The thermodynamic state of the tropical atmosphere plays an important role in the development of tropical cyclone(TC)intensity.This study reports new results that demonstrate a negative association between eastern Pac...The thermodynamic state of the tropical atmosphere plays an important role in the development of tropical cyclone(TC)intensity.This study reports new results that demonstrate a negative association between eastern Pacific TC intensity in offshore regions and dust aerosol optical depth(AOD)for the years 1980–2019.At the same time,a negative response of cloud water in the lower troposphere to dust AOD is reported by analyzing MERRA-2 reanalysis data and GCM simulations from CMIP6.This response can be explained by the dust semi-direct effect,in which dust aerosols absorb solar radiation,promoting the evaporation of clouds.In principle,this aerosol-driven vaporization modification could affect the enthalpy of the air surrounding a TC.Using potential intensity theory,the authors demonstrate that change in TC intensity related to dust AOD conditions is a consequence of the anomalous enthalpy of the air surrounding a TC caused by the dust semi-direct effect.展开更多
This paper reviews the development of forced motion apparatuses(FMAs) and their applications in wind engineering. A kind of FMA has been developed to investigate nonlinear and nonstationary aerodynamic forces consider...This paper reviews the development of forced motion apparatuses(FMAs) and their applications in wind engineering. A kind of FMA has been developed to investigate nonlinear and nonstationary aerodynamic forces considering the coupled effects of multiple degrees of freedom(DOFs). This apparatus can make section models to vibrate in a prescribed displacement defined by a numerical signal in time domain, including stationary and nonstationary movements with time-variant amplitudes and frequencies and even stochastic displacements. A series of validation tests show that the apparatus can re-illustrate various motions with enough precision in 3 D coupled states of two linear displacements and one torsional displacement. To meet the requirement of aerodynamic modeling, the flutter derivatives of a box girder section are identified, verifying its accuracy and feasibility by comparing with previously reported results. By simulating the nonstationary vibration with time-variant amplitude, the phenomena of frequency multiplication and memory effects are examined. In addition to studying the aerodynamics of a bluff body under large amplitudes and nonstationary vibrations, some potential applications of the proposed FMA are discussed in vehicle-bridge-wind dynamic analysis, pile-soil interaction, and line-tower coupled vibration aerodynamics in structural engineering.展开更多
基金This work was supported by National Natural Science Foundation of China[grant numbers 41675062 and 41375096]the Research Grants Council of the Hong Kong Special Administrative Region,China[project numbers CityU 11306417 and 11335316].
文摘The thermodynamic state of the tropical atmosphere plays an important role in the development of tropical cyclone(TC)intensity.This study reports new results that demonstrate a negative association between eastern Pacific TC intensity in offshore regions and dust aerosol optical depth(AOD)for the years 1980–2019.At the same time,a negative response of cloud water in the lower troposphere to dust AOD is reported by analyzing MERRA-2 reanalysis data and GCM simulations from CMIP6.This response can be explained by the dust semi-direct effect,in which dust aerosols absorb solar radiation,promoting the evaporation of clouds.In principle,this aerosol-driven vaporization modification could affect the enthalpy of the air surrounding a TC.Using potential intensity theory,the authors demonstrate that change in TC intensity related to dust AOD conditions is a consequence of the anomalous enthalpy of the air surrounding a TC caused by the dust semi-direct effect.
基金supported by the National Key Research and Development Program of China(Nos.2018YFC0809600 and 2018YFC0809604)the National Natural Science Foundation of China(No.51678451)the Independent Subject of State Key Laboratory of Disaster Reduction in Civil Engineering(No.SLDRCE19-B-11),Tongji University,China。
文摘This paper reviews the development of forced motion apparatuses(FMAs) and their applications in wind engineering. A kind of FMA has been developed to investigate nonlinear and nonstationary aerodynamic forces considering the coupled effects of multiple degrees of freedom(DOFs). This apparatus can make section models to vibrate in a prescribed displacement defined by a numerical signal in time domain, including stationary and nonstationary movements with time-variant amplitudes and frequencies and even stochastic displacements. A series of validation tests show that the apparatus can re-illustrate various motions with enough precision in 3 D coupled states of two linear displacements and one torsional displacement. To meet the requirement of aerodynamic modeling, the flutter derivatives of a box girder section are identified, verifying its accuracy and feasibility by comparing with previously reported results. By simulating the nonstationary vibration with time-variant amplitude, the phenomena of frequency multiplication and memory effects are examined. In addition to studying the aerodynamics of a bluff body under large amplitudes and nonstationary vibrations, some potential applications of the proposed FMA are discussed in vehicle-bridge-wind dynamic analysis, pile-soil interaction, and line-tower coupled vibration aerodynamics in structural engineering.
