Dynamic stall control using inflatable leading edge

2020 ◽  
Vol 34 (14n16) ◽  
pp. 2040108 ◽  
Author(s):  
Shi-Long Xing ◽  
He-Yong Xu ◽  
Zheng-Yin Ye ◽  
Ming-Sheng Ma ◽  
Yue Xu
Keyword(s):  
Lift Coefficient ◽  
Leading Edge ◽  
Adverse Pressure Gradient ◽  
Rotor Blades ◽  
Dynamic Stall ◽  
Elastic Membrane ◽  
Radius Of Curvature ◽  
Structural Dynamic ◽  
Pitching Airfoil ◽  
Stall Control

The inflatable leading edge (ILE) as a dynamic stall control concept for helicopter rotor blades was investigated numerically on a dynamically pitching airfoil. A fluid–structure interaction (FSI) numerical method for the elastic membrane structure was constructed based on unsteady Reynolds-averaged Navier–Stokes (URANS) equations and mass spring damper (MSD) structural dynamic model. The numerical results indicate that the ILE can change the radius of curvature of the airfoil leading edge, which could reduce the streamwise adverse pressure gradient and suppress the formation of dynamic stall vortex (DSV). Although the maximum lift coefficient of the airfoil is reduced by 8.2%, the maximum drag and pitching moment coefficients of the airfoil are reduced by up to 50.1% and 55.3%, respectively.

scholarly journals Inflatable Leading Edge-Based Dynamic Stall Control considering Fluid-Structure Interaction

2020 ◽  
Vol 2020 ◽  
pp. 1-28
Author(s):  
Shi-Long Xing ◽  
He-Yong Xu ◽  
Ming-Sheng Ma ◽  
Zheng-Yin Ye
Keyword(s):  
Lift Coefficient ◽  
Fluid Structure Interaction ◽  
Leading Edge ◽  
Dynamic Stall ◽  
Elastic Membrane ◽  
Radius Of Curvature ◽  
Structural Dynamic ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Stall Control

The inflatable leading edge (ILE) is explored as a dynamic stall control concept. A fluid-structure interaction (FSI) numerical method for the elastic membrane structure is constructed based on unsteady Reynolds-averaged Navier-Stokes (URANS) and a mass-spring-damper (MSD) structural dynamic model. Radial basis function- (RBF-) based mesh deformation algorithm and Laplacian and optimization-based mesh smoothing algorithm are adopted in flowfield simulations to achieve the pitching oscillation of the airfoil and to ensure the mesh quality. An airfoil is considered at a freestream Mach number of 0.3 and chord-based Reynolds number of 3.92×106. The airfoil is pitched about its quarter-chord axis at a sinusoidal motion. The numerical results indicate that the ILE can change the radius of curvature of the airfoil leading edge, which could reduce the streamwise adverse pressure gradient and suppress the formation of dynamic stall vortex (DSV). Although the maximum lift coefficient of the airfoil is slightly reduced during the control process, the maximum drag and pitching moment coefficients of the airfoil are greatly reduced by up to 66% and 75.2%, respectively. The relative position of the ILE has a significant influence on its control effect. The control laws of inflation and deflation also affect the control ability of the ILE.

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.

scholarly journals Wind Tunnel Test of the S814 Thick Root Airfoil

1996 ◽  
Vol 118 (4) ◽  
pp. 217-221 ◽  
Author(s):  
D. M. Somers ◽  
J. L. Tangler
Keyword(s):  
Wind Tunnel ◽  
Lift Coefficient ◽  
Wind Tunnel Test ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Rotor Blades ◽  
Roughness Effects ◽  
Root Region ◽  
University Of Technology ◽  
Thick Airfoil

The objective of this wind-tunnel test was to verify the predictions of the Eppler Airfoil Design and Analysis Code for a very thick airfoil having a high maximum lift coefficient designed to be largely insensitive to leading-edge roughness effects. The 24 percent thick S814 airfoil was designed with these characteristics to accommodate aerodynamic and structural considerations for the root region of a wind-turbine blade. In addition, the airfoil’s maximum lift-to-drag ratio was designed to occur at a high lift coefficient. To accomplish the objective, a two-dimensional wind tunnel test of the S814 thick root airfoil was conducted in January 1994 in the low-turbulence wind tunnel of the Delft University of Technology Low Speed Laboratory, The Netherlands. Data were obtained with transition free and transition fixed for Reynolds numbers of 0.7, 1.0, 1.5, 2.0, and 3.0 × 106. For the design Reynolds number of 1.5 × 106, the maximum lift coefficient with transition free is 1.32, which satisfies the design specification. However, this value is significantly lower than the predicted maximum lift coefficient of almost 1.6. With transition fixed at the leading edge, the maximum lift coefficient is 1.22. The small difference in maximum lift coefficient between the transition-free and transition-fixed conditions demonstrates the airfoil’s minimal sensitivity to roughness effects. The S814 root airfoil was designed to complement existing NREL low maximum-lift-coefficient tip-region airfoils for rotor blades 10 to 15 meters in length.

A Study of 3-Dimensional Reattachment on Rotor Blades After Dynamic Stall

2016 ◽  
Author(s):  
Vrishank Raghav ◽  
Nandeesh Hiremath ◽  
Narayanan Komerath
Keyword(s):  
Particle Image Velocimetry Data ◽  
Leading Edge ◽  
Rotor Blades ◽  
Stereoscopic Particle Image Velocimetry ◽  
Dynamic Stall ◽  
Test Case ◽  
Trailing Edge ◽  
3 Dimensional ◽  
Advance Ratio ◽  
Vorticity Transport

Stereoscopic Particle Image Velocimetry data from a 2-bladed rigid NACA0013 rotor undergoing retreating blade dynamic stall in a low-speed wind tunnel, are analyzed to understand the phenomenon of 3-dimensional reattachment at the end of the dynamic stall cycle. Continuing from prior studies on the inception and progression of 3-D rotating dynamic stall for this test case, phase-resolved, ensemble-averaged results are presented for two values of rotor advance ratio at two spanwise stations along the blade. The results show the nominal reattachment getting delayed in rotor azimuth with higher advance ratio. At low advance ratio reattachment starts at the leading-edge and progresses towards the trailing-edge with a vortex shedding transporting excess vorticity sheds from the leading-edge and convects away, with the flow reattaching behind it. At higher advance ratio, the vortical structure shrinks in size while the flow close to the trailing-edge appears to reattach. Spanwise vorticity transport appears to be the mechanism. The difference could be attributed to the lower chordwise velocity of the blade at higher advance ratio, bringing in a rotation effect.

Reducing Uncertainty in Dynamic Stall Measurements Through Data-Driven Clustering of Cycle-To-Cycle Variations

2021 ◽  
Vol 66 (1) ◽  
pp. 1-17
Author(s):  
Manikandan Ramasamy ◽  
Armaun Sanayei ◽  
Jacob S. Wilson ◽  
Preston B. Martin ◽  
Tanner Harms ◽  
...  
Keyword(s):  
Flow Behavior ◽  
Clustering Algorithms ◽  
Leading Edge ◽  
Initial Step ◽  
Dynamic Stall ◽  
Data Driven ◽  
Markov Analysis ◽  
Pitching Airfoil ◽  
Cluster Data ◽  
Flow Phenomena

Pitching airfoil measurements are known to exhibit significant scatter near stall angles of attack that can make meaningful correlation with modeling or simulation difficult. Application of data-driven clustering algorithms to dynamic stall experiments, conducted at two different research facilities, revealed the presence of furcation within the data scatter. Such furcation render the statistical mean and standard deviation as inadequate to represent the observed cycle-to-cycle variations. After ruling out facility effects, an alternative approach to conventional statistical analysis is developed through the use of cluster averages, associated variances, and group probability. Several existing clustering techniques are tested; however, their shortcomings led to the development of two new data-driven algorithms that use proper orthogonal decomposition to cluster data based on flow phenomena that contribute the most energy to flow variations. Several test cases are used to show the physical mechanisms leading to cycle-to-cycle variations, such as differences in separation location, boundary layer reattachment, occurrence of leading-edge/trailing-edge stall, and presence of a dynamic stall vortex (or vortices). In all cases, these physical processes and their effects are obscured by conventional phase-averaging. Further analyses on the effects of the Mach number, reduced frequency, mean angle, and amplitude of oscillation reveal trends in the probability of a given flow behavior. An initial step towards using these results for advanced semiempirical models using Markov analysis is discussed.

scholarly journals Improving the aerodynamic performance of a cycloidal rotor through active compliant morphing

2017 ◽  
Vol 121 (1241) ◽  
pp. 901-915
Author(s):  
L. Ferrier ◽  
M. Vezza ◽  
H. Zare-Behtash
Keyword(s):  
Negative Impact ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Micro Air Vehicles ◽  
Aerodynamic Performance ◽  
Dynamic Stall ◽  
Marine Vehicles ◽  
Aerospace Applications ◽  
Naca 0015 ◽  
Air Vehicles

ABSTRACTCycloidal rotors are a novel form of propulsion system that can be adapted to various forms of transport such as air and marine vehicles, with a geometrical design differing significantly from the conventional screw propeller. Research on cycloidal rotor design began in the early 1930s and has developed throughout the years to the point where such devices now operate as propulsion systems for various aerospace applications such as micro air vehicles, unmanned air vehicles and compound helicopters. The majority of research conducted on the cycloidal rotor’s aerodynamic performance have not assessed mitigating the dynamic stall effect, which can have a negative impact on the rotor performance when the blades operate in the rotor retreating side. A solution has been proposed to mitigate the dynamic stall effect through employment of active, compliant leading-edge morphing. A review of the current state of the art in this area is presented. A two-dimensional, implicit unsteady numerical analysis was conducted using the commercial computational fluid dynamics software package STAR CCM+, on a two-bladed cycloidal rotor. An overset mesh technique, otherwise known as a chimera mesh, was used to apply complex transient motions to the simulations. Active, compliant leading-edge morphing is applied to an oscillating NACA 0015 aerofoil to attempt to mitigate the dynamic stall whilst maintaining the positive dynamic lift coefficient (Cl) contributions. It was verified that by applying a pulsed input leading-edge rotational morphing schedule, the leading-edge vortex does not fully form and the large flow separation is prevented. Further work in this investigation will focus on coupling the active, leading-edge motion to the cycloidal rotor model with the aim to maximise aerodynamic performance.

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
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