To explore the water entry flow and impact load characteristics of northern gannets,we conducted water entry experiments using a northern gannet’s head model based on three-dimensional(3D)printing and several cone mo...To explore the water entry flow and impact load characteristics of northern gannets,we conducted water entry experiments using a northern gannet’s head model based on three-dimensional(3D)printing and several cone models under different Froude numbers.A high-speed camera was used to capture flow images,and an inertial measurement unit(IMU)was used to record the water entry impact loads.The results indicate that the geometric topology of the model considerably influenced the water entry flow and impact load.Specifically,the northern gannet’s head model created a smaller water entry splash crown,cavity geometry,and impact load compared with the cone models of similar sizes.展开更多
Understanding the evolution mechanisms of water-exit cavities and flow fields evolve during highintensity interactions between vehicles and floating ice is critical for advancing the application of submarine-launched ...Understanding the evolution mechanisms of water-exit cavities and flow fields evolve during highintensity interactions between vehicles and floating ice is critical for advancing the application of submarine-launched marine equipment in low-temperature ice-prone waters.A computational fluid dynamics-finite element method(CFD-FEM) coupled framework was established to simulate bidirectional fluid-structure interactions during the water-exit process of a ventilated vehicle impacting ice in brash environments.Distinct evolution characteristics were revealed by comparatively analyzing the cavity,flow fields,hydrodynamic loading,structural deformation,and trajectory stability across three scenarios:ice-free,single-ice,and multi-ice.Furthermore,the position-dependent impact effects were characterized.The findings reveal that the impact,friction,and compression effects of ice induce bending and wrinkling of the shoulder cavity,aggravating its collapse and increasing the wetting of the vehicle,resulting in a substantial expansion of the high-velocity and vortex-dominated regions within the flow field,accompanied by more obvious water splashes.The impact of ice notably increases the kinetic energy dissipation of the vehicle during the cross-water stage and diminishes its motion stability.In the center-symmetric layout,the vehicle collides with ice only once,with high stress confined to the head.Conversely,the radial-offset layout causes secondary or even multiple collisions,resulting in high-stress areas on the shoulder of the vehicle,making it deflect and ultimately causing the tail cavity to tilt and become destabilized.The design of new vehicles suitable for ice-prone environments should focus on enhancing the impact toughness of the head structure and optimizing the surface shape design to improve the adaptability to low-temperature complex environments.展开更多
A two-dimensional model,employing a dynamic mesh technology,is used to simulate numerically the transient multiphaseflowfield produced by two submerged parallel guns.After a grid refinement study ensuring grid inde-pende...A two-dimensional model,employing a dynamic mesh technology,is used to simulate numerically the transient multiphaseflowfield produced by two submerged parallel guns.After a grid refinement study ensuring grid inde-pendence,five different conditions are considered to assess the evolution of cavitation occurring in proximity to the gun muzzle.The simulation results show thatflow interference is enabled when the distance between the par-allel barrels is relatively small;accordingly,the generation and evolution of the vapor cavity becomes more com-plex.By means of the Q criterion for vorticity detection,it is shown that cavitation causes the generation of vorticity and the evolution of the vapor cavity can result in an asymmetric distribution of vorticity for a certain distance of the barrels.In particular,the evolution of the vapor cavity can hinder the expansion of the gas and force it toflow outward,while an asymmetric distribution of vorticity can lead to a gas jetflowing outward and rotating simultaneously.展开更多
The Bell-nonlocality of two initially entangled macroscopic fields in the double Jaynes-Cummings model is investigated. Moreover, the process by which detuning between the atomic transition frequency and the field fre...The Bell-nonlocality of two initially entangled macroscopic fields in the double Jaynes-Cummings model is investigated. Moreover, the process by which detuning between the atomic transition frequency and the field frequency affects the evolution of the Beil-nonlocality of two macroscopic fields is studied. The effect of the disparitv between the two coupling strengths is discussed.展开更多
基金Supported by the Guangdong Provincial Natural Science Foundation of China under Grant No.2021A1515011917the National Natural Science Foundation of China under Grant No.52371344 and U22A2012+1 种基金Fundamental Research Funds for the Central Universities,Sun Yat-sen University under Grant No.22qntd0601the start-up funding to Y.J.from Sun Yat-sen University.
文摘To explore the water entry flow and impact load characteristics of northern gannets,we conducted water entry experiments using a northern gannet’s head model based on three-dimensional(3D)printing and several cone models under different Froude numbers.A high-speed camera was used to capture flow images,and an inertial measurement unit(IMU)was used to record the water entry impact loads.The results indicate that the geometric topology of the model considerably influenced the water entry flow and impact load.Specifically,the northern gannet’s head model created a smaller water entry splash crown,cavity geometry,and impact load compared with the cone models of similar sizes.
文摘Understanding the evolution mechanisms of water-exit cavities and flow fields evolve during highintensity interactions between vehicles and floating ice is critical for advancing the application of submarine-launched marine equipment in low-temperature ice-prone waters.A computational fluid dynamics-finite element method(CFD-FEM) coupled framework was established to simulate bidirectional fluid-structure interactions during the water-exit process of a ventilated vehicle impacting ice in brash environments.Distinct evolution characteristics were revealed by comparatively analyzing the cavity,flow fields,hydrodynamic loading,structural deformation,and trajectory stability across three scenarios:ice-free,single-ice,and multi-ice.Furthermore,the position-dependent impact effects were characterized.The findings reveal that the impact,friction,and compression effects of ice induce bending and wrinkling of the shoulder cavity,aggravating its collapse and increasing the wetting of the vehicle,resulting in a substantial expansion of the high-velocity and vortex-dominated regions within the flow field,accompanied by more obvious water splashes.The impact of ice notably increases the kinetic energy dissipation of the vehicle during the cross-water stage and diminishes its motion stability.In the center-symmetric layout,the vehicle collides with ice only once,with high stress confined to the head.Conversely,the radial-offset layout causes secondary or even multiple collisions,resulting in high-stress areas on the shoulder of the vehicle,making it deflect and ultimately causing the tail cavity to tilt and become destabilized.The design of new vehicles suitable for ice-prone environments should focus on enhancing the impact toughness of the head structure and optimizing the surface shape design to improve the adaptability to low-temperature complex environments.
基金This work is supported by the National Natural Science Foundation of China(Grant No.52201385)the Natural Science Foundation of Shanxi Province(Grant No.20210302123023)the Shanxi Scholarship Council of China(Grant No.2020-106).
文摘A two-dimensional model,employing a dynamic mesh technology,is used to simulate numerically the transient multiphaseflowfield produced by two submerged parallel guns.After a grid refinement study ensuring grid inde-pendence,five different conditions are considered to assess the evolution of cavitation occurring in proximity to the gun muzzle.The simulation results show thatflow interference is enabled when the distance between the par-allel barrels is relatively small;accordingly,the generation and evolution of the vapor cavity becomes more com-plex.By means of the Q criterion for vorticity detection,it is shown that cavitation causes the generation of vorticity and the evolution of the vapor cavity can result in an asymmetric distribution of vorticity for a certain distance of the barrels.In particular,the evolution of the vapor cavity can hinder the expansion of the gas and force it toflow outward,while an asymmetric distribution of vorticity can lead to a gas jetflowing outward and rotating simultaneously.
基金supported by the Fujian Department of Education (No. JB08011)the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministrythe Doctoral Foundation of the Ministry of Education of China (No. 20070386002)
文摘The Bell-nonlocality of two initially entangled macroscopic fields in the double Jaynes-Cummings model is investigated. Moreover, the process by which detuning between the atomic transition frequency and the field frequency affects the evolution of the Beil-nonlocality of two macroscopic fields is studied. The effect of the disparitv between the two coupling strengths is discussed.
