Peatland drainage can affect headwater systems, causing changes in bed substrate composition and hydraulic geome-try in small brooks. We studied hydraulic geometry and sediment properties in 14 boreal forest brook rea...Peatland drainage can affect headwater systems, causing changes in bed substrate composition and hydraulic geome-try in small brooks. We studied hydraulic geometry and sediment properties in 14 boreal forest brook reaches (width < 2 m), characterised by well-vegetated banks, high sinuosity and low width-to-depth ratio, in north-east Finland. The aims were to obtain information from channel geometry and to study brook response to extensive sediment load from land use. The results indicate that bed sediment in brooks is almost continuously mobile, which negatively reflect to ecological status of the brooks. These headwater meandering parts have limited sediment transport capacity and require a long period to recover from artificially increased sediment input from peat drainage. However, different reaches can be prioritised for restoration according to the characteristics of silted bed sediment or sediment origins. Brook width appeared to have large natural variation, causing great local velocity variations. This needs to be taken into consideration when restoring straightened reaches in small headwater areas, e.g., width in restored reaches cannot be uniform but should include variations.展开更多
In the past few decades, world energy consumption grew considerably. Regarding this fact, wave energy should not be discarded as a valid alternative for the production of electricity. Devices suitable to harness this ...In the past few decades, world energy consumption grew considerably. Regarding this fact, wave energy should not be discarded as a valid alternative for the production of electricity. Devices suitable to harness this kind of renewable energy source and turn it into electricity are not yet commercially competitive. The work described in this paper aims to contribute to this field of research. It is focused on the design and construction of robust, simple and affordable hydraulic Power Take-Off using hydraulic commercial components.展开更多
Submerged gas injection into liquid leads to complex multiphase flow, in which nozzle geometries are crucial important for the operational expenditure in terms of pressure drop. The influence of the nozzle geometry on...Submerged gas injection into liquid leads to complex multiphase flow, in which nozzle geometries are crucial important for the operational expenditure in terms of pressure drop. The influence of the nozzle geometry on pressure drop between nozzle inlet and outlet has been experimentally studied for different gas flow rates and bath depths. Nozzles with circular, gear-like and four-leaf cross-sectional shape have been studied. The results indicate that, besides the hydraulic diameter of the outlet, the orifice area and the perimeter of the nozzle tip also play significant roles. For the same superficial gas velocity, the average pressure drop from the four-leaf-shaped geometry is the least. The influence of bath depth was found negligible. A correlation for the modified Euler number considering the pressure drop is proposed depending on nozzle geometric parameter and on the modified Froude number with the hydraulic diameter of the nozzle do as characteristic length.展开更多
Definition of hydraulic geometry of navigable canals and its expression are studied in this paper.The hydrodynamic and morphologic characteristics of navigable canals are analyzed on the basis of the data collected fr...Definition of hydraulic geometry of navigable canals and its expression are studied in this paper.The hydrodynamic and morphologic characteristics of navigable canals are analyzed on the basis of the data collected from field surveys conducted at two segments of the Grand Canal in Jiangsu Province,China.The channel morphologic factor and the ship hydrodynamic factor are adopted to describe the hydraulic geometry relation of navigable canals.The correlation analysis shows that the ship hydrodynamics can be a dominant factor influencing the channel evolution with larger determination coefficient.Furthermore,the undetermined index in the proposed hydraulic geometry relation is also discussed,which indicates that the index related to the intensity of water flow(qualitatively reflected by the integrated ship flow intensity)is within a range of 0.5 to 1.0.展开更多
基金partly funded by the forest brook restoration project led by the North Ostrobothnia Regional Environment Centre in Finlandsupport from KIRSU graduate school(Academy of Finland),Tor and Maj Nessling foundation,MVTT,Thule-institute at University of Oulu,Mod-Stream project by Academy of Finland and the Ministry of Agriculture and Forestry.
文摘Peatland drainage can affect headwater systems, causing changes in bed substrate composition and hydraulic geome-try in small brooks. We studied hydraulic geometry and sediment properties in 14 boreal forest brook reaches (width < 2 m), characterised by well-vegetated banks, high sinuosity and low width-to-depth ratio, in north-east Finland. The aims were to obtain information from channel geometry and to study brook response to extensive sediment load from land use. The results indicate that bed sediment in brooks is almost continuously mobile, which negatively reflect to ecological status of the brooks. These headwater meandering parts have limited sediment transport capacity and require a long period to recover from artificially increased sediment input from peat drainage. However, different reaches can be prioritised for restoration according to the characteristics of silted bed sediment or sediment origins. Brook width appeared to have large natural variation, causing great local velocity variations. This needs to be taken into consideration when restoring straightened reaches in small headwater areas, e.g., width in restored reaches cannot be uniform but should include variations.
文摘In the past few decades, world energy consumption grew considerably. Regarding this fact, wave energy should not be discarded as a valid alternative for the production of electricity. Devices suitable to harness this kind of renewable energy source and turn it into electricity are not yet commercially competitive. The work described in this paper aims to contribute to this field of research. It is focused on the design and construction of robust, simple and affordable hydraulic Power Take-Off using hydraulic commercial components.
基金Project(51676211) supported by the National Natural Science Foundation of ChinaProject(2017SK2253) supported by the Key R&D Plan of Hunan Province of China+1 种基金Project(2015zzts044) supported by Fundamental Research Funds for the Central Universities,ChinaProject(201606370092) supported by the China Scholarship Council
文摘Submerged gas injection into liquid leads to complex multiphase flow, in which nozzle geometries are crucial important for the operational expenditure in terms of pressure drop. The influence of the nozzle geometry on pressure drop between nozzle inlet and outlet has been experimentally studied for different gas flow rates and bath depths. Nozzles with circular, gear-like and four-leaf cross-sectional shape have been studied. The results indicate that, besides the hydraulic diameter of the outlet, the orifice area and the perimeter of the nozzle tip also play significant roles. For the same superficial gas velocity, the average pressure drop from the four-leaf-shaped geometry is the least. The influence of bath depth was found negligible. A correlation for the modified Euler number considering the pressure drop is proposed depending on nozzle geometric parameter and on the modified Froude number with the hydraulic diameter of the nozzle do as characteristic length.
基金the National Natural Science Foundation of China(No.51479035)the Scientific Research Foundation of Graduate School of Southeast University(No.YBPY1883)
文摘Definition of hydraulic geometry of navigable canals and its expression are studied in this paper.The hydrodynamic and morphologic characteristics of navigable canals are analyzed on the basis of the data collected from field surveys conducted at two segments of the Grand Canal in Jiangsu Province,China.The channel morphologic factor and the ship hydrodynamic factor are adopted to describe the hydraulic geometry relation of navigable canals.The correlation analysis shows that the ship hydrodynamics can be a dominant factor influencing the channel evolution with larger determination coefficient.Furthermore,the undetermined index in the proposed hydraulic geometry relation is also discussed,which indicates that the index related to the intensity of water flow(qualitatively reflected by the integrated ship flow intensity)is within a range of 0.5 to 1.0.
