Is it possible to generate one half of a Karman Vortex Street? The Karman Vortex Street is a type of phenomenon which is generally illustrated by examples in which a long, solid, smooth circular cylinder moves at constant velocity through a fluid. The long axis of the cylinder is perpendicular to the relative velocity vector. Eddies form on the downstream side of the cylinder and detach at a regular temporal rate. The eddies form alternately in two places either side of the "flow axis".  The downstream wake behind the cylinder can be described as a series of alternating, counter-rotating vortices.  Karman vortex streets can also be generated by cylinders with other cross-sections, even by flat plates.
My Question 
Is it possible to generate a "vortex street" which consists of a single series of co-rotating vortices? 
Example
Consider an infinitely wide river with a flat bottom and water flowing steadily from west to east and a solid, smooth cylinder with semi-circular x-section attached (curved surface upwards) to the riverbed  with its long axis running north-south. Now is it possible, under certain combinations of fluid viscosity, fluid velocity and cylinder geometry, that, on the downstream side of the cylinder, tubular vortices parallel to the cylinder will periodically form, grow and detach and be carried downstream at regular time intervals?
 A: Yes. 
These kind of corotating Karman Vortex Streets do exist.

I have made real video's about this, when I noticed it in nature. No CFD, but Real stuff.
https://www.youtube.com/watch?v=iXfkaFmpnL4&list=PLgUc9kJnDMMExJivT2dWh9dAjdYYUgOFE&index=8
I was studying Turbulence, and I am more interested in other aspects of this flow. (Optics)
But in the video you could see how this single vortexes or creating this "half street", they are same times divided to smaller ones and united to a single one. But anyhow, clearly only another half of the typical vortex street. 
It should be noted that all Vortexes are "single vortexes". I actually have even better example of this kind of Vortex. You can actually found this patented dropstructure, which energy dissipation is based on such a one half vortex street. 

So it's basically a open channel nozzle. At this case the one-sided rotation becomes very apparently, as there is a strong continuous counter-current at the riverbanks. 
You can see some of the benefits of the structure live here. 
