Open AccessAnalysis of Turbulent Characteristics of Sheared Convective Boundary Layer under Different Shear and Potential Temperature Gradients
Author(s) -
Anran Li,
Wenxian Lin,
Wenfeng Gao,
Tao Liu,
Yaowen Xia
Publication year - 2019
Publication title -
iop conference series. earth and environmental science
Language(s) - English
Resource type - Journals
eISSN - 1755-1307
pISSN - 1755-1315
DOI - 10.1088/1755-1315/300/3/032072
Subject(s) - convective boundary layer , entrainment (biomusicology) , buoyancy , boundary layer , turbulence , eddy , convection , mechanics , richardson number , mixed layer , temperature gradient , potential temperature , velocity gradient , shear (geology) , planetary boundary layer , physics , meteorology , geology , petrology , rhythm , acoustics
Effects of shear and potential temperature gradient on the formation mechanism and turbulence characteristics of the sheared convective boundary layer are studied through Large-Eddy Simulation (LES) experiments. Four cases with different velocity difference Δ U of 1.5ms −1 and 3.0ms −1 and different potential temperature gradient Γ θ of 0.006Km −1 and 0.015Km −1 were conducted in the horizontal homogeneous atmospheric convective boundary layer of 6000m × 6000m × 2000m. The results show that the formation of the entrainment layer is affected integratedly by the horizontal shear effect and the vertical buoyancy effect, in which turbulence shows strong anisotropy and intermittent characteristics, wherein the mixed layer is dominated by stable small eddies, and the entrainment layer by strip-shaped large eddies. Compared with the pure buoyancy boundary layer, the entrainment flux ratio A f is 0.176∼0.385, and the height of the entrainment layer z i is shifted to the side with bigger velocity ( U 2 ). Δ U promotes entrainment and Γ θ inhibits, especially for the upper limit of the entrainment layer h 2 . Obviously, the shear-shelter entrainment phenomenon appears under the weak shear and strong potential temperature gradient.