Effect of Three-Dimensional Aerodynamics and Dynamic Stall on Lead–Lag Damping of an Isolated Rotor

2021 ◽  
Vol 66 (1) ◽  
pp. 1-13
Author(s):  
Vellingiri Ramanujam R ◽  
Ranjith Mohan
Keyword(s):  
Radial Flow ◽  
Three Dimensional ◽  
Dynamic Stall ◽  
Forward Flight ◽  
Dimensional Effects ◽  
Flow Coupling ◽  
Aerodynamic Model ◽  
Wake Model ◽  
Torsionally Stiff ◽  
Edge Separation

This paper investigates three-dimensional aerodynamic effects due to radial flow on lead–lag damping of a rotor in forward flight conditions. Three-dimensional effects in this study are restricted to yawed flow aerodynamics and radial flow coupling between blade segments. These effects are included in the ONERA dynamic stall model, and lead–lag damping for an isolated torsionally stiff rotor is calculated for different forward flight conditions. This augmented aerodynamic model with three-dimensional effects and Peters–He dynamic wake model improves the correlation of lead–lag damping with experimental data at high advance ratios. The effect of modeling static lift characteristics on damping correlation is also presented. Finally, a modification to the trailing edge separation point–based static lift model for improved yawed flow modeling amenable to aeromechanical stability analysis is proposed.

A New Dynamic Stall Approach for Investigating Bifurcation and Chaos in Aeroelastic Response of a Blade Section with Flap Free-Play Section

2020 ◽  
Vol 30 (14) ◽  
pp. 2050200
Author(s):  
Reza Esbati Lavasani ◽  
Shahrokh Shams
Keyword(s):  
State Space ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Pitchfork Bifurcation ◽  
Equation Of Motion ◽  
Free Play ◽  
Dynamic Stall ◽  
Aerodynamic Model ◽  
Blade Section ◽  
Nonlinear Aerodynamic

This paper investigates the effects of the unsteady nonlinear aerodynamic, plunge/pitch cubic nonlinearities, flap free-play nonlinearity, and coupled nonlinear aeroelasticity on the dynamics of the three-dimensional blade section. The dynamic stall model is developed based on the unsteady Wagner aerodynamics. Coupling the developed nonlinear aerodynamic model and nonlinear elasticity model results in the nonlinear aeroelastic model. The nonlinear aeroelastic equation of motion is converted into a state-space form. The resulting nonlinear state-space equation of motion is simulated by a standard Runge–Kutta algorithm in MATLAB. The proposed model is validated against test data of distinct two- and three-degrees-of-freedom studies and is compared to the ONERA model. Bifurcation diagrams show that there is distinct airspeed, in which the system experiences limit cycle oscillations (LCOs) or chaos. Both hysteresis air loads and structural nonlinearity make the system unstable at airspeed less than linear flutter speed. The nonlinearity of the structure causes supercritical pitchfork bifurcation. Elastic-aerodynamic nonlinearity interaction causes sub-supercritical bifurcation at the lower airspeed and chaotic motion at a higher airspeed. Furthermore, the effects of the initial condition on the response of the nonlinear aero-servo-elastic system are investigated by the Lyapunov exponent method.

Numerical investigation of three-dimensional effects during dynamic stall

2015 ◽  
Vol 47 ◽  
pp. 216-237 ◽  
Author(s):  
M. Costes ◽  
F. Richez ◽  
A. Le Pape ◽  
R. Gavériaux
Keyword(s):  
Numerical Investigation ◽  
Three Dimensional ◽  
Dynamic Stall ◽  
Dimensional Effects

Aeroelastic stability analysis of hingeless rotor blades in hover using fully intrinsic equations and dynamic wake model

2019 ◽  
Vol 91 (8) ◽  
pp. 1113-1121
Author(s):  
Mohammadreza Amoozgar ◽  
Hossein Shahverdi
Keyword(s):  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Rotor Blades ◽  
New Approach ◽  
Content Type ◽  
Aerodynamic Model ◽  
Aeroelastic Analysis ◽  
Beam Equations ◽  
Wake Model ◽  
Composite Blades

PurposeThis paper aims to develop a new approach for aeroelastic analysis of hingeless rotor blades.Design/methodology/approachThe aeroelastic approach developed here is based on the geometrically exact fully intrinsic beam equations and three-dimensional unsteady aerodynamics.FindingsThe developed approach is accurate, fast and very useful in rotorcraft aeroelastic analysis.Originality/valueThis beam formulation has been never combined with three-dimensional aerodynamic model to be used for aeroelastic analysis of blades. In addition, it is possible to handle the composite blades, as well as blades with initial curvatures and twist with this proposed formulation.

A Prescribed Wake Aerodynamic Model for Vertical Axis Wind Turbines

1992 ◽  
Vol 206 (3) ◽  
pp. 159-166 ◽  
Author(s):  
B Basuno ◽  
F N Coton ◽  
R A Galbraith
Keyword(s):  
Three Dimensional ◽  
Vortex Method ◽  
Vertical Axis ◽  
Vertical Axis Wind Turbine ◽  
Aerodynamic Model ◽  
Vertical Axis Wind Turbines ◽  
Turbine Performance ◽  
Trailing Vortices ◽  
Wake Model ◽  
Turbine Wake

A new aerodynamic model for the prediction of vertical axis wind turbine performance is introduced. The model is fully three dimensional and is derived from consideration of both momentum and vortex theories. In the calculation process the turbine wake is modelled by a series of shed and trailing vortices. The overall shape of the wake, however, is determined from momentum theory. Comparison is made between the new model and a free vortex method. Although the accuracy levels of the two techniques are equivalent, the prescribed wake model is more than two orders of magnitude faster. The prescribed wake model is also shown to compare well with field data. Finally, the future development of the model is discussed.

A three-dimensional wake model for low earth orbit

1983 ◽  
Author(s):  
I. KATZ ◽  
D. COOKE ◽  
D. PARKS ◽  
M. MANDELL ◽  
A. RUBIN
Keyword(s):  
Three Dimensional ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Wake Model

Dynamic Stall Simulation of Flow Over NACA0012 Airfoil at 1 Million Reynolds Number

2015 ◽  
Author(s):  
Venkata Ravishankar Kasibhotla ◽  
Danesh Tafti
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Dynamic Stall ◽  
Sharp Drop ◽  
Airfoil Surface ◽  
Naca0012 Airfoil ◽  
Reduced Frequency ◽  
Edge Vortex

The paper is concerned with the prediction and analysis of dynamic stall of flow past a pitching NACA0012 airfoil at 1 million Reynolds number based on the chord length of the airfoil and at reduced frequency of 0.25 in a three dimensional flow field. The turbulence in the flow field is resolved using large eddy simulations with the dynamic Smagorinsky model at the sub grid scale. The development of dynamic stall vortex, shedding and reattachment as predicted by the present study are discussed in detail. This study has shown that the downstroke phase of the pitching motion is strongly three dimensional and is highly complex, whereas the flow is practically two dimensional during the upstroke. The lift coefficient agrees well with the measurements during the upstroke. However, there are differences during the downstroke. The computed lift coefficient undergoes a sharp drop during the start of the downstroke as the convected leading edge vortex moves away from the airfoil surface. This is followed by a recovery of the lift coefficient with the formation of a secondary trailing edge vortex. While these dynamics are clearly reflected in the predicted lift coefficient, the experimental evolution of lift during the downstroke maintains a fairly smooth and monotonic decrease in the lift coefficient with no lift recovery. The simulations also show that the reattachment process of the stalled airfoil is completed before the start of the upstroke in the subsequent cycle due to the high reduced frequency of the pitching cycle.

Three-Dimensional and Rotational Aerodynamics on the NREL Phase VI Wind Turbine Blade

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Alvaro Gonzalez ◽  
Xabier Munduate
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Three Dimensional ◽  
Separated Flow ◽  
Leading Edge ◽  
Wind Turbine Blade ◽  
Trailing Edge ◽  
Rotating Blade ◽  
Nrel Phase Vi ◽  
Edge Separation

This work undertakes an aerodynamic analysis over the parked and the rotating NREL Phase VI wind turbine blade. The experimental sequences from NASA Ames wind tunnel selected for this study respond to the parked blade and the rotating configuration, both for the upwind, two-bladed wind turbine operating at nonyawed conditions. The objective is to bring some light into the nature of the flow field and especially the type of stall behavior observed when 2D aerofoil steady measurements are compared to the parked blade and the latter to the rotating one. From averaged pressure coefficients together with their standard deviation values, trailing and leading edge separated flow regions have been found, with the limitations of the repeatability of the flow encountered on the blade. Results for the parked blade show the progressive delay from tip to root of the trailing edge separation process, with respect to the 2D profile, and also reveal a local region of leading edge separated flow or bubble at the inner, 30% and 47% of the blade. For the rotating blade, results at inboard 30% and 47% stations show a dramatic suppression of the trailing edge separation, and the development of a leading edge separation structure connected with the extra lift.

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