10 papers
Objective detection of coherent vortices from instantaneous flow data
Tiemo Pedergnana, Florian Kogelbauer
Vortices are swirling regions of fluid that structure motion in gases and liquids across a wide range of scales, from laboratory-scale experiments to vast atmospheric currents. The…
Non-Hydrodynamic Solutions to the linear Density-dependent BGK equation
Florian Kogelbauer
We prove the existence of non-hydrodynamic solutions to the linear density-dependent BGK equation in dimensions. Specifically, we show the existence of an initial condition for…
An Objective Measure of Unsteadiness
Florian Kogelbauer, Tiemo Pedergnana
Unsteadiness lies at the heart of turbulent fluid dynamics, eddy formation and instabilities in flows thus making it central to both understanding and controlling fluid systems. In…
A Note on Non-Hydrodynamic Solutions of Kinetic Systems
Florian Kogelbauer, Ilya Karlin
We show that the one-dimensional three-component Grad system admits solutions that violate the Chapman--Enskog scaling in Knudsen number. In particular, there exist solutions that…
Learning the Optimal Hydrodynamic Closure
Florian Kogelbauer, Candi Zheng, Ilya Karlin
We present the optimal hydrodynamic model for rarefied gas flows relative to a given kinetic model by combining the recent theory of slow spectral closure with machine learning tec…
Relativistic electrodynamics with a universal length scale
Tiemo Pedergnana, Florian Kogelbauer
We derive the analogues of the Dirac and Pauli equations from a spatially fourth-order Klein--Gordon equation with a universal length scale. Starting from a singularly perturbed va…