I forget what year off the top of my head, but here again, we have an oscillating grid that is generating wakes. This generates nearly isotropic turbulence. However, these facilities often have strong mean recirculations due to the single plane of uniform forcing. After the grid, several different types of facilities have been established to generate isotropic turbulence. These are just two examples, but there are approximately two or three dozen different types of these facilities now. They can involve rotating fans or propellers, as well as loudspeakers pulsating from a central core.

Moving on to my area of expertise, we have Random jet arrays. In this case, we have a planar array at the top of the tank with a grid of jets. The photo on the right shows a densely packed 16 by 16 array of jets. These jets are synthetic and recirculate cheap bilge pumps, injecting momentum but no net mass into the flow. As these jets turn on and off, the wakes spread and generate turbulence in the surrounding fluid. About two-thirds of the way down the tank, this generates a region of homogeneous, nearly isotropic flow. The resulting turbulence can interact with boundaries or beds, leading to decay, suspension, mixing, and transport depending on the specific boundary conditions.

For a quick visualization, here is an example of how this looks.