The causes of local scour are generally categorized into flow condition, structure, and riverbed material. A three-dimensional vortex flow generated with the influence of the structure is the main factors of the flow ...The causes of local scour are generally categorized into flow condition, structure, and riverbed material. A three-dimensional vortex flow generated with the influence of the structure is the main factors of the flow conditions, and the size of the particles is assumed to be the main factor of the riverbed case. Various studies about pier local scour have been carried out by researchers since the 1960s, and a large number of experimental formulas have been suggested. Difficulties were encountered by these past studies, however, in terms of considering the influence of various riverbed materials and scour changes (floods, etc.) on time, with the condition of maximum scour depth. In the case of Korea, especially, scour influenced by various riverbed materials and the frequency of floods have been determined to be very important factors. Therefore, the ultimate purpose of this study on pier scour is to suggest the scour examination method that could consider various riverbed materials and the frequency of floods. In this study, the periodic changes in local scour based on the differences in the diameters of four types of bed materials, and on the hydraulic condition of the initial scour, were determined and compared with those in former studies. Using the results of the comparison, this study aims to determine the changes in the shear-stress around piers for various bed materials through the effect of time on scour depth (S, Smax), the shear-stress around piers, and the particles’ critical shear stress (τc).展开更多
海上风电桩基的振荡对其局部冲刷的影响不容忽视。该文采用VOF(volume of fluid)两相流模型,对横纵振荡的风电桩基进行数值模拟。分析不同频率、振幅下的桩前和桩侧对称面在周期内流场分布、马蹄涡系变化和床面剪切应力,探究振荡桩基对...海上风电桩基的振荡对其局部冲刷的影响不容忽视。该文采用VOF(volume of fluid)两相流模型,对横纵振荡的风电桩基进行数值模拟。分析不同频率、振幅下的桩前和桩侧对称面在周期内流场分布、马蹄涡系变化和床面剪切应力,探究振荡桩基对局部冲刷的影响机理。研究结果表明:在振荡周期内,纵向振荡桩基桩前对称面内产生回流,在T/2时刻马蹄涡达到最大且床面剪切应力最大,不改变桩侧对称面内水流流动;横向振荡桩基会延展桩侧马蹄涡系,在T/2时刻马蹄涡最大但床面剪切应力最小,T时刻最大,不改变桩前对称面内水流流动。横向、纵向振荡会增大桩前和桩侧的床面剪切应力,加剧局部冲刷,当A=5 mm、f=2 Hz时,纵向振荡桩前对称面剪切应力较静止约增大0.75%,桩侧对称面约增大7%;横向振荡桩前对称面约增大2.5%;桩侧对称面约增大10%。展开更多
文摘The causes of local scour are generally categorized into flow condition, structure, and riverbed material. A three-dimensional vortex flow generated with the influence of the structure is the main factors of the flow conditions, and the size of the particles is assumed to be the main factor of the riverbed case. Various studies about pier local scour have been carried out by researchers since the 1960s, and a large number of experimental formulas have been suggested. Difficulties were encountered by these past studies, however, in terms of considering the influence of various riverbed materials and scour changes (floods, etc.) on time, with the condition of maximum scour depth. In the case of Korea, especially, scour influenced by various riverbed materials and the frequency of floods have been determined to be very important factors. Therefore, the ultimate purpose of this study on pier scour is to suggest the scour examination method that could consider various riverbed materials and the frequency of floods. In this study, the periodic changes in local scour based on the differences in the diameters of four types of bed materials, and on the hydraulic condition of the initial scour, were determined and compared with those in former studies. Using the results of the comparison, this study aims to determine the changes in the shear-stress around piers for various bed materials through the effect of time on scour depth (S, Smax), the shear-stress around piers, and the particles’ critical shear stress (τc).
文摘海上风电桩基的振荡对其局部冲刷的影响不容忽视。该文采用VOF(volume of fluid)两相流模型,对横纵振荡的风电桩基进行数值模拟。分析不同频率、振幅下的桩前和桩侧对称面在周期内流场分布、马蹄涡系变化和床面剪切应力,探究振荡桩基对局部冲刷的影响机理。研究结果表明:在振荡周期内,纵向振荡桩基桩前对称面内产生回流,在T/2时刻马蹄涡达到最大且床面剪切应力最大,不改变桩侧对称面内水流流动;横向振荡桩基会延展桩侧马蹄涡系,在T/2时刻马蹄涡最大但床面剪切应力最小,T时刻最大,不改变桩前对称面内水流流动。横向、纵向振荡会增大桩前和桩侧的床面剪切应力,加剧局部冲刷,当A=5 mm、f=2 Hz时,纵向振荡桩前对称面剪切应力较静止约增大0.75%,桩侧对称面约增大7%;横向振荡桩前对称面约增大2.5%;桩侧对称面约增大10%。
