Seminar über aktuelle Fragen zur Dynamik komplexer Fluide: Modelling thin film hydrodynamics with lattice Boltzmann
Seminar über aktuelle Fragen zur Dynamik komplexer Fluide
- Date: Apr 16, 2021
- Time: 10:15 AM - 11:15 AM (Local Time Germany)
- Speaker: Stefan Zitz
- Forschungszentrum Jülich
- Location: Max-Planck-Institut für Dynamik und Selbstorganisation (MPIDS)
- Room: Video conference at www.zoom.us, Meeting ID: 980 3913 9623, Passcode: 050762
- Host: MPIDS/DCF
- Contact: stefan.karpitschka@ds.mpg.de
Thin liquid films and droplets are ubiquitous phenomena that are encountered regularly in our everyday routines. To study and understand these flows and related problems we use a numerical approach. Instead of straight up solving the differential equations we use a solver that is based on a lattice Boltzmann method (LBM) for shallow water problems. There are two attractive advantages of our approach: First, the algorithm is relatively simple and straightforward to implement. Second, it is very efficient and easily parallelizable. Simplicity comes from the fact that the LBM can be split into two steps: a collision step, where the internal degrees of freedom relax towards their equilibrium and a streaming step, where those degrees are shifted by a constant factor. Due to the inherent parallelism of the collision operation this method is well suited to be used on accelerator devices such as GPUs. Combining these aspects with modern programming languages, such as Julia, allows us to write efficient code without knowledge of the underlying processor architecture.
Another gain of the LBM approach is the straightforward addition of force terms. With the example of thermal fluctuations we present a guideline that can be followed to include novel extensions of the thin film equation. To this end we show that thermal capillary waves alter the spectrum of a dewetting film as predicted by theory. Moving on to patterned substrates we present our results of the stochastic thin film simulations and their dependency on the equilibrium contact angle.
Finally, we demonstrate how switchable substrates can be used to manipulate flows. As an example, we simulate a spinodally dewetting thin film on a substrate with space and time dependent wettability. In agreement with previous research we show that the time dependency increases the stability and shifts the rupture of the film to later times. As a sneak peak we discuss how the morphology of the dewetting film depends on the time dependency of the wettability.
Another gain of the LBM approach is the straightforward addition of force terms. With the example of thermal fluctuations we present a guideline that can be followed to include novel extensions of the thin film equation. To this end we show that thermal capillary waves alter the spectrum of a dewetting film as predicted by theory. Moving on to patterned substrates we present our results of the stochastic thin film simulations and their dependency on the equilibrium contact angle.
Finally, we demonstrate how switchable substrates can be used to manipulate flows. As an example, we simulate a spinodally dewetting thin film on a substrate with space and time dependent wettability. In agreement with previous research we show that the time dependency increases the stability and shifts the rupture of the film to later times. As a sneak peak we discuss how the morphology of the dewetting film depends on the time dependency of the wettability.