Affiliation:
1. School of Civil Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China
Abstract
Based on the synchronous multi-point temperature data measured at different streamwise positions with the application of distributed temperature sensing, a field investigation on the applicability of Taylor's frozen hypothesis and elliptic model was performed in the atmospheric surface layer (ASL). In this work, several important spatial statistical functions of temperature field, such as longitudinal space–time correlation [ CTT( r, t)], space correlation [ RTT( r)], normalized second-order structure function [[Formula: see text]], and wavenumber spectrum [ ΦTT( k)] of temperature fluctuations, were directly measured in the ASL. By comparing the directly measured spatial statistical functions with the predicted results, our study indicates that both Taylor's frozen hypothesis and elliptic model are applicable in the near-neutral and stable ASLs when the turbulence level is low. However, only the elliptic model is substantially accurate in the unstable ASL when the turbulence level is high. The elliptic model can relate CTT( r, t) to RTT( rE), where rE = [( r− Ueτ)2+( Veτ)2]1/2, Ue is the convection velocity, and Ve is the sweeping velocity. With the application of Ue and Ve, RTT( r) and [Formula: see text] can be estimated by the elliptic model in the near-neutral, unstable, and stable ASLs.
Funder
National Natural Science Foundation of China
Subject
Condensed Matter Physics,Fluid Flow and Transfer Processes,Mechanics of Materials,Computational Mechanics,Mechanical Engineering