T. Wondrak | Searcharxiv

arXiv2024

Helicity oscillations in Rayleigh-Bénard convection of liquid metal in a cell with aspect ratio 0.5

In this paper, we present numerical and experimental results on helicity oscillations in a liquid-metal Rayleigh-Bénard (RB) convection cell, with an aspect ratio of 0.5. We find that helicity oscillations occur during transitions of flow states that are characterised by significant changes in the Reynolds number. Moreover, we also observe helicity oscillations at flow conditions where the temporal gradient of the change in the Reynolds number is significantly smaller than that of the helicity. Notably, the helicity oscillations observed during the transient double-roll state exhibit characteristics remarkably similar to those associated with the Tayler Instability.

physics.flu-dyn↗

arXiv2023

Current Tomography -- Localization of void fractions in conducting liquids by measuring the induced magnetic flux density

A novel concept of a measurement technology for the localization and determination of the size of gas bubbles is presented, which is intended to contribute to a further understanding of the dynamics of efficiency-reducing gas bubbles in electrolyzers. A simplified proof-of-concept (POC) model is used to numerically simulate the electric current flow through materials with significant differences in electrical conductivity. Through an automated approach, an extensive data set of electric current density and conductivity distributions is generated, complemented with determined magnetic flux densities in the surroundings of the POC cell at virtual sensor positions. The generated data set serves as testing data for various reconstruction approaches. Based on the measurable magnetic flux density, solving Biot-Savarts law inversely is demonstrated and discussed with a model-based solution of an optimization problem, of which the gas bubble locations are derived.

physics.flu-dyn↗