Elucidating the flow features around piles in local scouring processes is crucial for studies of local scouring mechanisms and scour depth estimates.This study details the flow turbulence characteristics of two submer...Elucidating the flow features around piles in local scouring processes is crucial for studies of local scouring mechanisms and scour depth estimates.This study details the flow turbulence characteristics of two submerged piles that are determined by solving the Navier-Stokes equations with the improved delayed detached eddy simulation model.This model is verified by comparing experimental and numerical results for hydrodynamic parameters with the literature for both square-crossing piles(SCPs)and circular-crossing piles(CCPs).Original topographies of flat and scoured beds(i.e.,the initial and equilibrium scouring stages)are based on experimental results obtained by the authors in the present paper.SCP and CCP flow features in the scouring process are discussed.The results indicate that during the scouring process,the time-averaged drag coefficient and root mean square(rms)of the lift coefficient increase linearly in the CCP test,while the rms of the lift coefficient in the SCP test decreases linearly.Moreover,the minimum pressure coefficient is always located in the upstream corners in the SCP case but moves from 72.5°to 79.5°when the scour hole is completely developed in the CCP case.Downward flow behind the pile,which is generated by separated boundary layers above the top face of the pile,can reach the sand bed and turn the separated shear layers into patches of small vortices in the near-wake regions.Thus,the high shear stress zones are mainly at the scour edges under scoured-bed conditions.展开更多
To improve the heat transfer efficiency of the coolant in lead-based fast reactors,this study optimized the configuration and rotational direction of the spacer wires in fuel assemblies to design a new-pattern fuel as...To improve the heat transfer efficiency of the coolant in lead-based fast reactors,this study optimized the configuration and rotational direction of the spacer wires in fuel assemblies to design a new-pattern fuel assembly.This study conducted detailed comparisons between traditional and new pattern fuel assembly rod bundles utilizing the open-source computational fluid dynamics platform,OpenFOAM.The results indicated that the new design may significantly reduce the pressure drop along the rod bundle,which is beneficial for lowering the pressure drop.Furthermore,this new design improved coolant mixing in the subchannels,which facilitated a more uniform temperature distribution and lower thermal gradients at the assembly outlet.These factors collectively reduced the thermal fatigue and creep in nearby internal components.Overall,the newpattern fuel assembly proposed in this study may have better heat transfer performance,thereby enhancing the Integrated Thermal-Hydraulic Factor by 48.2% compared to the traditional pattern.展开更多
During the design process of the ship,a lot of attention is given to tune-up parameters of the propeller,which is one of the most important part of the propulsion system.Designing new generation,more effective and eff...During the design process of the ship,a lot of attention is given to tune-up parameters of the propeller,which is one of the most important part of the propulsion system.Designing new generation,more effective and efficient propellers require knowledge of hydrodynamic phenomena occurring in the propeller area.For this reason,a lot of time and funds is spent on the propeller research and development.Usually these are experimental tests in cavitation tunnels and towing tanks.However,more and more research is carried out by CFD simulation.OpenFOAM software is open source CFD package,which becomes popular alternative to commercial codes.This paper attempts to answer the question:if OpenFOAM is suitable for such specific applications like accurate simulation of flow around the propeller?The paper presents the results of a CFD simulation of marine propeller created with OpenFOAM software.The obtained results were compared with the of the commercial CFD codes simulations and the experimental research.展开更多
基金support from the National Natural Science Foundation of China (Nos.52301324 and 52001276)the Natural Science Foundation of Zhejiang Province (No.LQ24E090001)+2 种基金the Open Fund of Key Laboratory of Estuary and Coast of Zhejiang Province (No.ZIHE21005)the Natural Science Foundation of Ningbo (No.2021J096)the Zhejiang Transportation Science and Technology (No.2021064)。
文摘Elucidating the flow features around piles in local scouring processes is crucial for studies of local scouring mechanisms and scour depth estimates.This study details the flow turbulence characteristics of two submerged piles that are determined by solving the Navier-Stokes equations with the improved delayed detached eddy simulation model.This model is verified by comparing experimental and numerical results for hydrodynamic parameters with the literature for both square-crossing piles(SCPs)and circular-crossing piles(CCPs).Original topographies of flat and scoured beds(i.e.,the initial and equilibrium scouring stages)are based on experimental results obtained by the authors in the present paper.SCP and CCP flow features in the scouring process are discussed.The results indicate that during the scouring process,the time-averaged drag coefficient and root mean square(rms)of the lift coefficient increase linearly in the CCP test,while the rms of the lift coefficient in the SCP test decreases linearly.Moreover,the minimum pressure coefficient is always located in the upstream corners in the SCP case but moves from 72.5°to 79.5°when the scour hole is completely developed in the CCP case.Downward flow behind the pile,which is generated by separated boundary layers above the top face of the pile,can reach the sand bed and turn the separated shear layers into patches of small vortices in the near-wake regions.Thus,the high shear stress zones are mainly at the scour edges under scoured-bed conditions.
基金supported partly by the Ministry of Science and Technology of the People’s Republic of China(No.2020YFB1902100)the China Postdoctoral Science Foundation(No.2023M731458)+3 种基金the Science and Technology Program of Gansu ProvinceChina(No.23JRRA1099)the Postdoctoral Fellowship Program of CPSF(No.GZB20230278)financially supported by the Shanghai Municipal Commission of Economy and Informatization(No.GYQJ-2018-2-02)。
文摘To improve the heat transfer efficiency of the coolant in lead-based fast reactors,this study optimized the configuration and rotational direction of the spacer wires in fuel assemblies to design a new-pattern fuel assembly.This study conducted detailed comparisons between traditional and new pattern fuel assembly rod bundles utilizing the open-source computational fluid dynamics platform,OpenFOAM.The results indicated that the new design may significantly reduce the pressure drop along the rod bundle,which is beneficial for lowering the pressure drop.Furthermore,this new design improved coolant mixing in the subchannels,which facilitated a more uniform temperature distribution and lower thermal gradients at the assembly outlet.These factors collectively reduced the thermal fatigue and creep in nearby internal components.Overall,the newpattern fuel assembly proposed in this study may have better heat transfer performance,thereby enhancing the Integrated Thermal-Hydraulic Factor by 48.2% compared to the traditional pattern.
文摘During the design process of the ship,a lot of attention is given to tune-up parameters of the propeller,which is one of the most important part of the propulsion system.Designing new generation,more effective and efficient propellers require knowledge of hydrodynamic phenomena occurring in the propeller area.For this reason,a lot of time and funds is spent on the propeller research and development.Usually these are experimental tests in cavitation tunnels and towing tanks.However,more and more research is carried out by CFD simulation.OpenFOAM software is open source CFD package,which becomes popular alternative to commercial codes.This paper attempts to answer the question:if OpenFOAM is suitable for such specific applications like accurate simulation of flow around the propeller?The paper presents the results of a CFD simulation of marine propeller created with OpenFOAM software.The obtained results were compared with the of the commercial CFD codes simulations and the experimental research.
