On the Rotor Lifting Line Wake Model

2017 ◽  
Vol 33 (01) ◽  
pp. 31-45
Author(s):  
Brenden Epps
Keyword(s):  
Horizontal Axis ◽  
Preliminary Design ◽  
Trailing Vortices ◽  
Line Theory ◽  
Wake Model ◽  
Model Versus ◽  
Line Design ◽  
Lifting Line ◽  
Lifting Line Theory ◽  
Horizontal Axis Turbine

This article comments on the wake model used in moderately loaded rotor lifting line theory for the preliminary design of propellers and horizontal-axis turbines. Mathematical analysis of the classic wake model reveals an inconsistency between the induced velocities numerically computed by the model versus those theoretically predicted by the model. An improved wake model is presented, which better agrees with theory than previous models and thus improves the numerical consistency and robustness of rotor lifting line design algorithms. The present wake model analytically relates the pitch of the trailing vortices to the pitch of the total inflow computed at the lifting line control points. For conciseness, the article focuses on the propeller case, although both propeller and horizontal-axis turbine examples are presented.

305 Analysis of Lifting Line Theory Using Damping of Trailing Vortices

2012 ◽  
Vol 2012.20 (0) ◽  
pp. 65-66
Author(s):  
Yusuke IKEDA ◽  
Mitsumasa NEMOTO ◽  
Osamu KOBAYASHI
Keyword(s):  
Trailing Vortices ◽  
Line Theory ◽  
Lifting Line ◽  
Lifting Line Theory

Integrated Rotor Performance Improvement and Vibration Reduction Using Active Camber Morphing

2019 ◽  
Author(s):  
Sumeet Kumar ◽  
Dominik Komp ◽  
Manfred Hajek ◽  
Jürgen Rauleder
Keyword(s):  
Active Control ◽  
Closed Loop ◽  
Vibration Reduction ◽  
Fish Bone ◽  
Open Loop ◽  
Beam Elements ◽  
Line Theory ◽  
Wake Model ◽  
Lifting Line ◽  
Lifting Line Theory

Abstract This paper discusses open-loop and closed-loop active control investigations of a full-scale Bo 105 helicopter rotor with active camber morphing. The potential of an active camber morphing concept to reduce non-rotating vibratory hub loads and rotor power using active control was investigated. The mechanism employed was a dynamically actuated airfoil camber morphing concept known as Fish Bone Active Camber (FishBAC) that smoothly deforms the camber over the aft section of the airfoil. A comprehensive rotorcraft aeromechanics analysis was used that modeled the blade elastic motion using one-dimensional finite beam elements combined with multibody dynamics. Aerodynamic forces were calculated with a free-vortex wake model together with lifting line theory for the blade aerodynamics. The open-loop investigation comprised of a parametric study of relevant control parameters that govern the active camber deflection cyclic actuation profile and their effects on rotor performance and hub vibration. It was found that active camber morphing using superimposed once-per-revolution (1P) and 2P control inputs was able to simultaneously reduce rotor power by 4.3% and overall vibratory hub loads by 27%. Additionally, a closed-loop adaptive multicyclic controller was used to identify the potential of this morphing concept for hub vibration reduction using multicyclic active control inputs. Active camber actuation using a sum of four control harmonic inputs, i.e. 1-4P, resulted in a maximum hub vibration reduction of 50%.

A Method for Predicting Contra Rotating Propellers Off-Design Performance

2014 ◽  
Author(s):  
Matthieu Dubosc ◽  
Nicolas Tantot ◽  
Philippe Beaumier ◽  
Grégory Delattre
Keyword(s):  
Design Tool ◽  
Preliminary Design ◽  
Detailed Design ◽  
One Dimensional ◽  
Open Rotor ◽  
Line Theory ◽  
Lifting Line ◽  
Lifting Line Theory ◽  
Complex Methods ◽  
Engine Cycle

This article presents a method for predicting contra rotating propellers individual and total performance which is fast and robust enough to be used in performance engine cycle and engine subsystems detailed design. The method is based on the use of single propeller maps and models mutual induced velocities thanks to one-dimensional theories. These velocities are responsible for interferences between propellers. This article goes through the assumptions on which stands the proposed method and shows that it is relevant compared against more complex methods such as lifting line theory and definitively provides a valuable easy-to-enforce preliminary design tool for open rotor propulsor controls sizing.

scholarly journals Modelling yawed wind turbine wakes: a lifting line approach

2018 ◽  
Vol 841 ◽  
Author(s):  
Carl R. Shapiro ◽  
Dennice F. Gayme ◽  
Charles Meneveau
Keyword(s):  
Initial Conditions ◽  
Transverse Velocity ◽  
Vortex Pair ◽  
Streamwise Velocity ◽  
Wake Flow ◽  
Wind Tunnel Experiments ◽  
Line Theory ◽  
Wake Model ◽  
Lifting Line ◽  
Lifting Line Theory

Yawing wind turbines has emerged as an appealing method for wake deflection. However, the associated flow properties, including the magnitude of the transverse velocity associated with yawed turbines, are not fully understood. In this paper, we view a yawed turbine as a lifting surface with an elliptic distribution of transverse lift. Prandtl’s lifting line theory provides predictions for the transverse velocity and magnitude of the shed counter-rotating vortex pair known to form downstream of the yawed turbine. The streamwise velocity deficit behind the turbine can then be obtained using classical momentum theory. This new model for the near-disk inviscid region of the flow is compared to numerical simulations and found to yield more accurate predictions of the initial transverse velocity and wake skewness angle than existing models. We use these predictions as initial conditions in a wake model of the downstream evolution of the turbulent wake flow and compare predicted wake deflection with measurements from wind tunnel experiments.

Unified Rotor Lifting Line Theory

2013 ◽  
Vol 57 (04) ◽  
pp. 181-201
Author(s):  
Brenden P. Epps ◽  
Richard W. Kimball
Keyword(s):  
Axial Flow ◽  
Preliminary Design ◽  
Propeller Design ◽  
Performance Curves ◽  
Line Theory ◽  
Parametric Studies ◽  
Lifting Line ◽  
Lifting Line Method ◽  
Lifting Line Theory ◽  
Line Analysis

A unified lifting line method for the design and analysis of axial flow propellers and turbines is presented. The method incorporates significant improvements to the classical lifting line methods for propeller design to extend the method to the design of turbines. In addition, lifting line analysis methods are developed to extend the usefulness of the lifting line model to allow generation of performance curves for off-design analysis. The result is a fast computational methodology for the design and analysis of propellers or turbines that can be used in preliminary design and parametric studies. Design and analysis validation cases are presented and compared with experimental data.

An improved nonlinear lifting-line theory.

AIAA Journal ◽  
1973 ◽  
Vol 11 (5) ◽  
pp. 739-742 ◽  
Author(s):  
CHUAN-TAU LAN
Keyword(s):  
Line Theory ◽  
Lifting Line ◽  
Lifting Line Theory
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