Abstract
The cross-spectral phases between velocity components at two heights are analyzed from observations at the Høvsøre test site under diabatic conditions. These phases represent the degree to which turbulence sensed at one height leads (or lags) in time the turbulence sensed at the other height. The phase angle of the cross-wind component is observed to be significantly greater than the phase for the along-wind component, which in turn is greater than the phase for the vertical component. The cross-wind and along-wind phases increase with stream-wise wavenumber and vertical separation distance, but there is no significant change in the phase angle of vertical velocity. The phase angles for all atmospheric stabilities show similar order in phasing. The phase angles from the Høvsøre observations under neutral condition are compared with a rapid distortion theory model which show similar order in phase shift.
Highlights
The structure of atmospheric turbulence can be analysed in terms of two-point statistics such as normalized cross-spectra, which are typically studied both experimentally and theoretically as a function of horizontal separation distance for homogeneous turbulence in the atmospheric surface-layer [1, 2]
In addition to the observations, we evaluate the phase angles from the Mann spectral tensor model [2] which incorporates rapid distortion theory (RDT) [13, 14]
The phase angles for neutral atmospheric boundary layer (ABL) are studied and compared with the RDT and LES model in Chougule el al. [5], where the winds at Høvsøre are selected from east
Summary
The structure of atmospheric turbulence can be analysed in terms of two-point statistics such as normalized cross-spectra ( known as coherences), which are typically studied both experimentally and theoretically as a function of horizontal separation distance for homogeneous turbulence in the atmospheric surface-layer [1, 2]. Chougule et al [5] studied the vertical phase angles for all three velocity components (i.e. φu , φv and φw ), including their behavior in the neutral, horizontally homogeneous atmospheric boundary layer (ABL) using measurement from Høvsøre and Cooperative Atmosphere-Surface. Heidrick et al [8] experimentally studied the phases of the axial velocity component in fully developed pipe flow using measurements taken at two different points, where the separation vector was oriented at different angles to the mean flow. Komori et al [9]
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