Vortex systems

To enrich the nutrient solution in the system with oxygen, a vortex system is often used. For some system types (aeroponics, NFT, etc.), this requirement is inherently eliminated. Here is a technical article on professional vortex systems. In most systems, depending on the type and amount of nutrient solution, oxygen enrichment as known from aquariums is sufficient. Keyword: airstone. The necessary aquarium air pump for this is often available for under 10 €.

Vortex systems are based on the Taylor-Couette flow, which refers to the flow of an incompressible viscous fluid located in the space between two coaxial cylinders rotating relative to each other. The flow between the cylinders depends not only on the rotational speed but also on whether the inner or the outer cylinder is rotating.

If the relative speed of the cylinders is low (see below) and the gap between them is small compared to their diameters, the flow can be treated as a plane laminar flow (Couette flow). The velocity profile is similar to the idealized case of a plane flow between two plates, one of which is moved slowly relative to the other. One plate can be considered stationary and the other moving.

The flow was named after Maurice Couette, who constructed the first functioning rotational viscometer at the end of the 19th century and used the laminar base flow (Couette flow) for it, and after Geoffrey Ingram Taylor, who investigated the instabilities at higher rotational speeds and explained them theoretically.^[1] Couette sought to avoid vortices and rotated only the outer cylinder.^[2] The fact that vortices form when the inner cylinder rotates was already suspected by George Stokes in 1880, was experimentally found by Henry R. A. Mallock (1888) among others, and Rayleigh, to whom Lord Kelvin communicated the phenomenon, published the fundamental explanation for it in 1916.^[3] They were analyzed in detail by Taylor, whose work was also fundamental to hydrodynamics in several respects (confirmation of no-slip boundary conditions in viscous fluids, confirmation of the validity of the Navier-Stokes equations, one of the first examples of linear stability analysis in hydrodynamics).

Further reading and source: https://de.wikipedia.org/wiki/Taylor-Couette-Str%C3%B6mung (Link to German Wikipedia article)

By TaylorCouette - Own work, CC BY-SA 3.0