Ocean liming: a LES analisys of feasibility and effects of discharging slaked lime in the wake of a ship

Climate change is one of the biggest challenges for humans in the modern world. Specifically, global warming due to greenhouse gases emissions constitutes a big part of it. Objective of The Paris Agreement, signed in 2016, is to maintain the global average temperature rise well below 2◦C above pre-industrial levels. However, global warming is strictly linked to another problem related to climate change: ocean acidification. Although various strategies that aim at counteracting global warming have been recently proposed and discussed, few are the technological solutions that prevent simultaneously global warming and ocean acidification. Among these, Ocean Liming technique is based on the idea of sequestering atmospheric carbon dioxide adding alkalinity to seawater, obtained by dissolution of slaked lime. The aim of this thesis work is to investigate the feasibility of Ocean Liming with the assessment of the calcium hydroxide concentration and seawater pH in the wake of a ship, conducted with a three dimensional reactive CFD modelling, in order to incorporate dynamic chemical parameters. The simulations have been conducted with a parallel Finite Differences – Large Eddy Simulation solver, wrote in Fortran 90. The work is divided in two main parts. The first one is focused on the code validation process, with the analysis of a laminar Poiseuille channel flow and a turbulent round jet. The second one consists in the simulation of slaked lime discharge in the near wake of a ship. In particular, the proposed configurations differ in slaked lime mass flow rate, type of injection (single or double) and the operational regime of the ship propeller (modelled with R-BET physical model). To complete the study, a preliminary analysis of the hull ship (modelled with a bluff body) effect on slaked lime dissolution is presented. The results are proposed with a study of space and time evolution of slaked lime concentration levels and pH variation across the computational domain. The solver could be used for future developments on this field of research, with the study of different slaked lime discharge configurations.

Copercini M. & Cusmai F., 2021. Ocean liming: a LES analisys of feasibility and effects of discharging slaked lime in the wake of a ship. MSc thesis, Politecnico di Milano, 141 p. Thesis.

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