scholarly journals Effects of trailing edge shape on vortex formation by pitching panels of small aspect ratio

2019 ◽  
Vol 4 (3) ◽  
Author(s):  
Arman Hemmati ◽  
Tyler Van Buren ◽  
Alexander J. Smits
Keyword(s):  
Aspect Ratio ◽  
Vortex Formation ◽  
Small Aspect Ratio ◽  
Trailing Edge

The Effect of Pitching Frequency on the Hydrodynamics of Oscillating Foils

2019 ◽  
Vol 86 (10) ◽  
Author(s):  
Arman Hemmati ◽  
Alexander J. Smits
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Strouhal Number ◽  
Vortex Formation ◽  
Free Swimming ◽  
Trailing Edge ◽  
Wake Structure ◽  
Abrupt Transition ◽  
Vortex Streets ◽  
Karman Street

Abstract The effects of two different pitching frequencies (that is, Strouhal number, St) on the wake structure generated by two foils of aspect ratio 1.0 are examined numerically at a Reynolds number of 10,000. Strouhal numbers of 0.5 and 0.2 were studied, the first corresponding approximately to the peak in efficiency and the second corresponding to the point where the thrust is equal to the drag (the free-swimming condition). The two foils have either a square trailing edge or a convex trailing edge that mimics the shape of the caudal fin exhibited by certain species of fish. In previous works, the convex trailing edge panel was found to have higher thrust and efficiency compared with the square panel trailing edge. Here, these differences are related to their characteristic vortex formation and detachment processes leading to differences in wake coherence and extension. The wake of the square panel at St = 0.2 transitions slowly from a reverse von Kármán street (2S) pattern to a paired (2P) system as the wake develops downstream, whereas at St = 0.5, the wake almost immediately takes on a 2P form with an attendant split in the wake structure. For the convex panel, the transition from a 2S to a 2P structure at St = 0.2 is slower than that seen for the square panel, and for St = 0.5, the wake undergoes an abrupt transition leading to two distinct vortex streets that evolve at a considerably slower rate than seen for the square panel.

Tip Flowfield of a Low Aspect Ratio Circulation Control Wing With Spanwise Variation in Efflux

2012 ◽  
Author(s):  
Matthew Perry ◽  
David Miklosovic
Keyword(s):  
Aspect Ratio ◽  
Vortex Formation ◽  
Stereoscopic Particle Image Velocimetry ◽  
Naval Research ◽  
Circulation Control ◽  
Trailing Edge ◽  
Planar Velocity ◽  
Momentum Coefficient ◽  
Component Velocity ◽  
Jet Interactions

A stereoscopic particle image velocimetry (SPIV) system was used in a low-speed wind tunnel to measure the external flowfield of a circulation control (CC) wing having an aspect ratio of 1.1. This ongoing project, sponsored by the Office of Naval Research, sought to further the knowledge of the jet interactions and the wingtip vortex formation through 3-component, planar velocity surveys. The CC wing tested had a 20% elliptic airfoil section with a trailing edge Coanda surface that was intended to increase circulation control effectiveness through a segmented system that could create spanwise massflow efflux profiles. To date, 1.2 TB of raw SPIV data have been acquired in one of two wake station planes at z/c = 1.25 over the vertical region of 0.13 < y/b < 0.87 (i.e, the tip region). The three-component velocity data revealed the nature of the interaction of the jet with the external flowfield and the temporal variability at an overall momentum coefficient of 0.08 with spanwise variations in the trailing edge efflux. The results from these tests will be used to quantify, for the first time, the effects of spanwise massflow distributions on the 3D velocity field near the trailing edge, the stall modes, jet interactions, and the overall performance of a CC wing of this geometry.

scholarly journals Aerofoil Theory for Swallow Tail Wings of Small Aspect Ratio

1954 ◽  
Vol 4 (1) ◽  
pp. 69-82 ◽  
Author(s):  
A. Robinson
Keyword(s):  
Exact Solution ◽  
Mach Number ◽  
Aspect Ratio ◽  
Drag Coefficient ◽  
Numerical Method ◽  
Small Aspect Ratio ◽  
Aerodynamic Forces ◽  
Trailing Edge ◽  
Induced Drag ◽  
Limiting Case

SummaryA method is developed for the calculation of the aerodynamic forces acting on a “swallow tail” wing (Figs. l(a) and l(b)) of small aspect ratio. For a given incidence, lift and induced drag coefficient are, within the limits of the theory, proportional to aspect ratio and independent of Mach number. The exact solution is derived for the limiting case of small sweepback of the trailing edge. A numerical method is indicated for the more general case.

Modification of MnS inclusion by tellurium in 38MnVS6 micro-alloyed steel

2020 ◽  
Vol 117 (6) ◽  
pp. 615
Author(s):  
Ping Shen ◽  
Lei Zhou ◽  
Qiankun Yang ◽  
Zhiqi Zeng ◽  
Kenan Ai ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Aspect Ratio ◽  
Strong Influence ◽  
Experimental Results ◽  
Alloyed Steel ◽  
Equivalent Diameter ◽  
Small Aspect Ratio ◽  
Steel Quality ◽  
Eds Analysis ◽  
Micro Alloyed Steel

In 38MnVS6 steel, the morphology of sulfide inclusion has a strong influence on the fatigue life and machinability of the steel. In most cases, the MnS inclusions show strip morphology after rolling, which significantly affects the steel quality. Usually, the MnS inclusion with a spherical morphology is the best morphology for the steel quality. In the present work, tellurium was applied to 38MnVS6 micro-alloyed steel to control the MnS inclusion. Trace tellurium was added into 38MnVS6 steel and the effect of Te on the morphology, composition, size and distribution of MnS inclusions were investigated. Experimental results show that with the increase of Te content, the equivalent diameter and the aspect ratio of inclusion decrease strikingly, and the number of inclusions with small aspect ratio increases. The inclusions are dissociated and spherized. The SEM-EDS analysis indicates that the trace Te mainly dissolves in MnS inclusion. Once the MnS is saturated with Te, MnTe starts to generate and wraps MnS. The critical Te/S value for the formation of MnTe in the 38MnV6 steel is determined to be approximately 0.075. With the increase of Te/S ratio, the aspect ratio of MnS inclusion decreases and gradually reaches a constant level. The Te/S value in the 38MnVS6 steel corresponding to the change of aspect ratio from decreasing to constant ranges from 0.096 to 0.255. This is most likely to be caused by the saturation of Te in the MnS inclusion. After adding Te in the steel, rod-like MnS inclusion is modified to small inclusion and the smaller the MnS inclusion, the lower the aspect ratio.

Finite Field Harmonics for Stellarators with Improved Aspect Ratio

1982 ◽  
Vol 37 (8) ◽  
pp. 866-875 ◽  
Author(s):  
W. Dommaschk
Keyword(s):  
Aspect Ratio ◽  
Finite Field ◽  
Small Aspect Ratio ◽  
Helical Symmetry ◽  
Magnetic Surfaces ◽  
The Law ◽  
Orthogonal Coordinates

A set of stellarator fields with magnetic surfaces of small aspect ratio is found by superposing recently introduced, easily computable field harmonics. The law of superposition is found analytically by closely approaching “helical symmetry” of these “new” fields in suitable orthogonal coordinates

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