Wakes of Lifting Propellers (rotors) in Ground Effect PDF Download
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Author: F. A. DuWaldt
Publisher:
ISBN:
Category : Rotors (Helicopters)
Languages : en
Pages : 110
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Book Description
The report presents the development of a wake model for a lifting propeller (rotor) in ground effect and the computational procedure used to determine the spacial distribution of wake vorticity and the induced velocity field accompanying that vorticity distribution. Sample calculations for a two-bladed rotor were carried out on an IBM 7044 computer. Locations of wake vortical elements and the associated induced velocities at selected field points are presented for advance ratios of 0, 0.02, 0.05, and 0.10 for an H/R (ratio of rotor height above ground to rotor radius) of 1.0. Also, a few results for a hovering case with H/R = 0.5 are presented. A calculated root-mean-square velocity map is compared with measured hovering data (time averaged) and good agreement is obtained in the outer half of the slipstream. The implications of computed results with respect to the flow field at a horizontal stabilizer or tail rotor are noted as examples of the use of the model. The wake vortex model used for these calculations is a distorted continuous helix emanating from each blade tip. (Author).
Author: F. A. DuWaldt
Publisher:
ISBN:
Category : Rotors (Helicopters)
Languages : en
Pages : 110
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Book Description
The report presents the development of a wake model for a lifting propeller (rotor) in ground effect and the computational procedure used to determine the spacial distribution of wake vorticity and the induced velocity field accompanying that vorticity distribution. Sample calculations for a two-bladed rotor were carried out on an IBM 7044 computer. Locations of wake vortical elements and the associated induced velocities at selected field points are presented for advance ratios of 0, 0.02, 0.05, and 0.10 for an H/R (ratio of rotor height above ground to rotor radius) of 1.0. Also, a few results for a hovering case with H/R = 0.5 are presented. A calculated root-mean-square velocity map is compared with measured hovering data (time averaged) and good agreement is obtained in the outer half of the slipstream. The implications of computed results with respect to the flow field at a horizontal stabilizer or tail rotor are noted as examples of the use of the model. The wake vortex model used for these calculations is a distorted continuous helix emanating from each blade tip. (Author).
Author: Albert Betz
Publisher:
ISBN:
Category : Ground-cushion phenomenon
Languages : en
Pages : 544
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Book Description
In what follows an estimate will be made of the magnitude of the ground effect. For the two cases where the distance a of the propeller from the ground is very small, and very large, respectively, in comparison with the propeller radius r(sub o) the relations may be simply expressed. We consider first the effect of the ground, assuming that the thrust is held constant, as may be done by a suitable change in the propeller speed.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 200
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Book Description
Author: Defense Documentation Center (U.S.)
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 784
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Book Description
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 1278
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Book Description
Author: Wayne Johnson
Publisher: Courier Corporation
ISBN: 0486131823
Category : Technology & Engineering
Languages : en
Pages : 1122
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Book Description
Monumental engineering text covers vertical flight, forward flight, performance, mathematics of rotating systems, rotary wing dynamics and aerodynamics, aeroelasticity, stability and control, stall, noise, and more. 189 illustrations. 1980 edition.
Author: Gordon J. Leishman
Publisher: Cambridge University Press
ISBN: 9780521858601
Category : Science
Languages : en
Pages : 860
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Book Description
Written by an internationally recognized teacher and researcher, this book provides a thorough, modern treatment of the aerodynamic principles of helicopters and other rotating-wing vertical lift aircraft such as tilt rotors and autogiros. The text begins with a unique technical history of helicopter flight, and then covers basic methods of rotor aerodynamic analysis, and related issues associated with the performance of the helicopter and its aerodynamic design. It goes on to cover more advanced topics in helicopter aerodynamics, including airfoil flows, unsteady aerodynamics, dynamic stall, and rotor wakes, and rotor-airframe aerodynamic interactions, with final chapters on autogiros and advanced methods of helicopter aerodynamic analysis. Extensively illustrated throughout, each chapter includes a set of homework problems. Advanced undergraduate and graduate students, practising engineers, and researchers will welcome this thoroughly revised and updated text on rotating-wing aerodynamics.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 46
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Book Description
Author: David V. Pauling
Publisher:
ISBN:
Category :
Languages : en
Pages : 180
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Book Description
A comparison is made of classical vortex theory with experimental and numerical results on statically thrusting propellers and rotors, and on propellers in forward flight. It is concluded that vortex theory can accurately predict the overall thrust and power of these propulsors when proper account is taken of normality between the vortex sheet and induced velocities in the wake. Further, it is necessary to include accurate airfoil section lift and drag coefficients as a function of Mach number and angle-of-attack in order to realize an accurate prediction. Also, although corrections to account for section thickness and wide-blade effects were found to be negligible, the prediction of rotor or propeller performance was found to depend rather strongly on the helix angle at the edge of the trailing-vortex sheet.
Author:
Publisher:
ISBN:
Category : Naval research
Languages : en
Pages : 480
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Book Description
