Showing papers on "Wing root published in 2019"

An Experimental Investigation of a Wing-Fuselage Junction Model in the NASA Langley 14- by 22-Foot Subsonic Tunnel

Abstract: Current turbulence models, such as those employed in Reynolds-averaged Navier-Stokes CFD, are unable to reliably predict the onset and extent of the three-dimensional separated flow that typically occurs in wing-fuselage junctions. To critically assess, as well as to improve upon, existing turbulence models, experimental validation-quality flow-field data in the junction region is needed. In this report, we present an overview of experimental measurements on a wing-fuselage junction model that addresses this need. The experimental measurements were performed in the NASA Langley 14- by 22-Foot Subsonic Tunnel. The model was a full-span wing-fuselage body that was configured with truncated DLR-F6 wings, both with and without leading-edge extensions at the wing root. The model was tested at a fixed chord Reynolds number of 2.4 million, and angles-of-attack ranging from -10 degrees to +10 degrees were considered. Flow-field measurements were performed with a pair of miniature laser Doppler velocimetry (LDV) probes that were housed inside the model and attached to three-axis traverse systems. One LDV probe was used to measure the separated flow field in the trailing-edge junction region. The other LDV probe was alternately used to measure the flow field in the leading-edge region of the wing and to measure the incoming fuselage boundary layer well upstream of the leading edge. Both LDV probes provided measurements from which all three mean velocity components, all six independent components of the Reynolds-stress tensor, and all ten independent components of the velocity triple products were calculated. In addition to the flow-field measurements, static and dynamic pressures were measured at selected locations on the wings and fuselage of the model, infrared imaging was used to characterize boundary-layer transition, oil-flow visualization was used to visualize the separated flow in the leading- and trailing-edge regions of the wing, and unsteady shear stress was measured at limited locations using capacitive shear-stress sensors. Sample results from the measurement techniques employed during the test are presented and discussed.

Computational investigation of wing-body interaction and its lift enhancement effect in hummingbird forward flight

Abstract: A lift enhancement mechanism due to wing-body interaction (WBI) was previously proved to be significant in the forward flight of insect flyers with wide-shape bodies, such as cicada. In order to further explore WBI and its lift enhancement effect in a flapping flight platform with different wing and body shapes, numerical investigations of WBI were performed on the forward flight of a hummingbird in this paper. A high-fidelity computational model of a hummingbird in forward flight was modeled with its geometric complexity. The wing kinematics of flapping flight were prescribed using experimental data from previous literature. An immersed-boundary-method-based incompressible Navier‒Stokes solver was used for the 3D flow simulations of the wing-body system. Analyses on aerodynamic performances and vortex dynamics of three models, including the wing-body (WB), wing-only (WO), and body-only (BO) models, were made to examine the effect of WBI. Results have shown significant overall lift enhancement (OLE) due to WBI. The total lift force of the WB model increased by 29% compared with its WO/BO counterparts. Vortex dynamics results showed formations of unique body vortex pairs on the dorsal thorax of hummingbird where low-pressure zones were created to generate more body lift. Significant interactions between body vortex and leading-edge vortex (LEV) were observed, resulting in strengthened LEVs near the wing root and enhanced wing lift generation during downstroke. Parametric studies showed strong OLEs over wide ranges of body angle and advance ratio, respectively. The contribution of OLE from the hummingbird body increased with increasing body angle, and the wing pair's contribution increased as advance ratio increased. Results from this paper supported that lift enhancement due to WBI is potentially a general mechanism adopted by different kinds of flapping-wing flyers, and demonstrated the potential of WBI in the design of flapping-wing micro aerial vehicle (MAV) that pursue higher performance.

Flexible Aircraft Gust Load Alleviation with Incremental Nonlinear Dynamic Inversion

Abstract: This paper designs an incremental nonlinear dynamic inversion control law for free-flying flexible aircraft, which can regulate rigid-body motions, alleviate gust loads, reduce the wing root bendin...

Fiber-Optics-Based Aeroelastic Shape Sensing

Abstract: This paper presents a numerical and experimental wind tunnel study of aeroelastic shape sensing using fiber-optic sensors. Strain measurements via both discrete and distributed dynamic fiber-optic ...

Effects of phase lag on the hovering flight of damselfly and dragonfly.

Abstract: In this work we studied the differences in flight kinematics and aerodynamics that could relate to differences in wing morphologies of a dragonfly and a damselfly. The damselflies and dragonflies normally fly with the fore wing or hind wing in the lead, respectively. The wing of the damselfly is petiolate, which means that the wing root is narrower than that of the dragonfly. The influence of the biological morphology between the damselfly and the dragonfly on their hovering strategies is worthy of clarification. The flight motions of damselflies and dragonflies in hovering were recorded with two high-speed cameras; we analyzed the differences between their hovering motions using computational fluid dynamics. The distinct mechanisms of the hovering flight of damselflies (Matrona cyanoptera) and dragonflies (Neurothemis ramburii) with different phase lags between fore and hind wings were deduced. The results of a comparison of the differences of wing phases in hovering showed that the rotational effect has an important role in the aerodynamics; the interactions between fore and hind wings greatly affect their vortex structure and flight performance. The wake of a damselfly sheds smoothly because of slender petiolation; a vertical force is generated steadily during the stage of wing translation. Damselflies hover with a longer translational phase and a larger flapping amplitude. In contrast, the root vortex of a dragonfly impedes the shedding of wake vortices in the upstroke, which results in the loss of a vertical force; the dragonfly hence hovers with a large amplitude of wing rotation. These species of Odonata insects developed varied hovering strategies to fit their distinct biological morphologies.

Bilevel Programming Weight Minimization of Composite Flying-Wing Aircraft with Curvilinear Spars and Ribs

Abstract: This paper studies weight minimization of a composite flying-wing aircraft using bioinspired arbitrarily shaped spars and ribs, known as SpaRibs, for the internal structural layout design. A genera...

Structural Optimization of Internal Structure of Aircraft Wings with Curvilinear Spars and Ribs

Abstract: A new framework for optimization of the internal structure of transport aircraft wings having curvilinear spars and ribs (SpaRibs) is described. SpaRibs are parameterized by third-order B-splines w...

Multi-Objective Optimal Control of the 6-DoF Aeroservoelastic Common Research Model with Aspect Ratio 13.5 Wing

Abstract: A new 6-DoF aeroservoelastic (ASE) Common Research Model (CRM) provided by The Boeing Company with aspect ratio 13.5 and 17 control surfaces per wing is utilized to demonstrate combined tracking and optimal multi-objective control. The multi-objective controller is derived on the closed loop tracking controller, and utilizes state and gust estimates provided by an extended state observer. Various methods of model reduction useful for control and estimation are presented. A computationally efficient MATLAB/Simulink simulation is presented which includes actuator dynamics, rate and deflection saturation limits, and gust disturbance inputs. The platform is used to demonstrate excellent 6-DoF tracking control performance coupled with the multi-objective controller, which is shown to effectively reduce structural mode movement, wing root bending moment, and drag. State and gust estimation is also shown to perform well, even when derived and/or implemented with significantly fewer states than the original full-sized model.

Energy Harvesting Performance of Plate Wing from Discrete Gust Excitation

Abstract: Energy harvesting from aeroelastic response tends to have a wide application prospect, especially for small-scale unmanned aerial vehicles. Gusts encountered in flight can be treated as a potential source for sustainable energy supply. The plate model is more likely to describe a low aspect ratio, thin plate wing structure. In this paper, the Von Karman plate theory and 3D doublet lattice method, coupled with a piezoelectric equation, are used to build a linear state-space equation. Under the load of “one-minus-cosine” discrete gust, the effects of flow speed and gust amplitude, thickness of piezoelectric ceramic transducer (PZTs) layers, and mounted load resistance are investigated. Results reveal that the PZTs layers on the wing root of the leading edge can obtain the highest electrical parameters. The flow velocity, thickness of the PZTs layers and load resistance are used to optimize energy harvesting data.

Influence of aspect ratio on wing–wake interaction for flapping wing in hover

Abstract: The interaction between an insect wing and its wake during hovering flight is inevitable. The effect of this wing–wake interaction (WWI) during stroke reversal is an intricate phenomenon that is difficult to forecast. Previous studies have mostly concentrated on the effect of aspect ratio (AR) on the leading-edge vortex (LEV) at the middle of stroke motion. However, the effect of AR on LEV during stroke reversal, which is where the intricate WWI phenomenon occurs, has not been fully exploited. This study aimed at revealing how AR affects WWI during stroke reversal at Re of ~ 104, and the role LEV plays. The experimental time-course measurement of force showed that the WWI at stroke reversal was strengthened by decreasing AR irrespective of pitching duration. A time-varying digital particle image velocimetry (DPIV) measurement revealed a jet-like flow induced by a pair of counter-rotating trailing edge vortex (TEV) as the primitive source of the interaction. This study found a WWI that appeared at the wing root contrary to the conventional type in literature, which appeared at the wing tip. The size of the LEV at the wing root played a key role by facilitating the effectiveness of the wing rotation. AR = 2 wing benefited much from this form of WWI by generating strong coherent shear layer at the end of stroke, and relatively weak LEV during stroke reversal. Thus, this type of WWI might be mostly beneficial for low AR wings (AR < 3).

Aerodynamic Performance of a Passive Pitching Model on Bionic Flapping Wing Micro Air Vehicles.

Abstract: Reducing weight and increasing lift have been an important goal of using flapping wing micro air vehicles (FWMAVs). However, FWMAVs with mechanisms to limit the angle of attack (α) artificially by active force cannot meet specific requirements. This study applies a bioinspired model that passively imitates insects’ pitching wings to resolve this problem. In this bionic passive pitching model, the wing root is equivalent to a torsional spring. α obtained by solving the coupled dynamic equation is similar to that of insects and exhibits a unique characteristic with two oscillated peaks during the middle of the upstroke/downstroke under the interaction of aerodynamic, torsional, and inertial moments. Excess rigidity or flexibility deteriorates the aerodynamic force and efficiency of the passive pitching wing. With appropriate torsional stiffness, passive pitching can maintain a high efficiency while enhancing the average lift by 10% than active pitching. This observation corresponds to a clear enhancement in instantaneous force and a more concentrated leading edge vortex. This phenomenon can be attributed to a vorticity moment whose component in the lift direction grows at a rapid speed. A novel bionic control strategy of this model is also proposed. Similar to the rest angle in insects, the rest angle of the model is adjusted to generate a yaw moment around the wing root without losing lift, which can assist to change the attitude and trajectory of a FWMAV during flight. These findings may guide us to deal with various conditions and requirements of FWMAV designs and applications.

A semi-structured approach to curvilinear mesh generation around streamlined bodies

Abstract: We present an approach for robust high-order mesh generation specially tailored to streamlined bodies. The method is based on a semi-sructured approach which combines the high quality of structured meshes in the near-field with the flexibility of unstructured meshes in the far-field. We utilise medial axis technology to robustly partition the near-field into blocks which can be meshed coarsely with a linear swept mesher. A high-order mesh of the near-field is then generated and split using an isoparametric approach which allows us to obtain highly stretched elements aligned with the flow field. Special treatment of the partition is performed on the wing root juntion and the trailing edge --- into the wake --- to obtain an H-type mesh configuration with anisotropic hexahedra ideal for the strong shear of high Reynolds number simulations. We then proceed to discretise the far-field using traditional robust tetrahedral meshing tools. This workflow is made possible by two sets of tools: CADfix, focused on CAD system, the block partitioning of the near-field and the generation of a linear mesh; and NekMesh, focused on the curving of the high-order mesh and the generation of highly-stretched boundary layer elements. We demonstrate this approach on a NACA0012 wing attached to a wall and show that a gap between the wake partition and the wall can be inserted to remove the dependency of the partitioning procedure on the local geometry.

Study on influence of ambient temperature on biaxial stress and strength of flexible inflatable wing film

Abstract: With advantages of small folding volume, light weight, simple structure, low cost and so on, the flexible inflatable wing has attracted many researchers' attention. However, the change of ambient temperature has a significant influence on the bearing stress of the flexible inflatable wing. Here the typical flat inflatable wing was taken as the object, and the biaxial stress analysis and the Mises stress of the influence of the ambient temperature of the inflatable wing were constructed adopting the mechanical theory and balance principle. And the finite element simulation calculation under different ambient temperature was also performed with the theoretical model. It is found that the biaxial stress and strength of the flexible wing film are closely related to the ambient temperature, and the temperature changings will cause the wing stress to change the Mises stress distribution law of the upper and lower airfoil surfaces, and the wing skin is a two-phase plane stress state. Moreover, with the increase of the ambient temperature, the changes of the Mises stress of the wing root, middle and wingtips of the whole airfoil are inconsistent, but the overall warping deformation is improved, which provides a theoretical reference for the structural optimization design and strength analysis of the flexible inflatable wing.

Numerical Study on Dynamic-Stall Characteristics of Finite Wing and Rotor

Abstract: To study the three-dimensional effects on the dynamic-stall characteristics of a rotor blade, the unsteady flowfields of the finite wing and rotor were simulated under dynamic-stall conditions, respectively. Unsteady Reynolds-averaged Navier–Stokes (URANS) equations coupled with a third-order Roe–MUSCL spatial discretization scheme were chosen as the governing equations to predict the three-dimensional flowfields. It is indicated from the simulated results of a finite wing that dynamic stall would be restricted near the wing tip due to the influence of the wing-tip vortex. By comparing the simulated results of the finite wing with the spanwise flow, it is indicated that the spanwise flow would arouse vortex accumulation. Consequently, the dynamic stall is restricted near the wing root and aggravated near the wing tip. By comparing the simulated results of a rotor in forward flight, it is indicated that the dynamic stall of the rotor would be inhibited due to the effects of the spanwise flow and Coriolis force. This work fills the gap regarding the insufficient three-dimensional dynamic stall of a helicopter rotor, and could be used to guide rotor airfoil shape design in the future.

An Integrated Flexible Aircraft Model for Optimization of Lift Distributions

Abstract: This paper summarizes an integrated modelling approach for controlled flexible aircraft, applicable for flight loads and flight dynamics analyses. It is particularly suited when numerous repeated design analyses throughout the different design phases of an aircraft development need to be considered. An underrepresented aspect so far is the utilization of active control systems as design parameter already in the early design stages and not merely as mitigation strategy for emerging design deficiencies. An active control system can be beneficial for the reduction of structural weight by the use of load alleviation functions, as well as for improvement of the cruise performance and therefore reducing the fuel consumption. This achieved by appropriately optimizing the lift distribution for different use cases. Regarding the lift distributions with respect to loads analysis: the wing structural weight is driven mainly by the loads it has to sustain. One of the most important load conditions is the 2.5 g vertical pull up manoeuvre. A Manoeuvre Load Alleviation function shifts the center of lift inboard by deflection of the available control surfaces and hence reduces the wing root bending moment, which is in turn the primary driver for structural weight. Another very important load condition to be considered is the Discrete Tuned Gust, which might also be a critical case sizing the wing. An active gust load alleviation (GLA) system needs to redistribute the lift and damp out the structural modes excited by the gust by actively actuating the available control surfaces without introducing undesirable excitation of structural modes by the system itself. In the case of cruise performance, the induced drag depends on the spanwise lift distribution. Due to flexiblity, the wing shape changes during the mission. Active lift adaption by control surface deflections can help to reduce the induced drag. The focus of this paper is on assessing the applicability of the proposed modelling approach for the described use cases.

Safe Flutter Tests Using Parametric Flutter Margins

Abstract: The recently developed numerical parametric flutter margin method is applied to perform safe flutter tests in which the flutter-onset conditions of a nominal configuration are positively identified...

Investigation of wind tunnel wall effect and wing-fuselage interference regarding the prediction of wing aerodynamics and its influence on the horizontal tail

Abstract: The calculation of aerodynamic characteristics of a wing is the basic problem for aerodynamic design of aircraft. Wing aerodynamics can be determined experimentally and numerically. The method of fixing the wing in the test chamber of wind tunnel is related to disturbance of flow through the wing. When the wing is entirely fixed in the test chamber, the disturbance is usually caused by the sting connecting the wing to the test chamber. The experiments in this paper fixed the wing by clamping to the wind tunnel wall at the wing symmetry surface (root section). With this wing fixation, it was possible to take advantage of the wingspan twice, but to obtain the 3D wing experiment results, it was necessary to evaluate the impact of the wind tunnel wall effect. As for aircrafts, the aerodynamic force of the aircraft’s wing will have certain difference than that of the wing alone. The intersection region between the wind tunnel wall and wing root (for the experiment), as well as between the fuselage and wing root have complex interactions of boundary layers, in particular separation phenomena in the boundary layers. By solving the differential equation for viscous flows, it was possible to visualize the picture of streamlines and flow separations in this interference region and the aerodynamic characteristics of the wing. The singularity method was also used to compare results within its application range. The aerodynamic coefficients in the two cases with and without interference were analyzed. Complex interactions in the interference region could alter the predicted aerodynamic force calculated for the wing alone, which should be estimated. Very strong separations in the wing-fuselage interference region at large angles of attack turned into vortices at the rear impacting on the horizontal tail aerodynamics that is related to the balance problem of the aircraft.

Double-shaft type folding wing mechanism and emitter thereof

Abstract: The utility model discloses a double-shaft type folding wing mechanism and an emitter thereof, the double-shaft type folding wing mechanism comprises two wings and fixing assemblies, the two wings area first wing and a second wing, each fixing assembly comprises a connecting plate, a first positioning cylinder, a second positioning cylinder, a first rotating shaft and a second rotating shaft, andthe first positioning cylinder is connected with the second positioning cylinder through the connecting plate; a guide notch is formed in one side, close to the lower end, of the side wall of the second positioning cylinder; the top of the first rotating shaft and the top of the second rotating shaft penetrate through the first positioning barrel and the second positioning barrel respectively andthen are connected with the wing root of the first wing and the wing root of the second wing respectively, and a first gear piece and a second gear piece are arranged at the bottom of the first rotating shaft and the bottom of the second rotating shaft respectively. And a first spring and a second spring are respectively sleeved on the first positioning cylinder and the second positioning cylinder. The two wings can be unfolded and folded by the aid of the simple rotary connecting structure, and the two wings can be coplanar after being unfolded.

Variable thickness's grid wing gradually

Abstract: The utility model discloses a variable thickness's grid wing gradually, including outline with set up in outline and with the inboard grid inner wall of being connected of outline, the wing root of grid wing one end for being close to the bomb body, the other end of the grid wing is the wing slightly, the grid wing arrives the wing slightly by the gradually variable thickness structure of favoringthe attenuation for the wing root The utility model adopts the above structure the grid wing, when its resistance reduced, the bomb body is regional to adopt thick grid wall because grid wing bottomis close to again, can be used to bear the grid wing self and produces great curved torch, can satisfy structural strength and the rigidity requirement of the grid wing when the in -service use, be applicable to all kinds of with the grid wing regard as the pneumatics steadily, control the aircraft of rudder face

Aircraft with variable-geometry rhombohedral wing structure

Abstract: In some embodiments, the aircraft (10) comprises a means for adapting the position of each wing root (17, 18) to suit the flight conditions.

Bionic flapping wing aircraft

Abstract: The invention discloses a bionic flapping wing aircraft. The aircraft comprises a power transmission mechanism, two sets of fin root flapping mechanism, two sets of fin rotating mechanism and a pair of wings; the power transmission mechanism is arranged in front of the entire mechanism, which acts to transfer power to the fins in the fin root flapping mechanism, fin rotating mechanisms are arrangeon the periphery of the fin roots rotating mechanisms, a pair of wings are symmetrically arranged on the two sides of the flapping-wing aircraft, and is connected with the wing root the flapping mechanism, in the fin root can be realized under the action of flapping mechanism, but also in the flapping fin root is realized under the action of the rotating mechanism to rotate to provide power for the aircraft. According to the aircraft, one end of the connecting rod and the second side face of the gear is eccentrically hinged, an eccentric boss and the sliding block of the rear side surface ofthe long strip-shaped hole in a matched manner, such a configuration makes the wing flapping and twisting two-direction rotation can be controlled, the flapping wing aircraft motion mode is more closeto the real birds, and can successfully complete the hovering, transverse fly, steering and the like flight operations.

Unmanned aerial vehicle folding wing expandes and stop device

Abstract: The utility model discloses an unmanned aerial vehicle folding wing expandes and stop device, including installing the pivot between left wing's root and right flank root, left wing's root is connected with the port wing, and the right flank root is connected with the starboard wing, and expert over twisting spring connection structure is connected between pivot and left wing's root and the rightflank root, and upper and lower stack of port wing and starboard wing is placed, is connected upper cover plate and pivot upper portion through four self tapping screw, and the concrete structure of torsional spring connection structure is: be two torsional springs that distribute from top to bottom including setting up in the pivot, two respective wherein one end of torsional spring are blocked respectively in the wing root draw -in groove on left wing's root and right flank root surface, and two respective other ends of torsional spring all are arranged in and change epaxial pivot draw -in groove, the utility model provides a wing of unmanned plane that exists among the prior art expand back stability, the synchronism is poor and the longer problem of duration of run.

Miniature bionic ornithopter with 8-shaped wing tip track

Abstract: The utility model discloses a miniature bionic ornithopter with an 8-shaped wingtip track. Including a machine frame, wherein the power mechanism, the double-crank rocker mechanism, the space mechanism based on the spherical hinge and the empennage mechanism are installed on the rack. The double-crank rocker mechanism comprises two crank conical teeth; the two crank conical teeth are meshed with each other; the power mechanism is in transmission connection with one of the crank bevel gears; the space mechanism based on the spherical hinge comprises two space multi-connecting-rod assemblies which are arranged in a bilateral symmetry mode. The two spatial multi-connecting-rod assemblies are connected with the two crank conical teeth in a one-to-one correspondence mode. The crank bevel gear drives the rocker to rock through the transmission connecting rod; the rocker drives the power input rod to swing around the third revolute pair, the wing root control rod is driven by the power inputrod to move under the constraint of the inertia constraint rod, and flapping, swinging and overturning actions of the wing root control rod are realized under the constraint of the three ball pairs, so that the flapping wing motion mode of the miniature bionic flapping-wing aircraft is closer to flying organisms. The utility model is used in the micro flapping-wing air vehicle.