ERC project THEIA

Rotating flows over relief

Flow over boundary relief generates waves and changes the forces on the surrounding solid. Laboratory experiments allow the geometry and rotation to be varied independently, and give access to flow regimes that are expensive to simulate.

Rotating-fluid apparatus at ISTerre

THEIA’s experimental programme moved from the original plan to use the CORIOLIS platform to a dedicated facility at ISTerre. We developed the WEBER rotating system, tank designs, rotation control, optical access and particle image velocimetry (PIV), which measures velocity in a plane from successive images of illuminated tracer particles.

The programme included mini-THEIA, an approximately 50 cm setup, and a temporary tank approximately one metre in diameter mounted on WEBER. The 1m-tank was used to develop rotation control, calibration and acquisition procedures. Max Solazzo, a permanent CNRS engineer at ISTerre, worked on mechanical design and integration with David Cébron and the experimental researchers.

Spin-up and topographic coupling

After a change in the container’s rotation rate, the fluid adjusts through an exchange of angular momentum with the boundaries. Comparing this spin-up over smooth and rough bottoms helps isolate the contribution of relief. Baptiste Penlou developed PIV acquisition and analysis procedures for these comparisons in the intermediate tank, following earlier experimental work, including Samuel Payen’s contribution in 2025.

The overall spin-up rate and the evolution of the radial velocity profile describe different aspects of this adjustment. Their interpretation requires accounting for boundary friction, waves and measurement uncertainties. The smooth- and rough-bottom PIV measurements remained unpublished in the final ERC record; they are not presented here as quantitative validation of a universal drag law.

The Giraud et al. (2026) study compares theory and direct simulations with the spin-up measurements published by Burmann and Noir in 2018. Its experimental comparison concerns those earlier data, separate from the work in THEIA’s one-metre tank.

Acoustic measurements

Collaborative work on modal acoustic velocimetry for libration-driven flows used acoustic resonances in the gas-filled ZoRo spheroid. Acoustic measurements complement optical methods where particle imaging is difficult. The publisher’s correction accompanies the article.

See the project results, numerical methods and gallery.