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
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
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
This research was conducted in the upstream watershed of the Mae Yom Irrigation Project, which was located in the Upper Yom River Basin in Phrae Province, Thailand. The most common troublesome in this area is flood an...This research was conducted in the upstream watershed of the Mae Yom Irrigation Project, which was located in the Upper Yom River Basin in Phrae Province, Thailand. The most common troublesome in this area is flood and drought and leads to poor water management by difficult river flow forecasting to an existing large weir without upstream dam. The Soil And Water Assessment Tool (SWAT) model was applied for the simulation of the hydrological system and predicting the daily river flow to the upstream weir during flood season in 2006 and 2011 as for simulating and comparing with observed data. The results were fitted to the observed data with Nash and Sutcliffe efficiency (NSE) of ?0.65, and root mean square error (RSME) of 228.0 whereas the mean inflow discharge during wet season in both years was 173.3 cubic meters per second, respectively.展开更多
A shock absorbing cushion has never been introduced into any traditional weir surface repair layer design. However, shocks induced by high discharge with heavy sediment can easily produce brittle fracture and peeling ...A shock absorbing cushion has never been introduced into any traditional weir surface repair layer design. However, shocks induced by high discharge with heavy sediment can easily produce brittle fracture and peeling over a weir surthce repair layer as it is impacted by floods accompanied by particles of different sizes. In this study, transcending traditional designs, the authors developed a composite unit designed with a shock absorbing cushion that has performed well during field tests, proving that the weir body can be effectively protected even if the composite units are directly laid on a severely uneven weir surface repair layer.展开更多
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.
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.
文摘This research was conducted in the upstream watershed of the Mae Yom Irrigation Project, which was located in the Upper Yom River Basin in Phrae Province, Thailand. The most common troublesome in this area is flood and drought and leads to poor water management by difficult river flow forecasting to an existing large weir without upstream dam. The Soil And Water Assessment Tool (SWAT) model was applied for the simulation of the hydrological system and predicting the daily river flow to the upstream weir during flood season in 2006 and 2011 as for simulating and comparing with observed data. The results were fitted to the observed data with Nash and Sutcliffe efficiency (NSE) of ?0.65, and root mean square error (RSME) of 228.0 whereas the mean inflow discharge during wet season in both years was 173.3 cubic meters per second, respectively.
基金Central Region Water Resources Bureau,Taiwan Water Resources Agency under Project No.MOEAWRA0990352
文摘A shock absorbing cushion has never been introduced into any traditional weir surface repair layer design. However, shocks induced by high discharge with heavy sediment can easily produce brittle fracture and peeling over a weir surthce repair layer as it is impacted by floods accompanied by particles of different sizes. In this study, transcending traditional designs, the authors developed a composite unit designed with a shock absorbing cushion that has performed well during field tests, proving that the weir body can be effectively protected even if the composite units are directly laid on a severely uneven weir surface repair layer.
