Numerical modeling of hydrodynamic processes of deep-sea hydrothermal plumes: A case study on Daxi hydrothermal field, Carlsberg Ridge

Abstract

A RANS-based computational fluid dynamic model is developed to simulate the propagation and turbulent mixing of hydrothermal plumes in a stratified deep-sea environment and it is employed to study the Daxi hydrothermal field (DHF), Carlsberg Ridge in the Indian Ocean. Based on the results of in-situ measurements of the hydrothermal plume in the DHF, the parameter sensitivity is analyzed to evaluate the effects of the volume flux released from the vent orifice and the ambient buoyancy frequency on the plume dynamics. The results reveal the three-layer velocity field and obtain several important scalings, including the maximum plume rise height and neutrally buoyant plume height. Thus, it can be concluded that the classical entrainment assumption is applicable only to the plume stem below 0.6 times of the maximum plume rise height, and above that level, the structure of the flow field tends to be complicated due to the lateral spreading in the neutrally buoyant layer and circulation in the plume cap region. In addition, the simulation results show that both turbulent kinetic energy and turbulence dissipation rate attain their maximum values near the vent. However, the maximum turbulent viscosity is observed in the plume cap region, indicating strong turbulent mixing in that region. A quantitative analysis of the hydrothermal plumes in the DHF is performed by the proposed model and verified by the in-situ measurements, and the results suggest that the discrete heat flux of the DHF is about 39.38 MW. The proposed model can provide useful information for tracing the submarine hydrothermal vents, studying the matter and energy cycling in the ocean basin, and the exploration of submarine polymetallic sulfides resources and environmental assessment.