A numerical modelling of gas exchange mechanisms between air and turbulent water with an aquarium chemical reaction

AbstractThis paper proposes a new numerical modelling to examine environmental chemodynamics of a gaseous material exchanged between the air and turbulent water phases across a gas–liquid interface, followed by an aquarium chemical reaction. This study uses an extended concept of a two-compartment model, and assumes two physicochemical substeps to approximate the gas exchange processes. The first substep is the gas–liquid equilibrium between the air and water phases, A(g)⇌A(aq), with Henryʼs law constant H. The second is a first-order irreversible chemical reaction in turbulent water, A(aq)+H2O→B(aq)+H+ with a chemical reaction rate κA. A direct numerical simulation (DNS) technique has been employed to obtain details of the gas exchange mechanisms and the chemical reaction in the water compartment, while zero velocity and uniform concentration of A is considered in the air compartment. The study uses the different Schmidt numbers between 1 and 8, and six nondimensional chemical reaction rates between 10−∞(≈0) to 101 at a fixed Reynolds number. It focuses on the effects of the Schmidt number and the chemical reaction rate on fundamental mechanisms of the gas exchange processes across the interface