Vortex Breakdown Effects on the Low-speed Aerodynamic Characteristics of Slender Delta Wings in Symmetrical Flow

1967 ◽  
Vol 71 (676) ◽  
pp. 319-322 ◽  
Author(s):  
D. Hummel ◽  
P. S. Srinivasan
Keyword(s):  
Vortex Breakdown ◽  
Vortex Formation ◽  
Vortex Sheet ◽  
Aerodynamic Characteristics ◽  
Flow Visualisation ◽  
Delta Wings ◽  
Vortex Sheets ◽  
The Core ◽  
Leading Edges ◽  
Slender Wing

Even at small angles of incidence, the flow separates from the sharp leading edges of a slender wing. These flow separations usually lead to the formation of two free vortex layers, joined to the leading edges of the wing and rolling up to form spiral-shaped vortex sheets above the upper surface of the wing. This vortex formation is illustrated schematically in Fig. 1. The streamlines on the vortex sheet follow helical paths. Smoke injected near the wing apex for flow visualisation remains concentrated close to the axis of the core of the vortex sheet.

Aerodynamic characteristics of delta wing–body combinations at high angles of attack

1994 ◽  
Vol 98 (975) ◽  
pp. 159-170 ◽  
Author(s):  
P. R. Viswanath ◽  
S. R. Patil
Keyword(s):  
Vortex Breakdown ◽  
Delta Wing ◽  
Aerodynamic Characteristics ◽  
Surface Flow ◽  
Flow Visualisation ◽  
Symmetric Flow ◽  
Gradual Process ◽  
Wing Sweep ◽  
The Mean ◽  
High Angles Of Attack

AbstractAn experimental study investigating the aerodynamic characteristics of generic delta wing-body combinations up to high angles of attack was carried out at a subsonic Mach number. Three delta wings having sharp leading edges and sweep angles of 50°, 60° and 70° were tested with two forebody configurations providing a variation of the nose fineness ratio. Measurements made included six-component forces and moments, limited static pressures on the wing lee-side and surface flow visualisation studies. The results showed symmetric flow features up to an incidence of about 25°, beyond which significant asymmetry was evident due to wing vortex breakdown, forebody vortex asymmetry or both. At higher incidence, varying degrees of forebody-wing vortex interaction effects were seen in the mean loads, which depended on the wing sweep and the nose fineness ratio. The vortex breakdown on these wings was found to be a gradual process, as implied by the wing pressures and the mean aerodynamic loads. Effects of forebody vortex asymmetry on the wing-body aerodynamics have also been assessed. Comparison of Datcom estimates with experimental data of longitudinal aerodynamic characteristics on all three wing-body combinations indicated good agreement in the symmetric flow regime.

Nonaxisymmetric Waves of a Stratified Vertical Vortex

1992 ◽  
Vol 59 (2) ◽  
pp. 445-449 ◽  
Author(s):  
Y. T. Fung
Keyword(s):  
Vortex Breakdown ◽  
Fluid Layer ◽  
Stability Boundary ◽  
Vortex Sheet ◽  
Boussinesq Approximation ◽  
Force Balance ◽  
Flow Profile ◽  
Vortex Sheets ◽  
Interfacial Conditions ◽  
The Stability

The interfacial conditions for a cylindrical and an axial vortex sheet or thin fluid layer are obtained for a general class of vortex flows in a radius and gravity-stratified environment. The flow is assumed to be inviscid and incompressible. No Boussinesq approximation is required. In addition to the kinematic and dynamic conditions that the flow has to satisfy in the centrifugal and gravitational directions, a third condition, which restrains the interaction of the centrifugal and gravitational force fields, has to be imposed on those vortex sheets. This is consistent with the previous derived criteria for this type of vortex motions, in which a third condition based on pressure and force balance must be satisfied. Nonaxisymmetric instability for a special flow profile is examined and the stability boundary is obtained to show the behavior of this type of stratified vertical vortex. The results provide us with some information on the instability mechanism for the generation of the horizontal vortices in the ocean and for the spiral type of vortex breakdown in tornadoes and waterspouts in the atmosphere.

The Estimation of the Non-Linear Lift of Delta Wings at Supersonic Speeds

1963 ◽  
Vol 67 (632) ◽  
pp. 476-480 ◽  
Author(s):  
L. C. Squire
Keyword(s):  
Mathematical Model ◽  
Linear Theory ◽  
Free Stream ◽  
Separated Flow ◽  
Leading Edge ◽  
Delta Wings ◽  
Non Linear ◽  
Leading Edges ◽  
The Mathematical Model ◽  
Slender Wing

Summary:Up to the present most of the methods used to calculate the flow over delta wings with leading edge separations have been based on slender wing theory. In this paper one of the simplest of these methods is carried over to linear theory and the overall lift calculated. In general the results are in agreement with experiment, in particular both show a fall in nonlinear lift as the leading edges of the wing approach the free stream Mach angles. The discrepancies which exist appear to arise mainly from the use of linear theory rather than from the mathematical model introduced to treat the separated flow.

Vortex interaction and breakdown over double-delta wings

2004 ◽  
Vol 108 (1079) ◽  
pp. 27-34 ◽  
Author(s):  
S. L. Gai ◽  
M. Roberts ◽  
A. Barker ◽  
C. Kleczaj ◽  
A. J. Riley
Keyword(s):  
High Speed ◽  
Passive Control ◽  
Fluorescent Dyes ◽  
Vortex Breakdown ◽  
Delta Wing ◽  
Laser Sheet ◽  
Diagnostic Methods ◽  
Flow Visualisation ◽  
Delta Wings ◽  
Pressure Sensitive

Modern high-speed aircraft, especially military, are very often equipped with single or compound delta wings. When such aircraft operate at high angles-of-attack, the major portion of the lift is sustained by streamwise vortices generated at the leading edges of the wing. This vortex-dominated flow field can breakdown, leading not only to loss of lift but also to adverse interactions with other airframe components such as the fin or horizontal tail. The wind tunnel and water studies described herein attempt to clarify the fluid mechanics of interaction between the strake and wing vortices of a generic 76°/40° double-delta wing leading to vortex breakdown. Some studies of passive control using fences at the apex and kink region are also described. Various diagnostic methods-laser sheet flow visualisation, fluorescent dyes, and pressure sensitive paints have been used.

Surface shaping to suppress vortex breakdown on delta wings

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 186-187
Author(s):  
S. Srigrarom ◽  
M. Kurosaka
Keyword(s):  
Vortex Breakdown ◽  
Delta Wings ◽  
Surface Shaping

Vortex breakdown over unsteady delta wings and its control

AIAA Journal ◽  
1997 ◽  
Vol 35 ◽  
pp. 571-574
Author(s):  
H. Yang ◽  
I. Gursul
Keyword(s):  
Vortex Breakdown ◽  
Delta Wings

Separated Flow Past a Slender Delta Wing at Incidence

1973 ◽  
Vol 24 (2) ◽  
pp. 120-128 ◽  
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.

scholarly journals Remarks on Stationary and Uniformly-rotating Vortex Sheets: Rigidity Results

2021 ◽  
Author(s):  
Javier Gómez-Serrano ◽  
Jaemin Park ◽  
Jia Shi ◽  
Yao Yao
Keyword(s):  
Angular Velocity ◽  
Disjoint Union ◽  
Vortex Sheet ◽  
Vortex Sheets ◽  
Smooth Curves ◽  
Rigidity Results ◽  
Positive Vorticity ◽  
Constant Vorticity ◽  
Concentric Circles ◽  
Finite Disjoint Union

AbstractIn this paper, we show that the only solution of the vortex sheet equation, either stationary or uniformly rotating with negative angular velocity $$\Omega $$ Ω , such that it has positive vorticity and is concentrated in a finite disjoint union of smooth curves with finite length is the trivial one: constant vorticity amplitude supported on a union of nested, concentric circles. The proof follows a desingularization argument and a calculus of variations flavor.

scholarly journals Collapse of n Point Vortices, Formation of the Vortex Sheets and Transport of Passive Markers

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 943
Author(s):  
Henryk Kudela
Keyword(s):  
Differential Equations ◽  
Point Vortex ◽  
Optimization Procedure ◽  
Vortex Sheet ◽  
Point Vortices ◽  
Vortex Sheets ◽  
Impermeable Barrier ◽  
Initial Location ◽  
Passive Tracers ◽  
Initial Iterate

In this paper, the motion of the n-vortex system as it collapses to a point in finite time is studied. The motion of vortices is described by the set of ordinary differential equations that we are able to solve analytically. The explicit formula for the solution demands the initial location of collapsing vortices. To find the collapsing locations of vortices, the algebraic, nonlinear system of equations was built. The solution of that algebraic system was obtained using Newton’s procedure. A good initial iterate needs to be provided to succeed in the application of Newton’s procedure. An unconstrained Leverber–Marquart optimization procedure was used to find such a good initial iterate. The numerical studies were conducted, and numerical evidence was presented that if in a collapsing system n=50 point vortices include a few vortices with much greater intensities than the others in the set, the vortices with weaker intensities organize themselves onto the vortex sheet. The collapsing locations depend on the value of the Hamiltonian. By changing the Hamiltonian values in a specific interval, the collapsing curves can be obtained. All points on the collapse curves with the same Hamiltonian value represent one collapsing system of vortices. To show the properties of vortex sheets created by vortices, the passive tracers were used. Advection of tracers by the velocity induced by vortices was calculated by solving the proper differential equations. The vortex sheets are an impermeable barrier to inward and outward fluxes of tracers. Arising vortex structures are able to transport the passive tracers. In this paper, several examples showing the diversity of collapsing structures with the vortex sheet are presented. The collapsing phenomenon of many vortices, their ability to self organize and the transportation of the passive tracers are novelties in the context of point vortex dynamics.

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