Brunt-Väisälä Oscillations

This numerical experiment consists in the study of the internal gravity waves generated by the free oscillations of an entropy bubble in an isothermal atmosphere.

We start the DNS by putting an entropy bubble in hydrostatic equilibrium using the following initial condition for the entropy in the 'start.in' file:

init_ss = 'blob_hs'

The bubble then oscillates and generates internal waves whom the eigenfrequencies can be found analytically for an isothermal atmosphere (e.g. Dintrans & Brandenburg 2004):









Questions:

• Change the sound speed value in order to change the density ratio across the layer (use the Python subroutines 'init.py' to plot the initial setup and 'pvid.py' for animations). How the mode and spectrum evolve with increasing H? Compare with the analytical eigenvectors (use the Python subroutines 'fourier.py' and 'profile'.py).
• Study the influence of the viscosity on the vertical momentum evolution (use the Python subroutine 'peaks.py').
• Change the aspect ratio of the box. How the kinetic energy spectrum is evolving with larger boxes?





References

Dintrans, B., & Brandenburg, A. 2004, Identification of gravity waves in hydrodynamical simulations, A&A, 421, 775 (astro-ph/0311094)

Numerical Experiments homepage

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$Date: 2009-04-27 12:22:29 $, $Author: pc $, $Revision: 1.11 $