The drag of an airfoil at zero angle of attack is a function of density, viscosity, and velocity, in addition to a length parameter

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 ₁ + 1 = 0  ₁ = -1 ;

-₁ - 2 = 0  ₁ = -2; -3(-1) + (-2) + ₁ + 1 = 0  ₁ = -2

 ₂ + 1 = 0  ₂ = -1 ;

-₂ - 1 = 0  ₂ = -1; -3(-1) + (-1) + ₂ - 1 = 0  ₂ = -1

 ₃ = ₃ = 0; ₃ = -1 (by inspection) 

 ₄ = 0, ₄ = -1; ₄ = 1 (by inspection) 

₁ = f (₂, ₃, ₄) 

 C_D = f (Re, St, d/D)
St : Strouhal number
For dynamic similarity, _Re = 1, _St = 1

and

Assume T_m = T_p ; p_m = p_p  _ = 1 ; _ = 1

D_m = _DD_p = 3(1.68”) = 5.04”

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