Impact of hydrodynamic factors on atmospheric reaeration based on dynamic reaeration coefficient model

Atmospheric reaeration is the primary source of dissolved oxygen (DO) in rivers. Most reaeration models generalize the reaeration coefficient (k2), neglecting its spatiotemporal variations and wave effects. This study investigates the DO transfer process at the air–water interface under coupled influences of water depth, flow velocity, and wave action through recirculating flume experiments. By integrating gas transfer theory with experimental data, we established a mapping relationship between k2 and hydrodynamic variables. Through analytical fitting, we derived the expression for k2 and developed a multi-parameter dynamic reaeration model incorporating the combined effects of water depth, flow velocity, and wave action. The model demonstrates high accuracy, with simulated DO concentrations showing less than 4.3% maximum deviation from experimental measurements. The results reveal that DO reaeration rate decreases with increasing water depth while increasing with flow velocity. Compared to models considering only water depth and flow velocity, the accuracy improvement reaches 8.9%, confirming the non-negligible influence of waves. The developed model dynamically captures k2 variations in fluctuating hydrological environments, enabling more accurate simulation of DO concentration distribution across space and time under complex hydrodynamic conditions. This model provides an effective method for assessing aquatic environmental health.