Three-dimensional flow structures and unsteady forces on pitching and surging revolving flat plates

Download
2015-02-01
Tomographic particle image velocimetry was used to explore the evolution of three-dimensional flow structures of revolving low-aspect-ratio flat plates in combination with force measurements at a Reynolds number of 10,000. Two motion kinematics are compared that result in the same terminal condition (revolution with constant angular velocity and 45. angle of attack) but differ in the motion during the buildup phase: pitching while revolving at a constant angular velocity; or surging with a constant acceleration at a fixed angle of attack. Comparison of force histories shows that the pitching wing generates considerably higher forces during the buildup phase which is also predicted by a quasi-steady model quite accurately. The difference in the buildup phases affects the force histories until six chords of travel after the end of buildup phase. In both cases, a vortex system that is comprised of a leading-edge vortex (LEV), a tip vortex and a trailing edge vortex is formed during the initial period of the motion. The LEV lifts off, forms an arch-shaped structure and bursts into substructures, which occur at slightly different phases of the motions, such that the revolving-surging wing flow evolution precedes that of the revolving-pitching wing. The delay is shown to be in accordance with the behavior of the spanwise flow which is affected by the interaction between the tip vortex and revolving dynamics. Further analysis shows that the enhanced force generation of the revolving-pitching wing during the pitch-up phase originates from: (1) increased magnitude and growth rate of the LEV circulation; (2) relatively favorable position and trajectory of the LEV and the starting vortex; and (3) generation of bound circulation during the pitching motion, whereas that of the revolving-surging wing is negligible in the acceleration phase.
EXPERIMENTS IN FLUIDS

Suggestions

Three-dimensional flow fields and forces on revolving flat plates
Perçin, Mustafa (null; 2014-11-23)
The evolution of three-dimensional flow structures of revolving low-aspect-ratio plates in the Reynolds number range of 10,000 to 20,000 was studied, combining Tomographic Particle Image Velocimetry with force measurements. Two motion kinematics were considered: (1) a revolving surge motion where the wing accelerates to a terminal velocity with a constant acceleration at a fixed angle of attack and then remains to revolve at a constant rate; (2) a revolving pitch motion which is initiated by a constant acce...
Three-dimensional flow and load characteristics of flexible revolving wings
van de Meerendonk, R.; Perçin, Mustafa; van Oudheusden, B. W. (2018-10-01)
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 ...
Grain-Scale Investigations of Deformation Heterogeneities in Aluminum Alloys
GÜLER, BARAN; Simsek, Ulke; Yalçınkaya, Tuncay; EFE, MERT (2018-04-25)
The an isotropic deformation of Aluminum alloys at micron scale exhibits localized deformation, which has negative implications on the macroscale mechanical and forming behavior. The scope of this work is twofold. Firstly, micro-scale deformation heterogeneities affecting forming behavior of aluminum alloys is investigated through experimental microstructure analysis at large strains and various strain paths. The effects of initial texture, local grain misorientation, and strain paths on the strain localiza...
Three-dimensional vortex wake structure of a flapping-wing micro aerial vehicle in forward flight configuration
Perçin, Mustafa; Eisma, H. E.; Remes, B. D. W. (2014-09-01)
This paper investigates the formation and evolution of the unsteady three-dimensional wake structures generated by the flapping wings of the DelFly II micro aerial vehicle in forward flight configuration. Time-resolved stereoscopic particle image velocimetry (Stereo-PIV) measurements were carried out at several spanwise-aligned planes in the wake, so as to allow a reconstruction of the temporal development of the wake of the flapping wings throughout the complete flapping cycle. Simultaneous thrust-force me...
Three-dimensional structural topology optimization of aerial vehicles under aerodynamic loads
Oktay, Erdal; AKAY, HASAN UMUR; Şehitoğlu, Onur Tolga (2014-03-20)
A previously developed density distribution-based structural topology optimization algorithm coupled with a Computational Fluid Dynamics (CFD) solver for aerodynamic force predictions is extended to solve large-scale problems to reveal inner structural details of a wing wholly rather than some specific regions. Resorting to an iterative conjugate gradient algorithm for the solution of the structural equilibrium equations needed at each step of the topology optimizations allowed the solution of larger size p...
Citation Formats
M. Perçin, “Three-dimensional flow structures and unsteady forces on pitching and surging revolving flat plates,” EXPERIMENTS IN FLUIDS, pp. 0–0, 2015, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/46193.