Hydrodynamics of large-scale recirculating aquaculture tanks equipped with paddlewheel aerators

Abstract

In the pond recirculating aquaculture system (PRAS), the paddlewheel aerator is vital for improving dissolved oxygen and hydrodynamic conditions in recirculating aquaculture tanks (RATs). Understanding its influence on the hydrodynamic characteristics of RATs can enhance energy efficiency, improve sewage collection, and ensure uniform dissolved oxygen (DO) distribution. This study focuses on a 15 m side length chamfered RAT in a partitioned PRAS. The flow numerical model was validated by conducting a series of comparative analyses with the scale test model. Hydrodynamic parameters include flow uniformity, velocity, vorticity, Froude number, and effective energy utilization coefficient were analyzed. The Pearson correlation coefficient method explored the relationships between the effective energy coefficient and the aerator's placement angle and distance. Results indicate that increasing the aerator's angle and distance raises flow velocity and strengthens water mixing, promoting settleable particle discharge. But when the distance is L/4 of the RAT side length and the angle exceeds 30°, a low-velocity turbulent zone forms, blocking waste particle discharge. When the distance is L/6 or L/4 and the angle ranges from 20° to 30°, energy utilization and water mixing performance improve remarkably, increasing suspended particle discharge rate. This study offers a theoretical basis for enhancing large-scale RAT operation efficiency and water quality regulation ability.