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Experimental Studies of the Turbulent Flow Structure of Leading—Edge Vortices

  • Chr. Breitsamter
Part of the Notes on Numerical Fluid Mechanics (NNFM) book series (NONUFM, volume 60)

Summary

This paper presents selected results from an extensive experimental investigation on velocity and surface pressure fluctuations caused by leading-edge vortices, in particular, when breakdown occurs. The models used include delta- and delta-canard configurations. The vortical structures are clearly shown by rms and spectral distributions. Downstream of bursting the velocity fluctuations are the strongest in an annular region around the vortex center. The related spectra indicate quasi-periodic oscillations arising from a helical mode instability. When breakdown moves over the wing to the apex there is a strong increase in surface pressure fluctuations. They exhibit dominant frequencies corresponding to those of the velocity fluctuations. A frequency parameter based on the local semi-span and the sinus of a can be used to estimate the frequencies of dynamic loads due to bursting.

Keywords

Turbulence Intensity Vortical Structure Vortex Center Annular Region Delta Wing 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Nomenclature

Cprms

rms value of pressure coefficient

ĉp

amplitude spectra of pressure fluctuations, \( \sqrt {2S\Delta kU\infty /l\mu } \)

Cr, Cc

wing root chord, canard root chord, [m]

f, fD

frequency, dominant frequency, [Hz]

k

reduced frequency, f l µ /U

l µ

wing mean aerodynamic chord, [m]

Rel µ

Reynolds number based on l µ , U l µ / ν

rms

root mean square value

S

spectral density, [1/Hz]

s, sl

wing semi-span, local wing semi-span, [m]

U

freestream velocity, [m/s]

u, v, w =

axial, lateral and vertical velocity (wind tunnel-axis system), [m/s]

\( {u_{xz}}_{_{rms}} \)

sum of axial and vertical rms velocity, \( \sqrt {1/2\left( {\overline {{{u'}^2}} + \overline {{{w'}^2}} } \right)} \)

Y, Z

nondimensionalized coordinates of the measurement planes, related to s l

x, y, z

wind tunnel axis system or model coordinate system, [m]

xB

chordwise coordinate of burst location, [m]

α, ß

aircraft angle of attack, aircraft angle of sideslip, [°]

ψw, ψc

wing leading-edge sweep, canard leading-edge sweep, [°]

Λw, Λc

wing aspect ratio, canard aspect ratio

ν

kinematic viscosity, [m 2/s]

Δf, Δk

frequency resolution of power spectral density

\( \overline {..} {\rm{ }},{\rm{ }}{\rm{..'}} \)

time-averaged, fluctuation part

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References

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Copyright information

© Friedr. Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig/Wiesbaden 1997

Authors and Affiliations

  • Chr. Breitsamter
    • 1
  1. 1.Lehrstuhl für FluidmechanikTechnische Universität MünchenGarchingGermany

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