Influence of Renolds number on generation and decay of aircraft wakes: Experimental investigation using generic models, F13 and F13X

Abstract

The development of multiple-vortex wake systems in the far field of a generic aircraft model is assessed by evaluation of experimental data obtained from MonoPIV measurements in the large towing tank facility of the Hamburg Ship Model Basin (HSVA). In the selected experimental configurations DLR's F13X vortex generator has been operated at two geometrical configurations for three different chord-based Reynolds numbers. From the tips of the rectangular main wing a 2-vortex system shed off, and adding a horizontal tail plane to the vortex generator produced a 4-vortex system of two unequal-strength counter-rotating vortex pairs. The 2-vortex systems showed a gradual decay, its characteristic parameters have been evaluated well into the wake far field up to vortex ages of 4.5 without providing any evidence for cooperative long-wavelength instabilities. Contrarily, for the same Re_c the counter-rotating vortex pairs of the 4-vortex systems underwent short-wavelength instabilities in the extended near field leading to a strong vortex interaction and rapid threedimensional reorganization. After the 'catastrophic event' only a weak 2-vortex systemremained that gradually decayed. Comparing the development of different 2-vortex systems in the given range of Re_c, the behavior in the far field is Re_c invariant. Also for the 4-vortex systems no distinct indication has been found for a significant Re_c dependance.