Velocity Spectra and Coherence Estimates in the Marine Atmospheric Boundary Layer
Autor: | Jasna Bogunovic Jakobsen, Etienne Cheynet, Joachim Reuder |
---|---|
Rok vydání: | 2018 |
Předmět: |
Physics
Atmospheric Science 010504 meteorology & atmospheric sciences Turbulence Planetary boundary layer Marine atmospheric boundary layer 01 natural sciences Power law 010305 fluids & plasmas Computational physics Physics::Fluid Dynamics Velocity spectrum Eddy Anemometer 0103 physical sciences Atmospheric instability Coherence (signal processing) Exponential decay Coherence Physics::Atmospheric and Oceanic Physics 0105 earth and related environmental sciences |
Zdroj: | Boundary-Layer Meteorology 429–460 |
ISSN: | 1573-1472 0006-8314 |
Popis: | Two years of continuous sonic anemometer measurements conducted in 2007 and 2008 at the FINO1 platform are used to investigate the characteristics of the single- and two-point velocity spectra in relation to the atmospheric stability in the marine atmospheric boundary layer. The goals are to reveal the limits of current turbulence models for the estimation of wind loads on offshore structures, and to propose a refined description of turbulence at altitudes where Monin–Obukhov similarity theory may be limited. Using local similarity theory, a composite spectrum model, combining a pointed and a blunt model, is proposed to describe the turbulence spectrum for unstable, neutral and stable conditions. Such a model captures the $$-1$$ power law followed by the velocity spectra at an intermediate frequency range in the marine atmospheric boundary layer. For the Monin–Obukhov similarity parameter $$\zeta < 0.3$$ , the Davenport coherence model captures the vertical coherence of the horizontal velocity components well. A two-parameter exponential decay function is found more appropriate for modelling the coherence of the vertical velocity component. Under increasingly stable conditions, the size of the eddies in the vertical coordinate reduces, such that smaller separation distances than that covered in the present dataset may be required to study the coherence with sufficient accuracy. |
Databáze: | OpenAIRE |
Externí odkaz: | |
Nepřihlášeným uživatelům se plný text nezobrazuje | K zobrazení výsledku je třeba se přihlásit. |