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PIV investigation of flowfield behind perforated Gurney-type flaps

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Abstract

The flow behind perforated Gurney-type flaps was investigated by using particle image velocimetry (PIV) at Re = 5.3 × 104. The PIV measurements were supplemented by force balance and surface pressure data. The near wake was disrupted and narrowed, indicative of a reduced drag, with increasing flap perforation and had a drastically suppressed fluctuating intensity. Depending on the strength of the perforation-generated jet, the vortex shedding process behind the flap could be eliminated. The flap porosity also led to reduced positive camber effects and the decompression of the cavity flow (upstream of the flap), as well as decreased upper and lower surface pressures, compared to the solid flap. The reduction in the drag, however, outweighed the loss in lift and rendered an improved lift-to-drag ratio.

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Abbreviations

b :

span

c :

airfoil chord

C d :

section drag coefficient

C d,min :

C d value at α = 0°

C l :

section lift coefficient

C p :

surface pressure coefficient

d :

hole diameter

f s :

vortex-shedding frequency

h :

flap height

Re :

Reynolds number (cu o/ν)

St :

Strouhal number (f s h/u o)

u o :

freestream velocity

u m ,v m :

mean streamwise and transverse velocity

u,v :

instantaneous streamwise and transverse velocity

u′:

streamwise fluctuating velocity (u − u m )

u rms, v rms :

root-mean-square turbulence intensity

x,y,z :

streamwise, transverse and spanwise distance

α:

angle of attack

αss :

lift stall angle

αzl :

zero-lift angle

σ:

porosity

ζ:

vorticity (∂v/∂x − ∂u/∂y)

ζ m :

mean vorticity

ν:

fluid viscosity

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Authors and Affiliations

  1. Department of Mechanical Engineering, McGill University, Montreal, Quebec, H3A 2K6, Canada

    Tim Lee & L. S. Ko

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  1. Tim Lee
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  2. L. S. Ko
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Correspondence to Tim Lee.

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Lee, T., Ko, L.S. PIV investigation of flowfield behind perforated Gurney-type flaps. Exp Fluids 46, 1005–1019 (2009). https://doi.org/10.1007/s00348-008-0606-1

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  • DOI: https://doi.org/10.1007/s00348-008-0606-1

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