Dr. Neil Balmforth

Stratified shear flow:

Kolmogorov flow is a simple type of shear flow with sinusoidal form. The special form of the shear flow allows quite a bit of analytical insight into this problem, which presumably led Kolmogorov to originally advocate the flow as a theoretical laboratory to study shear dynamics and the transition to turbulence. Some of the papers below record our efforts to look at the stratified version of the problem in which inverse cascade and layering play a role.

Another artifice for studying stratified shear instability is the "defect approximation" wherein sharp changes in vorticity and density are embedded within a linearly unstratified shear. The Kelvin-Helmholtz, Holmboe and Taylor-Caulfield instabilities are all captured within the defect formulation; sample movies are given below.

My collaborators in this work include Jeff Carpenter, Colm Caulfield, Tom Eaves, Greg Lawrence and Yuan-Nan Young.

Click to enlarge or play




Kelvin-Helmholtz instability in a stratified defect
Holmboe instability in a stratified defect
Taylor-Caulfield instability in a stratified defect
Stratified Kolmogorov flow I
Stratified Defects

Stratified Kolmogorov flow II
Forced baroclinic critical layers
Modal classification
Taylor-Caulfield Instability
Forced baroclinic critical layers II

Holmboe waves in a stratified defect
Catastrophic secondary instability of a TC billow

Department of Mathematics / Fluid Labs / Neil Balmforth / Research Interests