Session 6A.3 Stably stratified boundary layer simulations with a non-local closure model

Tuesday, 10 June 2008: 11:00 AM
Aula Magna Vänster (Aula Magna)
N. M. Colonna, Università del Piemonte Orientale, Alessandria, Italy; and E. Ferrero and U. Rizza

Presentation PDF (210.8 kB)

Simulations of stable boundary layer are nowadays essential in describing many geophysical flows both in the atmosphere and the ocean.

Reynolds Averaged Navier-Stokes (RANS) models have been largely developed in the last years for shear driven and buoyancy

driven buondary layer, while in the SBL RANS models performances are not yet completely assessed. In the present work a third-order

turbulence model is used to study the stable boundary layer (SBL).

The simulated case reproduces a flow over a flat surface in horizontally homogeneous

conditions. The simulation is carried out cooling from below the boundary layer at a constant and uniform rate

switched on at the initial time. The newness consists in the fact that turbulence in SBL is generally

considered local (at least as first approximation) while our model, resolving the third order moments (TOMs) dynamical equations, accounts

for the non-local transport which, as assessed in several previous works, is generally essential in describing the turbulence flows.

The model employed for the simulation has been tested and validate for shear driven and buoyancy driven boundary layers. The model solves dynamical equations for all

the moments up to the TOMs (following Canuto 1992 [1]) and the Quasi-Normal approximation, with a proper correction (proposed by us in a previous work [2]) to correctly damp

the TOMs, is adopted to close the fourth order moments (FOMs).

Here we present the comparison between our TOM model results and LES in the SBL. Furthermore the TOM model results are compared with the results of a SOM

model in order to verify the effective improvement apported by including the TOMs in the model. The general agreement is satisfactory.

[1] V.M. Canuto, "Turbulent convection with overshooting: Reynolds stress approach", Astroph. J. vol. 392, pp 218-232, 1992.\\

[2] E.Ferrero and N.M. Colonna, "Non local treatment of the buoyancy- shear-driven boundary layer", J. Atmos. Sci. vol. 63, pp 2653-2662, 2006.

- Indicates paper has been withdrawn from meeting
- Indicates an Award Winner