摘要
通过对杭州湾南北两侧共四个观测点近地层湍流特征分析发现:①湍流强度随风速增大而减小。低风速时,几乎与风速呈反比,高风速时基本保持为常数。可描述为:U≤U_0时,I_k=mk/U;U>U_0时,I_k=n_K。其中n_k=a_k/ln(z/z_0),mk=a_kU_0/ln(z/z_0)。a_x=1.0,ay=0.8,a_z=0.5。海岸附近,U_0=4m/s,深入内陆1.5千米以后,U_0=3m/s。②u_*/U=k/ψ(z/L)的 Businger 模式在海岸附近与观测结果吻合很好,在内陆,-1.0≤z/L≤0.3时二者吻合较好,在此范围以外,偏离较大。③不稳定条件下,水平风速标准差可用(?)描述,垂直风速标准差可用(?)描述。稳定条件下,可用(?)(?)描述。此外,稳定条件下,有σ_w/σ_u=0.48,σ_w/σ_v=0.59;不稳定条件下有σ_w/σ_u=0.53,σ_w/σ_v=O.67。
By analysing the data gathered in surface layer nearChinese eastern coastal region,it is found that:(1)The turbulence intensity is decreasing with wind speed increa-sing.At lower speed,it is inversely proportional to the wind speed,but at higher speed,it is basically a constant.It can be described bythe equations: I_k=m_k/U at U≤_U_o;I_k=n_k at U>U_o where n_k=α_k/ln(z/z_o)m_k=a_kU_o/ln(z/z_o),a_x=1.0,a_y=0.8,a_z=0.5,U_o=4m/s near coastlineand U_0=3m/s when the distance is larger than 1.5km.(2)The observed values of (?)/U near coastline is fitted very wellto the results predicted by Businger's(1971)model (?)/U=k/Ψ(z/L),describing the wind speed profile in the surface layer.On the land 1.5kmand farther from the coast,both observed and predicted results are fittedvery well in range—1.0≤z/L≤0.3,but they are deviant outside this range.(3) Under the unstable condition,the standard deviations ofhorizontal wind speeds can be described by(?),that of vertical wind speed,(?).Under stablecondition,they can be described by(?). It isalso found that σ_w/σ_u and σ_w/σ_v are basically constant regardless of thestabilities,but the average values show little different for the stablecondition and unstable condition.Under unstable condition,σ_w/σ_u=0.53,σ_w/σ_u=0.67;under stable condition,σ_w/σ_u=0.48,σ_w/σ_v=0.59.
关键词
湍流
特征
强度
风速标准差
turbulence characteristics
turbulence intensity
wind speed deviation
friction speed
turbulence in surface layer
