Relation between the lifting surface theory and the lifting line theory in the design of an optimum screw propeller

2012 ◽  
Vol 18 (2) ◽  
pp. 145-165 ◽  
Author(s):  
Koichi Koyama
Keyword(s):  
Surface Theory ◽  
Lifting Surface ◽  
Screw Propeller ◽  
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.

Induced Curved-Flow Effect in the Lifting-Surface Theory of the Widely Bladed Propellers

1967 ◽  
Vol 11 (01) ◽  
pp. 61-70
Author(s):  
Tetsuo Nishiyama ◽  
Takao Sasajima
Keyword(s):  
Present Theory ◽  
Surface Theory ◽  
Flow Effect ◽  
Lifting Surface ◽  
Line Theory ◽  
Lift Curve ◽  
Lifting Line ◽  
Lifting Line Theory ◽  
Good Agreement ◽  
Blade Element

The present paper is aimed to develop a more accurate lifting-surface theory of widely bladed propellers by applying the Scholz' technique. Curved-flow effect, which is of essential importance in the theory of widely bladed propellers, is analyzed and clarified in detail in the forms of correction coefficients to the lift-curve slope and zero lift angle of the blade element. Further, curved-flow correction to the lifting-line theory and the corresponding factor to the Ginzel's camber correction are shown by the present theory. The theoretical characteristics seem to be in good agreement with the experiment, so far as the assumption of linearization holds.

A New Approach To High-Aspect-Ratio Supercavitating Hydrofoils

1979 ◽  
Vol 23 (03) ◽  
pp. 218-227
Author(s):  
Teruhiko Kida ◽  
Yoshihiro Miyai
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Three Dimensional ◽  
Present Theory ◽  
Cavitation Number ◽  
New Approach ◽  
Surface Theory ◽  
Line Theory ◽  
Lifting Line ◽  
Lifting Line Theory

A three-dimensional cavity hydrofoil with a high aspect ratio is analyzed by a new lifting-line theory. Unlike Leehey's (1971) approach, which formulates the lifting-line theory from differential equations, the present theory has extracted the similar lifting-line theory from integral equations derived from the lifting-surface theory. The chief advantage of this method is that it is not necessary to match the inner and outer solutions. This lifting-line theory seems to be close to experimental results for the elliptic planform with aspect ratio 3 and 5, and for the rectangular planform with aspect ratio 6, in the case of δ/α ≥ 1, where σ is the cavitation number and α the incidence of the foil.

scholarly journals Prediction of Lift Coefficient for Tandem Wing Configuration or Multiple-Lifting-Surface System Using Prandtl’s Lifting-Line Theory

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Hao Cheng ◽  
Hua Wang
Keyword(s):  
Numerical Solutions ◽  
Hind Wing ◽  
Incidence Angle ◽  
Lift Coefficient ◽  
Design Parameters ◽  
Lifting Surface ◽  
Surface System ◽  
Line Theory ◽  
Lifting Line ◽  
Lifting Line Theory

In tandem airfoil configuration or multiple-lifting-surface layouts, due to the flow interaction among their lifting surfaces, the aerodynamic characteristics can be affected by each other. In accordance with Prandtl’s classical lifting-line theory, a method to calculate the section lift coefficient for the tandem wing configuration or multiple-lifting-surface system is presented. In that method, the form of Fourier sine series is used to express the variation of the section circulation which changes continuously along the wingspan. The accuracy of the numerical solutions obtained by the method has been validated by the data obtained from computational fluid dynamics and tunnel experiment. By varying the design parameters, such as the gap, the stagger, the incidence angle, the wingspan, the taper ratio as well as the aspect ratio, a series of tandem wing configurations are tested to analyze the lift coefficient and the induced drag of each lifting surface. From the results, it can be seen that the bigger negative gap and stagger can produce better lift characteristic for tandem wing configuration. Besides, it will also be beneficial for the lift characteristic when the incidence angle and the wingspan of fore wing are appropriately declined or if the incidence angle and the wingspan of hind wing are appropriately increased.

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.

Sign in / Sign up

Export Citation Format

Share Document