The effect of the aerofoil thickness on the performance of the MAV scale cycloidal rotor

2015 ◽  
Vol 119 (1213) ◽  
pp. 343-364 ◽  
Author(s):  
Y. Hu ◽  
H.L. Zhang ◽  
C. Tan
Keyword(s):  
Flow Pattern ◽  
Cfd Simulation ◽  
Leading Edge ◽  
Dynamic Stall ◽  
Test Cases ◽  
Sliding Mesh ◽  
Large Fluctuations ◽  
Edge Vortex ◽  
Rotor Cage ◽  
Different Thickness

AbstractThe numerical simulations for cycloidal propellers based on five aerofoils with different thickness are presented in this paper. The CFD simulation is based on sliding mesh and URANS. The results of CFD simulation indicates that all test cases share similar flow pattern. There are leading edge vortex and trailing-edge vortex due to blade dynamic stall. Interaction between the vortices shed from upstream blade and the downstream blade can be observed. There is variation of blade relative inflow velocity due to downwash in the cycloidal rotor cage. These factors result in large fluctuations of the aerodynamics forces on the blade. The comparison of the forces and flow pattern indicates that the thickness and leading edge radius of the aerofoil can significantly influent the flow pattern and hence the performance of the cycloidal propeller.

The aerodynamics of revolving wings I. Model hawkmoth wings

2002 ◽  
Vol 205 (11) ◽  
pp. 1547-1564 ◽  
Author(s):  
James R. Usherwood ◽  
Charles P. Ellington
Keyword(s):  
Insect Flight ◽  
Leading Edge ◽  
Dynamic Stall ◽  
Leading Edge Vortex ◽  
Force Coefficients ◽  
Attached Flow ◽  
Edge Vortex ◽  
Drag And Lift ◽  
Geometric Relationship ◽  
Spanwise Flow

SUMMARYRecent work on flapping hawkmoth models has demonstrated the importance of a spiral `leading-edge vortex' created by dynamic stall, and maintained by some aspect of spanwise flow, for creating the lift required during flight. This study uses propeller models to investigate further the forces acting on model hawkmoth wings in `propeller-like' rotation (`revolution'). Steadily revolving model hawkmoth wings produce high vertical (≈ lift) and horizontal (≈ profile drag) force coefficients because of the presence of a leading-edge vortex. Both horizontal and vertical forces, at relevant angles of attack, are dominated by the pressure difference between the upper and lower surfaces; separation at the leading edge prevents `leading-edge suction'. This allows a simple geometric relationship between vertical and horizontal forces and the geometric angle of attack to be derived for thin, flat wings. Force coefficients are remarkably unaffected by considerable variations in leading-edge detail, twist and camber. Traditional accounts of the adaptive functions of twist and camber are based on conventional attached-flow aerodynamics and are not supported. Attempts to derive conventional profile drag and lift coefficients from `steady' propeller coefficients are relatively successful for angles of incidence up to 50° and, hence, for the angles normally applicable to insect flight.

scholarly journals Unsteady Aerodynamic Characteristics Simulations of Rotor Airfoil under Oscillating Freestream Velocity

2020 ◽  
Vol 10 (5) ◽  
pp. 1822
Author(s):  
Qing Wang ◽  
Qijun Zhao
Keyword(s):  
Three Dimensional ◽  
Grid Method ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Critical Value ◽  
Dynamic Stall ◽  
Navier Stokes ◽  
Freestream Velocity ◽  
Unsteady Aerodynamic ◽  
Edge Vortex

The dynamic stall characteristics of rotor airfoil are researched by employing unsteady Reynolds-Averaged Navier-Stokes (RANS) method under oscillating freestream velocity conditions. In order to simulate the oscillating freestream velocity of airfoil under dynamic stall conditions, the moving-embedded grid method is employed to simulate the oscillating velocity. By comparing the simulated dynamic stall characteristics of two-dimensional airfoil and three-dimensional rotor, it is indicated that the dynamic stall characteristics of airfoil under oscillating freestream velocity reflect the actual dynamic stall characteristics of rotor airfoil in forward flight more accurately. By comparing the simulated results of OA209 airfoil under coupled freestream velocity/pitching oscillation conditions, it is indicated that the dynamic stall characteristics of airfoil associate with the critical value of Cp peaks (i.e., the dynamic stall characteristics of OA209 airfoil would be enhanced when the maximum negative pressure is larger than −1.08, and suppressed when this value is smaller than −1.08). By comparing the characteristics of vortices under different oscillating velocities, it indicates that the dissipation rate of leading edge vortex presents as exponent characteristics, and it is not sensitive to different oscillating velocities.

scholarly journals Numerical Investigation of a Dynamic Stall on a Single Rotating Blade

Aerospace ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 90
Author(s):  
Yin Ruan ◽  
Manfred Hajek
Keyword(s):  
Numerical Investigation ◽  
Vortex Structure ◽  
Leading Edge ◽  
Rotor Blades ◽  
Tip Vortex ◽  
Dynamic Stall ◽  
Leading Edge Vortex ◽  
Pitching Airfoil ◽  
Edge Vortex ◽  
High Reynolds

Dynamic stall is a phenomenon on the retreating blade of a helicopter which can lead to excessive control loads. In order to understand dynamic stall and fill the gap between the investigations on pitching wings and full helicopter rotor blades, a numerical investigation of a single rotating and pitching blade is carried out. The flow phenomena thereupon including the Ω-shaped dynamic stall vortex, the interaction of the leading edge vortex with the tip vortex, and a newly noticed vortex structure originating inboard are examined; they show similarities to pitching wings, while also possessing their unique features of a rotating system. The leading edge/tip vortex interaction dominates the post-stall stage. A newly noticed swell structure is observed to have a great impact on the load in the post-stall stage. With such a high Reynolds number, the Coriolis force exerted on the leading edge vortex is negligible compared to the pressure force. The force history/vortex structure of the slice r/R = 0.898 is compared with a 2D pitching airfoil with the same harmonic pitch motion, and the current simulation shows the important role played by the swell structure in the recovery stage.

Dynamic Stall Control Using Deployable Leading-Edge Vortex Generators

AIAA Journal ◽  
2012 ◽  
Vol 50 (10) ◽  
pp. 2135-2145 ◽  
Author(s):  
A. Le Pape ◽  
M. Costes ◽  
F. Richez ◽  
G. Joubert ◽  
F. David ◽  
...  
Keyword(s):  
Leading Edge ◽  
Vortex Generators ◽  
Dynamic Stall ◽  
Leading Edge Vortex ◽  
Edge Vortex ◽  
Stall Control

Numerical Investigations on Dynamic Stall of a Pitching-Lagging Motion Airfoil Under Unsteady Freestream

2019 ◽  
Author(s):  
Kai Xie ◽  
Laith K. Abbas ◽  
Dongyang Chen ◽  
Fufeng Yang ◽  
Xiaoting Rui
Keyword(s):  
Lift Coefficient ◽  
Vortex Formation ◽  
Leading Edge ◽  
Dynamic Stall ◽  
Vorticity Field ◽  
Freestream Velocity ◽  
Sst Turbulence Model ◽  
Edge Vortex ◽  
Computational Fluid Dynamics Cfd ◽  
Phase Differences

Abstract Lift coefficients of a pitching-lagging SC1095 airfoil with different phase differences and amplitudes under Re = 3.92 × 106 are investigated using computational fluid dynamics (CFD). A simulation results based on overset grid technology and k–ω shear stress transport (SST) turbulence model agrees with experimental results. Dynamic stall is associated with Leading Edge Vortex formation (LEV). The formation process during dynamic stall is shown using pressure superimposed with flow streamlines and dimensionless vorticity field contour. Five cases of phase difference between freestream velocity and lagging motion, φ = 0, 1/4π, 1/2π, π and three cases of amplitudes of lagging motion, hamp = 0.3m, 0.5m, 0.7m, are compared, which showed a regular effect on the lift coefficient loops.

Dynamic Stall Control by Leading Edge Vortex Generators

2008 ◽  
Vol 53 (1) ◽  
pp. 26 ◽  
Author(s):  
Holger Mai ◽  
Guido Dietz ◽  
Wolfgang Geißler ◽  
Kai Richter ◽  
Johannes Bosbach ◽  
...  
Keyword(s):  
Leading Edge ◽  
Vortex Generators ◽  
Dynamic Stall ◽  
Leading Edge Vortex ◽  
Edge Vortex ◽  
Stall Control

scholarly journals Visualization of vortical flows around a rapidly pitching wing and propeller

2017 ◽  
Vol 9 (1) ◽  
pp. 25-43
Author(s):  
Erlong Su ◽  
Ryan Randall ◽  
Lee Wilson ◽  
Sergey Shkarayev
Keyword(s):  
Boundary Layer ◽  
Leading Edge ◽  
Micro Air Vehicles ◽  
Dynamic Stall ◽  
Leading Edge Vortex ◽  
Edge Vortex ◽  
Effective Angle ◽  
Lift And Drag ◽  
Five Axis ◽  
Leading Edge Vortices

This study was conducted to visually investigate flows related to fixed-wing vertical-takeoff-and-landing micro air vehicles, using the smoke-wire technique. In particular, the study examines transition between forward flight and near-hover. The experimental model consists of a rigid Zimmerman wing and a propulsion system with contra-rotating propellers arranged in a tractor configuration. The model was pitched about the wing’s aerodynamic center at approximately constant rates using a five-axis robotic arm. Constant-rate pitching angles spanned 20° to 70°. No-pitching and four pitching-rates were used, along with three propulsive settings. Several observations were made during no-pitching tests. Turbulent wakes behind blades and laminar flow between them produces pulsations in the boundary layer. These pulsations alter the boundary layer from a laminar to turbulent state and back. An increase in lift and drag in the presence of a slipstream is a result of competing effects of the propulsive slipstream: (a) suppression of flow separation and increased velocity over the wing and (b) decrease of the effective angle of attack. Higher nose-up pitching-rates generally lead to greater trailing-edge vortex-shedding frequency. Nose-up pitching without a slipstream can lead to the development of a traditional dynamic-stall leading-edge vortex, delaying stall and increasing wing lift. During nose-up pitching, a slipstream can drive periodically shed leading-edge vortices into a larger vortical-structure that circulates over the upper-surface of a wing in a fashion similar to that of a traditional dynamic-stall leading-edge vortex. At lower nose-up pitching-rates, leading-edge vortices form at lower angles of attacks. As a slipstream strengthens, a few things occur: separation wakes diminish, separation occurs at a higher angle of attacks, and downward flow-deflection increases. Similar effects are observed for nose-up pitching, while nose-down pitching produces the opposite effects.

Further Consideration of ''Spilled" Leading-Edge Vortex Effects on Dynamic Stall

1977 ◽  
Vol 14 (6) ◽  
pp. 601-603 ◽  
Author(s):  
Lars E. Ericsson ◽  
J. Peter Reding
Keyword(s):  
Leading Edge ◽  
Dynamic Stall ◽  
Leading Edge Vortex ◽  
Edge Vortex

'Spilled' leading-edge vortex effects on dynamic stall characteristics

1976 ◽  
Vol 13 (4) ◽  
pp. 313-315 ◽  
Author(s):  
Lars E. Ericsson ◽  
J. Peter Reding
Keyword(s):  
Leading Edge ◽  
Dynamic Stall ◽  
Leading Edge Vortex ◽  
Edge Vortex

scholarly journals Simulations of Aerodynamic Separated Flows Using the Lattice Boltzmann Solver XFlow

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5146 ◽  
Author(s):  
M. Chávez-Modena ◽  
J. L. Martínez ◽  
J. A. Cabello ◽  
E. Ferrer
Keyword(s):  
Turbulent Flows ◽  
Lattice Boltzmann ◽  
Leading Edge ◽  
Dynamic Stall ◽  
Test Cases ◽  
High Lift ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Cost ◽  
3D Wing

We present simulations of turbulent detached flows using the commercial lattice Boltzmann solver XFlow (by Dassault Systemes). XFlow’s lattice Boltzmann formulation together with an efficient octree mesh generator reduce substantially the cost of generating complex meshes for industrial flows. In this work, we challenge these meshes and quantify the accuracy of the solver for detached turbulent flows. The good performance of XFlow when combined with a Large-Eddy Simulation turbulence model is demonstrated for different industrial benchmarks and validated using experimental data or fine numerical simulations. We select five test cases: the Backward-facing step the Goldschmied Body the HLPW-2 (2nd High-Lift Prediction Workshop) full aircraft geometry, a NACA0012 under dynamic stall conditions and a parametric study of leading edge tubercles to improve stall behavior on a 3D wing.

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