scholarly journals Unsteady Aerodynamics of Highly Maneuvering Flyers

2021 ◽  
Author(s):  
Mohamed Yehia Zakaria
Keyword(s):  
Unsteady Aerodynamics ◽  
Leading Edge ◽  
High Amplitude ◽  
Analytical Models ◽  
Lattice Method ◽  
Vortex Lattice Method ◽  
Classical Models ◽  
Zero Degree ◽  
Edge Vortex ◽  
Unsteady Lift

In this chapter, a set of analytical aerodynamic models, based on potential flow, that can be used to predict the unsteady lift response during pitching maneuvers are presented and assessed. The result examines the unsteady lift coefficients experienced by a flat plate in high-amplitude pitch ramp motion. The pitch ramps are chosen based on two ramp pitch maneuvers of a maximum amplitudes of 25 and 45 degrees starting from zero degree. The aim is investigate the use of such classical models in predicting the lift dynamics compared to a full physical-based model. Among all classical methods used, the unsteady vortex lattice method (without considering the leading edge vortex) is found to be a very good predictor of the motion lift dynamic response for the 25° ramp angle case. However, at high pitch maneuvers (i.e.,the 45° ramp angle case), could preserve the response pattern with attenuated amplitudes without high computational burden. These mathematical analytical models presented in this chapter can be used to obtain a fast estimate for aircraft unsteady lift during pitch maneuvers instead of high fidelity models, especially in the early design phases.

Unsteady aerodynamics investigation of deploying tandem-wing with different methods

2018 ◽  
Vol 233 (10) ◽  
pp. 3714-3733 ◽  
Author(s):  
Hao Cheng ◽  
Hua Wang ◽  
Qingli Shi ◽  
Mengying Zhang
Keyword(s):  
Fore Wing ◽  
Vortex Lattice ◽  
Lift Coefficient ◽  
Unsteady Aerodynamics ◽  
Lattice Method ◽  
Vortex Lattice Method ◽  
Induced Drag ◽  
Lifting Line ◽  
Lifting Line Method ◽  
Unsteady Lift

In the rapidly deploying process of the unmanned aerial vehicle with folding wings, the aerodynamic characteristics could be largely different owing to the effects of deformation rate and the aerodynamic interference. The investigation on the unsteady aerodynamics is of great significance for the stability analysis and control design. The lifting-line method and the vortex-lattice method are improved to calculate the unsteady aerodynamics in the morphing stage. It is validated that the vortex-lattice method predicts the unsteady lift coefficient more appropriately than the lifting-line method. Different tandem wing configurations with deployable wings are simulated with different deformation rates during the morphing stage by the vortex-lattice method. As results indicated, the unsteady lift coefficient and the induced drag of the fore wing rise with the deformation rate increasing, but it is reversed for the hind wing. Additionally, the unsteady lift coefficient of the tandem wing configuration performs well with a larger stagger, a larger magnitude of the gap and a larger wingspan of the fore wing; however, the total induced drag has a larger value for the configuration that the two lifting surfaces with the same wingspans are closer to each other.

Modeling and Simulation of Unsteady Aerodynamics on a Morphing Wing

2013 ◽  
Vol 427-429 ◽  
pp. 77-80 ◽  
Author(s):  
Zhi Gang Wang ◽  
Zhen Ning Zhang
Keyword(s):  
Modeling And Simulation ◽  
Unsteady Aerodynamics ◽  
Simulation Method ◽  
Computer Code ◽  
Morphing Wing ◽  
Lattice Method ◽  
Vortex Lattice Method ◽  
Induced Drag ◽  
Morphing Wings ◽  
Time Histories

Modeling and simulation method of unsteady aerodynamics on morphing wings were investigated. The Unsteady Vortex Lattice Method is employed to model the unsteady aerodynamics of 3-D potential flow field surrounding the wing. An UVLM computer code was then developed and validated for numerical simulation. A morphing wing which changes its dihedral angle with constant angular velocity was investigated by the code, and the lift, induced drag, and pitching moment coefficients time histories were obtained. The results show that the UVLM code is an effective tool for simulations of unsteady aerodynamics on morphing wings.

scholarly journals A computational fluid dynamic study of hawkmoth hovering

1998 ◽  
Vol 201 (4) ◽  
pp. 461-477 ◽  
Author(s):  
H Liu ◽  
C P Ellington ◽  
K Kawachi ◽  
C van den Berg ◽  
A P Willmott
Keyword(s):  
Fluid Dynamic ◽  
Translational Motion ◽  
Three Dimensional ◽  
Axial Flow ◽  
Unsteady Aerodynamics ◽  
Leading Edge ◽  
Flapping Wing ◽  
Leading Edge Vortex ◽  
Edge Vortex ◽  
Rotational Motions

A computational fluid dynamic (CFD) modelling approach is used to study the unsteady aerodynamics of the flapping wing of a hovering hawkmoth. We use the geometry of a Manduca sexta-based robotic wing to define the shape of a three-dimensional 'virtual' wing model and 'hover' this wing, mimicking accurately the three-dimensional movements of the wing of a hovering hawkmoth. Our CFD analysis has established an overall understanding of the viscous and unsteady flow around the flapping wing and of the time course of instantaneous force production, which reveals that hovering flight is dominated by the unsteady aerodynamics of both the instantaneous dynamics and also the past history of the wing. <P> A coherent leading-edge vortex with axial flow was detected during translational motions of both the up- and downstrokes. The attached leading-edge vortex causes a negative pressure region and, hence, is responsible for enhancing lift production. The axial flow, which is derived from the spanwise pressure gradient, stabilises the vortex and gives it a characteristic spiral conical shape. <P> The leading-edge vortex created during previous translational motion remains attached during the rotational motions of pronation and supination. This vortex, however, is substantially deformed due to coupling between the translational and rotational motions, develops into a complex structure, and is eventually shed before the subsequent translational motion. <P> Estimation of the forces during one complete flapping cycle shows that lift is produced mainly during the downstroke and the latter half of the upstroke, with little force generated during pronation and supination. The stroke plane angle that satisfies the horizontal force balance of hovering is 23.6 degrees , which shows excellent agreement with observed angles of approximately 20-25 degrees . The time-averaged vertical force is 40 % greater than that needed to support the weight of the hawkmoth.

scholarly journals Flow visualization and unsteady aerodynamics in the flight of the hawkmoth, Manduca sexta

1997 ◽  
Vol 352 (1351) ◽  
pp. 303-316 ◽  
Author(s):  
Alexander P. Willmott ◽  
Charles P. Ellington ◽  
Adrian L. R. Thomas
Keyword(s):  
Manduca Sexta ◽  
High Speed ◽  
Unsteady Aerodynamics ◽  
Leading Edge ◽  
Vortex Rings ◽  
Leading Edge Vortex ◽  
Smoke Visualization ◽  
Left Behind ◽  
Trailing Edges ◽  
Edge Vortex

The aerodynamic mechanisms employed durng the flight of the hawkmoth, Manduca sexta , have been investigated through smoke visualization studies with tethered moths. Details of the flow around the wings and of the overall wake structure were recorded as stereophotographs and high–speed video sequences. The changes in flow which accompanied increases in flight speed from 0.4 to 5.7 m s −1 were analysed. The wake consists of an alternating series of horizontal and vertical vortex rings which are generated by successive down– and upstrokes, respectively. The downstroke produces significantly more lift than the upstroke due to a leading–edge vortex which is stabilized by a radia flow moving out towards the wingtip. The leading–edge vortex grew in size with increasing forward flight velocity. Such a phenomenon is proposed as a likely mechanism for lift enhancement in many insect groups. During supination, vorticity is shed from the leading edge as postulated in the ‘flex’ mechanism. This vorticity would enhance upstroke lift if it was recaptured diring subsequent translation, but it is not. Instead, the vorticity is left behind and the upstroke circulation builds up slowly. A small jet provides additional thrust as the trailing edges approach at the end of the upstroke. The stereophotographs also suggest that the bound circulation may not be reversed between half strokes at the fastest flight speeds.

Comparative study on analytical and computational aerodynamic models for flapping wings MAVs

2020 ◽  
Vol 124 (1280) ◽  
pp. 1636-1665
Author(s):  
M.F. Valdez ◽  
B. Balachandran ◽  
S. Preidikman
Keyword(s):  
Cfd Simulation ◽  
Time History ◽  
Leading Edge ◽  
Micro Air Vehicles ◽  
Detailed Comparison ◽  
Flapping Wings ◽  
Lattice Method ◽  
Vortex Lattice Method ◽  
Analytical Potential ◽  
History Of

ABSTRACTA range of quasi-steady and unsteady aerodynamic models are used to predict the aerodynamic forces experienced by a flapping wing and a detailed comparison amongst these predictions in provided. The complexity of the models ranges from the analytical potential flow model to the computational Unsteady Vortex Lattice Method (UVLM), which allows one to describe the motion of the wake and account for its influence on the fluid loads. The novelty of this effort lies in a modification of the predicted forces as a generalisation of the leading edge suction analogy. This modification is introduced to account for the delayed stall mechanism due to leading edge flow separation. The model predictions are compared with two sets of independent experimental data and with computational fluid dynamics (CFD) simulation data available in the literature. It is found that both, the modified analytical model and the UVLM model can be used to describe the time history of the lift force, in some cases with better results than a high-fidelity CFD model. The models presented here constitute a useful basis for the aerodynamic design of bioinspired flapping-wings micro-air vehicles.

A vortex-lattice method for general, unsteady aerodynamics

1985 ◽  
Vol 22 (1) ◽  
pp. 43-49 ◽  
Author(s):  
P. Konstadinopoulos ◽  
D. F. Thrasher ◽  
D. T. Mook ◽  
A. H. Nayfeh ◽  
L. Watson
Keyword(s):  
Vortex Lattice ◽  
Unsteady Aerodynamics ◽  
Lattice Method ◽  
Vortex Lattice Method

Generalized vortex lattice method for planar supersonic flow

AIAA Journal ◽  
1997 ◽  
Vol 35 ◽  
pp. 1230-1233
Author(s):  
Paulo A. O. Soviero ◽  
Hugo B. Resende
Keyword(s):  
Supersonic Flow ◽  
Vortex Lattice ◽  
Lattice Method ◽  
Vortex Lattice Method
Sign in / Sign up

Export Citation Format

Share Document