Print Email Facebook Twitter Three-dimensional flow and load characteristics of flexible revolving wings Title Three-dimensional flow and load characteristics of flexible revolving wings Author van de Meerendonk, R. (TU Delft Aerodynamics) Perçin, M. (Middle East Technical University) van Oudheusden, B.W. (TU Delft Aerodynamics) Date 2018-10-01 Abstract The flow field and fluid-dynamic loads of revolving low-aspect-ratio chordwise-flexible wings are studied experimentally at a Reynolds number of 10,000. The investigation involves phase-locked tomographic particle image velocimetry (PIV) complemented with force measurements. The pressure fields are reconstructed from the three-dimensional velocity fields in a complete volume around the wing. For decreasing flexural stiffness, the coherence of this vortex system and spanwise transport of vorticity along the axis of the leading edge vortex (LEV) increase, which contribute to the stability and retention of the LEV. As the LEV low-pressure region becomes smaller with increasing flexibility, the total force on the wing is reduced, while it is tilted towards the lift direction due to the wing deformation. As a result, the drag is significantly suppressed, while the lift remains relatively high. Consequently, the lift-to-drag ratio increases with increasing flexibility and correlates well with the geometric angle of attack. While the sectional lift along the full span is comparable for the different wings, the sectional drag is significantly reduced at the outboard wing for increasing flexibility. The centroids of lift and drag are located at approximately 70% of the span for all wings throughout the complete revolving motion. Finally, the process of vortex breakdown is found to be related to the formation of a positive spanwise pressure gradient. To reference this document use: http://resolver.tudelft.nl/uuid:631d7f78-d126-45d6-b489-9baaff36bd8e DOI https://doi.org/10.1007/s00348-018-2613-1 ISSN 0723-4864 Source Experiments in Fluids: experimental methods and their applications to fluid flow, 59 (10) Part of collection Institutional Repository Document type journal article Rights © 2018 R. van de Meerendonk, M. Perçin, B.W. van Oudheusden Files PDF 10.1007_s00348_018_2613_1.pdf 15.3 MB Close viewer /islandora/object/uuid:631d7f78-d126-45d6-b489-9baaff36bd8e/datastream/OBJ/view