The classical momentum-blade element theory is improved by using the empirical formula while part of rotor blades enters into the turbulent wake state, and the performance of a horizontal-axis wind turbine (HAWT) at a...The classical momentum-blade element theory is improved by using the empirical formula while part of rotor blades enters into the turbulent wake state, and the performance of a horizontal-axis wind turbine (HAWT) at all speed ratios can be predicted. By using an improved version of the so-called secant method, the convergent solutions of the system of two-dimensional equations concerning the induced velocity factors a and a' are guaranteed. Besides, a solving method of multiple solutions for a and a' is proposed and discussed. The method provided in this paper can be used for computing the aerodynamic performance of HAWTs both ofrlow solidity and of high solidity. The calculated results coincide well with the experimental data.展开更多
The effect of uniform zonal winds on tropical cyclone(TC)genesis is examined on a beta plane using an idealized mesoscale model.The simulation results show that uniform easterly and westerly flows are both favorable f...The effect of uniform zonal winds on tropical cyclone(TC)genesis is examined on a beta plane using an idealized mesoscale model.The simulation results show that uniform easterly and westerly flows are both favorable for TC genesis.However,uniform easterly flows result in a faster TC genesis rate compared with uniform westerly flows.It is found that faster TC genesis is associated with greater surface heat fluxes and convection during the early stage.The superposition of uniform easterly flows and the beta effect results in greater surface heat fluxes and convection around the TC center compared with uniform westerly flows.Meanwhile,TC genesis is closely associated with the size and intensity of a mid-level circulation.The joint greater convection induced by the easterly flows and beta effect results in enhancement of the vertical temperature gradient,which is associated with the intensification of mid-level circulation.The strong and compact mid-level circulation is more favorable for efficient conversion of latent heat energy to the kinetic energy of the lower-level cyclonic winds.Thus,uniform easterly flows are more favorable for TC genesis than uniform westerly flows.展开更多
文摘The classical momentum-blade element theory is improved by using the empirical formula while part of rotor blades enters into the turbulent wake state, and the performance of a horizontal-axis wind turbine (HAWT) at all speed ratios can be predicted. By using an improved version of the so-called secant method, the convergent solutions of the system of two-dimensional equations concerning the induced velocity factors a and a' are guaranteed. Besides, a solving method of multiple solutions for a and a' is proposed and discussed. The method provided in this paper can be used for computing the aerodynamic performance of HAWTs both ofrlow solidity and of high solidity. The calculated results coincide well with the experimental data.
基金supported by the National Natural Science Foundation of China(Grant Nos.41505048,41461164005,41275001,41230527,and 41475074)
文摘The effect of uniform zonal winds on tropical cyclone(TC)genesis is examined on a beta plane using an idealized mesoscale model.The simulation results show that uniform easterly and westerly flows are both favorable for TC genesis.However,uniform easterly flows result in a faster TC genesis rate compared with uniform westerly flows.It is found that faster TC genesis is associated with greater surface heat fluxes and convection during the early stage.The superposition of uniform easterly flows and the beta effect results in greater surface heat fluxes and convection around the TC center compared with uniform westerly flows.Meanwhile,TC genesis is closely associated with the size and intensity of a mid-level circulation.The joint greater convection induced by the easterly flows and beta effect results in enhancement of the vertical temperature gradient,which is associated with the intensification of mid-level circulation.The strong and compact mid-level circulation is more favorable for efficient conversion of latent heat energy to the kinetic energy of the lower-level cyclonic winds.Thus,uniform easterly flows are more favorable for TC genesis than uniform westerly flows.
