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Saturday, April 25, 2020 | History

2 edition of Leading edge flows on highly swept wings found in the catalog.

Leading edge flows on highly swept wings

P. R. Ashill

Leading edge flows on highly swept wings

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  • 32 Currently reading

Published by Defence Research Agency in Farnborough .
Written in English


Edition Notes

StatementP.R. Ashill, C.J. Betts.
SeriesTechnical report -- 94026/1
ContributionsBetts, C. J., Defence Research Agency.
ID Numbers
Open LibraryOL21686758M

  With swept wings, the airflow wants to "slide" down the swept leading edge. On conventional swept wings, that leads to reduction in effectiveness of the ailerons, and can aid in the development of tip stall because the wing tip section is usually smaller and . What is the primary function of the leading edge flaps in landing configuration during the flare before touchdown. what is the free stream mach number which produces first evidence of local sonic flow. more effective than trailing edge devices on swept wings. high density altitude conditions result in. higher true airspeeds.   The Citation X uses leading edge slats to keep landing distance reduced. You can see that straight wing aircraft are slower, but land and takeoff in shorter distances. Swept wing aircraft fly faster, but take more runway length. Swept wings are heavier than a straight wing for the same lift, and more costly to build.


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Leading edge flows on highly swept wings by P. R. Ashill Download PDF EPUB FB2

Flow Separation on Wings with Highly Swept Leading Edge—Experimental Observations Posted by admin in UNSTEADY INCOMPRESSIBLE POTENTIAL FLOW on Febru The high angle of attack separated flow pattern, based on numerous flow visualizations (see Refs.

) over highly swept wings (e. g., a small-zR delta wing) in terms of the crossflow is depicted in Section BB. In this chapter, low‐speed aerodynamics of highly swept wings is discussed. Highly swept wings, known as delta wings, can fly at high angle of attack without stall.

This quality is invaluable for military aircraft during a high angle of attack maneuver. Leading‐edge vortices develop on highly swept wings as a result of flow separation and contribute to the lift : Ismet Gursul, Zhijin Wang.

Effects of leading­-edge tubercles on swept tapered wing flow characteristics that results in highly three­dimensional separation patterns.

effects of leading-edge tubercles on swept. LE Leading edge PF Potential Flow PV Primary Vortex SV Secondary Vortex TE Trailing Edge RP Reattachment Point SF Surface Flow (boundary layer) These next two drawings are a bit harder to find, especially in older books.

They also show the starboard wing. The flow physics of highly swept wings is dominated by a vortical flowfield, which occurs already at low angles of attack due to the separation of the flow at the leading edge.

Figure 1 shows an example of the complex vortical flowfield of a generic blended-wing/body configuration with a Cited by: 7. The water-tunnel observations were concerned with how sweeping back the leading edge could transform the highly turbulent flow of the leading-edge separated flow on a stalled unswept sharp-edged wing into the stable vortex-flow characteristics of a highly swept wing.

Physical Considerations of Leading Edge Flows. shear layer separating from the sharp leading edge of a highly swept wing. highly swept wings and at high angles of attack flight conditions.

Wings with subsonic leading edges have lower wave drag than those with supersonic edges. Consequently, highly swept wings (e.g., slender deltas) are the preferred configuration at supersonic speeds.

On the other hand, swept wings with supersonic leading edges tend to have a greater wave drag than do straight wings.

View chapter Purchase book. It will otherwise experience the same aerodynamic effects of a straight constant chord wing (ie. tip stall immunity, lack of increased spanwise flows associated with swept wings, same effective AOA from root to tips except for effects of spanwise flow of regular straight wings) since the leading edge is unswept.

Wings, tapered or untapered, that are swept to the extent that both leading edge. Provided that the wings are not too highly tapered, the flow over them tached type of leading-edge flow over the wing. Separation then takes place Aerodynamic Design of Swept Wings and Bodies 3. WING PLANFORM DESIGN As pointed out in the previous section, swept vsings with conventional File Size: 6MB.

Emphasis was placed on low speed performance, stability, and control characteristics of configurations with highly swept wings. Simple deflection of the leading edge, a variable camber leading edge system, and a leading edge vortex flow system were among the concepts studied.

The data are presented without analysis. Flight tests on the Handley Page suction wing showed that turbulence at the wing root can propagate along the leading edge and cause the whole flow to be turbulent.

The flow on the attachment line of a swept wing was studied in a Leading edge flows on highly swept wings book speed wind tunnel with particular reference to this problem of turbulent by:   Wei Z, New T H and Cui Y D a Aerodynamic performance and surface flow structures of leading-edge tubercled tapered swept-back wings AIAA J.

56 –31 Crossref Google Scholar Wei Z, Lian L and Zhong Y b Enhancing the hydrodynamic performance of a tapered swept-back wing through leading-edge tubercles Exp.

Fluids 59 Cited by: 3. highly-swept F XL, the wings have moderate leading-edge sweep values, from a slender wing perspective, that will be conducive to leading-edge vortex separation at maneuver angles of attack.

The double values for wing leading edge sweep represent the inboard and outboard angles for the cranked FXL and X wings. Overall theFile Size: 3MB. Vortex lift is that portion of lift due to the action of leading edge vortices. It is generated by wings with highly sweptback, sharp, leading edges or highly-swept wing-root extensions added to a wing of moderate sweep.

It is sometimes known as non-linear lift due to its rapid increase with angle of attack. and controlled separation lift, to distinguish it from conventional lift which occurs with attached flow. Well, spanwise flow happens because air behaves like a liquid and will take the path of least resistance.

In this case it's along the swept leading edge it tends to move as that offers less resistance than going over the wing to some degree (very simply explained - there's more to it).

A swept wing just looks like it has less drag. Explaining why is more difficult - and the answer may surprise you. Sweeping the wings makes the wing feel like it's flying slower.

That, in turn, delays the onset of supersonic airflow over the wing - which delays wave drag. But it's not all benefit - there's a hefty price which shows up at slow. The present work is investigating the vortex-dominated flow physics as well as the aerodynamic behavior of swept wing configurations with round leading edges.

The research is based on numerical simulations using the computational fluid dynamics method DLR TAU. The target configurations are swept wings of constant aspect ratio, variable leading-edge contours, and leading-edge sweep by: 7.

The detailed characteristics of the flow field associated with the leading-edge vortices are indeed very complicated. Certain simplifying approximations must be made in order to construct mathematical models to be used to predict the effects of the leading-edge vortices.

vortex flow on highly swept wings File Size: 1MB. The wing being based on a NACA airfoil had a round leading edge that prevented the generation of a leading edge vortex prior to tip trailing edge stall, thus its first pitch-up departure was due to flow separation at the tip. The interaction between the tip separation and the leading edge vortex resulted in another non-linear pitch behavior.

WIND TUNNEL TEST RESULTS OF A NEW LEADING EDGE FLAP DESIGN FOR HIGHLY SWEPT WINGS - A VORTEX FLAP L. James Runyan, Wilbur D. Middleton, and John A. Paulson, Boeing Commercial Airplane Company SUMMARY.

A new leading edge flap design for highly swept wings, called a vortex flap, has been tested on an arrow wing model in a low speed wind tunnel. supersonic wing designs. This leading-edge flow separation completely alters the character of the flow pattern over the wing.

Leading-edge flow separation is only one of the reasons why the predicted low drag levels of highly swept wings could not be obtained. The trailing edge of these highly swept wingsFile Size: KB. An alternate approach for controlling the leading-edge vortex for highly swept wings was proposed by Runyan (ref.

41), who investigated the effect of a leading-edge tab counterdeflected from the main portion of the flap. Project Description: Delta wings, a paradigmatic configuration of highly swept wings, are common platforms for investigating highly manoeuvrable and agile high-speed civil and military aircrafts.

At moderate angles of attack, two counter-rotating vortical structures form at the leading edge. A survey is presented of factors affecting blunt leading-edge separation for swept and semi-slender wings.

This class of separation often results in the onset and progression of separation-induced vortical flow over a slender or semi-slender wing.

The term semi-slender is used to distinguish wings with moderate sweeps and aspect ratios from the more traditional highly-swept, low-aspect-ratio. Ashill [7] provides interesting flow control applications on highly swept wings using sub-boundary layer (low-profile) vortex generators.

The experiments took place in the 13ft x 9ft Wind Tunnel at DERA, Bedford, on 60o leading-edge sweep delta wing models at a freestream Mach number of and a. The spanwise flow on swept wings produces airflow that moves the stagnation point on the leading edge of any individual wing segment further beneath the leading edge, increasing effective angle of attack of wing segments relative to its neighbouring forward segment.

The result is that wing segments farther towards the rear operate at increasingly higher angles of attack promoting early stall of those segments. Swept wings are beneficial at transonic flight regimes (M=). At transonic flight regimes there is a drastic increase in drag (CD is more or less constant up until that point) due to the effects of compressibility, which manifest themselves in local sonic regions on the wing (the plane itself can be flying at M=, yet over some portions of the wing, where the pressure is low.

Surface oil flow visualization is a relatively simple method that allows visualization of the time averaged flow over the surface of the model. By analyzing the oil flow pattern it is possible to locate areas of separated and reversed flow as well as leading-edge vortices on a swept wing.

This information can be used to better understand. Wing leading edge joint laminar flow tests (OCoLC) Online version: Drake, Aaron. Wing leading edge joint laminar flow tests (OCoLC) Material Type: Government publication, National government publication: Document Type: Book: All Authors / Contributors: Aaron Drake; Ames Research Center.

Vortex lift is caused by flow separation at the leading edge. While this indicates a severe stall on unswept wings, the separated flow along a highly swept edge will roll up and will produce a conical, stable vortex. The speeds due to this helical movement of air cause air pressure over the wing to drop, which provides the suction that produces.

This book illustrates the use of bio-inspired leading-edge tubercles derived from humpback whale flippers as passive flow control devices and discusses detailed scientific findings from both experimental and numerical investigations on leading-edge tubercles and their engineering implementations.

CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): SummaryThe simple model used by Brown and Michael to represent the flow past a slender delta wing with leading edge separation, is extended to treat wings which have pointed apexes, curved leading edges and straight, unswept trailing edges.

The vorticity of the fluid near the leading edge is represented by all. Improvements in Delta Wings. Due to the various disadvantages of delta wings considered there was a need for improvement which led to the development of compound delta wings.

In compound delta wings a more highly swept delta wing is added in front of the main delta wing. This creates a controlled vortex and further reduces the drag. Introduction. The leading-edge vortex (LEV) is a commonly found mechanism that, under the correct conditions, can significantly augment the lift generation of both manufactured and natural fliers [1–4].The LEV is robust to kinematic change [] and has been identified across a wide range of Reynolds numbers (Re) (table 1), from the laminar flow conditions (10Cited by: 4.

A thick wing, with a rounded leading edge, will have a very high wave drag if it experiences transonic or supersonic flows. In addition, wing sweep reduces the local mach number and delays the occurrence of wave drag in transonic flight.

This is why fast aircraft tend to have highly swept wings. Supersonic Laminar Flow Control (LFC) airplanes with externally braced highly swept LFC wings of high structural aspect ratio (with the sweep increasing towards the wing root) offer particularly high supersonic cruise (L/D)'s with low sonic boom the design cruise condition the flow in the direction normal to the upper surface isobars is transonic (with embedded Cited by:   There are two reasons why this happens: 1.

The downwash pattern on a swept wing tends to increase the AoA towards the wingtip. This is difficult to visualize because we normally think of downwash as caused by wingtip vortices, but aerodynamic theo. Get this from a library. Effects of leading-edge devices on the low-speed aerodynamic characteristics of a highly-swept arrow-wing.

[Samuel J Scott; Oran W Nicks; P K Imbrie; Langley Research Center.]. The flow structure that is largely responsible for the good performance of insect wings has recently been identified as a leading-edge vortex1,2.

But Cited by:. up at modest angles of attack (as low as 5˚) during low-speed flight due to leading edge vortex influence, flow separation and vortex breakdown. The work presented here describes an investigation conducted to study past research on the longitudinal aerodynamic characteristics of highly-swept cranked wing planforms, the development of a new methodFile Size: KB.

I remember reading something like if the shockwave was in front of the wing you'd get a subsonic flow component or something over the leading edge. If I recall that's why supersonic planes used conical-camber and some highly swept wings used blunt leading-edges.

From what I remember it didn't matter if the wave was a normal or oblique shock.Schematics of the Leading Edge Vortex over the Highly Swept Delta Wings The structure of the leading edge vortex over the delta wing is shown in the left figure.

It can be seen that the leading edge vortex over the delta wing is made up of three parts which are .