Function roll_damping_interference 

pub fn roll_damping_interference(
    span_m: f64,
    body_radius_m: f64,
    taper_ratio: f64,
) -> Result<f64, AeroError>

The body’s interference with the roll damping (Barrowman 1967 eq. 3-122 and 3-123), with τ = (s + r_t)/r_t and λ = c_t/c_r, for a chord falling linearly from root to tip:

k_R(B) = 1 + ((τ − λ)/τ − (1 − λ) ln τ/(τ − 1)) / ((τ + 1)(τ − λ)/2 − (1 − λ)(τ² + τ + 1)/3)

the integral 1 + r_t³∫c/ξ² dξ / ∫ξ c dξ over the span (eq. 3-121). It is 1 with no body, 2 as the span goes to 0, and 1.20 for the Arcas Robin’s fins. A fin of another shape takes it at its tip-to-root chord ratio: an elliptical fin as a triangle, about 5.5% too much damping. Below τ = 1.001 and past τ = 10⁶ it is held at its value there, as roll_forcing_interference is.

Errors

AeroError::Domain for a non-positive span, a negative body radius, or a negative or non-finite taper ratio (an inverse taper, above 1, is allowed).