying experimental parameters will be established that will help identify consistent trends in vortex behavior and lead to a better understanding of the governing physics. This database will be used by colleagues to validate and improve their computational algorithms. Nomenclature c =wing cord length [in.] Rec = Reynolds number based on cord length = uoox ul ( = axial velocity [ftls] U oo = freestream velocity [ftls] x = axial (streamwise) coordinate [in.] y = spanwise coordinate (along the wing) [in.] z =normal coordinate (normal to the wing) [in.] a = angle-of-attack [degrees] e = tangential coordinate Ue = tangential velocity [ftls