[GTP] GTP MMM CGD seminar TODAY --ROOM CHANGE

[Silvia Gentile]

Hello,

The seminar has been moved to FL2- Main Auditorium

Thank you,

Silvia Gentile


>
>
> Subgrid Modelling for Geophysical Flows
>
> Jorgen Frederiksen
>
> CSIRO Marine and Atmospheric Research
>
> Subgrid-scale parameterisations with self similar scaling laws are 
> developed for large eddy simulations (LESs) of atmospheric flows. Both 
> stochastic and a deterministic representations of the effects of 
> subgrid-scale eddies on the retained scales are considered. The 
> stochastic subgrid model consists of a stochastic backscatter noise 
> term and a drain eddy viscosity while in the deterministic subgrid 
> model the net effect of these two terms is represented by a net eddy 
> viscosity.
>
> In both cases the subgrid transfers are calculated self consistently 
> from the statistics of higher resolution reference direct numerical 
> simulations (DNSs). The dependence of the subgrid parameterisations on 
> the resolution of the DNSs is determined for DNSs having resolutions 
> up to triangular 504 wavenumber truncations. The subgrid 
> parameterisations are developed for typical large-scale atmospheric 
> flows and for different strengths and spectra of kinetic energy within 
> a quasi-geostrophic spectral model. LESs using the stochastic and 
> deterministic subgrid parameterisations are shown to replicate the 
> kinetic energy spectra of the reference DNS at the scales of the DNSs. 
> It is found that the maximum strengths of the drain, net and 
> backscatter viscosities satisfy scaling laws dependent on the LES 
> truncation wavenumber and that the dependence of these eddy 
> viscosities on total wavenumber can also be written as essentially 
> universal functions that depend on flow strength and resolution. The 
> universal scaling laws make the subgrid-scale parameterisations more 
> generally applicable in LESs and remove the need to generate them from 
> reference DNSs. The applicability of the methodology for determining 
> subgrid-scale vertical velocity variations needed in cloud models is 
> posed.
>
> Presenter(s): Jorgen Frederiksen
> Type of event: Seminar/Symposium
> Building: Room: FL3-2072 MMM Conf Rm
> Time: 11:30 am
>