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You are here: Home / Seminars / Experimental physics and modelling / Hydrothermal Plume Dynamics from LES and Observations

Hydrothermal Plume Dynamics from LES and Observations

Cyprien Lemarechal
When Jan 21, 2025
from 11:00 to 12:00
Where Amphi H
Attendees Cyprien Lemarechal
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In the ocean, unlike most of the abyssal plain, hydrothermal fields are oases of life and sites of complex chemistry, where hot fluids are discharged through vents from chimney structures as black smokers, i.e., buoyant plumes. They play a crucial role in vent fields by injecting significant buoyancy flux from centimeter- scale vents and rising hundreds of meters, yet their near-field dynamics remain poorly understood. Using a Large-Eddy Simulation approach with adaptive mesh refinement, we study these plumes at centimeter-scale resolution within a 6 m domain above the vent.

We study a typical black smoker in the forced plume regime to quantify the mean flow and spatial variability, investigating the link between turbulent structures and the entrainment rate α of surrounding water. Extreme temperatures above 100°C occur in the first two meters of the column, potentially lethal for or- ganisms. LES provides access to fluctuations in the flow field, unlike integral models. We show that exposure times for a proxy tracer are short, suggesting that hydrothermal plumes could serve as viable transport vectors for biological materials.

The results are then compared with in-situ data and plume theory, specifically the model from Morton, Taylor, and Turner (1956). The great depths involved make in-situ observations challenging, with data collection generally limited to the first few meters above the source to attribute measurements to a specific vent cluster. Numerical experiments allow for the interpretation of these mea- surements. Finally, data from the water column reveal the plume’s signal in the far-field of the source, corroborating numerical results obtained on a 200 m scale.

References
Morton, B., Taylor, G. I., & Turner, J. S. (1956). Turbulent gravitational con- vection from maintained and instantaneous sources. Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 234 (1196), 1–23.