Direct Numerical Simulations of Very Stable Atmospheric Boundary Layers
Final rept. 6 May 2008-5 May 2011
WASHINGTON UNIV SEATTLE OFFICE OF SPONSORED PROGRAMS
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The objective of the research is to address a number of outstanding issues related to very stable atmospheric boundary layers, including criteria for the collapse of the turbulence, the intermittent behavior and the strong anisotropy of turbulence, horizontal dispersion and meandering of plumes, and the local scaling of the velocities in terms of predictable or measurable parameters. The approach to the research is direct numerical simulation of stably stratified Ekman boundary layers. Very high resolution, three-dimensional, time-dependent simulations are carried out on computational grids of the order of 1,000 grid points in each spatial direction,using highly accurate spectral and compact numerical methods. The results of these simulations permit a complete statistical description of velocities, Reynolds stresses, and other terms in the energy budgets. The effect of stratification on the length-scales of the flow is investigated using horizontal spectra of various important dynamical quantities. The detailed information from the DNS allows the use of conditional sampling to compute the statistical properties of turbulent patches, as well as to identify their sources internal waves, low-level jets, etc.. Finally, the simulation results will also be useful as a guide to field measurements, and to perform a priori tests of turbulence models.
- Numerical Mathematics
- Fluid Mechanics