Date: Tuesday 10 Oct 2023 1:15pm
From: The University of Reading, Meterology
Location: 4 West 1.7 (Wolfson Room)
Title: Implicit Time Stepping for Atmospheric Transport

Transport in models of the global atmosphere can lead to severe time step restrictions, particularly over the poles of a latitude-longitude grid or where convective updrafts are resolved. This has been solved before by the use of semi-Lagrangian advection and by the use of quasi-uniform grids such as the cubed-sphere instead of latitude-longitude. However semi-Lagrangian transport is not conservative: the transported quantity is not conserved. And the use of quasi-uniform grids does not solve the problem of time step restrictions due to strong convective updrafts. Better ways are needed to ensure model stability either where winds (or updrafts) are strong or where grid spacing is small.

Implicit time stepping for transport is not popular in atmospheric science as it has been assumed to be expensive, complicated, inaccurate and does not scale well on large parallel computers. I will challenge these assumptions. Implicit time stepping can actually be simple to implement and, if it is used only where needed, then accuracy is maintained. Implicit advection is conservative, can be used with any grid structure of the sphere, can exploit improvements in solver efficiency and parallelisation and can provide stable solutions for large time steps. I will show how this can be achieve and will show solutions on pure transport cases and for solutions of the Navier-Stokes equations.

Date: Tuesday 17 Oct 2023 1:15pm
From: University of Strathclyde, Mathematics
Location: 4 West 1.7 (Wolfson Room)
Title: The evaporation of arrays of non-circular droplets and applications to OLED manufacture

The evaporation of droplets has been a much-studied problem in recent years, finding applications everywhere from the spraying of pesticides on leaves to diagnostic applications of blood drying. Unfortunately, many of the most critical industrial applications, such as the printing of OLED screens, involve arrays of droplets with polygonal footprints in close enough proximity to one another that the evaporative behaviours interfere with one another via the vapour phase. This is in stark contrast to the state of the theoretical literature in which we have only had techniques for dealing with droplets with circular or elliptic footprints, and even then, only for such droplets in isolation.

We discuss recent advancements in this area relaxing both of these constraints, demonstrating how arbitrary arrays of non-circular droplets may be analysed theoretically. We examine a variety of industrially relevant problems, including the evaporative behaviours of rectangular droplets (used for OLED screens), as well as a continuum formulation designed to cope with the extremely large arrays observed in 8K screens (O(10^8) droplets). We briefly discuss the uses of these solutions in other physical contexts.

In order to have the best experience, we have a strong preference to host the seminars in person. However, for accessibility, we also open it to online audiences as well. Please if you plan to join online, it is often helpful to let the organiser (Phil) know in advance—this means the speaker can be warned and/or we can ensure that all the tech is set up properly.

Join Zoom Meeting https://bath-ac-uk.zoom.us/j/98613925892?pwd=TURvbHlka2JpTzhoYXpraU5TdVBSZz09

Further details

Meeting ID: 986 1392 5892
Passcode: 052599

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