A Lifting-Line Equivalent Profile Method for Propeller Calculations

1985 ◽  
Vol 29 (04) ◽  
pp. 241-250
Author(s):  
G. K. Politis
Keyword(s):  
Sensitivity Analysis ◽  
Iteration Scheme ◽  
Test Results ◽  
Equivalent Radius ◽  
Profile Method ◽  
Constant Pitch ◽  
Power Loading ◽  
Line Theory ◽  
Lifting Line ◽  
Lifting Line Theory

The theoretical shortcomings of Lerbs' equivalent profile method are discussed and a novel equivalent profile method, using lifting-line theory, is presented. Details of the iteration scheme necessary for the solution of the resulting nonlinear problem are given. The problem of the equivalent radius is rationally formulated and uncertainties are shown to exist concerning the choice of the equivalent radius and the approximate relations for the efficiency and the power loading coefficient. The test results of five model propellers, with different geometric characteristics, are used in an extensive sensitivity-analysis procedure to demonstrate the good behavior of the proposed lifting-line equivalent profile method. A corresponding sensitivity analysis of Lerbs' equivalent profile method shows poor behavior with respect to changes in the equivalent radius, especially for non-constant-pitch propellers. The new method can easily be applied to wake-adapted propellers.

Theoretical Research on Propeller Type Current Meters

1975 ◽  
Vol 97 (4) ◽  
pp. 596-602
Author(s):  
R. Takeda
Keyword(s):  
Velocity Fields ◽  
Theoretical Research ◽  
High Pitch ◽  
Low Aspect Ratio ◽  
Constant Pitch ◽  
Calculation Results ◽  
Line Theory ◽  
Fundamental Equations ◽  
Lifting Line ◽  
Lifting Line Theory

This paper reports the analytical results of the motions of current meters with low aspect ratio blades. Results obtained tell that calculation values of the lifting surface theory coincide with experimental results at apparent runaway speed of all runners. If the results of the lifting line theory are compensated, calculation results of each high pitch model nearly become equal to each experimental value. Moreover, constant pitch meters show better characters than variable pitch meters, concerning velocity fields around runner blades. From the foregoing results, the fundamental equations of the current meter runner designs are brought out.

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

A comprehensive comparative investigation of the Lifting Line Theory and Blade Element Momentum Theory applied to small wind turbines

2021 ◽  
pp. 1-25
Author(s):  
K.A.R. Ismail ◽  
Willian Okita
Keyword(s):  
Wind Turbines ◽  
Power Coefficient ◽  
Computational Time ◽  
Local Flow ◽  
Small Wind Turbines ◽  
Wake Effects ◽  
Line Theory ◽  
Lifting Line ◽  
Lifting Line Theory ◽  
Blade Element

Abstract Small wind turbines are adequate for electricity generation in isolated areas to promote local expansion of commercial activities and social inclusion. Blade element momentum (BEM) method is usually used for performance prediction, but generally produces overestimated predictions since the wake effects are not precisely accounted for. Lifting line theory (LLT) can represent the blade and wake effects more precisely. In the present investigation the two methods are analyzed and their predictions of the aerodynamic performance of small wind turbines are compared. Conducted simulations showed a computational time of about 149.32 s for the Gottingen GO 398 based rotor simulated by the BEM and 1007.7 s for simulation by the LLT. The analysis of the power coefficient showed a maximum difference between the predictions of the two methods of about 4.4% in the case of Gottingen GO 398 airfoil based rotor and 6.3% for simulations of the Joukowski J 0021 airfoil. In the case of the annual energy production a difference of 2.35% is found between the predictions of the two methods. The effects of the blade geometrical variants such as twist angle and chord distributions increase the numerical deviations between the two methods due to the big number of iterations in the case of LLT. The cases analyzed showed deviations between 3.4% and 4.1%. As a whole, the results showed good performance of both methods; however the lifting line theory provides more precise results and more information on the local flow over the rotor blades.

Modern Adaptation of Prandtl's Classic Lifting-Line Theory

2000 ◽  
Vol 37 (4) ◽  
pp. 662-670 ◽  
Author(s):  
W. F. Phillips ◽  
D. O. Snyder
Keyword(s):  
Line Theory ◽  
Lifting Line ◽  
Lifting Line Theory

Some Remarks on Vortex Drag and its Spanwise Distribution in Incompressible Flow

1968 ◽  
Vol 72 (691) ◽  
pp. 623-625 ◽  
Author(s):  
H. C. Garner
Keyword(s):  
Theoretical Data ◽  
Leading Edge ◽  
List Type ◽  
Surface Theory ◽  
Lifting Surface ◽  
Line Theory ◽  
Lifting Line ◽  
Swept Wings ◽  
Lifting Line Theory ◽  
Drag Factor

Summary Theoretical data from lifting-surface theory are presented to illustrate (i) that the vortex drag factor is closely related to the half-wing spanwise centre of pressure on simple planforms without camber or twist, (ii) that lifting-line theory is useless for predicting the spanwise distribution of vortex drag on swept wings, (iii) that recent numerical improvements in lifting-surface theory help to reconcile the concepts of wake energy and leading-edge suction in relation to vortex drag.

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