Unsteady aerodynamics and control of delta wings with tangential leading-edge blowing

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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Comparison of Wind Tunnel Airfoil Performance Data With Wind Turbine Blade Data

Journal of Solar Energy Engineering ◽

10.1115/1.2929989 ◽

1992 ◽

Vol 114 (2) ◽

pp. 119-124 ◽

Cited By ~ 12

Author(s):

C. P. Butterfield ◽

George Scott ◽

Walt Musial

Keyword(s):

Wind Tunnel ◽

Wind Turbine ◽

Peak Power ◽

Unsteady Aerodynamics ◽

Leading Edge ◽

Operating Conditions ◽

Performance Data ◽

Horizontal Axis Wind Turbine ◽

Force Coefficients ◽

Basic Fluid

Horizontal axis wind turbine (HAWT) performance is usually predicted by using wind tunnel airfoil performance data in a blade element momentum theory analysis. This analysis assumes that the rotating blade airfoils will perform as they do in the wind tunnel. However, when stall-regulated HAWT performance is measured in full-scale operation, it is common to find that peak power levels are significantly greater than those predicted. Pitch-controlled rotors experience predictable peak power levels because they do not rely on stall to regulate peak power. This has led to empirical corrections to the stall predictions. Viterna and Corrigan (1981) proposed the most popular version of this correction. But very little insight has been gained into the basic cause of this discrepancy. The National Renewable Energy Laboratory (NREL), funded by the DOE, has conducted the first phase of an experiment which is focused on understanding the basic fluid mechanics of HAWT aerodynamics. Results to date have shown that unsteady aerodynamics exist during all operating conditions and dynamic stall can exist for high yaw angle operation. Stall hysteresis occurs for even small yaw angles and delayed stall is a very persistent reality in all operating conditions. Delayed stall is indicated by a leading edge suction peak which remains attached through angles of attack (AOA) up to 30 degrees. Wind tunnel results show this peak separating from the leading edge at 18 deg AOA. The effect of this anomaly is to raise normal force coefficients and tangent force coefficients for high AOA. Increased tangent forces will directly affect HAWT performance in high wind speed operation. This report describes pressure distribution data resulting from both wind tunnel and HAWT tests. A method of bins is used to average the HAWT data which is compared to the wind tunnel data. The analysis technique and the test set-up for each test are described.

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

Journal of the Royal Aeronautical Society ◽

10.1017/s0368393100073314 ◽

1960 ◽

Vol 64 (596) ◽

pp. 491-493 ◽

Cited By ~ 19

Author(s):

B. J. Elle

Keyword(s):

High Speed ◽

Information Assurance Technologies for the Global Command and Control System (GCCS) Leading Edge Services (LES)

10.21236/ada402371 ◽

2001 ◽

Author(s):

Richard O'Brien

Keyword(s):

Control System ◽

Information Assurance ◽

Command And Control ◽

Leading Edge ◽

And Control ◽

Command And Control System

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Errata: Unsteady Aerodynamics of Slender Delta Wings at Large Angles of Attack

Journal of Aircraft ◽

10.2514/3.58861 ◽

1977 ◽

Vol 14 (8) ◽

pp. 832-832 ◽

Cited By ~ 1

Author(s):

L.E. Ericsson ◽

J.P. Reding

Keyword(s):

Unsteady Aerodynamics ◽

Delta Wings

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Paper 20. Improvement of Control by Special Devices

Journal of Mechanical Engineering Science ◽

10.1243/jmes_jour_1972_014_075_02 ◽

1972 ◽

Vol 14 (7) ◽

pp. 150-154

Author(s):

H. Ritter

Keyword(s):

Large Angle ◽

Leading Edge ◽

Rotating Cylinder ◽

Practical Significance ◽

Trailing Edge ◽

Stall Angle ◽

Lift Control ◽

And Control

The paper discusses hydrodynamic devices for improving manoeuvring and control. Two hydrodynamic concepts are shown to be of practical significance for large craft: control of hydrofoil lift independent of incidence, and deflection of the propulsion jet through a large angle by means of a simple hydrofoil. Lift control independent of incidence is illustrated by the jet flap and the trailing edge rotating cylinder. Improved deflection of the propeller slipstream involves extending the rudder stall angle, and it is shown how this may be achieved by fitting the rudder with a leading edge rotating cylinder.

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An investigation of asymmetric vortical flows over delta wings with tangential leading-edge blowing at high angles of attack

10.2514/6.1990-103 ◽

1990 ◽

Cited By ~ 4

Author(s):

ZEKI CELIK ◽

LEONARD ROBERTS ◽

N. WOOD

Keyword(s):

Leading Edge ◽

Delta Wings ◽

Vortical Flows ◽

High Angles Of Attack

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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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Force and flowfield measurements to understand unsteady aerodynamics of cycloidal rotors in hover at ultra-low Reynolds numbers

International Journal of Micro Air Vehicles ◽

10.1177/1756829319833677 ◽

2019 ◽

Vol 11 ◽

pp. 175682931983367

Author(s):

Carolyn M Reed ◽

David A Coleman ◽

Moble Benedict

Keyword(s):

Separation Bubble ◽

Fluid Dynamic ◽

Unsteady Aerodynamics ◽

Leading Edge ◽

Reynolds Numbers ◽

Dynamic Stall ◽

Static Case ◽

Low Reynolds Numbers ◽

Curvature Effects ◽

Low Reynolds

This paper provides a fundamental understanding of the unsteady fluid-dynamic phenomena on a cycloidal rotor blade operating at ultra-low Reynolds numbers (Re ∼ 18,000) by utilizing a combination of instantaneous blade force and flowfield measurements. The dynamic blade force coefficients were almost double the static ones, indicating the role of dynamic stall. For the dynamic case, the blade lift monotonically increased up to ±45° pitch amplitude; however, for the static case, the flow separated from the leading edge after around 15° with a large laminar separation bubble. There was significant asymmetry in the lift and drag coefficients between the upper and lower halves of the trajectory due to the flow curvature effects (virtual camber). The particle image velocimetry measured flowfield showed the dynamic stall process during the upper half to be significantly different from the lower half because of the reversal of dynamic virtual camber. Even at such low Reynolds numbers, the pressure forces, as opposed to viscous forces, were found to be dominant on the cyclorotor blade. The power required for rotation (rather than pitching power) dominated the total blade power.

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