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Stably stratified airflow over a waved water surface. Part 1: Stationary turbulence regime
Author(s) -
Druzhinin O. A.,
Troitskaya Y. I.,
Zilitinkevich S. S.
Publication year - 2015
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.2677
Subject(s) - turbulence , dimensionless quantity , mechanics , boundary layer , physics , shear velocity , length scale , meteorology
Stably stratified turbulent boundary‐layer flows over both a waved water surface and a flat smooth surface are investigated through direct numerical simulation ( DNS ) for the bulk R eynolds numbers, Re , from 15000 to 80000. DNS expose the following basic properties of the flow. A statistically stationary turbulent regime is sustained if the turbulent R eynolds number, Re L , based on the Obukhov length‐scale and friction velocity, is larger than 10 2 . At Re L < 10 2 , turbulence over a flat surface degenerates completely, but over a waved surface it survives in the form of residual fluctuations, which are weaker for smaller wave slopes. In the stationary turbulent regime, at Re L > 10 2 , vertical profiles of the mean‐flow velocity and temperature have a log‐linear shape, as predicted by the M onin‐ O bukhov similarity theory, with the same empirical dimensionless constants as in laboratory and field experiments. The velocity and temperature roughness lengths, vertical turbulent fluxes of momentum and heat, and root mean square turbulent velocity and temperature fluctuations increase with increasing slope of the surface waves. At the same time, vertical profiles of the mean velocity and temperature keep the self‐similar shape predicted by the M onin– O bukhov theory, irrespective of the wave slope.