A colloquium on vortex dominated flows (DisCoVor 2022) was held in May 2022 in Switzerland (Co-chairs Karen Mulleners (EPFL) and Rajat Mittal (JHU)) which had over 60 participants and presenters from US, Europe, South America, Canada and India. At the culmination of this meeting, there was a consensus that there existed an opportunity to put together a special issue on this topic and solicit high-quality papers from this group of attendees as well as from the wider community of researchers involved in research in vortex dominated flows. DisCoVor 2023 was held in Colorado in May 2023 with nearly 90 participants from all over the world, and the special collection has been reopened to accept articles till the end of 2023.

Viscoplastic materials are a distinct class of complex fluids that exhibit a yield stress. When subjected to stresses smaller than a critical value, such materials exhibit a solid solid- like behavior (they deform but do not flow) and, for imposed stresses exceeding this threshold, they exhibit a fluid like flow behavior. This special class of materials is quite broad and includes emulsions, foams, pastes, colloidal and non-colloidal gels, suspensions of particles that have a number of key applications in pharmaceutics, cosmetics, food, oil, and construction industries. Biofluids, such as mucus, blood and saliva, and geophysical materials, e.g., sea ice, snow, muds, volcanic lava also belong to this class.

Within this special issue, we would like to provide a well-selected overview of the current state of theoretical and numerical research on flows of viscoplastic materials and highlight future developments. Topics of relevance include (but are not restricted to) dynamics of the solid-fluid transition in time dependent flows with a particular emphasis on the role of elasticity, transient flows over complex topographies, hydrodynamic instabilities, mixing, two phase flows, flows in porous media.

We intend to have a well-balanced mix of methodological papers focused on new numerical/theoretical developments and physics-oriented papers with authors from various communities (applied mathematics, physics, chemical and mechanical engineering etc.) working on the fluid mechanics of yield stress materials.

Submission deadline: 1.12.2024

Projected publication: 1.05.2025

Instructions: On the journal website, select "Submit your manuscript" and proceed with submission. Under the "Details" tab and the Collection section at the top of the page, please select "Special Issue: Stable and unstable time dependent flows of viscoplastic fluids."