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.
Thesis title: Linear optimal perturbations and transition to turbulence in strongly-stratified shear flows
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.
Project title: An experimental investigation of the Rossby two-slit problem [link]
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)
Thesis title: Modal decomposition of tidally-forced internal waves (reconstructed from timeseries data) [link]
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)
AK Kaminski, CP Caulfield, and JR Taylor 2017 Nonlinear evolution of linear optimal perturbations of strongly stratified shear layers. Journal of Fluid Mechanics 825, 213-244. [link]
RM Sahuri, AK Kaminski, MR Flynn, and M Ungarish 2015 Axisymmetric gravity currents in two-layer density-stratified media. Environmental Fluid Mechanics 15(5), 1035-1051. [link]
AK Kaminski, CP Caulfield, and JR Taylor 2014 Transient growth in strongly stratified shear layers. Journal of Fluid Mechanics 758, R4. [link]
Select conference presentations:
A Kaminski and W Smyth 2018 Stratified shear instability in a field of pre-existing turbulence. 2018 Ocean Sciences Meeting, Feb 11-16, 2018, Portland, OR, USA. [abstract]
A Kaminski and W Smyth 2017 The effect of existing turbulence on stratified shear instability. 70th Annual Meeting of the APS Division of Fluid Dynamics, Nov 19-21, 2017, Denver, CO, USA. [abstract]
A Kaminski, J Pedlosky, and K Helfrich 2016 An experimental investigation of the Rossby two-slit problem. 69th Annual Meeting of the APS Division of Fluid Dynamics, Nov 20-22, 2016, Portland, OR, USA. [abstract]
A Kaminski and J Taylor 2016 Stability and mixing of shear layers forced by standing internal waves. VIIIth International Symposium on Stratified Flows, Aug 29-Sept 1, 2016, San Diego, CA, USA. [conference paper]
A Kaminski, C Caulfield, and J Taylor 2016 Nonlinear evolution of optimal perturbations to strongly stratified shear layers. XXIVth International Congress of Theoretical and Applied Mechanics, Aug 21-26, Montreal, QC, Canada.
A Kaminski and JR Taylor 2016 Instability and mixing of stratified shear layers forced by internal wave strain. 2016 Ocean Sciences Meeting, Feb 21-26, 2016, New Orleans, LA, USA. [abstract]
A Kaminski and J Taylor 2015 Instability and mixing of stratified shear layers forced by internal wave strain. 68th Annual Meeting of the APS Division of Fluid Dynamics, Nov 22-24, 2015, Boston, MA, USA. [abstract]
AK Kaminski, CP Caulfield, and JR Taylor 2015 Transient stability of stratified shear layers. Euromech Colloquium 567: Turbulent Mixing in Stratified Flows, March 22-25, 2015, Cambridge, UK. [abstract]
A Kaminski, CP Caulfield, and J Taylor 2014 Turbulence and mixing from optimal perturbations to a stratified shear layer. 67th Annual Meeting of the APS Division of Fluid Dynamics, Nov 23-25, 2014, San Francisco, CA, USA. [abstract]
A Kaminski and J Taylor 2013 Linear optimal perturbations of a stratified shear layer. 66th Annual Meeting of the APS Division of Fluid Dynamics, Nov 24-26, 2013, Pittsburgh, PA, USA. [abstract]
AK Kaminski and MR Flynn 2012 Modal decomposition of tidally-forced internal waves. European Geosciences Union General Assembly 2012, April 22-27, 2012, Vienna, Austria. [abstract]