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The vortex dynamics of leading-edge vortices on plunging high-aspect-ratio (AR = 10) wings and airfoils were investigated by means of volumetric velocity measurements, numerical simulations and stability analysis to understand the deformation of the leading-edge vortex filament and spanwise instabilities. The vortex filaments on both the wing and airfoil exhibit spanwise waves, but with different origins. The presence of a wing-tip causes the leg of the vortex to remain attached to the wing upper surface, while the initial deformation of the filament near the wing tip resembles a helical vortex. The essential features can be modelled as the deformation of an initially L-shaped semi-infinite vortex column. In contrast, the instability of the vortices is well captured by the instability of counter-rotating vortex pairs, which are formed either by the trailing-edge vortices or the secondary vortices rolled-up from the wing surface. The wavelengths observed in the experiments and simulations are in agreement with the stability analysis of counter-rotating vortex pairs of unequal strength.

Due to the unsteady motion of a plunging plate, forces acting on the body experience a phase difference with respect to the motion. These phase relations are investigated experimentally for a harmonically plunging plate within an amplitude range of $$0.05\le {a/c}\le 0.6$$ , reduced frequency range of $$0.78

Three-dimensionality effects have been investigated for a flat plate undergoing an impulsive pitch-up motion in a large-scale, free-surface water channel with the presence and absence of an endplate to represent a symmetry plane and to prevent free-surface effects. To obtain the same aspect ratios without using the endplate, appropriately sized wings were also used in a fully submerged arrangement. The velocity fields were acquired in the near wake of the flat plate using a two-dimensional (2D) two-component digital particle image velocimetry system, and simultaneous force measurements were performed. The wing had an aspect ratio ranging from 2 to 8 and pitches up to 45 degrees in 1 or 6 convective times. The force measurement results revealed that major difference occurred after the motion was completed in which the lift and drag forces exhibited a local increase and decrease. Interactions between leading edge, trailing edge, and tip vortices were investigated; flow structures were correlated with the force-time histories, and variations with aspect ratio were also addressed. (C) 2017 American Society of Civil Engineers.

© 2016, (publisher Name). All Rights Reserved. The Applied Vehicle Technology Panel Task Group AVT-202 “Extension of Fundamental Flow Physics to Practical MAV Aerodynamics” has introduced four canonical cases. Rectilinear pitch is probably the most studied one, especially considering its parametric variations. The canonical case of rectilinear pitch considers a rectangular flat plate wing of aspect ratio 4, with a thickness of less than 5% and round edges, undergoing a pitch up motion in a freestream. In the beginning, the wing is at condition CL = 0 and then pitches up to 45° of effective incidence either in 1 or 6 chord lengths of travel relative to fluid (known as fast and slow cases), pivoting around its leading edge. This paper focuses on parametric variations of the aforementioned canonical case, namely variations in aspect ratio, leading edge and planform shapes.

In this study, the effect of chordwise flexibility has been investigated experimentally for a plunging foil. A Digital Particle Image Velocimetry (DPIV) system is used to determine instantaneous velocity and vorticity fields around and in the near-wake of the wings in conjunction with simultaneous direct force/moment measurements. The aerodynamic/hydrodynamic performance is studied for rigid and flexible wings undergoing plunge motion at different amplitudes and frequencies in a freestream of Re = 10 000. The thrust coefficient (\(C_T\)), the power input coefficient (\(C_P\)) and the efficiency (\(\eta \)) values are also obtained and linked with the flexibility, trailing edge motion and flow structures in the near-wake.

Ozgecmisler Ferhat KARAKAS ITU Ucak ve Uzay Bilimleri Fakultesi Ucak Muhendisligi Bolumu lisans son sinif ogrencisi. von Karman Akiskanlar Mekanigi Enstitusu’nde ses ustu hizlardaki akim yapilarinin hesaplamali olarak modellemesi uzerine staj calismasi yapmistir. Onur PACA 2014 yilinda ITU Uzay Muhendisligi Bolumu'nden lisans diplomasi alarak mezun oldu. Calismalarina aerodinamik alaninda sayisal olarak devam etmektedir. 2014 yilinda ITU Fen Bilimleri Enstitusu'nde Ucak ve Uzay Muhendisligi Disiplinlerarasi Lisansustu Programi ogrencisi oldu. Halen ayni bolumde yuksek lisans ogrencisidir. Cihad KOSE 2013 yilinda Istanbul Teknik Universitesi Ucak Muhendisligi Bolumu'nden lisans diplomasini aldi. Ayni yil Istanbul Teknik Universitesi Fen Bilimleri Enstitusu Ucak ve Uzay Muhendisligi Lisansustu Programi'nda yuksek lisans ogrencisi olarak egitime basladi ve halen bu programdaki egitimine devam etmektedir. Ayni zamanda ITU Trisonik Laboratuvari'nda yapilan arastirma projelerinde gorev almaktadir. Ars.Grv. Y.Muh. Onur SON 2008 yilinda ITU Ucak ve Uzay Bilimleri Fakultesi, Uzay Muhendisligi Bolumu’nden lisans, 2010 yilinda da Fen Bilimleri Enstitusu, Ucak ve Uzay Muhendisligi Programi’ndan yuksek lisans diplomasini aldi. 2010 yilinda ayni bolumde doktora programina kabul edilip, Uzay Muhendisligi Bolumu’nde arastirma gorevlisi olarak calismaya baslamistir. Ucak ve Uzay Bilimleri Fakultesi’ne bagli Trisonik Laboratuvari’nda cesitli projelerde gorev alip, Olcme Teknigi ve Deneysel Muhendislik derslerinin yardimciligini yurutmustur. Halen Uzay Muhendisligi bolumunde arastirma gorevlisi olarak calismakta olup, doktorasina devam etmektedir. Y.Muh. Berk ZALOĞLU 2004 yilinda ITU Ucak Muhendisligi Bolumu'nden lisans, 2008 yilinda Ucak ve Uzay ve Uzay Muhendisligi Bolumu'nden yuksek lisans diplomasini almistir. Yine ayni bolumde doktora egitimine devam etmektedir. ITU Trisonik Laboratuvari'nda deneysel akiskanlar mekanigi odakli bircok arastirmada yer almistir. 2013 yilindan beri Avrupa Birligi 7. Cerceve kapsamindaki NIOPLEX projesinde arastirmaci olarak calismaktadir. Dr. Idil FENERCIOĞLU 1999 yilinda ITU Uzay Muhendisligi Bolumu'nden lisans, 2002 yilinda Ucak ve Uzay Muhendisligi Bolumu'nden yuksek lisans diplomasi alarak ayni bolumden 2010 yilinda doktor unvanini aldi. Kisa sureli gorevlendirmeler ile RWTH-Aachen Sok Dalgasi Laboratuvari ve University of Bath Akiskanlar Mekanigi Laboratuvari'nda deneysel calisma gruplarinda gorev yapti. ITU Trisonik Laboratuvari'nda gerceklestirilen bir cok projede arastirmalara katildi ve calismalarini ayni laboratuvarda deneysel akiskanlar mekanigi konularinda surdurmeye devam etmektedir. 1999 yilinda Ucak ve Uzay Bilimleri Fakultesi'nde arastirma gorevlisi olarak calismaya basladi ve halen ayni fakultede Ogretim Gorevlisi olarak gorev yapmaktadir. Prof. Dr. Oksan CETINER ITU Ucak ve Uzay Bilimleri Fakultesi Ucak Muhendisligi Bolumu’nden 1992 yilinda lisans derecesini aldi. 1994 yilinda Ucak Muhendisligi Bolumunde arastirma gorevlisi olarak calismaya basladi ve 1995 yilinda yuksek lisans derecesini aldi. Amelia Earhart odulunu kazanmasi uzerine doktoraya Lehigh Universitesi’nde devam etti. 1999 yilinda Uzay Muhendisligi Bolumunde Yardimci Docent kadrosuna atandi. 2008 yilinda Docent unvanini aldi ve 2013 Kasim ayinda ise Profesor kadrosuna atandi. Ilgi ve calisma alanlari arasinda Akisin Uyardigi Titresimler, Akis-Yapi Etkilesimleri, PIV (Particle Image Velocimetry) ve Olcme Sistemleri sayilabilir. “Open Access: This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0) which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.”