The BvK instability can be generated in the wake of a single circular cylinder (diameter d and length L) or with an array of them. Our goal here is to understand the effects of an open loop control stratregy on the vortex shedding for three side-by-side cylinders. Vortex shedding will start when the Reynolds number is greater than the critical value creating a wake flow of three coupled von Karman streets.

For the case of two side-by-side cylinders, at low Reynolds numbers, both a symmetric and an asymmetric shedding mode of two parallel vortex streets can be observed. If we include a third cylinder in between two peripheral cylinders, we can fix the starting phase of all of three shedding modes using a numerical version of the wake control method by suction of the stagnation point at each cylinder.

A proper control of the shedding phase of will produce an array of vortices forming a kind of lattice where the number of shed vortices (at the Strohual frequency fs ) is determined with the control method and the lattice size with the wavelength l = U/fs and cylinder separation. The three-body situation allow us to increase the number of vortices over a transverse length scale, and to get a wider lattice-like vortex distribution. It also helps to understand the role of overall flow symmetries associated to local broken flow symmetries for each wake.