Aeroelastic Gust Response for the Von Kármán Spectrum Considering a Leading-edge Flap

2019 ◽  
Author(s):  
Natália Sayuri Masunaga ◽  
Douglas Bueno
Keyword(s):  
Leading Edge ◽  
Von Karman ◽  
Von Kármán Spectrum ◽  
Von Kármán ◽  
Gust Response

Vortex wakes of a flapping foil

2009 ◽  
Vol 633 ◽  
pp. 411-423 ◽  
Author(s):  
TEIS SCHNIPPER ◽  
ANDERS ANDERSEN ◽  
TOMAS BOHR
Keyword(s):  
Phase Diagram ◽  
Leading Edge ◽  
Vortex Street ◽  
Trailing Edge ◽  
Karman Vortex Street ◽  
Von Karman ◽  
Von Karman Vortex Street ◽  
Kármán Vortex Street ◽  
Karman Vortex ◽  
Von Kármán

We present an experimental study of a symmetric foil performing pitching oscillations in a vertically flowing soap film. By varying the frequency and amplitude of the oscillation we visualize a variety of wakes with up to 16 vortices per oscillation period, including von Kármán vortex street, inverted von Kármán vortex street, 2P wake, 2P+2S wake and novel wakes ranging from 4P to 8P. We map out the wake types in a phase diagram spanned by the width-based Strouhal number and the dimensionless amplitude. We follow the time evolution of the vortex formation near the round leading edge and the shedding process at the sharp trailing edge in detail. This allows us to identify the origins of the vortices in the 2P wake, to understand that two distinct 2P regions are present in the phase diagram due to the timing of the vortex shedding at the leading edge and the trailing edge and to propose a simple model for the vorticity generation. We use the model to describe the transition from 2P wake to 2S wake with increasing oscillation frequency and the transition from the von Kármán wake, typically associated with drag, to the inverted von Kármán wake, typically associated with thrust generation.

scholarly journals Golden Ratio Phenomenon of Random Data Obeying von Karman Spectrum

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Ming Li ◽  
Wei Zhao
Keyword(s):  
Golden Ratio ◽  
Point Of View ◽  
Self Similarity ◽  
Random Data ◽  
Von Karman ◽  
Speed Fluctuation ◽  
Fractional Differential ◽  
Navier Equation ◽  
Von Kármán Spectrum ◽  
Von Kármán

von Karman originally deduced his spectrum of wind speed fluctuation based on the Stokes-Navier equation. Taking into account, the practical issues of measurement and/or computation errors, we suggest that the spectrum can be described from the point of view of the golden ratio. We call it the golden ratio phenomenon of the von Karman spectrum. To depict that phenomenon, we derive the von Karman spectrum based on fractional differential equations, which bridges the golden ratio to the von Karman spectrum and consequently provides a new outlook of random data following the von Karman spectrum in turbulence. In addition, we express the fractal dimension, which is a measure of local self-similarity, using the golden ratio, of random data governed by the von Karman spectrum.

Quasi-Wavelet Model of Von Kármán Spectrum of Turbulent Velocity Fluctuations

2004 ◽  
Vol 112 (1) ◽  
pp. 33-56 ◽  
Author(s):  
G. H. Goedecke ◽  
Vladimir E. Ostashev ◽  
D. Keith Wilson ◽  
Harry J. Auvermann
Keyword(s):  
Turbulent Velocity ◽  
Velocity Fluctuations ◽  
Von Karman ◽  
Von Kármán Spectrum ◽  
Von Kármán
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