Formation of Bifurcated Wakes Behind Finite Span Flapping Wings

Nomenclature C = chord length, m C T = thrust coefficient f = flapping frequency, Hz h tip = plunge amplitude at the wing tip, m k = ωC∕U ∞ , reduced frequency l span = wingspan, m Re = U ∞ C∕ν, Reynolds number r z = z-directional distance away from the wing tip, m S wing = wing area, m 2 St = fh tip ∕U ∞ , Strouhal number U ∞ = freestream velocity, m∕s ν = kinematic viscosity of fluid, m 2 ∕s α, α 0 = pitch angle of the airfoil and initial pitch angle, respectively, deg ϕ, ϕ 0 = phase angle and initial phase angle, respectively, rad ω = angular frequency, rad∕s ω z = spanwise (z direction) vorticity