scholarly journals Practical Energy Dissipation Control of Near Space Glider on Independent Longitudinal Plane

2020 ◽  
Vol 2020 ◽  
pp. 1-22
Author(s):  
Zhigang Chen ◽  
Ying Wang ◽  
Mingwei Sun ◽  
Zenghui Wang ◽  
Zengqiang Chen
Keyword(s):  
Flight Time ◽  
Important Indicator ◽  
Pitch Control ◽  
Longitudinal Plane ◽  
Near Space ◽  
Typical Trajectory ◽  
Control Scheme ◽  
Bang Bang Control ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The near-space hypersonic aerodynamic glider has strong maneuverability in wide flight envelope. The glide is generally achieved in a smooth manner with no or weak altitude oscillations in the altitude. The maximum lift-to-drag ratio glide is a typical trajectory that can approximate the maximum glide range, which is a crucial indicator for a glider. However, another important indicator, the minimum glide range, which is used in some time-sensitive missions and is expected to reduce the velocity to a specified threshold in a short longitudinal range, is difficult to be realized. In practice, the excessive velocity or energy is usually dissipated during lateral manipulation, wherein either the entire glide range or the glide time is not shortened. An innovative guidance strategy is proposed for achieving the minimum glide range based on a typical maximum glide scheme and bang-bang control scheme only on the longitudinal plane, and the flight time can be reduced considerably. Then, a practical extended state observer based pitch control is utilized to efficiently track the bang-bang command within a wide velocity envelope to achieve the guidance objective. Extensive simulation results demonstrate the effectiveness of the proposed methods.

Gurney flap scaling for optimum lift-to-drag ratio

AIAA Journal ◽  
1997 ◽  
Vol 35 ◽  
pp. 1888-1890 ◽  
Author(s):  
Philippe Giguere ◽  
Guy Dumas ◽  
Jean Lemay
Keyword(s):  
Gurney Flap ◽  
Drag Ratio ◽  
Lift To Drag Ratio

scholarly journals A Parametric Study of Trailing Edge Flap Implementation on Three Different Airfoils Through an Artificial Neuronal Network

Symmetry ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 828
Author(s):  
Igor Rodriguez-Eguia ◽  
Iñigo Errasti ◽  
Unai Fernandez-Gamiz ◽  
Jesús María Blanco ◽  
Ekaitz Zulueta ◽  
...  
Keyword(s):  
Aerodynamic Coefficients ◽  
Trailing Edge ◽  
High Lift ◽  
Trailing Edge Flaps ◽  
Artificial Neural Network Ann ◽  
Lift And Drag ◽  
Artificial Neuronal Network ◽  
Naca 0012 ◽  
Drag Ratio ◽  
Lift To Drag Ratio

Trailing edge flaps (TEFs) are high-lift devices that generate changes in the lift and drag coefficients of an airfoil. A large number of 2D simulations are performed in this study, in order to measure these changes in aerodynamic coefficients and to analyze them for a given Reynolds number. Three different airfoils, namely NACA 0012, NACA 64(3)-618, and S810, are studied in relation to three combinations of the following parameters: angle of attack, flap angle (deflection), and flaplength. Results are in concordance with the aerodynamic results expected when studying a TEF on an airfoil, showing the effect exerted by the three parameters on both aerodynamic coefficients lift and drag. Depending on whether the airfoil flap is deployed on either the pressure zone or the suction zone, the lift-to-drag ratio, CL/CD, will increase or decrease, respectively. Besides, the use of a larger flap length will increase the higher values and decrease the lower values of the CL/CD ratio. In addition, an artificial neural network (ANN) based prediction model for aerodynamic forces was built through the results obtained from the research.

scholarly journals Fluid–structure interaction simulation on flight performance of a dragonfly wing under different pterostigma weights

2021 ◽  
Vol 37 ◽  
pp. 216-229
Author(s):  
Yung Jeh Chu ◽  
Poo Balan Ganesan ◽  
Mohamad Azlin Ali
Keyword(s):  
Optimization Design ◽  
Fluid Structure Interaction ◽  
Spatial Location ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Dragonfly Wing ◽  
Interaction Simulation ◽  
Wing Performance ◽  
Drag Ratio ◽  
Lift To Drag Ratio

Abstract The dragonfly wings provide insights for designing an efficient biomimetic micro air vehicle (BMAV). In this regard, this study focuses on investigating the effect of the pterostigma weight loading and its spatial location on the forewings of dragonfly by using the fluid–structure interaction simulation. This study also investigates the effect of change in the wing elasticity and density on the wing performance. The forewing, which mimics the real dragonfly wing, is flat with a 47.5 mm span and a 0.4 mm thickness. The wing was set to cruise at 3 m/s with a constant flapping motion at a frequency of 25 Hz. This study shows that a small increase of pterostigma loading (11% of wing weight) at the tip of the wing significantly improves the lift to drag ratio, CL/CD, which has 129.16% increment in comparison with no loading. The lift to drag ratio depends on the pterostigma location, pterostigma loading, elastic modulus and density. The results of this study can be used as a reference in future BMAV wing optimization design.

Aerodynamic study of single corrugated variable-camber morphing aerofoil concept

2021 ◽  
pp. 1-29
Author(s):  
K. Dhileep ◽  
D. Kumar ◽  
P.N. Gautham Vigneswar ◽  
P. Soni ◽  
S. Ghosh ◽  
...  
Keyword(s):  
Finite Volume ◽  
Interpolation Method ◽  
Beam Theory ◽  
Small Deformation ◽  
Aerodynamic Characteristics ◽  
Ansys Fluent ◽  
Aerodynamic Efficiency ◽  
Finite Element Software ◽  
Drag Ratio ◽  
Lift To Drag Ratio

Abstract Camber morphing is an effective way to control the lift generated by any aerofoil and potentially improve the range (as measured by the lift-to-drag ratio) and endurance (as measured by $C_l^{3/2}/C_d$ ). This can be especially useful for fixed-wing Unmanned Aerial Vehicles (UAVs) undergoing different flying manoeuvres and flight phases. This work investigates the aerodynamic characteristics of the NACA0012 aerofoil morphed using a Single Corrugated Variable-Camber (SCVC) morphing approach. Structural analysis and morphed shapes are obtained based on small-deformation beam theory using chain calculations and validated using finite-element software. The aerofoil is then reconstructed from the camber line using a Radial Basis Function (RBF)-based interpolation method (J.H.S. Fincham and M.I. Friswell, “Aerodynamic optimisation of a camber morphing aerofoil,” Aerosp. Sci. Technol., 2015). The aerodynamic analysis is done by employing two different finite-volume solvers (OpenFOAM and ANSYS-Fluent) and a panel method code (XFoil). Results reveal that the aerodynamic coefficients predicted by the two finite-volume solvers using a fully turbulent flow assumption are similar but differ from those predicted by XFoil. The aerodynamic efficiency and endurance factor of morphed aerofoils indicate that morphing is beneficial at moderate to high lift requirements. Further, the optimal morphing angle increases with an increase in the required lift. Finally, it is observed for a fixed angle-of-attack that an optimum morphing angle exists for which the aerodynamic efficiency becomes maximum.

Hydrodynamic Evaluation of a Generic Sail Used in an Innovative Prawn-Trawl Otter Board

2015 ◽  
Author(s):  
Cheslav Balash ◽  
David Sterling ◽  
Matt Broadhurst ◽  
Arno Dubois ◽  
Morgan Behrel
Keyword(s):  
Degrees Of Freedom ◽  
Design Feature ◽  
Hydrodynamic Characteristics ◽  
Flat Plates ◽  
Successful Operation ◽  
Six Degrees Of Freedom ◽  
Recent Innovation ◽  
Hydrodynamic Evaluation ◽  
Drag Ratio ◽  
Lift To Drag Ratio

In prawn-trawling operations, otter boards provide the horizontal force required to maintain net openings, and are typically low aspect ratio (∼0.5) flat plates operating on the seabed at high angles of attack (AOA; 35–40°). Such characteristics cause otter boards to account for up to 30% of the total trawling resistance, including that from the vessel. A recent innovation is the batwing otter board, which is designed to spread trawls with substantially less towing resistance and benthic impacts. A key design feature is the use of a sail, instead of a flat plate, as the hydrodynamic foil. The superior drag and benthic performance of the batwing is achieved by (i) successful operation at an AOA of ∼20° and (ii) having the heavy sea floor contact shoe in line with the direction of tow. This study investigated the hydrodynamic characteristics of a generic sail by varying its twist and camber, to identify optimal settings for maximum spreading efficiency and stability. Loads in six degrees of freedom were measured at AOAs between 0 and 40° in a flume tank at a constant flow velocity, and with five combinations of twist and camber. The results showed that for the studied sail, the design AOA (20°) provides a suitable compromise between greater efficiency (occurring at lower AOAs) and greater effectiveness (occurring at higher AOAs). At optimum settings (20°, medium camber and twist), a lift-to-drag ratio >3 was achieved, which is ∼3 times more than that of contemporary prawn-trawling otter boards. Such a result implies relative drag reductions of 10–20% for trawling systems, depending on the rig configuration.

scholarly journals Review of space vehicle control and guidance methods at atmosphere reentry

2021 ◽  
pp. 1-20
Author(s):  
Alexander Sergeevich Samotokhin
Keyword(s):  
Space Vehicle ◽  
Vehicle Control ◽  
Control Methods ◽  
The Moon ◽  
Reentry Vehicles ◽  
Drag Ratio ◽  
Lift To Drag Ratio

Review of control methods for statically stable reentry vehicles with low lift-to-drag ratio at returning from the Moon is presented. We are considering algorithms that have been used in Soviet and American Moon programs, as well as advanced algorithms that now are developed. General trends of advanced domestic and foreign methods are determined.

scholarly journals Aerodynamic and Vibration Characteristics of the Micro-Octocopter at Low Reynolds Number

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Xiaohua Zou ◽  
Mingsheng Ling ◽  
Wenzheng Zhai
Keyword(s):  
Reynolds Number ◽  
Load Capacity ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Aerodynamic Characteristics ◽  
Vibration Characteristics ◽  
Low Reynolds ◽  
Vibration Performance ◽  
Drag Ratio ◽  
Lift To Drag Ratio

With the development of flight technology, the need for stable aerodynamic and vibration performance of the aircraft in the civil and military fields has gradually increased. In this case, the requirements for aerodynamic and vibration characteristics of the aircraft have also been strengthened. The existing four-rotor aircraft carries limited airborne equipment and payload, while the current eight-rotor aircraft adopts a plane layout. The size of the propeller is generally fixed, including the load capacity. The upper and lower tower layout analyzed in this paper can effectively solve the problems of insufficient four-axis load and unstable aerodynamic and vibration performance of the existing eight-axis aircraft. This paper takes the miniature octorotor as the research object and studies the aerodynamic characteristics of the miniature octorotor at different low Reynolds numbers, different air pressures and thicknesses, and the lift coefficient and lift-to-drag ratio, as well as the vibration under different elastic moduli and air pressure characteristics. The research algorithm adopted in this paper is the numerical method of fluid-solid cohesion and the control equation of flow field analysis. The research results show that, with the increase in the Reynolds number within a certain range, the aerodynamic characteristics of the miniature octorotor gradually become better. When the elastic modulus is 2.5 E, the aircraft’s specific performance is that the lift increases, the critical angle of attack increases, the drag decreases, the lift-to-drag ratio increases significantly, and the angle of attack decreases. However, the transition position of the flow around the airfoil surface is getting closer to the leading edge, and its state is more likely to transition from laminar flow to turbulent flow. When the unidirectional carbon fiber-reinforced thickness is 0.2 mm and the thin arc-shaped airfoil with the convex structure has a uniform thickness of 2.5% and a uniform curvature of 4.5%, the aerodynamic and vibration characteristics of the octorotor aircraft are most beneficial to flight.

Augmentation of Lift-to-Drag Ratio for a Wing Using Thermal Forcing

2022 ◽  
Author(s):  
Mehul Varshney ◽  
Anchal Varshney ◽  
Faisal M. Baig
Keyword(s):  
Thermal Forcing ◽  
Drag Ratio ◽  
Lift To Drag Ratio

Kinematics of diving Atlantic puffins (Fratercula arctica L.):evidence for an active upstroke

2002 ◽  
Vol 205 (3) ◽  
pp. 371-378
Author(s):  
L. Christoffer Johansson ◽  
Björn S. Wetterholm Aldrin
Keyword(s):  
Three Dimensional ◽  
Fratercula Arctica ◽  
Induced Drag ◽  
Video Images ◽  
Hand Bones ◽  
On Line ◽  
Oscillating Motion ◽  
Drag Ratio ◽  
Wing Tip ◽  
Lift To Drag Ratio

SUMMARY To examine the propulsion mechanism of diving Atlantic puffins (Fratercula arctica), their three-dimensional kinematics was investigated by digital analysis of sequential video images of dorsal and lateral views. During the dives of this wing-propelled bird, the wings are partly folded, with the handwings directed backwards. The wings go through an oscillating motion in which the joint between the radius-ulna and the hand bones leads the motion, with the wing tip following. There is a large rotary motion of the wings during the stroke, with the wings being pronated at the beginning of the downstroke and supinated at the end of the downstroke/beginning of the upstroke. Calculated instantaneous velocities and accelerations of the bodies of the birds show that, during the downstroke, the birds accelerate upwards and forwards. During the upstroke, the birds accelerate downwards and, in some sequences analysed, also forwards, but in most cases the birds decelerate. In all the upstrokes analysed, the forward/backward acceleration shows the same pattern, with a reduced deceleration or even a forward acceleration during ‘mid’ upstroke indicating the production of a forward force, thrust. Our results show that the Atlantic puffin can use an active upstroke during diving, in contradiction to previous data. Furthermore, we suggest that the partly folded wings of diving puffins might act as efficient aft-swept wingtips, reducing the induced drag and increasing the lift-to-drag ratio. A movie is available on-line.

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