Many species of fish and birds travel in intermittent style,yet the combined influence of intermittency and other body kinematics on the hydrodynamics of a self-propelled swimmer is not fully understood.By formulating...Many species of fish and birds travel in intermittent style,yet the combined influence of intermittency and other body kinematics on the hydrodynamics of a self-propelled swimmer is not fully understood.By formulating a reduced-order dynamical model for intermittent swimming,we uncover scaling laws that link the propulsive performance(cursing Reynolds number Rec,thrust T̄,input power P̄and cost of transport COT to body kinematics(duty cycle DC,flapping Reynolds number Ref).By comparing the derived scaling laws with the data from several previous studies and our numerical simulation,we demonstrate the validity of the theory.In addition,we found that Re_(c),T̄,P̄and COT all increase with the increase of DC,Ref.The model also reveals that the intermittent swimming may not be inherently more energy efficient than continuous swimming,depending on the ratio of drag coefficients between active bursting and coasting.展开更多
The dwell effect of the material can reduce the fatigue lives of titanium alloys at room temperature. A unified fatigue life prediction method developed by the authors＇ group is modified in this paper to predict dwel...The dwell effect of the material can reduce the fatigue lives of titanium alloys at room temperature. A unified fatigue life prediction method developed by the authors＇ group is modified in this paper to predict dwell-fatigue crack growth taking into account the effects of dwell time and maximum stress. The modified model can be successfully used to predict the crack growth rate and calculate the fatigue life of different titanium alloys under pure fatigue and dwell-fatigue conditions. It is validated by comparing prediction results with the experimental data of several titanium alloys with different microstructures, dwell time, hydrogen contents, stress ratios and stress levels.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2022YFC2805200)the National Natural Science Foundation of China(Grant No.12102365)supported by the Startup Funding of New-joined PI of Westlake University(Grant Nos.041030150118,103110556022101),the Scientific Research Funding Project of Westlake University(Grant No.2021WUFP017).
文摘Many species of fish and birds travel in intermittent style,yet the combined influence of intermittency and other body kinematics on the hydrodynamics of a self-propelled swimmer is not fully understood.By formulating a reduced-order dynamical model for intermittent swimming,we uncover scaling laws that link the propulsive performance(cursing Reynolds number Rec,thrust T̄,input power P̄and cost of transport COT to body kinematics(duty cycle DC,flapping Reynolds number Ref).By comparing the derived scaling laws with the data from several previous studies and our numerical simulation,we demonstrate the validity of the theory.In addition,we found that Re_(c),T̄,P̄and COT all increase with the increase of DC,Ref.The model also reveals that the intermittent swimming may not be inherently more energy efficient than continuous swimming,depending on the ratio of drag coefficients between active bursting and coasting.
基金financially supported by Youth Foundation of Jiangsu Province‘‘Study on the time-scale crack growth rate model used in fatigue life assessment of pressure hull of deep-sea submersibles’’(No.BK2012095)the National Natural Science Foundation of China(Nos.51109100 and 51439004)+1 种基金the National Natural Science Foundation for Young Scholars of China(No.E091002/51109101)the Shanghai Committee of Science and Technology Projects(Nos.14DZ1205500 and 14DZ2250900)
文摘The dwell effect of the material can reduce the fatigue lives of titanium alloys at room temperature. A unified fatigue life prediction method developed by the authors＇ group is modified in this paper to predict dwell-fatigue crack growth taking into account the effects of dwell time and maximum stress. The modified model can be successfully used to predict the crack growth rate and calculate the fatigue life of different titanium alloys under pure fatigue and dwell-fatigue conditions. It is validated by comparing prediction results with the experimental data of several titanium alloys with different microstructures, dwell time, hydrogen contents, stress ratios and stress levels.
