Experimental studies of swimming organisms and reaction fronts in vortex array flows*

We present experiments that study both the motion of swimming brine shrimp (artemia) and of reaction fronts (the excitable Belousov-Zhabotinsky chemical reaction) in an array of stationary vortices. Previous studies have already established the presence of burning invariant manifolds (BIMs) that act as one-way barriers that inhibit the motion of reaction fronts in 2- and 3-dimensional fluid flows. The same BIMs are also a special case of swimming invariant manifolds (SwIMs) that block the motion of self-propelled particles in the same flow. We

test predictions that these BIMs act as ultimate barriers even for swimmers with noisy, tumbling behavior. The striking similarities between front propagation and the motion of self-propelled particles in fluid flows leads to a prediction of the maximum combined (and averaged) speed for swimmers in the flow, based on the shape of a hypothetical reaction front in the same flow.