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new trends in aerodynamics
- 1. MISSION ADAPTIVE COMPLIANT WINGS BY S TIWARI
- 2. LOOK AT THESE BIRDS
- 3. NOW LOOK AT THESE AIRCRAFT
- 4. MISSION ADAPTIVE COMPLIANT WINGS
- 5. INTRODUCTION Improving aircrafts efficiency is one of the key element of Aeronautics. For increasing aircraft efficiency, 50% of the researches are aimed To reduce drag. To increase lift. To reduce structural weight. To reduce system power take up.
- 6. BALANCING THE FOUR FORCES THE BIGGEST CHALLANGE
- 7. DRAG AND LIFT (a) Drag reduction is achieved by Reducing surface friction drag. Reducing form drag. Reducing induced drag. (b) Lift increase is achieved by Finding the most efficient Angle of Attack. Inventing new lift augmenting devices. Changing wing shape and size.
- 8. NEW TRENDS IN AERODYNAMICS Blended wing body or BWB. Twisteron. Fanwing. Spiroid Winglets. Mission adaptive compliant wings.
- 9. BLENDED WING BODY OR BWB
- 10. TWISTERON
- 11. SPIROID WINGLETS
- 12. FANWING
- 13. MISSION ADAPTIVE COMPLIANT WINGS
- 14. MISSION ADAPTIVE WINGS The mission adaptive wings are the wings which should be able to adapt itself to different flying conditions and should be able to fulfil conflicting mission requirements by morphing their wings.
- 15. CONFLICTING MISSION REQUIREMENTS We want our aircraft to be used as fighter i.e for high speed as well as bomber i.e for high lift. FIGHTER BOMBER
- 16. CONFLICTING MISSION REQUIREMENTS We want our aircrafts to cruise at relatively high speeds and at the same time it should be, easily or efficiently, able to support lower speeds such as those required for loitering, taking off, or landing.
- 17. MORPHING Morphing can be defined as “to cause something to change its outward Appearance”. Wing that can sense its environment and adapt its shape to perform optimally in a wide range of flight conditions.
- 18. SWIFT MORPHING OR ADAPTION HIGH SPEED LOW SPEED
- 19. CAN WE DO THIS?
- 20. MISSION ADAPTIVE COMPIANT WINGS
- 21. AERODYNAMICS BEHIND DIFFERENT SHAPES Different shapes and size produces different aerodynamic effects and different advantages.
- 22. AERODYNAMICS
- 25. MORPHING REQUIREMENTS Morphing requirements are:- Actuation system- Change in the airfoil shape in a controlled manner by different methods. Wing structural characteristics- withstand the aerodynamic forces and wing loadings. Must be able to achieve a seamless morph Compromise between stiffness and flexibility in the selected materials. Aerodynamic characteristics - Must ensure that the change in shape will result in measurable changes in flight characteristics.
- 26. MORPHING METHODS MULTIPLE ACTUATORS. •To control the camber of the aerofoil multiple actuators distributed throughout the wings were used. •Fibre glass flexi panels were bent by conventional rigid link mechanism. •These are aerodynamically superior than conventional flaps as their were no discontinuities and seams.
- 27. INCHWORM ACTUATORS Wing camber can be varied by employing inchworm actuators arranged in a truss manner within the wing ribs.
- 29. INTELLIGENT ACTUATORS PIEZOELECTRIC MATERIALS. Relation between mechanical stress and an electrical voltage. Its reversible process. Disadvantages. Inadequate displacement. Require excessive power, and/or are complex and heavy.
- 30. Shape Memory Alloy. Shape memory alloys (SMAs) are metals that "remember" their original shapes. SMAs actuators are materials that "change shape and mechanical characteristics in response to temperature or electromagnetic fields. Disadvantages. Insufficient Bandwidth. Require excessive power, and/or are complex and heavy.
- 31. THE MOST SUITABLE ALTERNATIVE APPROACH COMPLIANT MECHANISM
- 32. The energy was drawn from a few remotely located actuators and then this energy was distributed to the structure through some intermediary mechanism. Methodology employed is distributed compliance rather than distributed actuation Compliant Mechanisms (Structures) are structures that are specifically optimized to distribute localized actuation (strain) to change the shape of the structure.
- 33. COMPLIANT MECHANISMS SHEET GRIPPER
- 34. COMPLIANT MECHANISMS •Monolithic. •Joint Less Structures •These structures exploits elasticity of the material to produce desired functionalities. •These functionalities can include force or motion transmission, motion guidance, shape morphing and energy storage and release.
- 35. COMPLIANT MECHANISM The arrangement of the material within the compliant mechanism is optimized so compliance is distributed through small strains to produce large deformations.
- 36. COMPLIANT MECHANISM Note that the design does not embody any flexural joints, which create stress concentrations and poor fatigue life. Compliant structure deforms as a whole and avoids high-stress concentrations in which the flexion is concentrated in localized regions.
- 37. AMPLIFYING MOTION OR FORCE
- 38. COMPLIANT MECHANISM These are flexible mechanisms that transfer an input force or displacement to another point through elastic body deformation. These are usually monolithic (single-piece) or joint less structure.
- 39. ADVANTAGES Minimize or eliminate assembly requirements. Excellent repeatability since there is no backlash. No joints mean no joint friction, backlash, or need for lubrication. Can easily couple with modern actuators. Can create motions not possible with conventional rigid devices. Materials friendly. Weight reduction. Fatigue resistant.
- 40. COMPLIANT MECHANISM WINGS When normal aerofoils or wings are made mission adaptive by using the new technology called compliant mechanism then they are termed as mission adaptive compliant wings. The MACW technology provides lightweight, low-power, variable geometry re-shaping of the upper and lower surface with no seams or discontinuities.
- 42. MAKING OF MAW BY COMPLIANT MECHANISM FlexSys Inc, has developed a unique, variable-geometry, trailing edge flap that can re-contour the airfoil upper and lower surface.
- 43. Combined compliant flap system to a Natural Laminar Flow (NLF) airfoil. This airfoil can theoretically achieve up to 65% chord laminar flow on the upper surface and up to 90% chord laminar flow on the lower surface as opposed to a conventional hinged flap which can introduce flow separation at the flap knee.
- 44. The airfoil flap system is optimized to maximize the laminar boundary layer extent over a broad lift coefficient range. Data from flight testing revealed laminar flow was maintained over approximately 60% of the airfoil chord for much of the lift range. Drag results revealed that that was considerable decrease in drag and hence good lift/ drag ratio. FlexSys has developed morphing surfaces for both the leading and trailing edge.
- 46. SCHEMATIC OF COMPLIANT WING
- 47. POTENTIAL BENEFITS 25% decrease in drag and hence better lift/drag ratio than the conventional control surfaces, which resulted in fuel saving.
- 48. AERODYNAMIC BENEFITS OVER PLAIN FLAP
- 50. NOISE REDUCTION Compliant structures enable development of a seamless transition between the fixed and flapped portions of the wing as shown in Figure.
- 51. • The main purpose of this region is to reduce noise associated with the turbulent airflow generated by the discontinuous surfaces at the flap ends when the high lift flaps are deployed for landing. MAW FLAP CONVENTIONAL FLAP
- 52. MACW flaps can require less force and power than a comparably sized conventional flap. The MACW flap required 33% less actuation force. This is because a compliant flap with 33% shorter chord than a conventional flap can provide the same CL and Cm performance.
- 54. ADDITIONAL BENEFITS Can move into complex predetermined positions with minimal force. Can be locked in place at any desired configuration. Just as stiff and strong as a conventional control surface. The elimination of discontinuities in the flap surface can provide lower drag and higher control authority than comparable hinged flaps. The elimination of joints and seams make the flap more impervious to icing and fouling from debris.
- 55. CONCLUSION Sooner or later it will be possible to make wings without ailerons, flaps and thousands of individual parts. They will have in principle only one component, which continually changes shape.
- 56. ANY ?
- 57. THANK YOU
Notes de l'éditeur
- Do you find any similarities between these photograph? Yes, the similarity is that the both of them are changing the shape and size of there wings. But the question is why they are doing so? The answer is that they are trying to adopt themselves according to different flying condition.
- This type of wings are called mission adaptive wings and technology by which we will achieve this change is called compliant technology . Hence the wings which changes its shape and size according to the mission by using compliant technology is called mission adaptive compliant wings. Mission adaptive compliant wing improves the efficiency of the aircraft. How its improve the efficiency of the aircraft? What are the other methods to improve efficiency. Let’s see.
- Aircrafts efficiency can be increased by these methods. 50% of the researches to increase the aircraft efficiency are aimed to reduce drag, To increase lift To reduce structural weight To reduce system power take up. Look at these points carefully you will find that these are the four forces which balance the aircraft in the air.
- Balancing these four forces in a most efficient way has been the biggest challenge for Aerodynamic since its invention . As Managing the weight and thrust are structural and propulsion problems, we will look into lift and drag which are more or less aerodynamics problem
- By manipulating these forces we can use them to our advantage. To achieve this, the aero dynamists keep testing new designs. Lets have a look to some the latest trends to increase the efficiency of the aircraft by manipulating these two forces.
- These are some latest trends which increases the aircraft efficiency by reducing drag and increasing lift and good lift by drag ratio.
- Improved fuel economy due to less drag. Increase lift to drag ratio by an amazing 50%. Weight reduced by 25%. Reduced noise impact (if the engines are placed above the wings) Improved structural weight.
- Twisterons work by twisting the wings during flight. Twisting means aerodynamic washout (decreasing the camber towards wing tip) or geometric washout (decreasing angle of attack towards wing tip) The amount of twist the Twisterons use is determined by altitude, weight and the speed the airplane is traveling
- Cross-flow fan along the span of each wing. The fan pulls the air in at the front and then expels it over the wing's trailing edge. In transferring the work of the engine to the rotor, which spans the whole wing, the Fan Wing accelerates a large volume of air and achieves unusually high lift-efficiency.
- As the name suggests
- we want our aircraft to be used as fighter i.e high speed as well as bomber i.e high lift. Lets see what are conflicting mission requirements and morphing the two key word in definition.
- Structures that morph their shape in response to their surroundings may at first seem like the stuff of science fiction, but take a look at nature and you will see lots of examples of plants and animals that adapt to their environment. Have you ever seen a eagle or albatross flying for hours together without flapping their wings. They change the shape and size of their wings to improve their efficiency. Tree leaves curl up in high winds to reduce their drag; bird wings bend and flex to improve their aerodynamics.
- To control the camber of the aerofoil multiple actuators were used. These were distributed throughout the wings. In this figure we can see the trailing edge actuation of the wings by using the multiple actuators to vary the camber of the wing. Fibre glass flexi panels were bent by conventional rigid link mechanism. These are aerodynamically superior than conventional flaps as their were no discontinuities and seams. Unfortunately, there were so many drawbacks. So many mechanical linkages and multiple actuators resulted in weight penalties and made the system very complex
- In early 1995, during Phase I of the DARPA-funded Smart Wing Program, a variable wing camber system was investigated that employed inchworm actuators arranged in a truss manner within the wing ribs.
- The other efforts investigated the effects of changing the shape of a wing using many small actuators distributed throughout a helicopter rotor or a supersonic wing.
- The piezoelectric effect describes the relation between a mechanical stress and an electrical voltage in solids. It is reversbile: an applied mechanical stress will generate a voltage and an applied voltage will change the shape of the solid by a small amount (up to a 4% change in volume).
- Although in all these methods shape were changed by controlled structural deformation the flexibility of the underlying structure were not fully exploited.
- In this method instead of using a plethora of actuators to locally deform a stiff structure, an alternative approach was used. The energy was drawn from a few remotely located actuators and then this energy was distributed to the structure through some intermediary mechanism. The primary design methodology employed in this effort utilized distributed compliance rather than distributed actuation Compliant Mechanisms (Structures) are structures that are specifically optimized to distribute localized actuation (strain) to change the shape of the structure.
- In this method instead of using a plethora of actuators to locally deform a stiff structure, an alternative approach was used.
- . As we know all metal are elastic to some extent. Through compliant mechanism we can utilize the elasticity of underlying
- In contrast, compliance is distributed to lower maximum stress, thereby significantly improve fatigue life. Just as designs in nature are strong but compliant, so are bio-inspired complaint mechanisms, which enhance “value" in a number of ways:
- Just as designs in nature are strong but compliant, so are bio-inspired complaint mechanisms, which enhance “value" in a number of ways:
- with modern actuators are= piezoelectric, shape-memory alloy, electro-thermal, electrostatic, fluid pressure, and electromagnetic actuators. Materials friendly: can be built from any highly resilient material, including steel, aluminum, nickel Mission titanium alloys, polysilicon, ABS, polypropylene, polymer and metal matrix composites etc. Weight reduction: no need for restoring springs or bulky hinges.
- . Because NLF airfoils with long laminar runs have steep pressure gradients in the pressure recovery region, the gentle curvature change provided by a compliant flap can reduce or eliminate flow separation over the flap surface as opposed to a conventional hinged flap which can introduce flow separation at the flap knee.
- Research is targeted at minimizing the force required to morph surfaces while maintaining maximum stiffness to withstand external loading.
- The leading and trailing edge contain embedded compliant systems, consisting of a compliant mechanism, actuators, and a control system that triggers the actuators when flight conditions change.
- . Comparing equally sized trailing edge flaps, MACW flaps can provide up to a 40% increase in control authority per degree deflection over hinged control surfaces The boost in aerodynamic performance occurs not only at the aft portion where the trailing edge is located, but over the entire airfoil chord. For instance, at zero degree AOA, the compliant flap achieves nearly a 75% increase in L/D compared to the plain hinged flap
- allows the flap to be positioned with a linearly varying flap deflection along the wingspan. This has the benefit of allowing the flap to reshape the wing lift distribution closer to an elliptical distribution, reducing the lift levels on outboard sections of the wing in order to minimize the wing root bending moment – thus potentially saving weight. minimize the wing root bending moment – thus potentially saving weight.
- compliant structures enable development of a seamless transition between the fixed and flapped portions of the wing as shown in Figure. The main purpose of this region is to reduce noise associated with the turbulent airflow generated by the discontinuous surfaces at the flap ends when the high lift flaps are deployed for landing.
- One study comparing a MACW flap to a conventional trailing edge flap during a max G pull-up maneuver showed that the MACW flap required 33% less actuation force and 17% lower peak actuation power. This is because a compliant flap with 33% shorter chord than a conventional flap can provide the same CL and Cm performance.
- This design paradigm of distributed compliance While these structures have been described as “flexible,” they are optimized to resist deflection under significant external aerodynamic loading and are just as stiff and strong as a conventional control surface