The effect of random waves on vertical plane turbulent jets is studied numerically and the mechanism behind the interaction of the jet and waves is analyzed. The large eddy simulation method is used and the σ-coordin...The effect of random waves on vertical plane turbulent jets is studied numerically and the mechanism behind the interaction of the jet and waves is analyzed. The large eddy simulation method is used and the σ-coordinate system is adopted. Turbulence is modeled by a dynamic coherent eddy model. The σ-coordinate transformation is introduced to map the irregular physical domain with a wavy free surface and an uneven bottom onto a regular computational domain. The fractional step method is used to solve the filtered Navier–Stokes equations. Results presented include the distribution of velocity, the decay law of the mean velocity along the jet axis, self-similar characteristics and volume flux per unit width. In particular, the role of coherent structures on the momentum transfer along the jet centerline and the jet instantaneous characteristics in JONSWAP waves are a special focus of this research. The numerical results obtained are of great theoretical importance in understanding the behavior of turbulent jets in random wave environments.展开更多
This paper presents a numerical study on the hydrodynamic behaviours of a round buoyant jet under the effect of JONSWAP random waves. A three-dimensional large eddy simulation （LES） model is developed to simulate th...This paper presents a numerical study on the hydrodynamic behaviours of a round buoyant jet under the effect of JONSWAP random waves. A three-dimensional large eddy simulation （LES） model is developed to simulate the buoyant jet in a stagnant ambient and JONSWAP random waves. By comparison of velocity and concentration fields, it is found that the buoyant jet exhibits faster decay of centerline velocity, wider lateral spreading and larger initial dilution under the wave effect, indicating that wave dynamics improves the jet entrainment and mixing in the near field, and subsequently mitigate the jet impacts in the far field. The effect of buoyancy force on the jet behaviours in the random waves is also numerically investigated. The results show that the wave effect on the jet entrainment and mixing is considerably weakened under the existence of buoyancy force, resulting in a slower decay rate of centerline velocity and a narrower jet width for the jet with initial buoyancy.展开更多
The comprehensive numerical simulation of the tower shadow effect on floating offshore wind turbines(FOWTs),an area less explored compared to fixed-bottom wind turbines,is presented in this study.The atmospheric bound...The comprehensive numerical simulation of the tower shadow effect on floating offshore wind turbines(FOWTs),an area less explored compared to fixed-bottom wind turbines,is presented in this study.The atmospheric boundary layer inflow and the joint north sea wave project random wave are used as the operating conditions for FOWT.The combination of computational fluid dynamics(CFD)software simulator for wind farm applications and turbine simulation tool OpenFAST is used to implement fluid-structure interaction calculations.The output power,platform motion,wake velocity deficit and vortex structures are analyzed to reveal the influence of the tower shadow effect on the FOWT.The results indicate that due to the fluctuation caused by the turbulent wind and the floating platform motion,the tower shadow effect of FOWT is less significant for its periodic power decay than that of fixed-bottom wind turbines.And according to the velocity deficit analysis,the influence area of the tower shadow effect on the wake is mainly in the near wake region.展开更多
基金supported by the National Natural Science Foundation of China (50679023, 50879019)Ph.D. Programs Foundation of Ministry of Education of China (20070294012)+2 种基金the National Science Fund for Distinguished Young Scholars (50925932)Outstanding Doctoral Dissertation Incubation Program of Hohai University (2010B18814)Qing Lan Project of Jiangsu Province, and 333 High-Level Talent Training Program of Jiangsu Province (2017-B08038)
文摘The effect of random waves on vertical plane turbulent jets is studied numerically and the mechanism behind the interaction of the jet and waves is analyzed. The large eddy simulation method is used and the σ-coordinate system is adopted. Turbulence is modeled by a dynamic coherent eddy model. The σ-coordinate transformation is introduced to map the irregular physical domain with a wavy free surface and an uneven bottom onto a regular computational domain. The fractional step method is used to solve the filtered Navier–Stokes equations. Results presented include the distribution of velocity, the decay law of the mean velocity along the jet axis, self-similar characteristics and volume flux per unit width. In particular, the role of coherent structures on the momentum transfer along the jet centerline and the jet instantaneous characteristics in JONSWAP waves are a special focus of this research. The numerical results obtained are of great theoretical importance in understanding the behavior of turbulent jets in random wave environments.
基金supported by the National Key Basic Research Program of the Ministry of Science and Technology of China(Grant No.2010CB429001)the Special Fund of State Key Laboratory of China(Grant No.2011585812)+2 种基金the Fundamental Research Funds for the Central Universities(Grant No.2011B05614)the 111 Project of the Ministry of Educationthe State Administration of Foreign Experts Affairs,China(Grant No.B12032)
文摘This paper presents a numerical study on the hydrodynamic behaviours of a round buoyant jet under the effect of JONSWAP random waves. A three-dimensional large eddy simulation （LES） model is developed to simulate the buoyant jet in a stagnant ambient and JONSWAP random waves. By comparison of velocity and concentration fields, it is found that the buoyant jet exhibits faster decay of centerline velocity, wider lateral spreading and larger initial dilution under the wave effect, indicating that wave dynamics improves the jet entrainment and mixing in the near field, and subsequently mitigate the jet impacts in the far field. The effect of buoyancy force on the jet behaviours in the random waves is also numerically investigated. The results show that the wave effect on the jet entrainment and mixing is considerably weakened under the existence of buoyancy force, resulting in a slower decay rate of centerline velocity and a narrower jet width for the jet with initial buoyancy.
基金supported by the Key Laboratory of Ministry of Education for Coastal Disaster and Protection,Hohai University(Grant No.J202202)the National Natural Science Foundation of China(Grant No.11872174)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.B200202236)the Key Laboratory of Port,Waterway&Sedimentation Engineering Ministry of Communications,PRC(Grant No.Yk220001-2).
文摘The comprehensive numerical simulation of the tower shadow effect on floating offshore wind turbines(FOWTs),an area less explored compared to fixed-bottom wind turbines,is presented in this study.The atmospheric boundary layer inflow and the joint north sea wave project random wave are used as the operating conditions for FOWT.The combination of computational fluid dynamics(CFD)software simulator for wind farm applications and turbine simulation tool OpenFAST is used to implement fluid-structure interaction calculations.The output power,platform motion,wake velocity deficit and vortex structures are analyzed to reveal the influence of the tower shadow effect on the FOWT.The results indicate that due to the fluctuation caused by the turbulent wind and the floating platform motion,the tower shadow effect of FOWT is less significant for its periodic power decay than that of fixed-bottom wind turbines.And according to the velocity deficit analysis,the influence area of the tower shadow effect on the wake is mainly in the near wake region.
