= Mean transverse force from a rocking rod
{title2=$\langle F_y\rangle$}
For $x=\epsilon a\cos\omega t$ and a tangent $(\sin\theta,\cos\theta)$ with $\theta=\epsilon\cos(\omega t+\phi)$, the leading <force> on the fluid is $\langle F_y\rangle=-(c_\perp-c_\parallel)L\epsilon^2a\omega\sin\phi/2$. The sign changes under reversal of the tilt convention. Quadrature strokes maximize its magnitude; reciprocal strokes give zero, consistent with <kinematic reversibility of Stokes flow>.
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