MMM SEMINAR NCAR
Rotor Dynamics in the Lee of
Three-Dimensional Ridges
James D. Doyle
Naval Research Laboratory
Mountain waves forced by elongated ridges are often accompanied by low-level vortices that have horizontal circulation axes parallel to the ridgeline. These horizontal vortices, known as rotors, can be severe aeronautical hazards and have been cited as contributing to numerous aircraft accidents. Mountain-wave induced rotors still remain poorly understood, particularly with respect to the three-dimensional aspects. In this study, the dynamics of rotors forced by three-dimensional topography are investigated through a series of high-resolution idealized simulations with the non-hydrostatic COAMPS model. The focus of this investigation is on the internal structure of rotors and specifically on the dynamics of small-scale intense circulations within rotors, referred to here as “sub-rotors”. The simulation results indicate that coherent sub-rotor circulations develop due to an instability of the horizontal vortex sheet along the leading edge of the “parent” rotor. The characteristics of the sub-rotor vortices as well as the mechanism for vortex intensification will be addressed.
Tuesday, June 1, 2004, 3:45
PM
NCAR-Foothills
Laboratory
3450 Mitchell Lane
Bldg 2, Rm 1022,
Auditorium