Study on the influence of submersible water impeller on water replacement in Caohai Lake

Abstract

Caohai is a semi-enclosed shallow water lake, relies predominantly on wind fields for its hydrodynamics, resulting in slow water flow velocities and weak water exchange capacities. Consequently, pollutant deposition has led to a deteriorating water quality situation. In an effort to improve water quality, the Niulan River-Caohai Water Diversion Project uses the high-quality water source of the Niulan River to replace the existing water in the Caohai Lake, but the drainage scheme of the project is relatively simple and the water replacement efficiency is not ideal. To enhance water replacement rates and minimize water resource wastage, based on the collection and analysis of field measurement data, a three-dimensional wind field model for the Caohai Lake basin and a two-dimensional hydrodynamic-convection diffusion coupled model were established. This model was utilized to investigate the improvement effects of water replacement efficiency under various inflow forms and engineering measures. The research findings indicated:(1) the presence of surrounding mountainous terrain result in uneven distribution of wind fields across the lake surface.(2) Influenced by wind, the lake's flow field is complex, with multiple circulation patterns that hinder the water replacement process.(3) Removing certain guide flow barriers and installing 7.5 kW submersible propellers can play a “clear water introduction and pollution pushing” role, optimizing the water replacement process. This approach holds certain reference value for the optimization of water diversion project.

Keywords

wind driven current / hydrodynamic / water replacement / highland lake / MIKE / PHOENICS / Caohai / submersible water impeller