Vegetation in wetlands is a large-scale nature-based resource that can provide multiple benefits to human beings and the environment,such as wave attenuation in coastal zones.Traditionally,there are two main calibrati...Vegetation in wetlands is a large-scale nature-based resource that can provide multiple benefits to human beings and the environment,such as wave attenuation in coastal zones.Traditionally,there are two main calibration approaches to calculate the attenuation of wave driven by vegetation.The first method is a straightforward one based on the exponential attenuation of wave height in the direction of wave transmission,which,however,overlooks the crucial drag coefficient(CD).The other method is in accordance with more complicate equations for predicting the damping factor,which is regarded as a function of CD.In this study,a new relation,combining these above two conventional approaches,is proposed to predict the CD in an operative approach.Results show that values yielded by the new assessment method perform a strong linear relationship with a collection of historical observations,with a promising R2 value of 0.90.Besides,the linear regression derives a new predictive equation for the bulk drag coefficient.Additionally,a calibrated value of 4 for the empirical plant drag coefficient(CP)is revealed.Overall,this new equation,with the superiority of the convenient exponential regression,is expected to be a rapid assessment method for calculating wave attenuation by vegetation and predicting the drag coefficient.展开更多
The phenomenon of water aeration is serious after the overflow weir in the siphon well at the cooling water circulation system of coastal power plants.At present,designing special hydraulic structures is an effective ...The phenomenon of water aeration is serious after the overflow weir in the siphon well at the cooling water circulation system of coastal power plants.At present,designing special hydraulic structures is an effective way to reduce the intensity of aeration.In this paper,three engineering structure schemes were designed,and the three-dimensional Realizable k-ε turbulence model was used.The volume of fluid method was introduced to capture the free water surface,and the unstructured grid was used to construct the two-phase turbulent flow field.The aeration concentration and pressure distribution,obtained by numerical simulation,were basically consistent with the physical model test results.The results showed that the flow field at the orifice plates of cases 1 and 2 changed drastically,and the turbulent kinetic energy downstream of the orifice plate decreased with the increase of the number of holes.As for case 3,it showed that the high-speed water flow fell into the water cushion pool,tumbling and sucking up a lot of air,and the turbulent kinetic energy and Reynolds stress were significantly greater than the other two cases.The hydraulic structure changed the cavitation characteristics of the downflow water,and the sequence of aeration concentration of the horizontal section was case 3>case 1>case 2.The aeration concentration was only 9.18%-17.86% in case 2.The aeration concentration at stable time is expressed as a function of the relative water depth y/y_(90) and the turbulent diffusion coefficient D.The distribution formula of aeration concentration was established,and its validity was verified by literatures.The results of this study will provide a certain reference for in-depth analysis of water-air mixing motion characteristics,and simultaneously,it will have a guiding significance for the design of siphon well defoaming engineering.展开更多
Nitrogen in pond sediments is a major water quality concern and can impact the productivity of aquaculture.Dissolved oxygen is an important factor for improving water quality and boosting fish growth in aquaculture po...Nitrogen in pond sediments is a major water quality concern and can impact the productivity of aquaculture.Dissolved oxygen is an important factor for improving water quality and boosting fish growth in aquaculture ponds,and plays an important role in the conversion of ammonium-nitrogen(NH4-N)to nitrite-nitrogen(NO2--N)and eventually nitrate-nitrogen(NO3--N).A central goal of the study was to identify the best aeration method and strategy for improving water quality in aquaculture ponds.We conducted an experiment with six tanks,each with a different aeration mode to simulate the behavior of aquaculture ponds.The results show that a 36 hr aeration interval(Tc=36 hr:36 hr)and no aeration resulted in high concentrations of NH4-N in the water column.Using a 12 hr interval time(Tc=12 hr:12 hr)resulted in higher NO2--N and NO3--N concentrations than any other aeration mode.Results from an 8 hr interval time(Tc=8 hr:8 hr)and 24 hr interval time(Tc=24 hr:24 hr)were comparable with those of continuous aeration,and had the benefit of being in use for only half of the time,consequently reducing energy consumption.展开更多
基金The National Key Research and Development Program of China under contract No.2016YFC0402607the Key Research and Development Projects in Guangdong Province under contract No.2019B111101002+1 种基金the 2018 Guangzhou Science and Technology Project under contract No.201806010143the Water Resource Science and Technology Innovation Program of Guangdong Province under contract No.2017-17。
文摘Vegetation in wetlands is a large-scale nature-based resource that can provide multiple benefits to human beings and the environment,such as wave attenuation in coastal zones.Traditionally,there are two main calibration approaches to calculate the attenuation of wave driven by vegetation.The first method is a straightforward one based on the exponential attenuation of wave height in the direction of wave transmission,which,however,overlooks the crucial drag coefficient(CD).The other method is in accordance with more complicate equations for predicting the damping factor,which is regarded as a function of CD.In this study,a new relation,combining these above two conventional approaches,is proposed to predict the CD in an operative approach.Results show that values yielded by the new assessment method perform a strong linear relationship with a collection of historical observations,with a promising R2 value of 0.90.Besides,the linear regression derives a new predictive equation for the bulk drag coefficient.Additionally,a calibrated value of 4 for the empirical plant drag coefficient(CP)is revealed.Overall,this new equation,with the superiority of the convenient exponential regression,is expected to be a rapid assessment method for calculating wave attenuation by vegetation and predicting the drag coefficient.
文摘The phenomenon of water aeration is serious after the overflow weir in the siphon well at the cooling water circulation system of coastal power plants.At present,designing special hydraulic structures is an effective way to reduce the intensity of aeration.In this paper,three engineering structure schemes were designed,and the three-dimensional Realizable k-ε turbulence model was used.The volume of fluid method was introduced to capture the free water surface,and the unstructured grid was used to construct the two-phase turbulent flow field.The aeration concentration and pressure distribution,obtained by numerical simulation,were basically consistent with the physical model test results.The results showed that the flow field at the orifice plates of cases 1 and 2 changed drastically,and the turbulent kinetic energy downstream of the orifice plate decreased with the increase of the number of holes.As for case 3,it showed that the high-speed water flow fell into the water cushion pool,tumbling and sucking up a lot of air,and the turbulent kinetic energy and Reynolds stress were significantly greater than the other two cases.The hydraulic structure changed the cavitation characteristics of the downflow water,and the sequence of aeration concentration of the horizontal section was case 3>case 1>case 2.The aeration concentration was only 9.18%-17.86% in case 2.The aeration concentration at stable time is expressed as a function of the relative water depth y/y_(90) and the turbulent diffusion coefficient D.The distribution formula of aeration concentration was established,and its validity was verified by literatures.The results of this study will provide a certain reference for in-depth analysis of water-air mixing motion characteristics,and simultaneously,it will have a guiding significance for the design of siphon well defoaming engineering.
基金supported by the National Science Foundation of China(No.51579106)financial support from the China Scholarship Council(No.201806150070)
文摘Nitrogen in pond sediments is a major water quality concern and can impact the productivity of aquaculture.Dissolved oxygen is an important factor for improving water quality and boosting fish growth in aquaculture ponds,and plays an important role in the conversion of ammonium-nitrogen(NH4-N)to nitrite-nitrogen(NO2--N)and eventually nitrate-nitrogen(NO3--N).A central goal of the study was to identify the best aeration method and strategy for improving water quality in aquaculture ponds.We conducted an experiment with six tanks,each with a different aeration mode to simulate the behavior of aquaculture ponds.The results show that a 36 hr aeration interval(Tc=36 hr:36 hr)and no aeration resulted in high concentrations of NH4-N in the water column.Using a 12 hr interval time(Tc=12 hr:12 hr)resulted in higher NO2--N and NO3--N concentrations than any other aeration mode.Results from an 8 hr interval time(Tc=8 hr:8 hr)and 24 hr interval time(Tc=24 hr:24 hr)were comparable with those of continuous aeration,and had the benefit of being in use for only half of the time,consequently reducing energy consumption.
