Publications

A comprehensive assessment is made of transient and asymptotic two-dimensional perturbation 
growth in compressible shear flow using unbounded constant shear and the Couette problem as 
examples. The unbounded shear flow example captures the essential...

The structure and dynamics of axisymmetric tornado-like vortices are explored with a numerical model of 
axisymmetric incompressible flow based on recently developed numerical methods. The model is first shown 
to compare favorably with previous results...

The effects of stochastically excited asymmetric disturbances on two-dimensional vortices are investigated. 
These vortices are maintained by the radial inflow of fixed cylindrical deformation fields, which are chosen so 
that both one-celled and two...

The dynamics of both transient and exponentially growing disturbances in two-dimensional vortices that are 
maintained by the radial inflow of a fixed cylindrical deformation field are investigated. Such deformation fields 
are chosen so that both one...

Classical stability theory is extended to include growth processes. The central role of the nonnormality of the linearized dynamical system in the stability problem is emphasized, and a generalized, stability theory is constructed that is applicable to...

An extension of classical stability theory to address the stability of perturbations to time-dependent systems is described. Nonormality is found to play a central role in determining the stability of systems governed by nonautonomous operators associated...

The physics of tropical cyclone formation is not well understood, and more is known about the mature hurricane than the formative mechanisms that produce it. It is believed part of the reason for this can be traced to insufficient upper-level atmospheric...

Explaining the growth of disturbances superimposed on mean flows is a central problem in meteorology. Most widely studied models of the development process involve perturbations to shear flows with shear restricted to the meridional direction. Recently...

Properly configured disturbances are known to be effective in transferring the kinetic energy of a mean shear slow to neutrally stable modal and nonmodal waves Consideration of perturbation energetics requires that such oriented against the mean shear...

the origin and growth to moderate amplitude of disturbances in shear slow had been traditionally ascribed to the linear modal instability of the flow. Recent work on initial value problems has suggested that nonmodal growth of perturbations may be of...