1. HOW AESOP GOT A SUNTAN A fractured fairy tale (with apologies to the producers of the Rocky and Bullwinkle show)
The cast of this episode: Oliver Fringer and Bob Street
Environmental Fluid Mechanics Laboratory at Stanford University
Synopsis:
The context and collaborators
The tools and some pretty pictures
Some thoughts on our work plan
8 March 2005

2. Jim McWilliams, Sasha Shchepetkin, Yulia Kanarska,
The context: we are participating in AESOP and in NLIWI.
Our overall goals include collaboration with UCLA to support the continuing development of our models, SUNTANS and ROMS; their coupling; and the scientific issues to be set forth by the ONR NLIWI and AESOP DRI experiments.
Our collaborators:
Jim McWilliams, Sasha Shchepetkin, Yulia Kanarska,
UCLA

3. Our Tools
SUNTANS - a free-surface NS simulation code for the coastal ocean. Currently implemented for Monterey Bay applications.
LES - tools for the large-eddy simulation of the flows, including subfilter models that parameterize the unresolved motions.

4. SUNTANS Overview SUNTANS: Stanford Unstructured Nonhydrostatic
Terrain-following
Adaptive (not yet)
Navier-Stokes
Simulator
Parallel computing
Large-eddy simulation

5. High-resolution simulations must be nonhydrostatic
Doman size: 0.8 m by 0.1 m (grid: 400 by 100)

6. Simulation results using 500 m grid + MY2.5
north-south velocity contours. Max velocity = 5 cm/s

7. Along-canyon generation sites
Comparison of results to measurements
Of Petruncio, et al. (1998,2002)

8. Cross-canyon generation sites
Comparison of results to measurements
Of Lien and Gregg (2001)

9. LES Overview
Work based on decomposition of flow into resolved and subfilter motions by spatial filtering. Subfilter scales are further separated into
resolved subfilter scales [computational grid size is at least a factor of 2 smaller than spatial filter size]. Highly accurate representation possible; facilitates energy transfer to and from large scales.
subgrid scales. These must be modeled.
These ideas have been proven and are being introduced in to SUNTANS. SUNTANS currently employs a RANS approach with, e.g., Mellor-Yamada 2.5 closure.

10. RSFS and SGS scale partitioning
Resolved scales
Well-resolved
Resolved subfilter scales (RSFS)
Can be reconstructed
Subgrid scales (SGS)
Must be modeled
Numerical Errors (NE)
Limit reconstruction

11. Improvements near the wall as applied to a neutral boundary layer in the atmosphere.
Smagorinsky
Dynamic eddy viscosity
+ Near-wall model
Dynamic reconstruction
+ Near-wall model
Log law

12. Thoughts on contributions to DRI
High-resolution nonhydrostatic modeling of Monterey Bay (up to 10 m resolution) can be made available, i.e., simulation of scales from regional to those at which mixing takes place.
Simulated cruise tracks
Prediction and refinement via direct comparison to actual cruise tracks
Basis for evaluation of coarser resolution simulations and their parameterizations.
Boundary forcing for domains of simulators working on small scales.
Evaluation of RANS and LES turbulence models [ours and those of others] at submesoscale [100 m and up resolutions].
Nesting of SUNTANS into ROMS and follow-up simulations to assess value of high resolution in specific areas and how that impacts submesoscale parameterizations.