Through the analogy between the shallow water equations, the gravitational potential is simulated by means of a gravitational funnel. You may know gravitational funnels from museums or zoos. There donations are collected with it. The gravitational funnel has a radius of 25 cm. The SWADEX drain was height-adjustable. For the Standing Accretion Shock Instability (SASI) studies, the drain was at the bottom. If the flow velocity exceeds the phase velocity of the gravity wave, a hydraulic jump is formed. This can be seen in analogy to a shock. We could clearly observe a SASI-like instability. 

In the next step, we tried to investigate the magnetorotational instability (MRI). Magnetic fields are simulated with the help of polymer physics. Thus, we thought that we could build a system that could mimic both gravitational and MHD effects. To introduce rotation, we raised the drain and made it rotate. Interestingly, when we added the polymers, we were able to observe Keplerian profiles, as well as the outward transport of angular momentum expected for MRI. Unfortunately, the rotational profile in water was found to be similar to that of the Taylor-Coette system. At a uniform filling height, the effect of gravity is lost at the surface. Thus, this setup is not suitable for further MRI studies.

relevant publications

S. Sebold et al. 'Advective-acoustic cycle in a shallow water standing accretion shock experiment' Phys. Rev. E 102, 063103 (2020)

F. Günzkofer, P. Manz 'Outwards transport of angular momentum in a shallow water accretion disk experiment', Phys. Rev. Fluids 6, 054401 (2021)