Hydrodynamic Model And Its Application Based On ROMS For Bohai Bay

Bay has always been the producing, trading and living center for human becauseof its concentrated land-ocean interactions. In recent years, more and more wastewater,including industrial and domestic wastewater, have been discharged into Bohai Baythrough surface runoffs or submarine pipelines due to the rapidly economydevelopment in this area which have caused serious effects to the offshore ecosystem.It is necessary to study the water exchange characteristics and pollutant transportationin Bohai Bay to implement ocean ecological environment protection and marineresource reasonable utilization to ensure the sustainable development of coastaleconomy.In common hydrodynamic numerical simulation methods, three-dimensionalmodel was usually applied in regions of deepwater or issues involved wave breakingand sediment transporting. As to shallow ocean area like Bohai Bay, two-dimensionalconvection-diffusion model and two-dimensional hydrodynamic model were usuallyselected to simulate the pollutant convection-diffusion. Considering about the densityelement, the vertical distribution of pollutants would differ significantly since theindustrial wastewater was saline at intermediate temperature. Two-dimensional modelis incapable to simulate the scenario because of the vertical integrating on the depth.Thus, Regional Ocean Modeling System was applied in this paper to investigatethe water exchange and pollutant from Sewage Deep Sea Discharge Projectconvection-diffusion in Bohai Bay.The three-dimensional model was firstly verifiedby comparing the numerical solution with the analytical solution. The vertical velocitydistribution of a flat-bottom pool with wind driving on the surface was simulated toobtain relevant numerical values. As the results expressed, the numerical values werewell fit with the analytical solution of wind-driven currents. Then, the comparison ofthe numerical simulation results and the measured values of Bohai Bay includingparameters of depth, flow velocity, flow direction indicated that the three-dimensionalmodel could accurately simulate Bohai Bay tide and distribution of flow field in anydepth.Based on three-dimensional hydrodynamic model and convection-diffusionmodel, the water exchange condition of the offshore functional areas in Bohai Baywas investigated by relation matrix then compared with the results of three-dimensional and two-dimensional model. The water exchange activity levelsimulated by three-dimensional model was lower than that of two-dimensional modelwhich might be due to the more accurate description of the uneven distribution ofvertical velocity in three-dimensional model.The model established in this paper was applied to Sewage Deep Sea DischargeProject in Nangang Industrial Zone. The convection-diffusion of a variety ofpollutants from sewage outfall were simulated by the model with the effect of tidalcurrents combined with offshore functional areas division in Bohai Bay. Based on theconcentration distribution of six primary pollutants at different times which wasobtained by statistic of simulation results, the analyzed influence of sewage dischargeto each functional areas in the project were not obvious.