| Dredging works are the main means of daily maintenance of coastal or inland river basins and navigation channels.They can also be used for landfilling and land-laying.However,dredging projects will cause pollution to the surrounding water environment.Environmental dredging is different from traditional dredging methods.It has considered the influence to the surrounding environment that was caused by the Dredging works.And it has created favorable conditions for preventing the spread of pollution sources.As a non-suspended material diffusion technology that can meet the environmental protection standards of suspended matter diffusion and is suitable for navigation requirements,the bubble curtain anti-fouling system has its unique advantages in environmental dredging technology.At present,the research on bubble curtain mainly focuses on the mechanism research of bubble curtain and the improvement of the barrier efficiency of bubble curtain.Based on this,this paper uses the laboratory sink test,numerical simulation and construction field test to study the formation process and antifouling properties of bubble curtain.The specific research contents and results are as follows:(1)The test tank was set up to test the bubble formation characteristics.The influence of the structure and operating parameters of the bubble tube on the formation characteristics of the bubble curtain was studied.The CFD simulation method for bubble formation under undisturbed in a small area was also constructed.Then the CFD model results were compared with the experimental data to determine the key factors affecting bubble formation and to verify the accuracy of the CFD model.The results show that the bubble formation characteristics in the simulation and experiment are basically the same,the diameter of the orifice is the most important factor affecting the diameter of the bubble,and the ventilation speed/ventilation pressure is a secondary factor;the number of bubbles in the experiment is related to the ventilation pressure,the pipe structure and the water depth Correlation;in the numerical simulation of small areas,the formation of bubbles and the spacing of bubbles rising are mainly affected by the diameter of the orifice and the aeration speed.(2)The formation characteristics and anti-fouling characteristics of bubble curtain under water flow were simulated by CFD model.And the influence of operating parameters,structural parameters and environmental parameters on the flow field and anti-fouling characteristics of bubble curtain was analyzed.The results show that the horizontal deviation of the bubble curtain is mainly related to the aeration speed and the water flow velocity,and the effect of the water flow velocity is greater than the aeration velocity.The circulation action around the bubble curtain was related to operating parameters,structural parameters,environmental parameters,and pipe layout.And operating parameters,structural parameters,environmental parameters,particle size and piping layout have a great influence on the efficiency of bubble curtain barrier suspension diffusion.While water flow velocity is the main factor determining bubble curtain failure,and ventilation Speed is a secondary factor determining the failure of the bubble curtain;the diameter of the orifice and the configuration of the bubble curtain do not change the failure condition of the bubble curtain,and only change the antifouling efficiency when the bubble curtain does not fail.(3)The CFD model of bubble curtain movement in open water is established.And the influence of water depth,bubble curtain spacing,the distance between bubble curtain and pollution source on the flow field characteristics and anti-fouling characteristics of bubble curtain is analyzed.The main factor affecting the flow field distribution and particle motion and distribution around the bubble curtain is the water depth.The secondary factor is the bubble curtain spacing,while it is regardless of the distance between bubble curtain and pollution source.However,the water depth,the bubble curtain spacing and the distance between bubble curtain and pollution source has a great influence on the barrier efficiency.For a specific condition,there is a critical bubble curtain arrangement position,so that the barrier efficiency of the bubble curtain is optimized.(4)The on-site experiment of the bubble anti-stain curtain system was carried out to verify the feasibility of the bubble curtain anti-fouling system in the actual dredging project.In the engineering field experiment,the turbidity of the water body showed an overall downward trend before and after the bubble curtain,which proved that the bubble curtain system has practicality in the dredging project. |
PDF Full Text Request