Zegao Yin

Injecting carbon dioxide (CO2) bubbles into seawater is a potential approach for mitigating the greenhouse effect and climate change. This study conducts a series of physical experiments and a numerical model coupling computational fluid dynamics with CO2 mass transfer to investigate the hydrodynamic and mass transfer characteristics of CO2 bubble plumes under random waves, and a comparative analysis is performed with regular waves. The results showed that the dimensionless velocity half-width and the CO2 mass transfer coefficient (MTC) increase for regular and random waves with increasing wave height and wave period and decrease with increasing still water depth. Under random waves, the CO2 MTC exhibits a nonmonotonic trend with variations in the injection hole diameter and injection angle. In addition, dimensionless parameters of the waves and CO2 bubble plumes are utilized to develop a predictive equation for the CO2 MTC, and the equation is validated using the related data.

Carbon dioxide (CO2) bubble injection into seawater represents a promising approach to carbon storage and global climate change mitigation. This study conducted a series of experiments and developed a numerical model that couples computational fluid dynamics and CO2 mass transfer to investigate CO2 bubble plume dynamics and mass transfer characteristics under regular waves. The results indicate that at the seaside and leeside of the CO2 bubble plume, the surface water flows in opposing directions in two circulation areas. The dissolved carbon dioxide concentration is high near the bubble plume and wave surface. The dimensionless velocity half-width and CO2 mass transfer coefficient of the bubble plume increase with the incident wave height, wave period, and CO2 flow rate; however, they decrease with increasing still-water depth. These findings shed light on interactions between wave and CO2 bubbles, CO2 mass transfer mechanisms, and CO2 capture and storage in the ocean.

The dissolved oxygen concentration (DOC) and its vertical distribution are essential to ensuring seawater quality and fish growth. In this study, a two-dimensional (2D) numerical model consisting of a numerical water tank and dissolved oxygen (DO) transport is conducted to investigate the DO destratification process under the coexistence of a planar water jet and regular waves. The effects of the wave and jet parameters are analyzed using the destratification ratio (DR) of the DOC, as well as the stratification index at the initial time (SI0) and sampling time (SI1). It was found that SI1 decreases and DR increases as the wave height increases and the DOC of the injected water decreases. As the wave period increases, SI1 first decreases and then increases, and DR exhibits the opposite trend. Both SI1 and DR increase with increasing SI0. A symbolic regression algorithm is used to obtain an empirical equation for predicting DR with relatively high accuracy.

Shell-based constructed oyster reefs (CORs) serve as nature-based coastal stabilization structures in living shoreline applications. This study investigates oyster colonization effects on the interactions of currents and waves with CORs on a slope. Using the computational fluid dynamics framework OpenFOAM®, a validated numerical model simulates the hydrodynamic performance over CORs with simple geometric surrogates for the oysters. Simulations are conducted considering: (1) unidirectional currents and regular wave conditions, (2) different oyster rugosities (R), and (3) still water depth variations on the flat seabed. Oyster colonization alters water velocity and turbulence distribution patterns. Under unidirectional currents, oysters expand wake regions and amplify upstream-propagating waves. Under pure waves, turbulent kinetic energy exhibits uneven distribution above oyster-colonized CORs, with maxima near wave-breaking zones. Oysters enhance wave nonlinearity, driving energy transfer from the primary harmonic to higher harmonics. Oyster-colonized CORs induce more wave height attenuation than bare CORs, though they produce an increase in wave shoaling and local energy. Along the slope, wave height attenuation varies significantly, with differences between R = 0 and R = 1.61 reaching up to 34% downstream of the landward COR. Lower oyster density may optimize wave dissipation through edge vortex formation and undertow intensification. Furthermore, increased still water depth reduces wave height attenuation by oyster-colonized CORs but enhances oyster-induced energy dissipation. These findings offer critical insights for designing oyster reef restoration strategies that balance ecological and coastal protection goals.