Open questions in turbulent stratified mixing:Do we even know what we do not know? by C.P. Caulfield

ABSTRACT:

Understanding how turbulence leads to the enhanced irreversible transport of heat and other scalars (such as salt and pollutants) in density-stratified fluids is a fundamental and central problem in geophysical and environmental fluid dynamics. There is a wide range of highly important applications, not least the description and parameterization of diapycnal transport in the world's oceans, a key area of uncertainty in climate modelling. Recently, due not least to the proliferation of data obtained through direct observation, numerical simulation and laboratory experimentation, there has been an explosion in research activity directed at improving community understanding, modelling and parameterization of the subtle interplay between energy conversion pathways, turbulence, and irreversible mixing in density-stratified fluids. However, as I will discuss in this talk, there are still leading order open questions and areas of profound uncertainty concerning turbulent stratified mixing. Therefore, I will present a personal perspective on some priorities for further research into this hugely complex, important and fascinating fluid dynamical challenge.

0:00:00 Open questions in turbulent stratified mixing: Do we even know what we do not know?
0:04:30 Can Fluid Dynamics Save the Planet?
0:12:59 Mixing: How does stratification tax turbulence?
0:20:26 Other Key Definitions of Mixing: Variance
0:22:29 Parameters of Mixing
0:28:54 Variation of Gamma (or not...)
0:30:03 Review Consensus 2008: Ivey et al
0:30:30 Review Consensus 2018: Gregg et al (Washington School)
0:31:12 (Body) forced statistically steady flow: Osborn regime?
0:34:15 High Dynamic Range Asymptotic Portwood et al 2019
0:35:02 Is mixing always associated with weak stratification?
0:37:07 How about transient open shear flows?
0:38:36 Is Holmboe-induced turbulence critical? Salehipour et al 2018
0:41:16 Is I 0.2 always? Err... no...maybe 0.5?
0:43:51 Strong stratification in Taylor-Collette flow
0:45:55 Mixing in strong stratification: Simulations
0:47:49 Mixing in strong stratification: Sheared forced IGWs Rio ~ I
0:52:42 Robust identification of flow regions: Portwood et al. 2016
0:57:43 (Some of the) Still Open Questions
0:59:39 Acknowledgements: The people who did all the work
0:59:46 Q&A
1:01:59 (Body) forced statistically steady flow: Osborn regime?
1:05:10 Is mixing always associated with weak stratification?
1:07:49 Robust identification of flow regions: Portwood et al. 2016
1:14:53 Review "Consensus" 2021: Cambridge School
1:16:33 Can Fluid Dynamics Save the Planet?
1:24:55 Strong stratification in Taylor-Collette flow