Mechanism Of Water Salinity Stratification Removal Of The Water-lifting Tube

Pond culture is one of the major aquaculture methods in China,accounting for more than 49%of the country’s total aquatic product output annually.However,pond culture is susceptible to external influences because of its shallow water and relatively closed culture environment.Due to global climate change,extreme environments,such as high temperatures and low oxygen levels,are gradually normalising.This leads to the stratification of pond culture water,increasing the probability of the death of aquaculture objects.Recently,the problem of water stratification in aquaculture ponds has been gaining increasing attention.In recent years,by injecting compressed air into vertical pipes,the research of carrying bottom water body to surface water body to release water stratification device has become a hot topic.Therefore,this research team simplified it by referring to the design of water-lifting aeration.A simple water-lifting tube device was designed to simulate the salinity stratification of the loose water in aquaculture ponds through a glass water tank,and the process and mechanism of the application of the water-lifting tube device to the aquaculture pond to remove salinity stratification were explored.In this experiment,through the observation of the experimental process,the salinity stratification process of the water pump device is divided into four stages: preparation,start-up,mixing,and mixing.Using the control variable method,we carried out research on three influencing factors,i.e.aeration amount,stratified water salinity difference and target distance.The major research results are as follows.(1)The water-lifting tube carries high-density brine to the surface of low-density fresh water by means of air-lifting water for release,forming a gravity flow of brine and continuous entrainment and mixing with the surrounding low-density water body,forming an intermediate layer at the stratified interface of the stratified water body.In the density layer,with the enhancement of the mixing degree of the stratified water body,the thickness of the intermediate density layer also increases,and when the thickness reaches 40 cm,the stratified water body is completely mixed.(2)Based on the control variable method,with varying aeration rates(32,90,140 and 240 m L/min)of the water-lifting tube,the mixing of salinity-stratified water body accelerated with increasing aeration rate;the time taken to completely mix the water body was reduced from 210 to 28 min.(3)Using the control variable method,with changing salinity differences(10,20,30 and 40)of the salinity-stratified water body,the time required for complete mixing of the salinity stratified water body was reduced from 210 to 120 min.(4)Using the control variable method,under varying target distances(-39.4,-34.4,-29.4,-24.4 and-19.4 cm)of the water-lifting tube,the water body at a height below the target distance(depth of the water inlet)of the water-lifting tube cannot release the gas bomb through the water-lifting tube and transport it to the water body’s surface for release,preventing the water body with salinity stratification to completely mix.