Based on mechanical characteristics such as large vertical load, large horizontal load, large bending moment and complex geological conditions, a large scale composite bucket foundation （CBF） is put forward. Both th...Based on mechanical characteristics such as large vertical load, large horizontal load, large bending moment and complex geological conditions, a large scale composite bucket foundation （CBF） is put forward. Both the theoretical analysis and numerical simulation are employed to study the bearing capacity of CBF and the relationship between loads and ground deformation. Furthermore, monopile, high-rise pile cap, tripod and CBF designs are compared to analyze the bearing capacity and ground deformation, with a 3-MW wind generator as an example. The resuits indicate that CBF can effectively bear horizontal load and large bending moment resulting from upper structures and environmental load.展开更多
The key in the force transmission between the tower and the foundation for offshore wind turbines is to transfer the large moment and horizontal loads. The finite element model of a large-scale prestressing bucket fou...The key in the force transmission between the tower and the foundation for offshore wind turbines is to transfer the large moment and horizontal loads. The finite element model of a large-scale prestressing bucket founda- tion for offshore wind turbines is set up and the structural characteristics of the arc transition structure of the founda- tion are analyzed for 40-60 channels(20-30 rows) arranged with prestressing steel strand under the same ultimate load and boundary conditions. The mechanical characteristics of the key parts of the foundation structures are illus- trated by the peak of the principal tensile stress, the peak of the principal compressive stress and the distribution areas where the principal tensile stress is larger than 2.00 MPa. It can be concluded that the maximum principal tensile stress of the arc transition decreases with the increasing number of channels, and the amplitude does not change signifi- cantly; the maximum principal compressive stress increases with the increasing number of channels and the amplitude changes significantly; however, for the distribution areas where the principal tensile stress is larger than 2.00 MPa, with different channel numbers, the phenomenon is not obvious. Furthermore, the principal tensile stress at the top of the foundation beams fluctuantly increases with the increasing number of channels and for the top cover of the bucket, the principal tensile stress decreases with the increasing number of channels.展开更多
In order to study the towing dynamic properties of the large-scale composite bucket foundation the hydrodynamic software MOSES is used to simulate the dynamic motion of the foundation towed to the construction site.Th...In order to study the towing dynamic properties of the large-scale composite bucket foundation the hydrodynamic software MOSES is used to simulate the dynamic motion of the foundation towed to the construction site.The MOSES model with the prototype size is established as the water draft of 5 and 6 m under the environmental conditions on site.The related factors such as towing force displacement towing accelerations in six degrees of freedom of the bucket foundation and air pressures inside the bucket are analyzed in detail.In addition the towing point and wave conditions are set as the critical factors to simulate the limit conditions of the stable dynamic characteristics.The results show that the large-scale composite bucket foundation with reasonable subdivisions inside the bucket has the satisfying floating stability.During the towing process the air pressures inside the bucket obviously change little and it is found that the towing point at the waterline is the most optimal choice.The characteristics of the foundation with the self-floating towing technique are competitive for saving lots of cost with few of the expensive types of equipment required during the towing transportation.展开更多
Achieving water purity in Poyang Lake has become a major concern in recent years, thus appropriate evaluation of spatial and temporal water quality variations has become essential. Variations in 11 water quality param...Achieving water purity in Poyang Lake has become a major concern in recent years, thus appropriate evaluation of spatial and temporal water quality variations has become essential. Variations in 11 water quality parameters from 15 sampling sites in Poyang Lake were investigated from 2009 to 2012. An integrative fuzzy variable evaluation(IFVE) model based on fuzzy theory and variable weights was developed to measure variations in water quality. Results showed that: 1) only chlorophyll-a concentration and Secchi depth differed significantly among the 15 sampling sites(P < 0.01), whereas the 11 water quality parameters under investigation differed significantly throughout the seasons(P < 0.01). The annual variations of all water quality variables except for temperature, electrical conductivity, suspended solids and total phosphorus were considerable(P < 0.05). 2) The IFVE model was reasonable and flexible in evaluating water quality status and any possible ′bucket effect′. The model fully considered the influences of extremely poor indices on overall water quality. 3) A spatial analysis indicated that anthropogenic activities(particularly industrial sewage and dredging) and lake bed topography might directly affect water quality in Poyang Lake. Meanwhile, hydrological status and sewage discharged into the lake might be responsible for seasonal water quality variations.展开更多
Flip buckets are commonly used to discharge flow away from a hydraulic structure into the downstream to dissipate energy.A new leak-floor flip bucket is presented,making the ski-jump water jet a typical long-narrow na...Flip buckets are commonly used to discharge flow away from a hydraulic structure into the downstream to dissipate energy.A new leak-floor flip bucket is presented,making the ski-jump water jet a typical long-narrow nappe.Based on the model experiments and numerical simulation,the flow pattern,formation process and mechanism of the leak-floor flip bucket are studied.The results show that cross section flow shape develops from the"Y-type"to"|-type",and this is because the natural pressure difference is generated when water flows through the leak-floor area and moves transversely from both sides to the center.Different from the slit-type flip bucket with sidewall contraction,the leak-floor flit bucket makes the water jet narrow and long without high pressure on the side walls of the flip bucket.Under the same jet length condition,the maximum sidewall pressure of the slit-type is 4.67 times that of the leak-floor flip bucket.The effects of flow discharge on the jet length are less significant for the leak-floor bucket than for the slit-type bucket.展开更多
The energy dissipation is a key index in the evaluation of energy dissipation elements.In the present work,a flip bucket with a slot,called the slot-type flip bucket,is theoretically and experimentally investigated by...The energy dissipation is a key index in the evaluation of energy dissipation elements.In the present work,a flip bucket with a slot,called the slot-type flip bucket,is theoretically and experimentally investigated by the method of estimating the energy dissipation.The theoretical analysis shows that,in order to have the energy dissipation,it is necessary to determine the sequent flow depth h1 and the flow speed V1 at the corresponding position through the flow depth h2 after the hydraulic jump.The relative flow depth h2/ho is a function of the approach flow Froude numberFro,the relative slot widthb/Bo,and the relative slot angleθ/β.The expression for estimating the energy dissipation is developed,and the maximum error is not larger than 9.21%.展开更多
The large-scale bucket foundation with 30 m in diameter and 6 m in height was used as the foundation of wind turbine. The wide-shallow foundation is different from the traditional bucket foundation with high ratio of ...The large-scale bucket foundation with 30 m in diameter and 6 m in height was used as the foundation of wind turbine. The wide-shallow foundation is different from the traditional bucket foundation with high ratio of height to diameter. The cover-load-bearing mode of the new type foundation can resist more external loadings. To achieve the bearing mode, the muddy soil inside the bucket should be reinforced, which will improve the soil strength and make the soil and foundation into a whole part to resist the external loadings. The vacuum and electro-osmotic soil reinforc- ing methods were used in the experiments. The results showed that the bearing behavior of the muddy soil were effec- tively improved by the negative pressure and electro-osmotic effect, and the improved muddy soil with better strength could work together with the bucket foundation, meaning that the top-cover bearing mode of the new bucket founda- tion was achieved. During the soil reinforcing process, the foundation moved downward, i.e., the settlement of founda- tion was almost finished during the pre-loading process caused by the vacuum and electro-osmotic method.展开更多
In the present work, an alternative numerical methodology is developed for a fast and effective simulation and analysis of the complex flow and energy conversion in Pelton impulse hydro turbines. The algorithm is base...In the present work, an alternative numerical methodology is developed for a fast and effective simulation and analysis of the complex flow and energy conversion in Pelton impulse hydro turbines. The algorithm is based on the Lagrangian approach and the unsteady free-surface flow during the jet-bucket interaction is simulated by tracking the trajectories of representative fluid particles at very low computer cost. Modern regression tools are implemented in a new parameterization technique of the inner bucket surface. Key-feature of the model is the introduction of additional terms into the particle motion equations to account for various hydraulic losses and the flow spreading, which are regulated and evaluated with the aid of experimental data in a Laboratory Pelton turbine. The model is applied to study the jet-runner interaction in various operation conditions and then to perform numerical design optimization of the bucket shape, using a stochastic optimizer based on evolutionary algorithms. The obtained optimum runner attains remarkably higher hydraulic efficiency in the entire load range. Finally, a new small Pelton turbine （150 kW） is designed, manufactured and tested in the Laboratory, and its performance and efficiency verify the model predictions.展开更多
文摘Based on mechanical characteristics such as large vertical load, large horizontal load, large bending moment and complex geological conditions, a large scale composite bucket foundation （CBF） is put forward. Both the theoretical analysis and numerical simulation are employed to study the bearing capacity of CBF and the relationship between loads and ground deformation. Furthermore, monopile, high-rise pile cap, tripod and CBF designs are compared to analyze the bearing capacity and ground deformation, with a 3-MW wind generator as an example. The resuits indicate that CBF can effectively bear horizontal load and large bending moment resulting from upper structures and environmental load.
基金Supported by Creative Research Groups of National Natural Science Foundation of China (No. 51021004)Program for Changjiang Scholars and Innovative Research Team in University (No. IRT0851)
文摘The key in the force transmission between the tower and the foundation for offshore wind turbines is to transfer the large moment and horizontal loads. The finite element model of a large-scale prestressing bucket founda- tion for offshore wind turbines is set up and the structural characteristics of the arc transition structure of the founda- tion are analyzed for 40-60 channels(20-30 rows) arranged with prestressing steel strand under the same ultimate load and boundary conditions. The mechanical characteristics of the key parts of the foundation structures are illus- trated by the peak of the principal tensile stress, the peak of the principal compressive stress and the distribution areas where the principal tensile stress is larger than 2.00 MPa. It can be concluded that the maximum principal tensile stress of the arc transition decreases with the increasing number of channels, and the amplitude does not change signifi- cantly; the maximum principal compressive stress increases with the increasing number of channels and the amplitude changes significantly; however, for the distribution areas where the principal tensile stress is larger than 2.00 MPa, with different channel numbers, the phenomenon is not obvious. Furthermore, the principal tensile stress at the top of the foundation beams fluctuantly increases with the increasing number of channels and for the top cover of the bucket, the principal tensile stress decreases with the increasing number of channels.
基金The National Natural Science Foundation of China(No.51109160)the National High Technology Research and Development Program of China(863 Program)(No.2012AA051705)+1 种基金the International S&T Cooperation Program of China(No.2012DFA70490)the Natural Science Foundation of Tianjin(No.13JCQNJC06900,13JCYBJC19100)
文摘In order to study the towing dynamic properties of the large-scale composite bucket foundation the hydrodynamic software MOSES is used to simulate the dynamic motion of the foundation towed to the construction site.The MOSES model with the prototype size is established as the water draft of 5 and 6 m under the environmental conditions on site.The related factors such as towing force displacement towing accelerations in six degrees of freedom of the bucket foundation and air pressures inside the bucket are analyzed in detail.In addition the towing point and wave conditions are set as the critical factors to simulate the limit conditions of the stable dynamic characteristics.The results show that the large-scale composite bucket foundation with reasonable subdivisions inside the bucket has the satisfying floating stability.During the towing process the air pressures inside the bucket obviously change little and it is found that the towing point at the waterline is the most optimal choice.The characteristics of the foundation with the self-floating towing technique are competitive for saving lots of cost with few of the expensive types of equipment required during the towing transportation.
基金Under the auspices of National Basic Research Program of China(No.2012CB417006)National Natural Science Foundation of China(No.41271500,41571107,41601041)
文摘Achieving water purity in Poyang Lake has become a major concern in recent years, thus appropriate evaluation of spatial and temporal water quality variations has become essential. Variations in 11 water quality parameters from 15 sampling sites in Poyang Lake were investigated from 2009 to 2012. An integrative fuzzy variable evaluation(IFVE) model based on fuzzy theory and variable weights was developed to measure variations in water quality. Results showed that: 1) only chlorophyll-a concentration and Secchi depth differed significantly among the 15 sampling sites(P < 0.01), whereas the 11 water quality parameters under investigation differed significantly throughout the seasons(P < 0.01). The annual variations of all water quality variables except for temperature, electrical conductivity, suspended solids and total phosphorus were considerable(P < 0.05). 2) The IFVE model was reasonable and flexible in evaluating water quality status and any possible ′bucket effect′. The model fully considered the influences of extremely poor indices on overall water quality. 3) A spatial analysis indicated that anthropogenic activities(particularly industrial sewage and dredging) and lake bed topography might directly affect water quality in Poyang Lake. Meanwhile, hydrological status and sewage discharged into the lake might be responsible for seasonal water quality variations.
基金supported by the National Natural Science Foundation of China(Grant Nos.51379138&51179113)Sichuan Province Funds for Distinguished Young Scientists(Grant No.2013JQ0007)
文摘Flip buckets are commonly used to discharge flow away from a hydraulic structure into the downstream to dissipate energy.A new leak-floor flip bucket is presented,making the ski-jump water jet a typical long-narrow nappe.Based on the model experiments and numerical simulation,the flow pattern,formation process and mechanism of the leak-floor flip bucket are studied.The results show that cross section flow shape develops from the"Y-type"to"|-type",and this is because the natural pressure difference is generated when water flows through the leak-floor area and moves transversely from both sides to the center.Different from the slit-type flip bucket with sidewall contraction,the leak-floor flit bucket makes the water jet narrow and long without high pressure on the side walls of the flip bucket.Under the same jet length condition,the maximum sidewall pressure of the slit-type is 4.67 times that of the leak-floor flip bucket.The effects of flow discharge on the jet length are less significant for the leak-floor bucket than for the slit-type bucket.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51579076,51479057)
文摘The energy dissipation is a key index in the evaluation of energy dissipation elements.In the present work,a flip bucket with a slot,called the slot-type flip bucket,is theoretically and experimentally investigated by the method of estimating the energy dissipation.The theoretical analysis shows that,in order to have the energy dissipation,it is necessary to determine the sequent flow depth h1 and the flow speed V1 at the corresponding position through the flow depth h2 after the hydraulic jump.The relative flow depth h2/ho is a function of the approach flow Froude numberFro,the relative slot widthb/Bo,and the relative slot angleθ/β.The expression for estimating the energy dissipation is developed,and the maximum error is not larger than 9.21%.
基金National Hi-tech Research and Development Program of China("863"Program,No.2012AA051705)National Natural Science Foundation of China(No. 51109160)
文摘The large-scale bucket foundation with 30 m in diameter and 6 m in height was used as the foundation of wind turbine. The wide-shallow foundation is different from the traditional bucket foundation with high ratio of height to diameter. The cover-load-bearing mode of the new type foundation can resist more external loadings. To achieve the bearing mode, the muddy soil inside the bucket should be reinforced, which will improve the soil strength and make the soil and foundation into a whole part to resist the external loadings. The vacuum and electro-osmotic soil reinforc- ing methods were used in the experiments. The results showed that the bearing behavior of the muddy soil were effec- tively improved by the negative pressure and electro-osmotic effect, and the improved muddy soil with better strength could work together with the bucket foundation, meaning that the top-cover bearing mode of the new bucket founda- tion was achieved. During the soil reinforcing process, the foundation moved downward, i.e., the settlement of founda- tion was almost finished during the pre-loading process caused by the vacuum and electro-osmotic method.
文摘In the present work, an alternative numerical methodology is developed for a fast and effective simulation and analysis of the complex flow and energy conversion in Pelton impulse hydro turbines. The algorithm is based on the Lagrangian approach and the unsteady free-surface flow during the jet-bucket interaction is simulated by tracking the trajectories of representative fluid particles at very low computer cost. Modern regression tools are implemented in a new parameterization technique of the inner bucket surface. Key-feature of the model is the introduction of additional terms into the particle motion equations to account for various hydraulic losses and the flow spreading, which are regulated and evaluated with the aid of experimental data in a Laboratory Pelton turbine. The model is applied to study the jet-runner interaction in various operation conditions and then to perform numerical design optimization of the bucket shape, using a stochastic optimizer based on evolutionary algorithms. The obtained optimum runner attains remarkably higher hydraulic efficiency in the entire load range. Finally, a new small Pelton turbine （150 kW） is designed, manufactured and tested in the Laboratory, and its performance and efficiency verify the model predictions.
