This paper focuses on the flow characteristic and local resistance of non-Newtonian power law fluid in a curved 90° bend pipe with circular cross-sections, which are widely used in industrial applications. By emp...This paper focuses on the flow characteristic and local resistance of non-Newtonian power law fluid in a curved 90° bend pipe with circular cross-sections, which are widely used in industrial applications. By employing nu- merical simulation and theoretical analysis the properties of the flow and local resistance of power law fluid under different working conditions are obtained. To explore the change rule the experiment is carried out by changing the Reynolds number, the wall roughness and differcnt diameter ratio of elbow pipe. The variation of the local resistance coefficient with the Reynolds number, the diameter ratio and the wall roughness is presented comprehensively in the paper. The results show that the local resistance force coefficient hardly changes with Reynolds number of the power law fluid; the wall roughness has a significant impact on the local resistance coefficicnt. As the pipe wall roughness increasing, the coefficient of local resistance force will increase. The main reason of the influence of the roughness on the local resistance coefficient is the increase of the eddy current region in the power law fluid flow, which increases the kinetic energy dissipation of the main flow. This paper provides theoretical and numerical methods to understand the local resistance property of non-Newtonian power law fluid in elbow pipes.展开更多
在核电站管道破前漏设计(Leak Before Break,LBB)过程中,准确计算流过管道贯穿裂纹的流体泄漏量是最为核心的因素,是确保泄漏量监测系统成功运行,有效预防管道断裂事故发生的关键。如何准确计算裂纹通道的摩擦系数又是管道裂纹泄漏量计...在核电站管道破前漏设计(Leak Before Break,LBB)过程中,准确计算流过管道贯穿裂纹的流体泄漏量是最为核心的因素,是确保泄漏量监测系统成功运行,有效预防管道断裂事故发生的关键。如何准确计算裂纹通道的摩擦系数又是管道裂纹泄漏量计算中的核心问题之一。通过数值计算探讨了管道贯穿裂纹的全局粗糙度、局部粗糙度以及破口尺寸对裂纹通道摩擦系数的影响,研究结果表明:摩擦系数与全局粗糙度、局部粗糙度以及破口位移大小密切相关,破口位移δ与全局粗糙度μg的比值是判定摩擦系数计算中粗糙度取值的关键指标,当δ/μg<5.0,即应当考虑局部粗糙度对管道裂纹摩擦系数的影响。展开更多
The numerical solution of the stable basic flow on a 3-D boundary layer is obtained by using local ejection, local suction, and combination of local ejection and suction to simulate the local rough wall. The evolution...The numerical solution of the stable basic flow on a 3-D boundary layer is obtained by using local ejection, local suction, and combination of local ejection and suction to simulate the local rough wall. The evolution of 3-D disturbance T-S wave is studied in the spatial processes, and the effects of form and distribution structure of local roughness on the growth rate of the 3-D disturbance wave and the flow stability are discussed. Numerical results show that the growth of the disturbance wave and the form of vortices are accelerated by the 3-D local roughness. The modification of basic flow owing to the evolvement of the finite amplitude disturbance wave and the existence of spanwise velocity induced by the 3-D local roughness affects the stability of boundary layer. Propagation direction and phase of the disturbance wave shift obviously for the 3-D local roughness of the wall. The flow stability characteristics change if the form of the 2-D local roughness varies.展开更多
基金supported by Shandong Provincial Natural Science Foundation,China(No.ZR2014JL039)
文摘This paper focuses on the flow characteristic and local resistance of non-Newtonian power law fluid in a curved 90° bend pipe with circular cross-sections, which are widely used in industrial applications. By employing nu- merical simulation and theoretical analysis the properties of the flow and local resistance of power law fluid under different working conditions are obtained. To explore the change rule the experiment is carried out by changing the Reynolds number, the wall roughness and differcnt diameter ratio of elbow pipe. The variation of the local resistance coefficient with the Reynolds number, the diameter ratio and the wall roughness is presented comprehensively in the paper. The results show that the local resistance force coefficient hardly changes with Reynolds number of the power law fluid; the wall roughness has a significant impact on the local resistance coefficicnt. As the pipe wall roughness increasing, the coefficient of local resistance force will increase. The main reason of the influence of the roughness on the local resistance coefficient is the increase of the eddy current region in the power law fluid flow, which increases the kinetic energy dissipation of the main flow. This paper provides theoretical and numerical methods to understand the local resistance property of non-Newtonian power law fluid in elbow pipes.
文摘在核电站管道破前漏设计(Leak Before Break,LBB)过程中,准确计算流过管道贯穿裂纹的流体泄漏量是最为核心的因素,是确保泄漏量监测系统成功运行,有效预防管道断裂事故发生的关键。如何准确计算裂纹通道的摩擦系数又是管道裂纹泄漏量计算中的核心问题之一。通过数值计算探讨了管道贯穿裂纹的全局粗糙度、局部粗糙度以及破口尺寸对裂纹通道摩擦系数的影响,研究结果表明:摩擦系数与全局粗糙度、局部粗糙度以及破口位移大小密切相关,破口位移δ与全局粗糙度μg的比值是判定摩擦系数计算中粗糙度取值的关键指标,当δ/μg<5.0,即应当考虑局部粗糙度对管道裂纹摩擦系数的影响。
文摘The numerical solution of the stable basic flow on a 3-D boundary layer is obtained by using local ejection, local suction, and combination of local ejection and suction to simulate the local rough wall. The evolution of 3-D disturbance T-S wave is studied in the spatial processes, and the effects of form and distribution structure of local roughness on the growth rate of the 3-D disturbance wave and the flow stability are discussed. Numerical results show that the growth of the disturbance wave and the form of vortices are accelerated by the 3-D local roughness. The modification of basic flow owing to the evolvement of the finite amplitude disturbance wave and the existence of spanwise velocity induced by the 3-D local roughness affects the stability of boundary layer. Propagation direction and phase of the disturbance wave shift obviously for the 3-D local roughness of the wall. The flow stability characteristics change if the form of the 2-D local roughness varies.
