Opposite-handed counterrotating helical swimmer
= Opposite-handed counterrotating helical swimmer
{title2=$U=-\frac{2nBD\omega}{AD(1+n)^2-B^2(1-n)^2}$}
Two coaxial opposite-handed <helices> linked by an internal motor share a translation speed but counterrotate. In an additive local-drag model, a length ratio $n$ multiplies the second <helix>'s diagonal resistances by $n$ and reverses its coupling. With $\Omega_1-\Omega_2=\omega$, force and torque balance give $U=-2nBD\omega/[AD(1+n)^2-B^2(1-n)^2]$.