A sandy,braided river is a typical type of river that exists in ancient and modern alluvial plains and is inherent with significant seasonal water discharge variations.The variations play an important role in the depo...A sandy,braided river is a typical type of river that exists in ancient and modern alluvial plains and is inherent with significant seasonal water discharge variations.The variations play an important role in the depositional process and the formation of the sedimentary architecture of braided rivers.In this paper,a braided river outcrop along the Yellow River in Fugu is used to describe the effects of seasonal hydrodynamic variations on braided river sedimentary architecture.The results show that the braided channel network exhibits two different patterns during flood period and normal period.During flood periods,the main braided channels surrounding channel bars and the secondary braided channels distributed on the top of the channel bars coexist,forming a highly braided channel network.Migration of the main braided channels control the formation of middle channel bars and side bars.The generation and evolution of the secondary braided channels reformed the upper part of preexisting channel bars and produced affiliated bars along their flow path.During the normal period,water levels decrease,causing the secondary river channels to be abandoned and forming abandoned channels,and only the main braided channels stay active.In the long term sedimentation process,strong water flow during the flood period continuously erodes pre-existing sediments and forms new sediments,while weak water flow during the normal period can only reform the main braided channels and their adjacent channel bar sediments.Based on differences in sedimentary processes and associated hydrodynamic conditions,braided river sediments are divided into two combinations.The strong hydrodynamic combination includes main braided channels,middle channel bar,and side bar,while the weak hydrodynamic combination includes secondary braided channels,abandoned channels,and affiliated bars.The proportion of strong hydrodynamic combinations is much larger than that of weak hydrodynamic combinations.Based on this,we construct a braided river sedimentary architecture model that is helpful for the fine characterization of subsurface oil and gas reservoirs.展开更多
Improper design of volute geometry can be the main cause that leads to unsteady pressure pulsation and radial force in pumps. Therefore, it is important to understand the influence of volute geometrical parameters on ...Improper design of volute geometry can be the main cause that leads to unsteady pressure pulsation and radial force in pumps. Therefore, it is important to understand the influence of volute geometrical parameters on hydrodynamic characteristics of pump and the mechanism. However, the existing studies are limited to investigate the influence of only one or two volute geometrical parameters each time, and a systematic study of the influence of the combinations of different volute geometrical parameters on the pump＇s hydrodynamic characteristics is missing. In this paper, a study on the understanding of the influence of volute geometrical variations on hydrodynamic characteristics of a high speed circulator pump by using computational fluid dynamics（CFD） technology is presented. Five main volute geometrical parameters D3, A8, a0, j0 and Rt are selected and 25 different volute configurations are generated by using design of experiments（DOE） method. The 3D unsteady flow numerical simulations, which are based on the SST k-w turbulence model and sliding mesh technique provided by CFX, are executed on the 25 different volute configurations. The hydraulic performance, pressure pulsation and unsteady radial force inside the pump at design condition are obtained and analyzed. It has been found that volute geometrical parameters D3 and A8 are major influence factors on hydrodynamic characteristics of the pump, while a0, j0 and Rt are minor influence factors. The minimum contribution from both D3 and A8 is 58% on head, and maximum contribution from both D3 and A8 is 90% on pressure pulsation. Regarding the pressure pulsation intensity, two peaks can be found. One is in the tongue area and the other is in the diffusor area. The contributions are around 60% from tongue and 25% from diffusor, respectively. The amplitude of pressure pulsation has a quadratic polynomial functional relationship with respect to D3/D2 and A8/A（10）, and fluctuating level of radial force has a quadratic polynomial functional relationship with respect to D3/D2. While for the other volute parameters a0, j0 and Rt, no special function has been found related to pressure pulsation and radial force. The presented work could be a useful guideline in engineering practice when designing a circulator pump with low hydrodynamic force.展开更多
In this paper, the variational principles of hydrodynamic problems for the incompressible and compressible viscous fluids are established. These principles are principles of maximum power losses. Their generalized var...In this paper, the variational principles of hydrodynamic problems for the incompressible and compressible viscous fluids are established. These principles are principles of maximum power losses. Their generalized variational principles are also discussed on the basis of Lagrangian multiplier methods.展开更多
By establishing a 3-dimensional hydrodynamic model of the Hongtang Bay and the validation tests,tidal currents of the area before and after the construction of the Sanya new airport project,which include two artificia...By establishing a 3-dimensional hydrodynamic model of the Hongtang Bay and the validation tests,tidal currents of the area before and after the construction of the Sanya new airport project,which include two artificial islands built respectively to accommodate the airport and its connected technology park,are simulated.The hydrodynamic impacts of the islands on the Hongtang Bay and surrounding waters were analyzed by comparing flow fields and velocities of tidal currents under the two conditions.展开更多
文摘A sandy,braided river is a typical type of river that exists in ancient and modern alluvial plains and is inherent with significant seasonal water discharge variations.The variations play an important role in the depositional process and the formation of the sedimentary architecture of braided rivers.In this paper,a braided river outcrop along the Yellow River in Fugu is used to describe the effects of seasonal hydrodynamic variations on braided river sedimentary architecture.The results show that the braided channel network exhibits two different patterns during flood period and normal period.During flood periods,the main braided channels surrounding channel bars and the secondary braided channels distributed on the top of the channel bars coexist,forming a highly braided channel network.Migration of the main braided channels control the formation of middle channel bars and side bars.The generation and evolution of the secondary braided channels reformed the upper part of preexisting channel bars and produced affiliated bars along their flow path.During the normal period,water levels decrease,causing the secondary river channels to be abandoned and forming abandoned channels,and only the main braided channels stay active.In the long term sedimentation process,strong water flow during the flood period continuously erodes pre-existing sediments and forms new sediments,while weak water flow during the normal period can only reform the main braided channels and their adjacent channel bar sediments.Based on differences in sedimentary processes and associated hydrodynamic conditions,braided river sediments are divided into two combinations.The strong hydrodynamic combination includes main braided channels,middle channel bar,and side bar,while the weak hydrodynamic combination includes secondary braided channels,abandoned channels,and affiliated bars.The proportion of strong hydrodynamic combinations is much larger than that of weak hydrodynamic combinations.Based on this,we construct a braided river sedimentary architecture model that is helpful for the fine characterization of subsurface oil and gas reservoirs.
基金Supported by National Natural Science Foundation of China(Grant No.51239005)Zhejiang Provincial Natural Science Foundation of China(Grant Nos.LQ15E090004,LQ15E090005)Project of Zhejiang Education,China(Grant No.Y201432222)
文摘Improper design of volute geometry can be the main cause that leads to unsteady pressure pulsation and radial force in pumps. Therefore, it is important to understand the influence of volute geometrical parameters on hydrodynamic characteristics of pump and the mechanism. However, the existing studies are limited to investigate the influence of only one or two volute geometrical parameters each time, and a systematic study of the influence of the combinations of different volute geometrical parameters on the pump＇s hydrodynamic characteristics is missing. In this paper, a study on the understanding of the influence of volute geometrical variations on hydrodynamic characteristics of a high speed circulator pump by using computational fluid dynamics（CFD） technology is presented. Five main volute geometrical parameters D3, A8, a0, j0 and Rt are selected and 25 different volute configurations are generated by using design of experiments（DOE） method. The 3D unsteady flow numerical simulations, which are based on the SST k-w turbulence model and sliding mesh technique provided by CFX, are executed on the 25 different volute configurations. The hydraulic performance, pressure pulsation and unsteady radial force inside the pump at design condition are obtained and analyzed. It has been found that volute geometrical parameters D3 and A8 are major influence factors on hydrodynamic characteristics of the pump, while a0, j0 and Rt are minor influence factors. The minimum contribution from both D3 and A8 is 58% on head, and maximum contribution from both D3 and A8 is 90% on pressure pulsation. Regarding the pressure pulsation intensity, two peaks can be found. One is in the tongue area and the other is in the diffusor area. The contributions are around 60% from tongue and 25% from diffusor, respectively. The amplitude of pressure pulsation has a quadratic polynomial functional relationship with respect to D3/D2 and A8/A（10）, and fluctuating level of radial force has a quadratic polynomial functional relationship with respect to D3/D2. While for the other volute parameters a0, j0 and Rt, no special function has been found related to pressure pulsation and radial force. The presented work could be a useful guideline in engineering practice when designing a circulator pump with low hydrodynamic force.
文摘In this paper, the variational principles of hydrodynamic problems for the incompressible and compressible viscous fluids are established. These principles are principles of maximum power losses. Their generalized variational principles are also discussed on the basis of Lagrangian multiplier methods.
文摘By establishing a 3-dimensional hydrodynamic model of the Hongtang Bay and the validation tests,tidal currents of the area before and after the construction of the Sanya new airport project,which include two artificial islands built respectively to accommodate the airport and its connected technology park,are simulated.The hydrodynamic impacts of the islands on the Hongtang Bay and surrounding waters were analyzed by comparing flow fields and velocities of tidal currents under the two conditions.
