2025-07-22 マックス・プランク研究所（MPG）
This photo shows the upper part of the water tornado model. The acrylic glas tank has a diameter of 50 centimetres and is illuminated with LED strips. The water forms a vortex whose surface shape reproduces the profile of a gravitational field. The analysis showed that the motion of the water closely resembles the behaviour seen in protoplanetary discs.
© S. Schütt (University of Greifswald)
＜関連情報＞
- https://www.mpg.de/25075124/water-tornado-in-the-laboratory-a-simple-experiment-simulates-planet-formation
- https://academic.oup.com/mnrasl/article/542/1/L67/8185399
竜巻に基づくケプラー流の実験室モデル A tornado-based laboratory model for Keplerian flows
S Knauer , S Schütt , M Flock , F Scharmer , S Haag , N Fahrenkamp , A Melzer , D M Siegel , P Manz
Monthly Notices of the Royal Astronomical Society: Letters Published:03 July 2025
DOI:https://doi.org/10.1093/mnrasl/slaf070
ABSTRACT
We introduce a laboratory experiment utilizing a water tornado to model Keplerian flows, which are relevant to astrophysical accretion discs. The tornado is generated by opposing water jet streams, creating a hyperbolic free surface that acts like a gravitational potential. Key findings demonstrate that tracer particles show a Keplerian rotation profile with Ω∝r-3/2 and conserved area speed, aligning with Kepler’s third and second law. The experiment enables the determination of dimensionless quantities such as the flow’s Reynolds number and the tracer particles’ Stokes numbers. The effective Reynolds numbers measured,Re2×105, are within the range for turbulent protoplanetary discs of Re103–105. The recovered Stokes numbers (ranging between 10-2and 10-5) show excellent agreement with the major dust component. Furthermore, the set-up’s advantages include its ability to achieve a large ratio between inner and outer radii, allowing for the study of global dynamics instead of local shear flows. It is diagnostically very accessible and geometrically flexible. The experiment opens a new avenue for studying the interaction between dust and gas in protoplanetary discs, relevant to grain growth and planet formation.
