Wind turbine blades are inevitable to be eroded in wind-sand environment,so it is crucial to identify the flow conditions under which the erosion happens.Here,the effect of the sand diameter on wind turbine airfoil is...Wind turbine blades are inevitable to be eroded in wind-sand environment,so it is crucial to identify the flow conditions under which the erosion happens.Here,the effect of the sand diameter on wind turbine airfoil is first investigated.When the sand diameter is less than 3μm,the sands will bypass the airfoil and no erosion occurs.When the sand diameter is larger than 4μm,the sand grains collide with the airfoil and the erosion happens.Thus,there must be a critical sand diameter between 3μm and 4μm,at which the erosion is initiated on the airfoil surface.To find out this critical value,aparticle Stokes number is introduced here.According to the range of the critical sand diameter mentioned above,the critical value of particle Stokes number is reasonably assumed to be between 0.007 8and 0.014.The assumption is subsequently validated by other four factors influecing the erosion,i.e.,the angle of attack,relative thickness of the airfoil,different series airfoil,and inflow velocity.Therefore,the critical range of Stokes number has been confirmed.展开更多
We calculate the quark number susceptibility （QNS） around the chiral critical end point （CEP）. The CEP is found to be located at （μc,Tc）= （80 MeV, 148 MeV） where μc and Tc are the critical chemical potential...We calculate the quark number susceptibility （QNS） around the chiral critical end point （CEP）. The CEP is found to be located at （μc,Tc）= （80 MeV, 148 MeV） where μc and Tc are the critical chemical potential and temperature, respectively. The QNS is found to have the highest and sharpest peak at the CEP. It is also found that, when the chemical potential μ is in the range of 60MeV≤ μ ≤ 110MeV, the QNS near the transition temperature is larger than the free field result, which indicates that the space-like damping mode dominates the degree of freedom of motion near the CEP.展开更多
A large eddy simulation of wall-adapting local eddy-viscosity model(LES-WALE)is used to simulate the threedimensional flow around a circular cylinder with a diameter of 0.25 m from sub-critical to super-critical Reyno...A large eddy simulation of wall-adapting local eddy-viscosity model(LES-WALE)is used to simulate the threedimensional flow around a circular cylinder with a diameter of 0.25 m from sub-critical to super-critical Reynolds numbers at 1×10^(5),2.5×10^(5),and 7.2×10^(5),respectively.The present results such as drag crisis,surface pressure distribution,and Strouhal number are in good agreement with the classical experimental data.When entering the critical region,a small plateau was found on the pressure distribution curves,corresponding to the appearance of laminar separation bubbles,and the separation point is delayed and the recirculation bubbles become narrowed and shortened.The tangential velocity of the cylinder surface changes from positive to negative at the separation point.The instantaneous vorticity and timeaveraging separation bubbles embody an unstable feature.Within the separation bubble,the pressure varies dramatically with time,but not with position.The surface pressure fluctuates greatly after the laminar separation bubble appears,and it is gradually stabilized until the basic pressure is reached.The process of laminar separation,transition from laminar flow to turbulent flow and turbulent reattachment is also shown.The three-dimensional Q criterion of vortex structure and the two-dimensional spanwise vorticity reveal the phenomenon that the wake structure narrows with the increase of the Reynolds number.展开更多
基金supported partly by the National Basic Research Program of China(″973″Program)(No.2014CB046201)the National Natural Science Foundation of China(No.51166009)+4 种基金the National High Technology Research and Development Program of China(No.2012AA052900)the Natural Science Foundation of Gansu ProvinceChina(No.1308RJZA283145RJZA059)the Gansu Province University Scientific Research ProjectChina(No.2013A-026)
文摘Wind turbine blades are inevitable to be eroded in wind-sand environment,so it is crucial to identify the flow conditions under which the erosion happens.Here,the effect of the sand diameter on wind turbine airfoil is first investigated.When the sand diameter is less than 3μm,the sands will bypass the airfoil and no erosion occurs.When the sand diameter is larger than 4μm,the sand grains collide with the airfoil and the erosion happens.Thus,there must be a critical sand diameter between 3μm and 4μm,at which the erosion is initiated on the airfoil surface.To find out this critical value,aparticle Stokes number is introduced here.According to the range of the critical sand diameter mentioned above,the critical value of particle Stokes number is reasonably assumed to be between 0.007 8and 0.014.The assumption is subsequently validated by other four factors influecing the erosion,i.e.,the angle of attack,relative thickness of the airfoil,different series airfoil,and inflow velocity.Therefore,the critical range of Stokes number has been confirmed.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11105122,11275097 and 11475085the Foundation of Graduate School of Nanjing University under Grant No 2014CL02
文摘We calculate the quark number susceptibility （QNS） around the chiral critical end point （CEP）. The CEP is found to be located at （μc,Tc）= （80 MeV, 148 MeV） where μc and Tc are the critical chemical potential and temperature, respectively. The QNS is found to have the highest and sharpest peak at the CEP. It is also found that, when the chemical potential μ is in the range of 60MeV≤ μ ≤ 110MeV, the QNS near the transition temperature is larger than the free field result, which indicates that the space-like damping mode dominates the degree of freedom of motion near the CEP.
基金The National Natural Science Foundation of China(Grant Nos.12172218 and 52088102)Joint Funds of the National Natural Science Foundation of China(Grant No.U19B2013).
文摘A large eddy simulation of wall-adapting local eddy-viscosity model(LES-WALE)is used to simulate the threedimensional flow around a circular cylinder with a diameter of 0.25 m from sub-critical to super-critical Reynolds numbers at 1×10^(5),2.5×10^(5),and 7.2×10^(5),respectively.The present results such as drag crisis,surface pressure distribution,and Strouhal number are in good agreement with the classical experimental data.When entering the critical region,a small plateau was found on the pressure distribution curves,corresponding to the appearance of laminar separation bubbles,and the separation point is delayed and the recirculation bubbles become narrowed and shortened.The tangential velocity of the cylinder surface changes from positive to negative at the separation point.The instantaneous vorticity and timeaveraging separation bubbles embody an unstable feature.Within the separation bubble,the pressure varies dramatically with time,but not with position.The surface pressure fluctuates greatly after the laminar separation bubble appears,and it is gradually stabilized until the basic pressure is reached.The process of laminar separation,transition from laminar flow to turbulent flow and turbulent reattachment is also shown.The three-dimensional Q criterion of vortex structure and the two-dimensional spanwise vorticity reveal the phenomenon that the wake structure narrows with the increase of the Reynolds number.
