Coherent structures and dynamics in a neutrally stratified planetary boundary layer flow

Coherent structures and the dynamics of a neutrally stratified planetary boundary layer flow are studied through a large eddy simulation, which includes surface roughness, Coriolis force, and a capping inversion. Quadrant analysis and flow visualization show that low‐speed negative momentum flux (ej...

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Bibliographic Details
Published in:Physics of fluids (1994) 1996-10, Vol.8 (10), p.2626-2639
Main Authors: Lin, Ching‐Long, McWilliams, James C., Moeng, Chin‐Hoh, Sullivan, Peter P.
Format: Article
Language:English
Subjects:
Computer simulation
Finite difference method
Flow visualization
Navier Stokes equations
Oscillations
Pressure
Statistical mechanics
Surface roughness
Velocity
Vortex flow
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Summary:Coherent structures and the dynamics of a neutrally stratified planetary boundary layer flow are studied through a large eddy simulation, which includes surface roughness, Coriolis force, and a capping inversion. Quadrant analysis and flow visualization show that low‐speed negative momentum flux (ejection) is the dominant feature throughout most of the boundary layer. The initiation of vortical structures is observed to be associated with vorticity sheets and pressure maxima, which are formed dynamically when low‐speed negative momentum flux collides with either high‐speed negative momentum flux (sweep) or the mean flow. Four dimensional conditional averages are used to study the statistical behavior of ejections and sweeps. The shape, strength, lifetime, and origin of the conditionally sampled structures at three different heights are discussed. Near the surface, sweeps are observed to induce ejections when colliding with the surface. The evolution of sweep‐induced ejections near the wall is discussed.
ISSN:1070-6631
1089-7666
DOI:10.1063/1.869048