Numerical Simulation Of Mixing Process Of Gas-Liquid With Radical Jetting Into Ship's Ballast Water Discharge Pipe

Invasive spread of alien organism is one of the four threats against marine environment. Alien species can flourish in suitable environment,posing devastating impact on the ecosystem and local species.Ship ballast water,which is the most important channel of alien species spreading,has lead to massive loss to global economy,it is urgent to ensure proper treatment of ship ballast water.Significant progress has been achieved in water treatment with advanced oxidation technology like hydroxyl radical,research results showed that the hydroxyl radical can effectively kill microorganism in the provision of rapid mingling with ballast water. The method has drawn attention from International Maritime Organization.However, problems are discovered in the research on the treatment of ship's ballast water by hydroxyl radicals.①The diameter of the pipeline for ballast water emptying is great, in which the velocity and the flux is high,taking challenge on the fast and uniform gasliquid mixture of radicals and the ballast water.②The length of the pipeline for ballast water emptying is limited and the lifetime of the radical is short,therefore,only when the radicals and the ballast water are mixed fast and uniformly in the extremely short time and extremely short way,is the good result of the external invasion small biology deactivation guaranteed.③Only the conveyance capacity of pipe is not affected when the radicals and the ballast water are mixed fast and uniformly,can the increasing of the ballast pump power and the diameter of the pipeline be avoided.So the extent that the fast and uniform gas-liquid mixture of radicals and the ballast water determines the final effect of the ballast water treatment,which becomes one of the restriction factors to engineering process ballast water.It is proposed for the first time that the key factor for industrial application is homogenous mixture of hydroxyl radical and ballast water.After evaluation of various mixers,Tee pipe is picked us as the mixer of hydroxyl and ballast water.Elurian-Elurian model is used to investigate Tee mixer,and deep research into ratio of jet into crossflow, diameter ratio and etc is conducted,the results showed that the diffuse degree is affected by momentum ratio and diameter ration.As for the single Tee mixer,there is always a dead zone,and can not realize rapid mixture of hydroxyl radical and ballast water. For the double Tee mixer,mixture degree is influenced by momentum ration,diameter ratio and width between two tubes.A nonuniform degree of 0.5%is reached under the following conditions,R_L=0.05,R_m≥6.40,R_d≥0.10.The process of mixture poses almost no impact on the tube.In the paper a Tee mixer is designed for allowing rapid mixture of hydroxyl radical and ballast water.The mixture facility can be easily fitted into the existing pipeline,and a nonuniform degree of 0.5 is achieved,thus the bottle neck restricting the treatment of alien organism is broken,and necessary data are collected for the development of online treatment facility.