Carl F. v. Carmer

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.

Evaluation of Large-Scale Wing Vortex Wakesfrom Multi-Camera PIV Measurements in Free-Flight Laboratory

Multiple-vortex systems of aircraft wakes have been investigated experimentally in a unique large-scale laboratory facility, the free-flight B20 catapult bench, ONERA Lille. 2D/2C PIV measurements have been performed in a translating reference frame, which provided time-resolved crossvelocity observations of the vortex systems in a Lagrangian frame normal to the wake axis. A PIV setup using a moving multiple-camera array and a variable double-frame time delay has been employed successfully. The large-scale quasi-2D structures of the wake-vortex system have been identified using the QW criterion based on the 2D velocity gradient tensor ∇H u, thus illustrating the temporal development of unequal-strength corotating vortex pairs in aircraft wakes for nondimensional times tU0∕b≲45.