8th European Postgraduate Fluid Dynamics Conference

6th – 9th July 2016
Warsaw, Poland


Plenary lectures

Piotr Szymczak

Title: Self-focusing of the flow: On the growth of karst conduits and river networks

Abstract: “The waves of the sea, the little ripples on the shore, the sweeping curve of the sandy bay between the headlands, the outline of the hills, the shape of the clouds, all these are so many riddles of form, so many problems of morphology, and all of them the physicist can more or less easily read and adequately solve" - wrote D'Arcy Wentworth Thompson in 1917 in his famous book "On growth and form". Modern physics has progressed along the way outlined by Thompson, discovering the principles by which multiplicity of relatively simple interactions can give rise to the emergence of organized structures or qualitatively new behaviors. In this talk, I will give two examples of self-organizing growth processes driven by the flow: the growth of "wormholes" in a dissolving rock during early stages of cave formation and the growth of seepage channels incised by groundwater flow. In particular, I will discuss the question why the initially planar fracture is dissolving in an inhomogeneous manner, leading to the appearance of karst conduits and why the tributaries of Apalachicola river in Florida join each other at an angle of 72 degrees.

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Piotr Smolarkiewicz

Title: All-Scale Finite-Volume Module for Global Weather Prediction

Abstract: My lecture highlights the development of a global nonhydrostatic finite-volume module (FVM) designed to enhance established spectral-transform based numerical weather prediction (NWP) models. The state-of-the-art NWP models, such as the Integrated Forecast System (IFS) of ECMWF, produce 10 days forecast, at about nine billion points discretising 85 km deep global atmosphere, in no more than 1 hour of wall-clock time. This extreme efficiency owes to hydrostatic primitive PDEs integrated with a spectral-transform based semi-implicit semi-Lagrangian (SISL) algorithms executed in parallel on nearly eight thousand supercomputer cores. However, this computational apparatus cannot sustain the status quo of global NWP at nonhydrostatic resolutions (anticipated by 2020) by simply scaling up number of cores; Wedi et al. 2015, 760. Recognising the predictive skills of the legacy codes, we seek to mitigate their shortcomings by supplying flexibility in choices of complementary numerical procedures, compact discretisation stencils, local connectivities and communication patterns unavailable in the SISL spectral models. The first step towards realising this paradigm is the development of an autonomous FVM capable of working on the IFS grid, and in principle, on any horizontal grid; Smolarkiewicz et al. 2016. The key technologies of the FVM are numerical procedures expressed in time-dependent generalized curvilinear coordinates, pairing the mathematical apparatus of differential geometry with modern CFD, most notably the emerging novel edge-based non-oscillatory control volume integrators for nonhydrostatic dynamics; Smolarkiewicz et al.. Because FVM operates at the nodes of the IFS grid, it seamlessly inherits the advanced parallelisation scheme of the IFS, with multiple layers of parallelism hybridising MPI tasks and OpenMP threads. Theoretical considerations are illustrated with idealised simulations of global weather.

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Gregory Falkovich

Title: “There is life at low Reynolds numbers”

Abstract: The lecture is devoted to fundamental problems and modern applications of very viscous flows, from bacteria and microfluidics to quark-gluon plasma and electron flows in graphene. I start from explaining the nature of viscosity and then describe the purely geometrical world of inertia-less flows. I then describe new phenomena discovered in microfluidics and viscous electronics, from elastic turbulence to negative electric resistance.

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