University of Minnesota
Aerospace Engineering and Mechanics
Fall 1999 Seminar Series



Rotating Turbulence Forced Randomly at Small Scales


Prof. Leslie Smith

Department of Mathematics, University of Wisconsin


Abstract


Rotating turbulence is important in engineering and geophysical applications, and presents a challenge for turbulence modeling. We study the problem of rotating turbulence forced randomly at small scales by using direct numerical simulations in a triply periodic box. The implications of several new results will be discussed. First, weak small-scale forcing leads to the transfer of energy to scales larger than the forcing scale. This is in contrast to non-rotating 3D turbulence in which energy is transferred only to scales smaller than the forcing scale. Second, the large-scales motions are predominantly 2D, in the plane perpendicular to the rotation axis, in spite of the decoupling of these 2D motions at lowest order in weak turbulence theory. Third, the energy spectrum of the large-scale motions varies inversely with the cube of the wavelength, consistent with heuristic arguments based on dimensional analysis using the rotation rate as the only relevant parameter. Thus the transfer of energy to 2D large scales in forced, rotating 3D turbulence is distinctly different from a 2D inverse cascade characterized by an energy spectrum inversely proportional to the 5/3 power of the wavelength.

Friday, October 1, 1999
209 Akerman Hall
2:30-3:30 p.m.


Refreshments served after the seminar in 227 Akerman Hall.
Disability accomodations provided upon request.
Contact Kristal Belisle, Senior Secretary, 625-8000.