[Objective]The construction of weirs changes the hydraulic characteristics of rivers and affects the structure of phytoplankton communities and the health of aquatic ecosystems in the river.This study aims to explore ...[Objective]The construction of weirs changes the hydraulic characteristics of rivers and affects the structure of phytoplankton communities and the health of aquatic ecosystems in the river.This study aims to explore the nonlinear response relationship between phytoplankton community structure and its driving factors in spring and autumn in Furong Creek under the construction of cascade weirs.[Methods]The structure of phytoplankton communities and related environmental factors were investigated in Furong Creek from 2023 to 2024.This study focused on the analysis of the changes of nutrient concentrations and biomass of phytoplankton in autumn and spring within the same dry season in Furong Creek.Redundancy analysis was used to identify the key factors influencing the structure of phytoplankton communities.The MIKE 11 model was employed to simulate the hydrodynamic changes in the river.Combined with total nitrogen and permanganate index,a GAM model of phytoplankton diversity index and hydrodynamic factors was developed,and the change of phytoplankton diversity after the optimized layout of the cascade weirs was fitted.[Results]The result showed that the annual average value of Shannon-Wiener diversity index of phytoplankton in Furong Creek was 2.79,which was in a state of mild pollution.A total of 239 species from 95 genera in 8 phyla were identified.Among the phytoplankton,Chlorophyta was the dominant group throughout the year in Furong Creek,followed by Bacillariophyta and Cyanophyta.The cell abundance of phytoplankton ranged from 3.11 to 20.64 mg/L and from 0.23 to 6.31 mg/L in spring and autumn,which indicated a clear seasonal succession of phytoplankton community structure.Compared with autumn,the relative abundance of Cyanophyta significantly decreased in spring across the whole river section,while Chrysophyta and Dinophyta showed significant increase at some monitoring sites,leading to water bloom phenomenon and a noticeable decline in the diversity of phytoplankton.The dominant species in the water bodies throughout the year were Cyclotella catenata,Chlorella vulgaris,Scenedesmus bijuga,Scenedesmus quadricauda,Chroomonas acuta,Cryptomonas ovata,and Cryptomonas erosa.Redundancy analysis(RDA)showed that hydrodynamic factors(v,h)and water environmental factors(TN,COD_(Mn))were the main influencing factors of phytoplankton community structure.[Conclusion]The result show that the nutrient concentration,phytoplankton biomass,and density in Furong Creek in spring are significantly higher than in autumn.The GAM model,constructed by combining hydrodynamic and environmental factors,can effectively reflect the nonlinear relationship between phytoplankton diversity index and its driving factors.In spring,with an increase in nutrient concentration,the habitat conditions of low flow speed and high water depths formed by overflow weirs will lead to a decrease in the Shannon-Wiener index of phytoplankton and an intensified risk of eutrophication.However,a reasonable layout scheme of cascade weirs will improve the diversity of phytoplankton and reduce the risk of eutrophication in the river.The findings of this study can help deepen the understanding of the ecological and environmental effects of cascade weir construction in the river.展开更多
Research on scale effects on flows over weirs has been conducted on a limited basis, primarily focusing on flows upstream of a single-type weir, such as ogee, broad-crested, and sharp-crested (linear and non-linear) w...Research on scale effects on flows over weirs has been conducted on a limited basis, primarily focusing on flows upstream of a single-type weir, such as ogee, broad-crested, and sharp-crested (linear and non-linear) weirs. However, the scale effects downstream of these single-type weirs have not been thoroughly investigated. This study examined the scale effects on flows over a combined weir system consisting of an ogee weir and a sharp-crested weir, both upstream and downstream, utilizing physical modeling at a 1:33.33 scale based on Froude similarity and three-dimensional (3D) computational fluid dynamics (CFD) modeling. The sharp-crested weir in this study was represented by two sluice gates that remain closed and submerged during flood events. The experimental data confirmed that the equivalent discharge coefficients of the combined weir system behaved similarly to those of a sharp-crested weir across various H/P (where H is the total head, and P is the weir height) values. However, scale effects on the discharge rating curve due to surface tension and viscosity could only be minimized when H/P > 0.4, Re > 26 959, and We > 240 (where Re and We are the Reynolds and Weber numbers, respectively), provided that the water depth exceeded 0.042 m above the crest. Additionally, Re greater than 4 × 104 was necessary to minimize scale effects caused by viscosity in flows in the spillway channel and stilling basin (with baffle blocks). The limiting criteria aligned closely with existing literature. This study offers valuable insights for practical applications in hydraulic engineering in the future.展开更多
Tundish is an important metallurgical reactor in the continuous castingprocess. In order to control the fluid flow in tundish and thus take full advantage of the residencetime available for the removal of inclusions f...Tundish is an important metallurgical reactor in the continuous castingprocess. In order to control the fluid flow in tundish and thus take full advantage of the residencetime available for the removal of inclusions from molten steel, the effect of weir and dam on thefluid flow has been studied in a water model based on the characteristic number Froude and Reynoldnumber similarity criteria. The residence time distribution curves of the flow were measured bySG800. The optimum arrangement of darn and weir and the nonstationary flow in tundish werediscussed. The results show that the combination of weir and dam is benefit for the flow pattern intundish, weir can prevent the upper recirculating flow, dam can cut off the bottom flow and turn toupwards, it is advantageous to separate the nonmetallic inclusions. Furthermore, it is important toexceed the critical depth of bath during exchange ladles, not only for the inclusion floatation butalso for avoiding tundish slag drainage earlier.展开更多
Weirs are a type of hydraulic structure, used for water level adjustment, flow measurement, and diversion of water in irrigation systems. In this study, experiments were conducted on sharp-crested weirs under free-flo...Weirs are a type of hydraulic structure, used for water level adjustment, flow measurement, and diversion of water in irrigation systems. In this study, experiments were conducted on sharp-crested weirs under free-flow conditions and an optimization method was used to determine the best form of the discharge coefficient equation based on the coefficient of determination （R2） and root mean square error （RMSE）. The ability of the numerical method to simulate the flow over the weir was also investigated using Fluent software. Results showed that, with an increase of the ratio of the head over the weir crest to the weir height （h/P）, the discharge coefficient decreased nonlinearly and reached a constant value of 0.7 for hiP 〉 0.6. The best form of the discharge coefficient equation predicted the discharge coefficient well and percent errors were within a ±5% error limit. Numerical results of the discharge coefficient showed strong agreement with the experimental data. Variation of the discharge coefficient with Reynolds numbers showed that the discharge coefficient reached a constant value of 0.7 when hiP 〉 0.6 and Re 〉 20000.展开更多
Fluid-structure interaction(FSI)has a strong relation with layout of fluid delivery system.FSI is liable to cause local damage.Thus,FSI analysis is necessary in many cases,especially for flexible pipe systems.FSI mode...Fluid-structure interaction(FSI)has a strong relation with layout of fluid delivery system.FSI is liable to cause local damage.Thus,FSI analysis is necessary in many cases,especially for flexible pipe systems.FSI modeling consists of eight governing equations and then completely solved via the finite volume method(FVM).Friction,Poisson and joint couplings were discussed in detail to reveal the influence of a Z-shaped pipe with different supports and elbows on FSI.After the feasibility of solving FSI by FVM was verified,the different effects of free,fixed and elastic supports on FSI in the commonly used and simplified Z-shaped pipe were further analyzed.Results indicated that different support stiffness lead to various FSI responses.If coupling occurs at the elbow and less support is considered,then the pipe has a relatively large amplitude and complex pressure fluctuation.展开更多
This study focused on hydraulic characteristics around a gear-shaped weir in a straight channel. Systematic experiments were carried out for weirs with two different gear heights and eight groups of geometrical parame...This study focused on hydraulic characteristics around a gear-shaped weir in a straight channel. Systematic experiments were carried out for weirs with two different gear heights and eight groups of geometrical parameters. The impacts of various geometrical parameters of gear-shaped weirs on the discharge capacity were investigated. The following conclusions are drawn from the experimental study:(1) The discharge coefficient(m_c) was influenced by the size of the gear: at a constant discharge, the weir with larger values of a/b(a is the width of the gear, and b is the width between the two neighboring gears) and a/c(c is the height of the gear) had a smaller value of m_c. The discharge capacity of the gear-shaped weir was influenced by the water depth in the weir.(2) For type C1 with a gear height of 0.01 m, when the discharge was less than 60m^3/h and H_1=P < 1.0(H_1 is the water depth at the low weir crest, and P is the weir height), m_c significantly increased with the discharge and H_1=P; with further increases of the discharge and H_1=P, m_cshowed insignificant decreases and fluctuated within small ranges. For type C2 with a gear height of 0.02 m, when the discharge was less than 60m^3/h and H_1=P < 1.0, m_csignificantly increased with the discharge and H_1=P; when the discharge was larger than 60m^3/h and H_1=P > 1.0, m_c slowly decreased with the increases of the discharge and H_1=P for a=b 1.0 and a=c 1.0, and slowly increased with the discharge and H_1=P for a=b > 1.0 and a=c > 1.0.(3) A formula of m_cfor gear-shaped weirs was established based on the principle of weir flow, with consideration of the water depth in the weir, the weir height and width, and the height of the gear.展开更多
Restoration of fracture alignment by osteotomy is crucial for the management of humeral nonunion. In the present study, we introduced a new way of osteotomy (Z-shaped) in treating humeral shaft nonunion secondary to f...Restoration of fracture alignment by osteotomy is crucial for the management of humeral nonunion. In the present study, we introduced a new way of osteotomy (Z-shaped) in treating humeral shaft nonunion secondary to failed plate osteosynthesis. Clinical data of 24 patients with humeral shaft nonunion following implant failure (from 2010 to 2014) were retrospectively evaluated. These patients underwent Z-shaped osteotomy in revision surgery after the initial surgery, plate osteosynthesis, was failed. Outcomes were evaluated using visual analogue scale (VAS) and Constant and Murley score. Repeated analysis of variance (ANOVA) was used for statistical analysis. Patients were followed up for a minimum of 24 months (26.83±4.33 months). The operative time was 102.33±10.16 min, and hospital stay averaged 9.75±2.13 days. All patients achieved clinical union at the latest follow-up. Complications included radial palsy (n=1) and superficial wound infection (n=1). The postoperative VAS scores decreased significantly compared to preoperative score (F=257.99, P<0.01). Constant and Murley score increased and reached 81.33±0.95 at 24 months' follow-up 0=247.35, P<0.01). Among all the cases, 15 cases were graded as "excellent", and 9 as "good". In conclusion, Z-shaped osteotomy was easy to perform, and it provided additional medial support with more bone contact areas. Revision surgery using locking plate and Z-shaped osteotomy achieved high union rate and improved functional outcome. It was a reasonable and safe option for treating humeral nonunion following implant failure.展开更多
The water flow over a semicircular weir is investigated numerically and experimentally in this paper. The numerical model solves the Reynolds equation for a mean flow field with thek-ε-turbulent model. To trace the m...The water flow over a semicircular weir is investigated numerically and experimentally in this paper. The numerical model solves the Reynolds equation for a mean flow field with thek-ε-turbulent model. To trace the motion of the free surface, the COF method with geometric reconstruction is employed. The velocity of the flow is measured by means of LDV technique. Four types of flow patterns, the position of the separation and reattachment point, the distribution of shear stress on the bed at downstream of the weir are presented and discussed. The numerical results agree well with the experiment data.展开更多
A circular sharp-crested weir is a circular control section used for measuring flow in open channels, reservoirs, and tanks. As flow measuring devices in open channels, these weirs are placed perpendicular to the side...A circular sharp-crested weir is a circular control section used for measuring flow in open channels, reservoirs, and tanks. As flow measuring devices in open channels, these weirs are placed perpendicular to the sides and bottoms of straight-approach channels. Considering the complex patterns of flow passing over circular sharp-crested weirs, an equation having experimental correlation coefficients was used to extract a stage-discharge relation for weirs. Assuming the occurrence of critical flow over the weir crest, a theoretical stage-discharge relation was obtained in this study by solving two extracted non-linear equations. To study the precision of the theoretical stage-discharge relation, 58 experiments were performed on six circular weirs with different diameters and crest heights in a 30 cm-wide flume. The results show that, for each stage above the weirs, the theoretically calculated discharge is less than the measured discharge, and this difference increases with the stage. Finally, the theoretical stage-discharge relation was modified by exerting a correction coefficient which is a function of the ratio of the upstream flow depth to the weir crest height. The results show that the modified stage-discharge relation is in good agreement with the measured results.展开更多
文摘[Objective]The construction of weirs changes the hydraulic characteristics of rivers and affects the structure of phytoplankton communities and the health of aquatic ecosystems in the river.This study aims to explore the nonlinear response relationship between phytoplankton community structure and its driving factors in spring and autumn in Furong Creek under the construction of cascade weirs.[Methods]The structure of phytoplankton communities and related environmental factors were investigated in Furong Creek from 2023 to 2024.This study focused on the analysis of the changes of nutrient concentrations and biomass of phytoplankton in autumn and spring within the same dry season in Furong Creek.Redundancy analysis was used to identify the key factors influencing the structure of phytoplankton communities.The MIKE 11 model was employed to simulate the hydrodynamic changes in the river.Combined with total nitrogen and permanganate index,a GAM model of phytoplankton diversity index and hydrodynamic factors was developed,and the change of phytoplankton diversity after the optimized layout of the cascade weirs was fitted.[Results]The result showed that the annual average value of Shannon-Wiener diversity index of phytoplankton in Furong Creek was 2.79,which was in a state of mild pollution.A total of 239 species from 95 genera in 8 phyla were identified.Among the phytoplankton,Chlorophyta was the dominant group throughout the year in Furong Creek,followed by Bacillariophyta and Cyanophyta.The cell abundance of phytoplankton ranged from 3.11 to 20.64 mg/L and from 0.23 to 6.31 mg/L in spring and autumn,which indicated a clear seasonal succession of phytoplankton community structure.Compared with autumn,the relative abundance of Cyanophyta significantly decreased in spring across the whole river section,while Chrysophyta and Dinophyta showed significant increase at some monitoring sites,leading to water bloom phenomenon and a noticeable decline in the diversity of phytoplankton.The dominant species in the water bodies throughout the year were Cyclotella catenata,Chlorella vulgaris,Scenedesmus bijuga,Scenedesmus quadricauda,Chroomonas acuta,Cryptomonas ovata,and Cryptomonas erosa.Redundancy analysis(RDA)showed that hydrodynamic factors(v,h)and water environmental factors(TN,COD_(Mn))were the main influencing factors of phytoplankton community structure.[Conclusion]The result show that the nutrient concentration,phytoplankton biomass,and density in Furong Creek in spring are significantly higher than in autumn.The GAM model,constructed by combining hydrodynamic and environmental factors,can effectively reflect the nonlinear relationship between phytoplankton diversity index and its driving factors.In spring,with an increase in nutrient concentration,the habitat conditions of low flow speed and high water depths formed by overflow weirs will lead to a decrease in the Shannon-Wiener index of phytoplankton and an intensified risk of eutrophication.However,a reasonable layout scheme of cascade weirs will improve the diversity of phytoplankton and reduce the risk of eutrophication in the river.The findings of this study can help deepen the understanding of the ecological and environmental effects of cascade weir construction in the river.
基金supported by the Ministry of Public Works and Housing of Indonesia and Parahyangan Catholic University(Grant No.II/PD/2023-07/02-SJ).
文摘Research on scale effects on flows over weirs has been conducted on a limited basis, primarily focusing on flows upstream of a single-type weir, such as ogee, broad-crested, and sharp-crested (linear and non-linear) weirs. However, the scale effects downstream of these single-type weirs have not been thoroughly investigated. This study examined the scale effects on flows over a combined weir system consisting of an ogee weir and a sharp-crested weir, both upstream and downstream, utilizing physical modeling at a 1:33.33 scale based on Froude similarity and three-dimensional (3D) computational fluid dynamics (CFD) modeling. The sharp-crested weir in this study was represented by two sluice gates that remain closed and submerged during flood events. The experimental data confirmed that the equivalent discharge coefficients of the combined weir system behaved similarly to those of a sharp-crested weir across various H/P (where H is the total head, and P is the weir height) values. However, scale effects on the discharge rating curve due to surface tension and viscosity could only be minimized when H/P > 0.4, Re > 26 959, and We > 240 (where Re and We are the Reynolds and Weber numbers, respectively), provided that the water depth exceeded 0.042 m above the crest. Additionally, Re greater than 4 × 104 was necessary to minimize scale effects caused by viscosity in flows in the spillway channel and stilling basin (with baffle blocks). The limiting criteria aligned closely with existing literature. This study offers valuable insights for practical applications in hydraulic engineering in the future.
基金supported by NSFC(No.10871216 and No.11071267)Natural Science Foundation Project of CQ CSTC+1 种基金Science and Technology Research Project of Chongqing Municipal Education Commission(No.K J100419)the Excellent Young Teachers Program of Chongqing Jiaotong University,Chongqing,China
文摘Tundish is an important metallurgical reactor in the continuous castingprocess. In order to control the fluid flow in tundish and thus take full advantage of the residencetime available for the removal of inclusions from molten steel, the effect of weir and dam on thefluid flow has been studied in a water model based on the characteristic number Froude and Reynoldnumber similarity criteria. The residence time distribution curves of the flow were measured bySG800. The optimum arrangement of darn and weir and the nonstationary flow in tundish werediscussed. The results show that the combination of weir and dam is benefit for the flow pattern intundish, weir can prevent the upper recirculating flow, dam can cut off the bottom flow and turn toupwards, it is advantageous to separate the nonmetallic inclusions. Furthermore, it is important toexceed the critical depth of bath during exchange ladles, not only for the inclusion floatation butalso for avoiding tundish slag drainage earlier.
文摘Weirs are a type of hydraulic structure, used for water level adjustment, flow measurement, and diversion of water in irrigation systems. In this study, experiments were conducted on sharp-crested weirs under free-flow conditions and an optimization method was used to determine the best form of the discharge coefficient equation based on the coefficient of determination （R2） and root mean square error （RMSE）. The ability of the numerical method to simulate the flow over the weir was also investigated using Fluent software. Results showed that, with an increase of the ratio of the head over the weir crest to the weir height （h/P）, the discharge coefficient decreased nonlinearly and reached a constant value of 0.7 for hiP 〉 0.6. The best form of the discharge coefficient equation predicted the discharge coefficient well and percent errors were within a ±5% error limit. Numerical results of the discharge coefficient showed strong agreement with the experimental data. Variation of the discharge coefficient with Reynolds numbers showed that the discharge coefficient reached a constant value of 0.7 when hiP 〉 0.6 and Re 〉 20000.
文摘Fluid-structure interaction(FSI)has a strong relation with layout of fluid delivery system.FSI is liable to cause local damage.Thus,FSI analysis is necessary in many cases,especially for flexible pipe systems.FSI modeling consists of eight governing equations and then completely solved via the finite volume method(FVM).Friction,Poisson and joint couplings were discussed in detail to reveal the influence of a Z-shaped pipe with different supports and elbows on FSI.After the feasibility of solving FSI by FVM was verified,the different effects of free,fixed and elastic supports on FSI in the commonly used and simplified Z-shaped pipe were further analyzed.Results indicated that different support stiffness lead to various FSI responses.If coupling occurs at the elbow and less support is considered,then the pipe has a relatively large amplitude and complex pressure fluctuation.
基金supported by the National Natural Science Foundation of China(Grant No.51409155)
文摘This study focused on hydraulic characteristics around a gear-shaped weir in a straight channel. Systematic experiments were carried out for weirs with two different gear heights and eight groups of geometrical parameters. The impacts of various geometrical parameters of gear-shaped weirs on the discharge capacity were investigated. The following conclusions are drawn from the experimental study:(1) The discharge coefficient(m_c) was influenced by the size of the gear: at a constant discharge, the weir with larger values of a/b(a is the width of the gear, and b is the width between the two neighboring gears) and a/c(c is the height of the gear) had a smaller value of m_c. The discharge capacity of the gear-shaped weir was influenced by the water depth in the weir.(2) For type C1 with a gear height of 0.01 m, when the discharge was less than 60m^3/h and H_1=P < 1.0(H_1 is the water depth at the low weir crest, and P is the weir height), m_c significantly increased with the discharge and H_1=P; with further increases of the discharge and H_1=P, m_cshowed insignificant decreases and fluctuated within small ranges. For type C2 with a gear height of 0.02 m, when the discharge was less than 60m^3/h and H_1=P < 1.0, m_csignificantly increased with the discharge and H_1=P; when the discharge was larger than 60m^3/h and H_1=P > 1.0, m_c slowly decreased with the increases of the discharge and H_1=P for a=b 1.0 and a=c 1.0, and slowly increased with the discharge and H_1=P for a=b > 1.0 and a=c > 1.0.(3) A formula of m_cfor gear-shaped weirs was established based on the principle of weir flow, with consideration of the water depth in the weir, the weir height and width, and the height of the gear.
文摘Restoration of fracture alignment by osteotomy is crucial for the management of humeral nonunion. In the present study, we introduced a new way of osteotomy (Z-shaped) in treating humeral shaft nonunion secondary to failed plate osteosynthesis. Clinical data of 24 patients with humeral shaft nonunion following implant failure (from 2010 to 2014) were retrospectively evaluated. These patients underwent Z-shaped osteotomy in revision surgery after the initial surgery, plate osteosynthesis, was failed. Outcomes were evaluated using visual analogue scale (VAS) and Constant and Murley score. Repeated analysis of variance (ANOVA) was used for statistical analysis. Patients were followed up for a minimum of 24 months (26.83±4.33 months). The operative time was 102.33±10.16 min, and hospital stay averaged 9.75±2.13 days. All patients achieved clinical union at the latest follow-up. Complications included radial palsy (n=1) and superficial wound infection (n=1). The postoperative VAS scores decreased significantly compared to preoperative score (F=257.99, P<0.01). Constant and Murley score increased and reached 81.33±0.95 at 24 months' follow-up 0=247.35, P<0.01). Among all the cases, 15 cases were graded as "excellent", and 9 as "good". In conclusion, Z-shaped osteotomy was easy to perform, and it provided additional medial support with more bone contact areas. Revision surgery using locking plate and Z-shaped osteotomy achieved high union rate and improved functional outcome. It was a reasonable and safe option for treating humeral nonunion following implant failure.
文摘The water flow over a semicircular weir is investigated numerically and experimentally in this paper. The numerical model solves the Reynolds equation for a mean flow field with thek-ε-turbulent model. To trace the motion of the free surface, the COF method with geometric reconstruction is employed. The velocity of the flow is measured by means of LDV technique. Four types of flow patterns, the position of the separation and reattachment point, the distribution of shear stress on the bed at downstream of the weir are presented and discussed. The numerical results agree well with the experiment data.
文摘A circular sharp-crested weir is a circular control section used for measuring flow in open channels, reservoirs, and tanks. As flow measuring devices in open channels, these weirs are placed perpendicular to the sides and bottoms of straight-approach channels. Considering the complex patterns of flow passing over circular sharp-crested weirs, an equation having experimental correlation coefficients was used to extract a stage-discharge relation for weirs. Assuming the occurrence of critical flow over the weir crest, a theoretical stage-discharge relation was obtained in this study by solving two extracted non-linear equations. To study the precision of the theoretical stage-discharge relation, 58 experiments were performed on six circular weirs with different diameters and crest heights in a 30 cm-wide flume. The results show that, for each stage above the weirs, the theoretically calculated discharge is less than the measured discharge, and this difference increases with the stage. Finally, the theoretical stage-discharge relation was modified by exerting a correction coefficient which is a function of the ratio of the upstream flow depth to the weir crest height. The results show that the modified stage-discharge relation is in good agreement with the measured results.
