| In recent years,with the rapid development of the industrialization and urbanization,living and ecological water consumption has been increasing.And that,a large amount of domestic sewage,industrial and agricultural wastewater and "thermal pollution" are discharged into the receiving waters like rivers,lakes and sea areas,causing a series of water ecological and environmental problems,for instance,black odor,frequent "water bloom",and plentiful aquatic organism deaths,and further resulting in serious weakness of the "three water,problems such as water resources,water environment and water ecology.Meanwhile,the large-scale construction of cascade hydraulic engineering further aggravated the deterioration of river ecological environment.Faced the increasingly prominent water ecological and environmental problems,ecological hydraulics model provides the strong technical support for water pollution prevention and control,habitat protection and water ecological restoration.While,with the increase of spatial scale and the continuous improvement of simulation accuracy,most ecological hydraulics models may have some problems,such as numerical instability,low simulation accuracy and efficiency,partial influencing factors and poor model generality.Thus,based on the physical,chemical and biological mechanism,the interaction between hydrodynamic forces and aquatic ecosystems was considered,and GPU parallel computing technology was introduced to build a multi-functional,multi-media,efficient and high-resolution eco-hydraulics model based on fully coupled mechanism process.Besides,combined with measured data,this model was applied to the actual case,and the research results of theoretical significance and practical value were obtained.The research content and innovation results of this paper were as follows:ⅰ.A 2D-high-resolution hydrodynamic model for the complex terrain hydrodynamic processes was established.Based on the Godunov scheme finite volume method and the second-order algorithm applicable to any complex grids to solve 2D-shallow water equations,the 2D-high-resolution hydrodynamic model was established.This model was verified by adopting typical hydrodynamic and the flood propagation with complex terrain.The results showed that this model has good harmony and stability.Compared with the physical experiment,the maximum error variables MAE and RMSE were only about 0.28,and NSE was above 0.98,which can provide accurate and reliable hydrodynamic conditions for describing other processes associated with it.ⅱ.The GPU parallel computing technology based on CUDA architecture was successfully introduced.GPU parallel computing technology based on CUDA architecture was introduced to improve simulation efficiency.This model was applied to study the dam-break flood process of Malpasset and sudden pollutant transport process in Odense estuary under different topographic resolution to test its high efficiency.The results showed that with the improvement of GPU hardware performance,its efficiency became more prominent.Based on the above example,compared with CPU operation,the acceleration efficiency ratio of this model was 15.85 times on a single GTX1080 and 44.6 times on a single Tesla P100,and showing remarkable efficiency.iii.Numerical solutions of the convective and diffusion term were realized.Based on the hydrodynamic model,the convection and diffusion terms were solved by the integrated mass convection HLLC approximation method and the second-order central difference method,and the stability of convection and diffusion terms was verified by the typical mass transport examples.The results showed that the numerical solution was consistent with the analytical solution,and the maximum error variable MAE was only 0.008,NSE was above 0.95,and no numerical oscillations and dissipation were generated.The dynamic mass transport process could be clearly tracked,and the high efficiency and synchronization of the coupling solution could be realized,which could provide a certain technical support for the simulation of water temperature and water environment in rivers,lakes and sea areas.iv.A comprehensive water temperature model considering different influence mechanisms was established.Based on the hydrodynamic model,the principle of heat conservation and convective and diffusion,the influence mechanisms of the water-gas heat exchange process and industrial "thermal pollution" on water temperature were considered,and GPU parallel computing technology was introduced to build an efficient and high-resolution comprehensive water temperature model.Based on this model,the thermal discharge and natural water temperature transport of ideal and natural rivers were studied.The results showed that compared with the analytical and measured water temperature,the error variable NSE can reach more than 0.940.this model results are reliable,consistent with the actual variation of thermal discharge and natural water temperature,and can provide accurate and reasonable water temperature data for water ecological environment assessment of rivers,lakes and sea areas.v.A multi-media water environment and eutrophication evaluation model based on physical-chemical-biological mechanism was developed.Based on the established hydrodynamic model,the principle of the biochemical reaction between substances and convection and diffusion,the multi-component water quality,water environment and eutrophication principles were considered respectively,and GPU parallel computing technology was introduced to build the multi-media water environment and eutrophication evaluation model.Combined with the measured data,the water environment simulation and evaluation of different complex water bodies were carried out based on this model.The results showed that the error variables of MAE,RMSE and NSE were 0～0.943,0～3.001 and 0.7298～1.0,respectively.This model has high reliability and is a powerful simulation tool for studying various complex water environments in rivers,lakes and sea areas.vi.Habitat assessment of the aquatic organisms in rivers based on habitat suitability models was carried out.Based on the hydrodynamic model,the preference curve method and fuzzy logic method were considered to build an efficient and high-resolution aquatic habitat model.Based on this model,the spawning habitat of Gymnocypris eckloni in the downstream of dam of the hydropower stations under construction or planning in the upper reaches Yellow River were simulated.According to the variation law of effective spawning habitat area,the discharge flow of Maerdang hydropower station should be 74 m3/s,the normal storage level of Erduo hydropower station should be 3070～3072 m,as well as the minimum ecological discharge of Yangqu hydropower station should be 87.5 m3/s and the appropriate ecological discharge of 499.2 m3/s,so as to ensure the sustainable development of water ecosystem in the downstream reaches of the dam.vii.The application of multi-process coupled ecological hydraulics model was studied.Coupled hydrodynamics,comprehensive water temperature and environment and eutrophication evaluation modules to form a fully coupled multi-functional,multi-media,efficient and high-resolution ecological hydraulics model based on mechanism process.Furthermore,based on this model,the multi-process coupling of hydrodynamic force,water temperature and water environment was fully considered to comprehensively evaluate the spawning habitat environment of Gymnocypris eckloni in the lower reaches of Maerdang hydropower station.According to the variation law of effective spawning habitat area and the actual hydrological situation,it was determined that the natural inflow process should be simulated from April 24 to May 24 after the completion of this hydropower station for ecological scheduling to ensure that the aquatic organisms habitat environment in the downstream reaches of the dam was in a good state. |
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