Abstract
An investigation of the dependence of the lift-induced drag coefficient C Di of a square-tipped, cambered wing model on Reynolds number for Re ≤ 1 × 106 was conducted. Computed based on the vorticity distribution inferred from the near-field cross-flow velocity measurements of the tip vortex, different C Di prediction schemes were used. The effect of measurement plane size and grid resolution on the C Di calculations was also identified. The C Di estimated by the integral method was found to increase with increasing Re and was below the C Di = C 2l /πeAR prediction. Limits on the measurement plane size and grid resolution were determined to be at least 40% larger than the vortex outside diameter and no larger than 0.63% chord, respectively, in order to provide a good estimate of the induced drag.
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Abbreviations
- AR:
-
aspect ratio, = b 2/S
- b :
-
semi-wing span
- c :
-
chord
- C Di :
-
induced drag coefficient = D i/½ρu 2∞ S
- C l :
-
lift coefficient
- D i :
-
lift-induced drag
- e :
-
span efficiency factor
- M ∞ :
-
freestream Mach number
- r :
-
radial position
- r c :
-
vortex core radius
- r o :
-
vortex outer radius
- Re :
-
Reynolds number, = u ∞ c/ν
- S :
-
wing area
- t max :
-
maximum airfoil thickness
- u, v, w :
-
axial, transverse and spanwise velocities
- u ∞ :
-
free-stream velocity
- v θ :
-
tangential velocity
- x, y, z :
-
streamwise, transverse and spanwise directions
- ζ:
-
streamwise vorticity
- Γ:
-
circulation or vortex strength
- Γb :
-
bound circulation
- Γc :
-
core circulation
- Γo :
-
total circulation
- α :
-
angle of attack
- ψ:
-
stream function
- φ :
-
velocity potential
- ρ :
-
fluid density
- ν :
-
kinematic viscosity
- σ :
-
a source term in Eq. 2
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Gerontakos, P., Lee, T. Lift-induced drag of a cambered wing for Re ≤ 1 × 106 . Exp Fluids 42, 363–369 (2007). https://doi.org/10.1007/s00348-006-0242-6
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DOI: https://doi.org/10.1007/s00348-006-0242-6