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Interaction of an oscillating vortex with a turbulent boundary layer

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Abstract

An oscillating vortex embedded within a turbulent boundary layer was generated experimentally by forcing a periodic lateral translation of a half-delta wing vortex generator. The objective of the experiment was to investigate the possibility that a natural oscillation, or meander, might be responsible for flattened vortex cores observed in previous work, which could also have contaminated previous turbulence measurements. The effect of this forced oscillation was characterized by comparison of measurements of the mean velocities and Reynolds stresses at two streamwise stations, for cases with and without forcing. The Reynolds stresses, especially ′w′, were affected significantly by the forced oscillation, mainly through contributions from the individual production terms, provided the vortex was not too diffuse.

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Abbreviations

a :

amplitude of forced vortex motion

f :

frequency of forced vortex generator motion

l :

vortex generator root chord

L :

flow length scale

R Y , R Z :

vortex core radial dimensions in vertical and spanwise directions, respectively

Rr :

vortex circulation Reynolds number Rг = Г/ν

u, v, w :

instantaneous velocity components in X, Y, Z directions

U, V, W :

mean velocities; shorthand notation for u, υ, w

X, Y, Z :

right-hand Cartesian streamwise, vertical, and spanwise coordinate directions

δ :

boundary-layer thickness

Γ :

overall circulation

ν :

air kinematic viscosity

ω x :

streamwise vorticity, ω X = ∂W/∂Y−∂V/d+t6Z

( )0 :

reference value (measured at X = 10 cm)

( )c :

refers to vortex center

( ) max :

maximum value for a particular crossflow plane

( ) :

(overbar) time average

( )′:

(prime) fluctuating component, e.g., u=U+u′

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Authors and Affiliations

  1. NASA Ames Research Center M/S 227-2, 94035, Moffett Field, CA, USA

    R. V. Westphal

  2. Dept. of Aeronautics and Astronautics, JIAA, Stanford University, 94305, Stanford, CA, USA

    R. D. Mehta

Authors
  1. R. V. Westphal
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  2. R. D. Mehta
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Westphal, R.V., Mehta, R.D. Interaction of an oscillating vortex with a turbulent boundary layer. Experiments in Fluids 7, 405–411 (1989). https://doi.org/10.1007/BF00193423

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  • DOI: https://doi.org/10.1007/BF00193423

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