Alexis Kaminski

About me:

I am a postdoctoral research associate in the Ocean Mixing Group at the College of Earth, Ocean, and Atmospheric Sciences at Oregon State University, working with Bill Smyth. My research interests lie in the area of geophysical fluid dynamics, in particular the stability of stratified shear flows and internal waves and how these flows transition to turbulence and mix the background stratification.

My current work focuses on studying transition to turbulence and mixing in stratified shear flows via high-resolution direct numerical simulations of shear instabilities. Our simulations are inspired by oceanic observations of turbulence and mixing; in particular, we are interested in how ambient turbulence (frequently present in geophysical flows but often neglected in theoretical investigations) might affect the evolution of shear instabilities. The numerical simulations will then be compared to the observations with the aim of improving understanding of the turbulent mixing and developing better parameterizations of turbulent fluxes for large-scale models.

In addition, I am a regular participant in the Woods Hole summer geophysical fluid dynamics program, and in September 2017 I participated in a research cruise as part of the ONR Inner Shelf project.

Education:

PhD, Applied Mathematics & Theoretical Physics, Churchill College, University of Cambridge, Cambridge, UK (2012-2016)

My PhD work at DAMTP focused on investigating the transient stability of strongly stratified shear flows. I considered both parallel, steady shear flows as well as more complicated flows with added internal wave strain (motivated by oceanographic observations). Using a direct-adjoint looping technique, I was able to identify computationally the initial conditions leading to maximum perturbation energy gain over finite times, and found that substantial perturbation energy growth may occur even for flows predicted to be stable by classical stability analysis. I also ran complementary direct numerical simulations initialized with the computed optimal initial conditions, and showed that transient growth may be sufficient to trigger transition to turbulence and mixing in these strongly-stratified flows.

Geophysical fluid dynamics fellowship, Woods Hole Oceanographic Institution, Woods Hole, MA, USA (2014)

As a fellow in the geophysical fluid dynamics program at WHOI, I examined the problem of large-scale Rossby waves impinging on topography with small gaps in a laboratory setting. Linear inviscid theory predicts that, for certain forcing symmetries, incident Rossby waves should be able to transmit through a barrier with small gaps. I ran a series of experiments with different forcing amplitudes and frequencies and showed that, to leading order, the waves are able to pass through the barrier as predicted by the theory; however, nonlinearity and viscosity lead to additional physics in the form of boundary currents and vortex formation.

MSc, Mechanical Engineering, University of Alberta, Edmonton, AB, Canada (2010-2012)

My master's research in mechanical engineering at the University of Alberta consisted of developing an algorithm which would allow a user to identify the spatiotemporal structure of polychromatic internal wave field (i.e. a flow with internal waves forced at multiple frequencies) using velocity timeseries data alone. The algorithm could be used for uniform or nonuniform stratifications, and in the constant-N case, allowed for viscous effects (relevant for analyzing laboratory data).

BSc, Mechanical Engineering, University of Alberta, Edmonton, AB, Canada (2006-2010)

Publications:

Select conference presentations: