Skin Friction Fields and Surface Dye Patterns on Delta Wings in Water Flows

This paper discusses the relationship between skin friction fields and surface dye patterns in surface luminescent dye visualizations in water flows, providing a theoretical foundation for extraction of high-resolution skin friction fields. The limiting form of the mass diffusion equation at a wall is recast as an optical flow equation connecting skin friction with the luminescent dye intensity. Snapshot solutions are obtained from a time sequence of luminescent intensity images by solving the optical flow equation via the variational method, and then a normalized skin friction field is reconstructed by averaging the snapshot solutions. An error analysis is given to identify the major error sources and the limitations of the technique. To evaluate the feasibility of this technique, surface luminescent dye visualizations on a 65 deg delta wing and a 76/40 deg double-delta wing are conducted in a water tunnel. The extracted skin friction topology on the delta wings and the velocity fields obtained by using particle image velocimetry (PIV) are discussed.

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The leading-edge vortex of swift wing-shaped delta wings

Royal Society Open Science ◽

10.1098/rsos.170077 ◽

2017 ◽

Vol 4 (8) ◽

pp. 170077 ◽

Cited By ~ 7

Author(s):

Rowan Eveline Muir ◽

Abel Arredondo-Galeana ◽

Ignazio Maria Viola

Keyword(s):

Reynolds Number ◽

Delta Wing ◽

Leading Edge ◽

Trailing Edge ◽

Delta Wings ◽

Leading Edge Vortex ◽

Wing Model ◽

Image Velocimetry ◽

Edge Vortex ◽

First Time

Recent investigations on the aerodynamics of natural fliers have illuminated the significance of the leading-edge vortex (LEV) for lift generation in a variety of flight conditions. A well-documented example of an LEV is that generated by aircraft with highly swept, delta-shaped wings. While the wing aerodynamics of a manoeuvring aircraft, a bird gliding and a bird in flapping flight vary significantly, it is believed that this existing knowledge can serve to add understanding to the complex aerodynamics of natural fliers. In this investigation, a model non-slender delta-shaped wing with a sharp leading edge is tested at low Reynolds number, along with a delta wing of the same design, but with a modified trailing edge inspired by the wing of a common swift Apus apus . The effect of the tapering swift wing on LEV development and stability is compared with the flow structure over the unmodified delta wing model through particle image velocimetry. For the first time, a leading-edge vortex system consisting of a dual or triple LEV is recorded on a swift wing-shaped delta wing, where such a system is found across all tested conditions. It is shown that the spanwise location of LEV breakdown is governed by the local chord rather than Reynolds number or angle of attack. These findings suggest that the trailing-edge geometry of the swift wing alone does not prevent the common swift from generating an LEV system comparable with that of a delta-shaped wing.

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$$ T\overline{T} $$-like flows in non-linear electrodynamic theories and S-duality

Journal of High Energy Physics ◽

10.1007/jhep04(2021)187 ◽

2021 ◽

Vol 2021 (4) ◽

Author(s):

H. Babaei-Aghbolagh ◽

Komeil Babaei Velni ◽

Davood Mahdavian Yekta ◽

H. Mohammadzadeh

Keyword(s):

Type Theory ◽

Free Action ◽

Momentum Tensor ◽

Flow Equation ◽

Supersymmetric Model ◽

Deformation Problem ◽

Dimensional Spacetime ◽

Non Linear ◽

The Relationship ◽

Simple Integration

Abstract We investigate the $$ T\overline{T} $$ T T ¯ -like flows for non-linear electrodynamic theories in D(=2n)-dimensional spacetime. Our analysis is restricted to the deformation problem of the classical free action by employing the proposed $$ T\overline{T} $$ T T ¯ operator from a simple integration technique. We show that this flow equation is compatible with $$ T\overline{T} $$ T T ¯ deformation of a scalar field theory in D = 2 and of a non-linear Born-Infeld type theory in D = 4 dimensions. However, our computation discloses that this kind of $$ T\overline{T} $$ T T ¯ flow in higher dimensions is essentially different from deformation that has been derived from the AdS/CFT interpretations. Indeed, the gravity that may be exist as a holographic dual theory of this kind of effective Born-Infeld action is not necessarily an AdS space. As an illustrative investigation in D = 4, we shall also show that our construction for the $$ T\overline{T} $$ T T ¯ operator preserves the original SL(2, ℝ) symmetry of a non-supersymmetric Born-Infeld theory, as well as $$ \mathcal{N} $$ N = 2 supersymmetric model. It is shown that the corresponding SL(2, ℝ) invariant action fixes the relationship between the $$ T\overline{T} $$ T T ¯ operator and quadratic form of the energy-momentum tensor in D = 4.

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Separated Flow Past a Slender Delta Wing at Incidence

Aeronautical Quarterly ◽

10.1017/s0001925900006508 ◽

1973 ◽

Vol 24 (2) ◽

pp. 120-128 ◽

Cited By ~ 8

Author(s):

J E Barsby

Keyword(s):

Delta Wing ◽

Separated Flow ◽

Leading Edge ◽

Vortex Sheet ◽

Simultaneous Equations ◽

Delta Wings ◽

Nested Iteration ◽

Finite Difference Technique ◽

Flow Past ◽

Vortex Systems

SummarySolutions to the problem of separated flow past slender delta wings for moderate values of a suitably defined incidence parameter have been calculated by Smith, using a vortex sheet model. By increasing the accuracy of the finite-difference technique, and by replacing Smith’s original nested iteration procedure, to solve the non-linear simultaneous equations that arise, by a Newton’s method, it is possible to extend the range of the incidence parameter over which solutions can be obtained. Furthermore for sufficiently small values of the incidence parameter, new and unexpected results in the form of vortex systems that originate inboard from the leading edge have been discovered. These new solutions are the only solutions, to the author’s knowledge, of a vortex sheet leaving a smooth surface.Interest has centred upon the shape of the finite vortex sheet, the position of the isolated vortex, and the lift, and variations of these quantities are shown as functions of the incidence parameter. Although no experimental evidence is available, comparisons are made with the simpler Brown and Michael model in which all the vorticity is assumed to be concentrated onto an isolated line vortex. Agreement between these two models becomes very close as the value of the incidence parameter is reduced.

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Numerical Simulation of Heat Transfer Enhanced Tube Inserted Delta-Wing

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.535.66 ◽

2014 ◽

Vol 535 ◽

pp. 66-70

Author(s):

Chen Hong Zhao ◽

Yong Gang Lei

Keyword(s):

Heat Transfer ◽

Numerical Simulation ◽

Pressure Drop ◽

Inclination Angle ◽

Delta Wing ◽

Delta Wings ◽

Enhanced Tube ◽

Delta Winglet

Heat transfer and resistance characteristics of a tube inserted delta-winglet (inclination angle is 10 °) are studied by numerical simulation. The results show that the delta-winglet enhance the heat transfer of the enhancement tube inserted delta-winglet and improve the PEC with modest pressure drop penalties. Compared with based tubes, the delta-wings structure enhance the heat transfer 19.52%-31%.

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Images, Imagination, and Movement: Pictorial Representations and Their Development in the Work of James Gibson

Perception ◽

10.1068/p2976 ◽

2000 ◽

Vol 29 (6) ◽

pp. 635-648 ◽

Cited By ~ 4

Author(s):

James E Cutting

Keyword(s):

Vector Field ◽

Optical Flow ◽

Spherical Representation ◽

Pictorial Representations ◽

The Relationship

For more than 30 years James Gibson studied pictures and he studied motion, particularly the relationship between movement through an environment and its visual consequences. For the latter, he also struggled with how best to present his ideas to students and fellow researchers, and employed various representations and formats. This article explores the relationships between the concepts of the fidelity of pictures (an idea he first promoted and later eschewed) and evocativeness as applied to his images. Gibson ended his struggle with an image of a bird flying over a plane surrounded by a spherical representation of a vector field, an image high in evocativeness but less than completely faithful to optical flow.

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Estimation of three-dimensional crustal movements in the 2011 Tohoku-oki, Japan earthquake from TerraSAR-X intensity images

Natural Hazards and Earth System Sciences Discussions ◽

10.5194/nhessd-2-7383-2014 ◽

2014 ◽

Vol 2 (12) ◽

pp. 7383-7408

Author(s):

W. Liu ◽

F. Yamazaki ◽

M. Matsuoka ◽

T. Nonaka ◽

T. Sasagawa

Keyword(s):

Three Dimensional ◽

Short Time Period ◽

Sar Images ◽

Crustal Movements ◽

Surface Displacements ◽

Time Period ◽

Intensity Images ◽

Short Time ◽

The Relationship ◽

Gps Observations

Abstract. The Tohoku-Oki earthquake on 11 March 2011 caused significant widespread crustal movements. In a previous study, we proposed a method for capturing two-dimensional (2-D) surface displacements from a pair of pre- and post-event TerraSAR-X (TSX) intensity images. However, it is difficult to detect three-dimensional (3-D) displacements from one pair of TSX images. In this study, three pairs of pre- and post-event TSX images taken on different paths were used to estimate 3-D crustal movements. The relationship between the actual 3-D displacements and the converted 2-D movements in the SAR images was derived based on the observation model of a SAR sensor. The 3-D movements were then calculated from three sets of detected 2-D movements that occurred within a short time period. Compared with GPS observations, the proposed method was found to be capable of detecting the 3-D crustal movements with sub-pixel accuracy.

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An integrated platform to facilitate the calculation, validation and visualization of optical flow velocities in biological images

Journal of The Royal Society Interface ◽

10.1098/rsif.2021.0248 ◽

2021 ◽

Vol 18 (179) ◽

pp. 20210248

Author(s):

Xianbin Yong ◽

Cheng-Kuang Huang ◽

Chwee Teck Lim

Keyword(s):

Optical Flow ◽

Qualitative Assessment ◽

Biological Images ◽

Image Velocimetry ◽

Integrated Platform ◽

Matching Procedure ◽

Simulated Images ◽

Imaging Conditions ◽

Artificial Tracers ◽

Flow Velocities

Optical flow algorithms have seen poor adoption in the biological community compared with particle image velocimetry for quantifying cellular dynamics because of the lack of proper validation and an intuitive user interface. To address these challenges, we present OpFlowLab, an integrated platform that integrates our motion estimation workflow. Using routines in our workflow, we demonstrate that optical flow algorithms are more accurate than PIV in simulated images of the movement of nuclei. Qualitative assessment with actual nucleus images further supported this finding. Additionally, we show that refinement of the optical flow velocities is possible with a simple object-matching procedure, opening up the possibility of obtaining reasonable velocity estimates under less ideal imaging conditions. To visualize velocity fields, we employ artificial tracers to allow for the drawing of pathlines. Through the adoption of OpFlowLab, we are confident that optical flow algorithms will allow for the exploration of dynamic biological systems in greater accuracy and detail.

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A Note on the Vorticity Distribution on the Surface of Slender Delta Wings with Leading Edge Separation

Journal of the Royal Aeronautical Society ◽

10.1017/s0001924000093520 ◽

1961 ◽

Vol 65 (603) ◽

pp. 195-198 ◽

Cited By ~ 5

Author(s):

B. J. Elle ◽

J. P. Jones

Keyword(s):

Experimental Evidence ◽

Delta Wing ◽

Leading Edge ◽

Water Tunnel ◽

Delta Wings ◽

Vorticity Distribution ◽

Edge Separation

A description is given of the distribution of vorticity in the surface of thin wings with large leading edge sweep. Although the delta wing is chosen as the basic plan form the deductions are general and applicable to other types of wing. The conclusions are illustrated with experimental evidence from a water tunnel.

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