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.

On the Breakdown at High Incidences of the Leading Edge Vortices on Delta Wings

1960 ◽  
Vol 64 (596) ◽  
pp. 491-493 ◽  
Author(s):  
B. J. Elle
Keyword(s):  
High Speed ◽  
Recent Article ◽  
Vortex Breakdown ◽  
Leading Edge ◽  
Critical Value ◽  
Delta Wings ◽  
Edge Separation ◽  
Leading Edge Vortices

In a recent article, H. Werlé, has described how the free spiral vortices on delta wings with leading edge separation suddenly expand if the incidence is increased beyond a critical value. His description conforms to a great extent with the results, arrived at during an English investigation of the same phenomenon (called the vortex breakdown), but the interpretations of the observations, suggested by the two sources, are different. Against this background it is felt that some further comments and some pertinent high speed observations, may be of interest.

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.

DPIV Around a Flexible Circular Cylinder Undergoing Cross-Flow Forced Oscillations

2012 ◽  
Author(s):  
Francisco J. Huera-Huarte ◽  
Zafar A. Bangash
Keyword(s):  
Circular Cylinder ◽  
High Speed ◽  
Continuous Wave ◽  
Laser Sheet ◽  
Cross Flow ◽  
Forced Oscillations ◽  
Flow Visualisation ◽  
Flexible Cylinder ◽  
Image Velocimetry ◽  
Structural Mode

This research is motivated by early experiments [1, 2], in which the main time consistent flow structures in the wake of a flexible oscillating circular cylinder were studied. We have now investigated the wake of a circular cylinder undergoing forced vibrations, by using Planar Digital Particle Image Velocimetry (DPIV) and long exposure photographs for flow visualisation. The focus is given to the node to anti-node transition when the cylinder oscillates in its second structural mode. A flexible cylinder is supported by a structure consisting of a frame that includes a motor that drives a shaft, that actuates a pusher connected to the cylinder at two points, through a crank slider mechanism. We are able to produce forced oscillations of the cylinder, either in its first mode when the pushers are in phase, or in its second mode if the pushers are configured out-of-phase. We have used a high speed camera together with a continuous wave laser, to image seeding particles being illuminated by the laser sheet, at two different heights along the length of the cylinder: the node and the anti-node. We have also produced long exposure images of the particles leading to flow visualisation.

Control of shock-induced vortex breakdown on a delta-wing-body configuration in the transonic regime

2021 ◽  
pp. 1-25
Author(s):  
Rajan B. Kurade ◽  
L. Venkatakrishnan ◽  
G. Jagadeesh
Keyword(s):  
Vortex Breakdown ◽  
Delta Wing ◽  
Pressure Fluctuations ◽  
Angle Of Attack ◽  
Aerodynamic Coefficients ◽  
Delta Wings ◽  
Drag Ratio ◽  
Lift To Drag Ratio ◽  
Sudden Jump ◽  
Modest Level

Abstract Shock-induced vortex breakdown, which occurs on the delta wings at transonic speed, causes a sudden and significant change in the aerodynamic coefficients at a moderate angle-of-attack. Wind-tunnel tests show a sudden jump in the aerodynamic coefficients such as lift force, pitching moment and centre of pressure which affect the longitudinal stability and controllability of the vehicle. A pneumatic jet operated at sonic condition blown spanwise and along the vortex core over a 60° swept delta-wing-body configuration is found to be effective in postponing this phenomenon by energising the vortical structure, pushing the vortex breakdown location downstream. The study reports that a modest level of spanwise blowing enhances the lift by about 6 to 9% and lift-to-drag ratio by about 4 to 9%, depending on the free-stream transonic Mach number, and extends the usable angle-of-attack range by 2°. The blowing is found to reduce the magnitude of unsteady pressure fluctuations by 8% to 20% in the aft portion of the wing, depending upon the method of blowing. Detailed investigations carried out on the location of blowing reveal that the blowing close to the apex of the wing maximises the benefits.

Experimental Control of Vortex Breakdown by Pulsed Blowing Over a Delta Wing With Rounded Leading-Edge

2002 ◽  
Author(s):  
Renac Florent ◽  
Molton Pascal ◽  
Barberis Didier
Keyword(s):  
Vortex Breakdown ◽  
Delta Wing ◽  
Laser Sheet ◽  
Leading Edge ◽  
Control Device ◽  
Surface Flow ◽  
Sweep Angle ◽  
Laminar To Turbulent Transition ◽  
Pressure Distributions ◽  
Oil Flow

The purpose of this study is to construct and test an experimental device to control vortex on a delta wing. The model has a root chord of c = 690mm and a sweep angle of Λ = 60°. The control system is based on four rectangular slits 50 mm long and 0.2 mm wide running along the leading edge. This configuration produces jets normal to the leading edge. The mass flow rates and frequencies of injection can be varied independently. The results are shown in the form of surface flow visualizations, with the skin friction pattern exhibited by oil flow visualization, and the laminar-to-turbulent transition by acenaphthene. Mean and instantaneous surface pressure distributions were determined with Kulite™ sensors and the velocity field was determined by 3D laser Doppler velocimetry (LDV) measurements. Control device efficiencies were evaluated by laser sheet visualization.

Some Experiments with Vortex Breakdown

1964 ◽  
Vol 68 (641) ◽  
pp. 343-346 ◽  
Author(s):  
M. V. Lowson
Keyword(s):  
Pressure Gradient ◽  
Steady Flow ◽  
Vortex Breakdown ◽  
Delta Wing ◽  
Flow Visualisation ◽  
Water Tunnel ◽  
General Part ◽  
New Phenomena ◽  
Axisymmetric Instability ◽  
Flow States

SummaryWater tunnel flow visualisation experiments on a slender delta wing have revealed some new phenomena connected with vortex breakdown. Vortex breakdown hysteresis has been found, there being two steady flow states at some incidences, one with breakdown on the wing and one without. The formation of vortex breakdown has been studied and found to be a non-axisymmetric instability. It is suggested that pressure gradient plays a more general part in the phenomenon than has been thought hitherto.

Alleviation of pitch-up on delta wings using distributed porosity

1999 ◽  
Vol 103 (1025) ◽  
pp. 339-347 ◽  
Author(s):  
L. W. Traub ◽  
B. Moeller ◽  
S. F. Galls
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Delta Wing ◽  
Leading Edge ◽  
Surface Flow ◽  
Force Balance ◽  
Flow Visualisation ◽  
Surface Porosity ◽  
Delta Wings ◽  
Field Surveys

Abstract An experimental investigation was undertaken to determine the effectiveness of distributed surface porosity for the alleviation of pitch-up on a delta wing. Tests were undertaken using a 65° sweep delta wing with distributed porosity evaluated at various locations on the wing. Force balance, on and off surface flow visualisation and flow field surveys using a multi-hole probe were undertaken. The data shows that distributed porosity applied along the wing leading edge at the apex is effective in eliminating pitch-up whilst incurring a minimal performance cost. Trailing edge porosity generally degraded performance.

scholarly journals Aerodynamic Analysis of a Supersonic Transport Aircraft at Landing Speed Conditions

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6615
Author(s):  
Andrea Aprovitola ◽  
Pasquale Emanuele Di Nuzzo ◽  
Giuseppe Pezzella ◽  
Antonio Viviani
Keyword(s):  
High Speed ◽  
Cfd Simulation ◽  
Vortex Breakdown ◽  
Delta Wing ◽  
Research Effort ◽  
Static Stability ◽  
Commercial Aviation ◽  
Supersonic Flight ◽  
Supersonic Transport ◽  
Wide Range

Supersonic flight for commercial aviation is gaining a renewed interest, especially for business aviation, which demands the reduction of flight times for transcontinental routes. So far, the promise of civil supersonic flight has only been afforded by the Concorde and Tupolev T-144 aircraft. However, little or nothing can be found about the aerodynamics of these aeroshapes, the knowledge of which is extremely interesting to obtain before the development of the next-generation high-speed aircraft. Therefore, the present research effort aimed at filling in the lack of data on a Concorde-like aeroshape by focusing on evaluating the aerodynamics of a complete aircraft configuration under low-speed conditions, close to those of the approach and landing phase. In this framework, the present paper focuses on the CFD study of the longitudinal aerodynamics of a Concorde-like, tailless, delta-ogee wing seamlessly integrated onto a Sears–Haack body fuselage, suitable for civil transportation. The drag polar at a Mach number equal to 0.24 at a 30 m altitude was computed for a wide range of angles of attack (0∘,60∘), with a steady RANS simulation to provide the feedback of the aerodynamic behaviour post breakdown, useful for a preliminary design. The vortex-lift contribution to the aerodynamic coefficients was accounted for in the longitudinal flight condition. The results were in agreement with the analytical theory of the delta-wing. Flowfield sensitivity to the angle of attack at near-stall and post-stall flight attitudes confirmed the literature results. Furthermore, the longitudinal static stability was addressed. The CFD simulation also evidenced a static instability condition arising for 15∘≤α≤20∘ due to vortex breakdown, which was accounted for.

Recent developments in delta wing aerodynamics

2004 ◽  
Vol 108 (1087) ◽  
pp. 437-452 ◽  
Author(s):  
I. Gursul
Keyword(s):  
Shear Layer ◽  
Vortex Breakdown ◽  
Delta Wing ◽  
Layer Structure ◽  
Vortical Flow ◽  
Time Lags ◽  
Delta Wings ◽  
Vortex Interactions ◽  
Recent Developments ◽  
Wing Aerodynamics

Abstract Recent developments in delta wing aerodynamics are reviewed. For slender delta wings, recent investigations shed more light on the unsteady aspects of shear-layer structure, vortex core, breakdown and its instabilities. For nonslender delta wings, substantial differences in the structure of vortical flow and breakdown may exist. Vortex interactions are generic to both slender and nonslender wings. Various unsteady flow phenomena may cause buffeting of wings and fins, however, vortex breakdown, vortex shedding, and shear layer reattachment are the most dominant sources. Dynamic response of vortex breakdown over delta wings in unsteady flows can be characterised by large time lags and hysteresis, whose physical mechanisms need further studies. Unusual flow–structure interactions for nonslender wings in the form of self-excited roll oscillations have been observed. Recent experiments showed that substantial lift enhancement is possible on a flexible delta wing.

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.

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