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.

Prediction of tunnel wall upwash for delta wings including vortex breakdown effects

1999 ◽  
Vol 103 (1021) ◽  
pp. 139-142 ◽  
Author(s):  
L. W. Traub
Keyword(s):  
Vortex Breakdown ◽  
Side Wall ◽  
Vortical Flow ◽  
Navier Stokes ◽  
Wall Effects ◽  
Integral Expression ◽  
Image System ◽  
Tunnel Wall ◽  
Delta Wings ◽  
Side Walls

AbstractAn incompressible method is presented to predict the upwash corrections associated with vortical flow as a result of wind-tunnel side wall effects. An image system is used to simulate the tunnel side walls which are assumed to be solid. An integral expression is formulated, representing the average upwash induced over the wing by the image system. Wall effects may be determined for flows with and without vortex breakdown. Comparisons of the results with upwash predictions from a Navier-Stokes study show close accord. The upwash expression also displayed the ability to successfully predict corrections for flows involving vortex breakdown.

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.

scholarly journals APPLICATION OF AN EULER SOLVER TO SELECTED PROBLEMS IN FLIGHT DYNAMICS

Aviation ◽  
2007 ◽  
Vol 11 (2) ◽  
pp. 13-22
Author(s):  
Janusz Sznajder ◽  
Jerzy Zółtak
Keyword(s):  
Unsteady Flow ◽  
Steady Flow ◽  
Vortex Breakdown ◽  
Delta Wing ◽  
Flow Analysis ◽  
Vortical Flow ◽  
Flow Equations ◽  
Euler Solver ◽  
Unsteady Flow Analysis

Several applications of a Euler solver with the formulation of the flow equations in the noninertial reference system with steady and unsteady flow analysis are presented. The steady‐flow applications include determination of aerodynamic derivatives with respect to angular velocity and analysis of vortical flow over a delta wing at high angles of attack with the determination of aerodynamic coefficients and analysis of vortex breakdown. The unsteady flow analysis is applied in the simulation of a rapid manoeuvre for the determination of unsteady forces. The results of this simulation are compared with results of simulations using steady‐flow approximation in order to assess the advantages of unsteady flow analysis in the simulation of aircraft manoeuvres.

Vortex flows on UAVs: Issues and challenges

2004 ◽  
Vol 108 (1090) ◽  
pp. 597-610 ◽  
Author(s):  
I. Gursul
Keyword(s):  
Vortex Breakdown ◽  
Unsteady Aerodynamics ◽  
Micro Air Vehicles ◽  
Vortical Flow ◽  
Vortical Flows ◽  
Vortex Interactions ◽  
Low Reynolds Number Flows ◽  
Wing Stall ◽  
Reynolds Number Flows ◽  
Air Vehicles

Abstract Separated and vortical flows are dominant over various unmanned air vehicles (UAVs). In this article, issues and challenges of vortical flows for future UAVs are reviewed. These include shear layer instabilities, vortex breakdown and wing stall, vortex interactions, nonslender vortices, multiple vortices, and manoeuvring wing vortices. There are also issues relating to vortical flows in certain flow/structure interactions, as well as in aerodynamics/propulsion interactions. Separated and vortical flows are even more dominant at low Reynolds number flows. The main features of vortical flows, unsteady aerodynamics, and propulsion related vortical flow isssues relevant to mini- and micro air vehicles, are discussed.

A Multidisciplinary Analysis of Tail Buffeting Alleviation Using Streamwise Fences

2003 ◽  
Vol 9 (5) ◽  
pp. 583-604 ◽  
Author(s):  
Essam F. Sheta
Keyword(s):  
Data Transfer ◽  
Vortex Breakdown ◽  
Delta Wing ◽  
Vortical Flow ◽  
Geometrical Shape ◽  
Fighter Aircraft ◽  
Grid Deformation ◽  
Multidisciplinary Analysis ◽  
Wide Range ◽  
High Angles Of Attack

A multidisciplinary analysis of vertical tail buffeting and buffeting alleviation of generic fighter aircraft is conducted. This complex multidisciplinary problem is solved for the fluid dynamics, structure dynamics, fluid-structure coupling, and grid deformation using a computing environment that controls the temporal synchronization of the data transfer between the analysis modules. The generic fighter aircraft consists of a sharp-edged delta wing with an aspect ratio of one and a swept-back, flexible, vertical twin tail with a taper ratio of 0.23. Twin streamwise fences are located at the 30% chord-station of the delta wing. The fences are used to alter the vortical flow and to delay the onset of vortex breakdown above the delta wing, in order to alleviate the twin-tail buffeting. The effect of the geometrical shape of the fences on the buffeting responses is investigated. The performance of the fences over a wide range of high angles of attack is also investigated. The trapezoidal configuration of the fences at a taper ratio of 0.7 produced the most favorable results. The results indicated that the fences are effective in reducing the aeroelastic loads and responses, especially at angles of attack less than 30°.

The Suppression of Single-Fin Buffeting Using Tangential Leading Edge Blowing on a Delta Wing

1992 ◽  
Vol 206 (2) ◽  
pp. 93-104
Author(s):  
D E Bean ◽  
N J Wood ◽  
D G Mabey
Keyword(s):  
Flow Visualization ◽  
Delta Wing ◽  
Leading Edge ◽  
Light Sheet ◽  
Vortical Flow ◽  
Delta Wings ◽  
Pressure Transducers ◽  
Buffeting Response ◽  
Flexible Fin ◽  
The University

The application of tangential leading edge blowing to reduce levels of single-fin buffeting has been studied. The tests were performed at the University of Bath in the 2.1 m × 1.5 m wind tunnel using two cropped 60° delta wings. To measure the buffet excitation, a rigid fin instrumented with miniature differential pressure transducers was used. A flexible fin of similar planform and size was used to measure the buffeting response. Steady state static pressure data and laser light sheet flow visualization were employed to aid interpretation of the vortical flow over the wings, and hence identify the causes of the buffeting. The profiles of the buffet excitation and response were found to match each other very closely. It was observed that the leading edge blowing modified the leading edge vortices by reducing the ‘effective angle of attack’ of the vortex. Blowing at a constant rate shifted the buffet excitation and response to higher angles of attack. Flow visualization confirmed that the mechanism at peak buffeting had not changed, but had been merely shifted. It has been shown that the use of an optimum blowing programme could completely suppress the buffeting response.

Unsteady Characteristics over Dynamic Delta Wings

2011 ◽  
Vol 128-129 ◽  
pp. 350-353
Author(s):  
Ming Lu Zhang ◽  
Yi Ren Yang ◽  
Zhi Yong Lu
Keyword(s):  
Wind Tunnel ◽  
Vortex Breakdown ◽  
Delta Wing ◽  
Water Channel ◽  
Spiral Wave ◽  
Leading Edge ◽  
Wave Frequency ◽  
Delta Wings ◽  
Static State ◽  
Unsteady Characteristics

A study of flow and frequency characteristics of the leading-edge vortices over a delta wing undergoing pitching up-stop motions is presented. The experiments with the dynamic delta wings were conducted in a water channel and a wind tunnel respectively. Among them, the test of the flow visualization was completed in the water channel with the delta wing with pitching up-stop motions. The result shows that in the case of pitching up-stop movement the vortex breakdown position is dependent on the range of incidence at which the wing is subject to pitching up-stop and the reduced frequency k (k=c/2U∞). Analysis of the pressure signal measured in the wind tunnel shows when the delta wing is subject to pitching-up the nondimensional spiral wave frequency at nominal incidence in post-breakdown is higher than that at corresponding static state and the bigger the k is, the higher the nondimensional spiral wave frequency is. The same conclusion is fitted with different sweep delta wing.

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.

High-Order Computational Techniques for Unsteady Vortical Flows Over Delta Wings

2006 ◽  
Author(s):  
Raymond E. Gordnier ◽  
Miguel R. Visbal
Keyword(s):  
Difference Scheme ◽  
Delta Wing ◽  
High Order ◽  
Vortical Flow ◽  
Compact Difference Scheme ◽  
Delta Wings ◽  
Vortical Flows ◽  
Compact Difference ◽  
Moderate Reynolds Number ◽  
The Impact

A high-order computational method for the highly unsteady, complex vortical flows over delta wings is presented. A sixth-order compact difference scheme with an eighth-order low pass filter is used to solve the Navier-Stokes equations. Two approaches to turbulence modeling are investigated. The first scheme is an implicit LES (ILES) method which exploits the high-order accuracy of the compact difference scheme and uses the discriminating higher-order filter to regularize the flow. The second approach is a new hybrid RANS/ILES method which employs a standard k–ε model in regions where the grid resolution is unable to capture the turbulent behavior, and transitions to the ILES method in the vortical flow region where large scale turbulent structures are resolved. Computational simulations have been performed for a 50° sweep delta wing at 15° angle of attack and a moderate Reynolds number, Re = 2 × 106. Solutions employing the two turbulence models are evaluated on a baseline grid. A fine mesh computation has been performed for the ILES approach to investigate the impact of mesh resolution on this scheme. Computed results are also compared with the limited experimental measurements available. Computations exploring the control of the vortical flows above a swept delta wing by use of a dialectric-barrier-discharge actuator are also presented. With the actuator located near the apex, significant movement of the vortex breakdown location and a dramatic transformation of the shear-layer sub-structures are demonstrated.

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