Analysis of Flow Field Measurements Obtained in a Large Tow Tank Regarding the Decay of Wake Vortices in the Far- Field for Two- and Four-Vortex Systems

Stereo PIV measurements on a 2- and 4-vortex system have been performed in a large tow tank of SVA in Potsdam. The considered 4-vortex system consists of two counter-rotating vortex pairs generated by wings of a span width ratio of b 2 /b 1 = 0.3 and a circulation ratio of Γ 2 /Γ 1 = -0.3. As reference the corresponding 2-vortex system is also considered. A submersible Stereo PIV system attached to a vertical traversing system was employed. Cross-plane velocity fields are obtained of the descending wake vortex system to access the vortex dynamics well into the wake far field (x/b > 500, τ > 11). The spatio-temporal evolutions of the vortex systems are analyzed with respect to the vortex trajectories, circulations and core radii as well as the total kinetic energy contained in the measured flow field.