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Development of a method for predicting the performance and stresses of vtol-type propellers

01 Jun 1966-

Abstract: : The report presents a theoretical method which allows the prediction of performance and stress characteristics of a single VTOL-type of propeller- wing-nacelle combination operating in various flight conditions from hovering through transition and into axial flight. The method includes (1) the effects of a distorted wake, i. e., the effects of contraction and radial and axial velocity variations; (2) the effects of hovering close to the ground; (3) the interference effects from a nacelle and wing buried in the propeller slipstream. Also presented are experimental thrust and torque data. However, because of the insufficient accuracy of the experimental data collected, no definite evaluation of the model is made.
Topics: Propeller (61%), Slipstream (58%), Thrust (53%), Nacelle (52%), Wake (50%)

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Task 1D121401A142
Cornell Aeronautical
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01 Jan 2014
Abstract: The aerodynamics of a wind turbine is governed by the flow around the rotor, where the prediction of air loads on rotor blades in different operational conditions and its relation to rotor structural dynamics is crucial for design purposes. One of the most important challenges in wind turbine aerodynamics is therefore to accurately predict the forces on the blade, where the blade and wake are modeled by different approaches such as the Blade Element Momentum (BEM) theory, the vortex method and Computational Fluid Dynamics (CFD). A free vortex wake method, based on the potential, inviscid and irrotational flow, is developed to study the aerodynamic loads. The results are compared with the BEM method, the GENUVP code and CFD.

14 citations

01 Jan 1973
Abstract: This thesis is concerned with the development of a theory for determining the aerodynamic forces for unsteady, compressible subsonic flow on a propeller and helicopter rotor. The acceleration potential method was used in developing the basic equations and the method has been programmed for the propeller on a computer and some results are given. The integral equations was solved by the doublet-lattice method, which consists of placing "load" lines at certain locations on the chord and satisfying the down-vash condition at other selected positions. The examples presented include the spanvise and chordwise loading on a rotating propeller for incompressible flow, an example of compressible flow calculations and finally, a calculation illustrating the loss of aerodynamic damping of a propeller blade due to the passage of the blade over its own wake.

13 citations

01 Jan 2016
Abstract: Wind power is currently one of the cleanest and widely distributed renewable energy sources serving as an alternative to fossil fuel generated electricity. Exponential growth of wind turbines all around the world makes it apt for different research disciplines. The aerodynamics of a wind turbine is governed by the flow around the rotor, where the prediction of air loads on rotor blades in different operational conditions and its relation to rotor structural dynamics is crucial for design, development and optimization purposes. This leads us to focus on high-fidelity modeling of the rotor and wake aerodynamics. There are different methods for modeling the aerodynamics of a wind turbine with different levels of complexity and accuracy, such as the Blade Element Momentum (BEM) theory, Vortex method and Computational Fluid Dynamics (CFD). Historically, the vortex method has been widely used for aerodynamic analysis of airfoils and aircrafts. Generally, it may stand between the CFD and BEM methods in terms of the reliability, accuracy and computational efficiency. In the present work, a free vortex filament method for wind turbine aerodynamics was developed. Among different approaches for modeling the blade (e.g. a lifting line or a lifting surface) and wake (e.g. a prescribed or a free wake model), the Vortex Lattice Free Wake (VLFW) model known as the most accurate and computationally expensive vortex method was implemented. Because of the less restrictive assumptions, it could be used for unsteady load calculations, especially for time-varying flow environment which are classified according to the atmospheric conditions, e.g. wind shear and turbulent inflow together with the turbine structure such as yaw misalignment, rotor tilt and blade elastic deformation. In addition to the standard potential method for aerodynamic load calculation using the VLFW method, two additional methods, namely the 2D static airfoil data model and the dynamic stall model were implemented to increase capability of the free vortex wake method to predict viscous phenomena such as drag and separation using tabulated airfoil data. The implemented VLFW method was validated against the BEM and CFD methods, the GENUVP code by National Technical University of Athens (NTUA), Hono turbine measurement data and MEXICO wind tunnel measurements. The results showed that the VLFW model might be used as a suitable engineering method for wind turbine’s aerodynamics covering a broad range of operating conditions.

4 citations

Cites methods from "Development of a method for predict..."

  • ...Several simplified methods by Brady [40] and Trenka [41]...


  • ...Several simplified methods by Brady [40] and Trenka [41] 2 have been developed to model the wake by vortex rings or vortex tubes....


Proceedings ArticleDOI
Leonard1, Segel1, Ray W. Murphy1Institutions (1)
01 Feb 1967

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158 citations

"Development of a method for predict..." refers background in this paper

  • ...Also printed is the azimuthal distribution of (7) thrust, (8) torque, (9) normal and side forces, and (10) pitching and yawing moments....


  • ...Hence, when Equation (9) is substituted into Equation (8) and the wake terms regrouped, the following is obtained from Equation (7),...


  • ...For a detailed derivation of Equation (9), see Appendix III, page 64....


01 Feb 1965
Abstract: : The report discusses the development of a propeller wake model and computational procedure aimed at the determination of the spatial distribution of wake vorticity and the associated induced velocity distribution. Numerical calculations were made for a number of vortex-ring configurations corresponding to a hovering rotor at onehalf, one and two ring radii above the ground, as well as out-of-ground effect. Both unsteady and time-averaged velocities were computed at various points in the wake for several cases. A model is proposed for the wake flow of a rotor in steady forward flight. Instead of the vortexring representation, the tip vortices are represented by continuous finite-core vortices. For purposes of numerical calculation, the continuous vortex is approximated by short straight-line segments. This model will enable the calculation of the time-dependent wake-vortex configuration, within the limitations of practicable computing running time, in which the various vortex elements move under mutual influence according to the laws of vortex dynamics. (Author)

7 citations

"Development of a method for predict..." refers background or methods in this paper

  • ...The test procedure for those points of mutual interest to CAL and Ames was as follows: (1) Wind-tunnel variables (i....


  • ...These coordinates are computec;,including the effects of (1) free-stream velocity, (2) wake contraction, (3) wing interference, and (4) nacelle interference in any combination desired....


  • ...Because of the errors associated with (1) data recording and reduction, (2) the nonperiodicity of the loads, and (3) the above noted anomalies in the experimental thrust and torque, the data presented in this report for the thrust and torque are believed to be good only to within i 10%....


  • ...effects of (1) wake contraction and radial and axial variation of the wake velocity, (2) free-stream velocity, and (3) the perturbing effect of a wing and nacelle completely immersed in the slipstream....


  • ...where = local section lift coefficient bj = local blade semichord Then from (1) and (2),...


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