Complex Fluids Seminar – University of Copenhagen

Atmospheric complexity > Complex Fluids

Complex Fluids Seminar

Starting in August, 2017, at Niels Bohr Institute, University of Copenhagen, we are starting a new seminar series titled “Complex Fluids”, which brings together the complex systems and geophysical fluid dynamics fields. 

Scope. The scope of this seminar is to encourage models that describe complex processes in fluids, e.g. those involving some type of emergent aspect, self-organization, bistability, oscillations, scale interactions, long-ranged order, you name it ;) Examples are bistability in the climate system, convective processes, extreme events, self-similarity and pattern formation in geology or atmospheric processes, interactions and feedbacks between atmosphere and biosphere, etc.

Conceptual models. We are interested in conceptual (but not necessarily complicated) models that are able to capture the core dynamical processes and (some of) the feedbacks in a fluid dynamical system, without getting lost in comprehensive models and many parameters. The sacrifice may sometimes be, that not all processes are considered, and that quantitative detail is missing.

The gain however lies in the theoretical understanding of the model and thereby at least some aspects of reality. We therefore encourage talks that offer a speculate, provocative view on crucial processes, e.g. in the climate system, that are currently not well understood or uncertain.

When? Wednesdays at noon (communal informal lunch). Presentations start around 12:30 and normally take around 45 minutes. Initially, the seminar will be approximately twice per month.

Where? Kc7, C-floor of K-building, Blegdamsvej 17, 2100 København Ø.

The seminar will be complementary to the existing BioComplexity seminar (both in terms of schedule and topics). 

Sign up for the mailing list! We encourage subscription to the Complex Fluids mailing list, to receive information about upcoming seminars.

upcoming seminar:

Peter Ditlevsen (Niels Bohr Institute)

Time: Wednesday, August 16th, noon (lunch, cafeteria), seminar starts: 12:30 p.m.

Location: Aud D (Blegdamsvej 17)

Title and Abstract: T.B.A.

past seminars:

Nicholas Rathmann (Niels Bohr Institute)

Time: Wednesday, August 9th, noon (lunch, cafeteria), seminar starts: 12:30 p.m.

Location: Aud M (Blegdamsvej 17)

2D-like turbulence embedded within 3D turbulent flows

2D turbulence is fundamentally different from 3D turbulence. In 2D flows, unlike 3D, a second positive-definite integral quantity, enstrophy, is invincidly conserved besides kinetic energy.
In 2D flows, such as highly stratified flows, this causes a blocking of the forward energy cascade from the forcing scale of motion to the small Kolmogorov scale where viscous energy dissipation occurs, implying the cascade is instead reversed to larger scales. By applying the Fourier-helical decomposition to the Navier--Stokes equations, we show, both theoretically and numerically, that a subset of the spectral (triad) interactions conserve a new enstrophy-like quantity, suggesting 3D flows in general might have hidden, embedded 2D-like flows.

further queries (e.g. speaker suggestions):

Jan O. Haerter (Atmospheric Complexity)

Peter Ditlevsen (climate research, turbulence, meteorology, complex systems, time series analysis and statistical physics)

Markus Jochum (Watermass transformation in the Nordic Seas and the Arctic Ocean, Dansgaard-Oeschger Events)

Joachim Mathiesen (earth patterns, predicting petrophysical parameters, flow in transforming porous media)

Eigil Kaas (climate dynamics, meteorology and numerical methods used in atmospheric models, and coupled atmospheric chemistry transport models)

Mogens H. Jensen (chaos, fractals, oscillations, turbulence)