Tip Vortex Conservation on a Main Rotor in Slow Descent Flight Using Vortex-Adapted Chimera Grids

2006 ◽  
Author(s):  
Markus Dietz ◽  
Ewald Krämer ◽  
Siegfried Wagner
Keyword(s):  
Tip Vortex ◽  
Main Rotor

Wake Unsteadiness and Tip Vortex System of Full-Scale Helicopters in Ground Effect

2021 ◽  
Author(s):  
C. Christian Wolf ◽  
Armin Weiss ◽  
Clemens Schwarz ◽  
Johannes N. Braukmann ◽  
Stefan Koch ◽  
...  
Keyword(s):  
High Speed ◽  
Low Frequency ◽  
Ground Effect ◽  
Tip Vortex ◽  
Minor Role ◽  
Main Rotor ◽  
Forward Flight ◽  
Tip Vortices ◽  
Velocity Statistics ◽  
Vertical Takeoff

The main rotor wakes of the free-flying DLR test helicopters Airbus Bo105 and EC135 were investigated in ground effect during hover, vertical takeoff, and forward flight. A high-speed schlieren system tracked the blade tip vortices at about 60 images per revolution. In addition, a constant temperature anemometry system utilized arrays of fiber film sensors, providing velocity statistics and spectra in the rotor flow. The overall wake structure agreed to preceding studies, but the velocity profiles and tip vortex trajectories were sensitive towards the environmental wind conditions. The tip vortices were observed in the schlieren images up to an age corresponding to about two revolutions below the rotor plane, before developing instabilities and falling below the detection limit. Systematic vortex pairing was found for the Bo105 but not for the EC135. The remnants of the tip vortices were identified further downstream in the wake by means of rotor-harmonic velocity signals, but they play a minor role in comparison to broad-banded turbulent fluctuations with a Kolmogorov-like spectrum. For vertical takeoff cases, the rotor wake had a hover-like structure until breaking down into low-frequency oscillations when exceeding a hub height of approximately 1.4 rotor radii. In forward flight, different types of wake velocity footprints were categorized on the basis of the normalized advance ratio. Blade–vortex interactions were found in the frontal area of the main rotor planes and between the main rotor tip vortices and the Bo105's tail rotor. The interactions prevent a further evolution of the tip vortices.

Prediction of Blade-Vortex Interaction Airloads With Higher-Harmonic Pitch Controls Using the 2GCHAS Comprehensive Code

2001 ◽  
Vol 123 (4) ◽  
pp. 469-474 ◽  
Author(s):  
Joon W. Lim ◽  
Chee Tung ◽  
Yung H. Yu
Keyword(s):  
Tip Vortex ◽  
Vortex Interaction ◽  
Main Rotor ◽  
Scaled Model ◽  
Harmonic Control ◽  
Blade Vortex Interaction ◽  
Higher Harmonic Control ◽  
Blade Tip ◽  
Higher Harmonic ◽  
Analysis System

Analytically predicted results of blade-vortex interaction (BVI) airloads, using the second- generation comprehensive helicopter analysis system (2GCHAS), are presented with the experimental results obtained from the higher-harmonic-control aeroacoustic rotor test (HART) program using a 40-percent, Mach-scaled model of the hingeless BO-105 main rotor. Correlations include airloads, blade tip deflections, and tip vortex geometry. The effects on blade airload predictions are studied with higher-harmonic pitch controls (HHC). It was concluded that the blade torsional deflection and the wake system play a very important role in predicting BVI airloads.

Tip Vortex Conservation on a Helicopter Main Rotor Using Vortex-Adapted Chimera Grids

AIAA Journal ◽  
2007 ◽  
Vol 45 (8) ◽  
pp. 2062-2074 ◽  
Author(s):  
Markus Dietz ◽  
Manuel Keßler ◽  
Ewald Krämer ◽  
Siegfried Wagner
Keyword(s):  
Tip Vortex ◽  
Main Rotor ◽  
Helicopter Main Rotor

Measurements in rollup region of the tip vortex from a rectangular wing

AIAA Journal ◽  
1997 ◽  
Vol 35 ◽  
pp. 1837-1843 ◽  
Author(s):  
B. R. Ramaprian ◽  
Youxin Zheng
Keyword(s):  
Tip Vortex

DTNS3D Computer Code Simulation of Tip-Vortex Formation: RANS Code Validation

1997 ◽  
Author(s):  
John G. Telste ◽  
Roderick M. Coleman ◽  
Joseph J. Gorski
Keyword(s):  
Vortex Formation ◽  
Computer Code ◽  
Tip Vortex ◽  
Code Validation

scholarly journals Configuration Study of Electric Helicopters for Urban Air Mobility

Aerospace ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 54
Author(s):  
Julia A. Cole ◽  
Lauren Rajauski ◽  
Andrew Loughran ◽  
Alexander Karpowicz ◽  
Stefanie Salinger
Keyword(s):  
Conceptual Design ◽  
Urban Areas ◽  
Design Space ◽  
Design Method ◽  
Urban Air ◽  
Main Rotor ◽  
Potential Benefits ◽  
Compound Helicopter ◽  
Configuration Changes

There is currently interest in the design of small electric vertical take-off and landing aircraft to alleviate ground traffic and congestion in major urban areas. To support progress in this area, a conceptual design method for single-main-rotor and lift-augmented compound electric helicopters has been developed. The design method was used to investigate the feasible design space for electric helicopters based on varying mission profiles and technology assumptions. Within the feasible design space, it was found that a crossover boundary exists as a function of cruise distance and hover time where the most efficient configuration changes from a single-main-rotor helicopter to a lift-augmented compound helicopter. In general, for longer cruise distances and shorter hover times, the lift-augmented compound helicopter is the more efficient configuration. An additional study was conducted to investigate the potential benefits of decoupling the main rotor from the tail rotor. This study showed that decoupling the main rotor and tail rotor has the potential to reduce the total mission energy required in all cases, allowing for increases in mission distances and hover times on the order of 5% for a given battery size.

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