Role of Trailing-Edge Vortices on the Hawkmothlike Flapping Wing

2015 ◽  
Vol 52 (4) ◽  
pp. 1256-1266 ◽  
Author(s):  
Jong-seob Han ◽  
Jo Won Chang ◽  
Joong-kwan Kim ◽  
Jae-hung Han
Keyword(s):  
Flapping Wing ◽  
Trailing Edge

A theoretical model for multiply connected wings

1998 ◽  
Vol 9 (6) ◽  
pp. 607-634
Author(s):  
P. BASSANINI ◽  
C. M. CASCIOLA ◽  
M. R. LANCIA ◽  
R. PIVA
Keyword(s):  
Three Dimensional ◽  
Inviscid Flow ◽  
Linear Functional Equation ◽  
Trailing Edge ◽  
Vortex Sheets ◽  
Kutta Condition ◽  
Multiply Connected ◽  
Flow Solution ◽  
Multiplicative Factor

Steady incompressible inviscid flow past a three-dimensional multiconnected (toroidal) aerofoil with a sharp trailing edge TE is considered, adopting for simplicity a linearized analysis of the vortex sheets that collect the released vorticity and form the trailing wake. The main purpose of the paper is to discuss the uniqueness of the bounded flow solution and the role of the eigenfunction. A generic admissible flow velocity u has an unbounded singularity at TE; and the physical flow solution requires the removal of the divergent part of u (the Kutta condition). This process yields a linear functional equation along the trailing edge involving both the normal vorticity ω released into the wake, and the multiplicative factor of the eigenfunction, a1. Uniqueness is then shown to depend upon the topology of the trailing edge. If δTE=[empty ], as, for example, in an annular-aerofoil configuration, both ω and a1 are uniquely determined by the Kutta condition, and the bounded flow u is unique. If δTE≠[empty ], as, for example, in a connected-wing configuration, there is an infinity of bounded flows, parametrized by a1. Numerical results of relevance for these typical configurations are presented to show the different role of the eigenfunction in the two cases.

scholarly journals The Effect of Gurney Flap and Trailing-edge Wedge on the Aerodynamic Behavior of an Axial Turbine Blade

2021 ◽  
Vol 2 (4) ◽  
pp. 293-305
Author(s):  
Mohammad Mahdi Mahzoon ◽  
Masoud Kharati-Koopaee
Keyword(s):  
Angle Of Attack ◽  
Vortex Generator ◽  
Aerodynamic Performance ◽  
Trailing Edge ◽  
Blunt Trailing Edge ◽  
Gurney Flap ◽  
Maximum Increment ◽  
Lift And Drag ◽  
Lift And Drag Coefficient

In this research, the effect of Gurney flap and trailing-edge wedge on the aerodynamic behavior of blunt trailing-edge airfoil Du97-W-300 which is equipped with vortex generator is studied. To do this, the role of Gurney flap and trailing-edge wedge on the lift and drag coefficient and also aerodynamic performance of the airfoil is studied. Validation of the numerical model is performed by comparison of the obtained results with those of experiment. Results show that before stall, Gurney flap leads to the increase in the aerodynamic performance in a wider range of angle of attack. Numerical findings reveal that the maximum increment for the aerodynamic performance is obtained at low angle of attack when trailing-edge wedge is employed. It is found that for the highest considered value of Gurney flap and trailing-edge wedge heights, where the highest values for the lift occur, the higher aerodynamic performance at low angle of attack is obtained when trailing-edge wedge is used and at high angle of attack, the Gurney flap results in a higher aerodynamic performance. It is also shown that when high aerodynamic performance is concerned, addition of Gurney flap to the airfoil leads to the higher value for the lift. Doi: 10.28991/HIJ-2021-02-04-03 Full Text: PDF

scholarly journals Kindlin-2 promotes rear focal adhesion disassembly and directional persistence in cell migration

2020 ◽  
pp. jcs.244616
Author(s):  
Jie Liu ◽  
Zhongzhen Liu ◽  
Keng Chen ◽  
Wei Chen ◽  
Xiyuan Fang ◽  
...  
Keyword(s):  
Cell Migration ◽  
Focal Adhesion ◽  
Light Chain ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Molecular Level ◽  
Trailing Edge ◽  
Serum Stimulation ◽  
Actomyosin Contractility

Cell migration involves front-rear asymmetric FA dynamics, which facilitates trailing edge detachment and directional persistence. Here we show that kinldin-2 is critical for FA sliding and disassembly in migrating cells. Loss of kindlin-2 markedly reduced FA number and selectively impaired rear FA sliding and disassembly, resulting in defective rear retraction and reduced directional persistence during cell migration. Kindlin-2 deficient cells failed to develop serum-induced actomyosin-dependent tension at FAs. At the molecular level, kindlin-2 directly interacted with myosin light chain kinase (MLCK), which was enhanced in response to serum stimulation. Serum deprivation inhibited rear FA disassembly, which was released in response to serum stimulation. Overexpression of the MLCK-binding kindlin-2 F0F1 fragment (aa 1-167), which inhibits the interaction of endogenous kindlin-2 with MLCK, phenocopied kindlin-2 deficiency-induced migration defects. Inhibition of MLCK, like loss of kindlin-2, also impaired trailing edge detachment, rear FA disassembly and directional persistence. These results suggest a role of kindlin-2 in promoting actomyosin contractility at FAs, leading to increased rear FA sliding and disassembly and directional persistence in cell migration.

scholarly journals To stabilize neutrophil polarity, PIP3 and Cdc42 augment RhoA activity at the back as well as signals at the front

2006 ◽  
Vol 174 (3) ◽  
pp. 437-445 ◽  
Author(s):  
Alexandra Van Keymeulen ◽  
Kit Wong ◽  
Zachary A. Knight ◽  
Cedric Govaerts ◽  
Klaus M. Hahn ◽  
...  
Keyword(s):  
Positive Feedback ◽  
Filamentous Actin ◽  
Trailing Edge ◽  
Rhoa Activity ◽  
Rhoa Activation ◽  
Actomyosin Contraction ◽  
Established Role ◽  
Positive Effect ◽  
Feedback Pathways

Chemoattractants like f-Met-Leu-Phe (fMLP) induce neutrophils to polarize by triggering divergent signals that promote the formation of protrusive filamentous actin (F-actin; frontness) and RhoA-dependent actomyosin contraction (backness). Frontness locally inhibits backness and vice versa. In neutrophil-like HL60 cells, blocking phosphatidylinositol-3,4,5-tris-phosphate (PIP3) accumulation with selective inhibitors of PIP3 synthesis completely prevents fMLP from activating a PIP3-dependent kinase and Cdc42 but not from stimulating F-actin accumulation. PIP3-deficient cells show reduced fMLP-dependent Rac activity and unstable pseudopods, which is consistent with the established role of PIP3 as a mediator of positive feedback pathways that augment Rac activation at the front. Surprisingly, such cells also show reduced RhoA activation and RhoA-dependent contraction at the trailing edge, leading to the formation of multiple lateral pseudopods. Cdc42 mediates PIP3's positive effect on RhoA activity. Thus, PIP3 and Cdc42 maintain stable polarity with a single front and a single back not only by strengthening pseudopods but also, at longer range, by promoting RhoA-dependent actomyosin contraction at the trailing edge.

scholarly journals Simulation of Trailing Edge Vortex Shedding in a Transonic Turbine Cascade

1996 ◽  
Author(s):  
Tom C. Currie ◽  
William E. Carscallen
Keyword(s):  
Vortex Shedding ◽  
Navier Stokes ◽  
Numerical Dissipation ◽  
Turbine Cascade ◽  
Trailing Edge ◽  
Edge Vortex ◽  
Transonic Turbine ◽  
Exit Mach Number ◽  
Good Agreement

Mid-span losses in the NRC transonic turbine cascade peak at an exit Mach number (M2) of ∼1.0 and then decrease by ∼40% as M2 is increased to the design value of 1.16. Since recent experimental results suggest that the decrease may be related to a reduction in the intensity of trailing edge vortex shedding, both steady and unsteady quasi-3D Navier-Stokes simulations have been performed with a highly refined (unstructured) grid to determine the role of shedding. Predicted shedding frequencies are in good agreement with experiment, indicating the blade boundary layers and trailing edge separated free shear layers have been modelled satisfactorily, but the agreement for base pressures is relatively poor, probably due largely to false entropy created downstream of the trailing edge by numerical dissipation. The results emphasize the importance of accounting for the effect of vortex shedding on base pressure and loss.

Role of Trailing-Edge Geometry in Open Cavity Flow Control

AIAA Journal ◽  
2019 ◽  
Vol 57 (2) ◽  
pp. 876-878 ◽  
Author(s):  
Q. Liu ◽  
F. Gómez
Keyword(s):  
Flow Control ◽  
Cavity Flow ◽  
Open Cavity ◽  
Trailing Edge ◽  
Edge Geometry

scholarly journals Recent progress in flexibility effects on wing aerodynamics and acoustics

2020 ◽  
pp. 095440622093220
Author(s):  
Prasert Prapamonthon ◽  
Bo Yin ◽  
Guowei Yang ◽  
Mohan Zhang ◽  
Panpan Lu
Keyword(s):  
Recent Progress ◽  
Leading Edge ◽  
Micro Air Vehicles ◽  
Aerodynamic Performance ◽  
Flapping Wing ◽  
Small Scale ◽  
Flexible Wings ◽  
Tip Vortices ◽  
Wing Aerodynamics

Since the theoretical aeroelasticity for flapping-wing aerodynamics was introduced in the 1920s, the effects of flexibility on aeroelasticity have been paid more attention to aerodynamic design. In recent years, the trait of the wing flexibility is applied for small-scale wings of biomimetic flyers including micro air vehicles and mini unmanned aerial vehicles. Until now, the aerodynamic performance and great agility of these flyers, which are beneficially used for military missions and other civilian applications, have been improved through surrogate flapping wings with the favorable effects of the flexibility. As per the aeroelasticity principle for the forward flying, the chordwise flexibility of an elastic flapping wing can generate thrust and lift redistributions, whereas the spanwise flexibility can result in variations of the angle of attack and the shift of phase along the wingspan direction. Consequently, all vortices generated by the flapping wing i.e. (1) leading-edge vortices, (2) tip vortices, and (3) trailing-edge vortices are blended supportively, thereby improving the aerodynamic performance and agility. Hence, the growth of research and development of the aerodynamic performance and agility for these flyers under the influence of flexible wings increases through experimental and computational studies dynamically and rapidly. This review aims to highlight the important role of the flexibility in the recent progress in wing aerodynamics of these flyers through several wing models done by famous groups of experts in this field. In addition, this review includes the acoustics of the wings under the flexibility effects which is considered as a new key for better flyer design and improvement. A comprehensive understanding of the integrated aerodynamics and acoustics under the wing flexibility is, therefore, needed.

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