Stirring by periodic arrays of microswimmers

Resonant effects in scattering by periodic arrays

This paper is concerned with resonant effects caused by the scattering of a plane wave by a periodic array of vertical circular cylinders. The scattered field is known to consist of a finite set of plane waves, and an infinite number of evanescent modes which decay exponentially as the perpendicular distance between array and observer is increased. The problem is said to be resonant when the di...

Fluid mixing by curved trajectories of microswimmers.

We consider the tracer diffusion D(rr) that arises from the run-and-tumble motion of low Reynolds number swimmers, such as bacteria. Assuming a dilute suspension, where the bacteria move in uncorrelated runs of length λ, we obtain an exact expression for D(rr) for dipolar swimmers in three dimensions, hence explaining the surprising result that this is independent of λ. We compare D(rr) to the ...

Ocean Stirring by Swimming Bodies

Stable multicolor periodic-wave arrays.

We study the existence and stability of periodic-wave arrays propagating in uniform quadratic nonlinear media and discover that they become completely stable above a threshold light intensity. To the best of our knowledge, this is the first example in physics of completely stable periodic-wave patterns propagating in conservative uniform media supporting bright solitons.

Stability of Periodic Arrays of Vortices

The stability of periodic arrays of Mallier-Maslowe or Kelvin-Stuart vortices is discussed. We derive with the energy-Casimir stability method the nonlinear stability of this solution in the inviscid case as a function of the solution parameters and of the domain size. We exhibit the maximum size of the domain for which the vortex street is stable. By adapting a numerical time-stepping code, we...