= Axisymmetric stresslet from a Stokeslet pair
{title2=$S=Fa$}
Opposite forces $\pm F\mathbf e$ applied to the fluid at $\pm(a/2)\mathbf e$ have no net force or torque. Their leading <Stokeslet> difference is $-Fa(\mathbf e\cdot\nabla)[J(\mathbf r)\mathbf e]$, equal to the axial <stresslet> with strength $S=Fa$. Positive $S$ drives outward flow on the axis and inward flow in the equatorial plane, corresponding to a <pusher microswimmer>; negative $S$ gives a <puller microswimmer>.
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