4. Description:
TITLE: Saw Toothed Leading Edge Delta Wings

FIELD OF THE INVENTION

The present invention relates to the field of aerodynamics, more particularly subsonic aerodynamics to determine the aerodynamic behavior of the delta wings at higher angles of attack with leading edge protuberances.

BACKGROUND OF THE INVENTION

A leading-edge protuberance or an extension acts like a passive control device, which improves the airflow over the wing to sustain high angle of attack flight. Saw toothed leading edges also acts like a protuberance which encourages a vortex flow on the surface of the delta wing by which stall can be delayed to higher angles of attack.

A dog tooth can also improve airflow and reduce drag at higher speeds. A Leading edge slat is an aerodynamic surface running spanwise just ahead of the wing leading edge. It directs air over the wing surface, helping to maintain smooth airflow at low speeds and high angles of attack. This delays the stall, allowing the aircraft to fly at a higher angle of attack. Slats may be made fixed, or retractable in normal flight to minimize drag.

Earlier prior art shows about dogtooth extension, wherein the said dog tooth extension is a small, sharp zig zag break in the leading edge of the wing. It is usually used on a swept wing, to generate a vortex flow field to prevent separated flow from progressing outboard at high angle of attack. The effect is the same as a wing fence. It can also be used on straight wings in a Drooped Leading Edge arrangement.

Soderman studied the effect of saw-tooth edge attached to the leading edge of a two-dimensional airfoil. The results showed that saw-tooth pattern leading edge can reduce the separation region and drag coefficient.

Cranston et al. created serrations (saw-tooth like pattern) on flat plates and showed that the size of the serrations for low Reynolds number flow affects the aerodynamics

characteristics and bubble separation. They found that the use of serrations is more efficient at higher Reynolds numbers. The use of small serrations results in increase in lift coefficient, while the use of large serrations showed reduction in lift.

Dr. Fish [2] discovered that the Humpback Whale even after its huge weight can able to do sharp maneuvers just because of large aspect ratio wings along with tubercles present on their leading edge. He has later shown that sinusoidal tubercles improve the efficiency of high aspect ratio wings.

Many researchers have investigated the phenomenon of the saw toothed leading edges over two dimensional aerofoils (infinite wings), finite wings which are in rectangular planform. But no investigations have been reported on the leading edge of the delta wings. The same concept is considered but with a sharp saw tooth on a 65 degree sweep angle delta wing. Part of leading edges of the delta wing is designed with saw tooth, sharp corners directly facing the oncoming flow field.

Since highly swept black wings like delta wings already have stable vortices at low to medium ranges of angle of attack, reports shows that the stabilization of vortices have been done in many ways excluding the proposed method here.

The present invention on delta wing is expected to increase the high angle of attack performance of aircrafts during incompressible subsonic to compressible subsonic Mach numbers. The aerodynamic mechanism of saw tooths works on the delta wing in different way than on a normal rectangular wing. The design of saw tooths has to be chosen in such a way that they stabilize the existing vortices make them to be attached over a greater downstream length and also towards higher angles of attack.

OBJECTIVE OF THE INVENTION
1. The primary object of the present invention is to improve the post stall characteristics of the delta wings.
2. Another objective is to use a kind of 'Z' shaped saw tooth protuberances, facing their sharp corners directly to oncoming wind stream to encourage the vortex flow on the surface of the delta wing.

3. It is yet another objective of the present invention to delay the stall towards higher angles of attack.

SUMMARY OF THE INVENTION

It will be understood that this disclosure is not limited to the particular systems, and methodologies described, as there can be multiple possible embodiments of the present disclosure which are not expressly illustrated in the present disclosure. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present disclosure.

The present invention comprises of a saw tooth on the part of the length of beveled leading edge of delta wings which are like protuberance encouraging a vortex flow on the surface of the delta wing. This further provides a stable pair of vortex formation at higher angles of attack enhancing the delay in the stall.

The protuberance like various leading edge patterns alter the vortex behavior by making them attached to the surface at higher angles of attack, provided if sufficient vorticity is induced in to the flow, whereby the post stall performance can be improved.
The Saw tooth delays the stalling characteristics by stabilising vortices and making them attached to the surface to longer extent in the flow direction. These stabilized vortices creates low pressure zone over the surface of the delta wing up to higher angles of attack, by which lift increases and maneuver performance can also be expected to increase.

BRIEF DESCRIPTION OF DRAWINGS:

For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:

Fig 1 illustrates an exemplary embodiment of the saw toothed 65 degree swept angle flat plate delta wing..

Fig 2 illustrates an exemplary embodiment of the left view of the saw toothed 65 degree swept angle flat plate delta wing.
DETAILED DESCRIPTION OF THE INVENTION:

The following detailed description illustrates by way of example and not by way of limitations.

Embodiments of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings in which like numerals represent like elements throughout the several figures, and in which example embodiments are shown.
Embodiments of the claims may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. The examples set forth herein are non-limiting examples and are merely examples among other possible examples.

In the disclosure herein, consideration or use of a particular element number in a given FIGURE or corresponding descriptive material can encompass the same, an equivalent, or an analogous element number identified in another FIGURE or descriptive material corresponding thereto. Some embodiments of this invention, illustrating all its features, will now be discussed in detail. The words "comprising," "having," "containing," and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items.

It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any systems and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, the preferred, systems and methods are now described.

Some embodiments may be described using the expression "one embodiment" or "an embodiment" along with their derivatives. These terms mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment. Further, some embodiments may be described using the expression "coupled" and "connected" along with their derivatives. These terms are not necessarily intended as synonyms for each other. For example, some embodiments may be described using the terms "connected" and/or "coupled" to indicate that two or more elements are in direct physical or electrical contact with each other. The term "coupled," however, may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other.

Referring to the drawings, Fig 1 and 2 illustrates an exemplary embodiment of the saw toothed 65 degree delta wing 100, 200 and 300 wherein the said delta wing comprises of sharp saw tooths 110 at the leading edge. The saw tooth at the leading edge of delta wing acts like passive control device. The said passive control device utilizes energy present in the flow to alter the flow pattern.

As illustrated in fig 1,2 and 3 the saw tooth comprises of tooth 110 which look like mirror images of English alphabet Z 115. The said saw tooth comprises of moderate corner angles. Further, the sharp saw tooth is placed on a triangular planform 65 degree 120 sweep angle delta wing. Moreover, only part of the leading edges of the delta wing is designed with saw tooth.

As illustrated in fig 1 and 2 the saw tooth sharp corners are made in such a way that they are straight projected to the oncoming flow whereby they induce some amount of vorticity in to the full free stream flow (not the component of free stream velocity) acting like a pin-point disturbance. The said saw tooth is made on the part of the length on both sides of leading edges leaving 20% of length in terms of maximum chord near the apex to allow undisturbed oncoming flow field and similarly part of trailing edge is left to allow smooth leaving of flow field or formed vortex.

Moreover, saw tooth sharp corners generates small vortices and add them to the existing bigger vortex, which will continue towards the trailing edge for longer lengths than for a plane delta wing. The said wings are made of aerofoil cross section or flat plate, if made with a flat plate, leading edge should have a bevel angle in order to avoid the affect of bluntness. The figure 2 illustrates the 65 degree flat plate delta wing with saw toothed leading edges having 45 degree bevel angle 200.

Since, the saw tooth induces some amount of vorticity in to the flow, they act like a disturbance to oncoming free stream. The location of protuberances to be placed on the wing is chosen such that these protuberances can alter the the flow physics at the vortex shedding locations on the surface of the delta wing. The approximate vortex shedding location for a plane leading edge delta wing can be traced from oil flow visualization or CFD studies. Therefore, location of saw tooth is chosen 20% of maximum chord distance away from the apex. This allowable distance from the apex also encourages natural vortex which exists for a delta wing to form smoothly. As the flow becomes weak near the trailing edge, protuberances in this location cannot show their influence. Hence part of trailing edge is left as plane trailing edge. Also this kind of design encourages a smooth leaving of the flow near the trailing edge.

The wave length is chosen to be 10-20% of the maximum chord (36mm here) or can be chosen such that whether the number of teeth provided is able to stabilize the vortices formed on the upper surface. Placing the protuberances throughout the length of the leading edge may give high amount of drag rise. Hence, protuberances should be placed such that they can alter the flow physics at the required zone or region.

Also the number of the tooth and their frequency is to be chosen based on the optimization of the drag rise and amount of vorticity to be induced in to the flow. For example, more number of tooth may show better higher angle characteristics, but it gives drag penalty.

The materials used as described above can be any one of the following: natural material, such as any type of wood, any form of metal, composite materials made out of fibre and resin combinations. Fibres can be natural or syntheitc - more particularly

glass fibre, carbon fibre, aramid fibre, boron fibre, nylon fibre, jute fibre, sisal hemp fibre along with any of the resins including isophthallic or bisphenol or Vinyl or Vinyl superior; Polymers either thermoplastic or thermoset and more particularly from any one of U-poly vinyl chloride, ABS, polyethylene, PET, polyoxy methylene, polytetrafluoroethylene, poly vinylidene fluorde or bakelite.

It is emphasized that the Abstract of the Disclosure is provided to allow a reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment. In the appended claims, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein," respectively. Moreover, the terms "first," "second," "third," and so forth, are used merely as labels, and are not intended to impose numerical requirements on their objects.

What has been described above includes examples of the disclosed architecture. It is, of course, not possible to describe every conceivable combination of components and/or methodologies, but one of ordinary skill in the art may recognize that many further combinations and permutations are possible. Accordingly, the novel architecture is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims.

Without further description, it is believed that one of ordinary skill in the art can, using the preceding description and the illustrative examples, make and utilize the present invention and practice the claimed methods. It should be understood that the foregoing discussion and examples merely present a detailed description of certain

preferred embodiments. It will be apparent to those of ordinary skill in the art that various modifications and equivalents can be made without departing from the spirit and scope of the invention.

5. Claims: We claim:
1. A saw toothed leading edge delta wings, comprising of sharp saw tooths on the part of leading edge of the delta wings, wherein the said saw tooth acts as a passive control device to induce vorticity in to the flow.
2. A saw toothed leading edge delta wings as claimed in claim 1, wherein the said saw tooth can be designed for any sweep angle delta wing.
3. A saw toothed leading edge delta wings as claimed in claim 1, wherein the said saw tooth, is in the shape of alphabet cz' facing the sharp corner directly to the oncoming flow field.
4. A saw toothed leading edge delta wings as claimed in claim 1, wherein the said leading edge comprises of parts without tooth to allow undisturbed oncoming flow field.
5. A saw toothed leading edge delta wings as claimed in claim 1, wherein the said saw tooth delta wings comprises of aerofoil cross section or flat plate.
6. A saw toothed leading edge delta wings as claimed in claim 1, wherein the said saw tooth delta wings is placed in the region where flow physics is to be altered.
7. A saw toothed leading edge delta wings as claimed in claim 1, wherein the said saw tooth induces vorticity in to the flow and acts as a disturbance to oncoming free stream.

8. A saw toothed leading edge delta wings as claimed in claim 1, wherein the said saw tooth are made on the length on both sides of the leading edge.
9. A saw toothed leading edge delta wings as claimed in claim 1, wherein the said saw tooth and its frequency is based on the optimization of the drag rise and amount of vorticity to be induced in to the flow.