Upcoming Events

09

2023.10

Vortex-sheet modeling of two vortex-dominatedclassical unsteady flows

Two unsteady,vortex-dominated flows will be discussed.The first is the starting vortex generated at both the leading and trailing edges of a flat plate airfoil that is accelerated from rest with power-law translational and rotational motion.A general inviscid theory with starting vortices modelled by thin vortex sheets is discussed by invoking the Kutta condition at the sharp edges,and making use of the Birkhoff-Rott equation for the vortex-sheet dynamics.
13

2023.10

Multiscale Understanding of Deformation Twinning in Hexagonal Metals

Twinning and de-twinning,which are the dominant deformation mechanisms in hexagonal-close-packed (HCP)metals,exhibit more complex nucleation,propagation,thickening mechanisms than those in cubic structures (FCC and BCC).Specifically,twinning and de-twinning cause unidirectional shear and crystallographic reorientation,associated with atomistic shuffling.Due to the coupled movements of shear displacement and shuffle displacements,twinning mechanisms are subject to some debate among pure-shuffle vs shear-shuffle.
26

2023.09

Hydraulic Fracturing in Geothermal Formations by Water and by CO2 in the Phase Field and Fluid-Rock Surface Energy

Fracturing of granite by water and by CO2 are presented with consideration of thermoporoelasticity.The phase-field approach with incorporation of critical energy release rate is the basis of the rock failure and fracture propagation.Critical energy release rate is a key parameter of numerical simulation of fracturing by different fluids.Molecular and atomistic simulations are conducted to get firm ideas on the critical energy release rate.
20

2023.09

The long-wave dynamics of coastal flows

Coastal or boundary currents are an integral part of global ocean circulation.For example,currents may respond to external forcing or intrinsic instability by expelling vortex filaments or larger eddies into the ocean,with implications for the mixing of coastal and ocean waters;and currents driven by outflows are important for the transport of freshwater,pollutants,and land-derived nutrients.There is also much interest in the behavior of 'free'fronts,i.e.,those that are far from the coast,which can be used to model western boundary currents such as the Gulf Stream or the Kuroshio Extension.In the limit of rapid rotation,the governing equations reduce to the quasi-geostrophic equations-a modified form of the two-dimensional Euler equations.
20

2023.09

Diagnostics of Fourier triad-phase synchronization via a phase-frozen model in 1D Burgers and 3D Navier-Stokes flows 文档正文文档附件(0)

Nonlinear triadic interaction plays a key role in the multiscale energy transfer of turbulence.It has been observed that the Fourier triad phases are synchronised to pi/2 when energy transfer is enhanced in the 1D Burgers equation,either with the stochastic forcing (Murray and Bustamante,J.Fluid Mech.(2018))or in the developing process from specific initial conditions(Kang et al.,ar Xiv:2105.09425).The focus of this work is twofold.The first objective is to understand what triggers the phase synchronisation.We revisit the ID Burgers equation with a staircase initial condition(Fang et al.,J.Turbul.(2020))..It is found that all the triad phases are strictly synchronised to pi/2 as the energy spectrum develops.A recursive formula of triad-phase relation is proposed to demonstrate that this strict synchronisation is triggered by the convective term in the Fourier space.
18

2023.09

Dynamical behaviors of KdV-Burgers-Kuramoto Equation

In this talk,we consider dynamics of a class of the KdV-Burgers-type systems by starting with Burgers-type equations,and then focus on the KdV- Burgers-Kuramoto equation,a partial differential equation that occupies a prominent position in describing some physical processes in motion of turbulence and other unstable process systems.We limit our attention to various wave solutions and their asymptotic behaviors.
25

2023.08

“Solids-that-flow” picture of glass-forming liquids

This is a slightly philosophical talk,asking the question:Are liquids approaching the glass transition like ordinary liquids (water,molten metals,etc)merely with an extremely high viscosity-or are they qualitatively different? Based on old work [1,2],I shall argue that the latter is the case,i.e.,that glass-forming liquids should be thought of as more like solids that.This point of view is not generally accepted,but several papers have appeared the last half decade going in this direction.Note that some of the seminal papers in glass science argue in much the same way [3,4],meaning that this is far from a new idea.
25

2023.08

Inside Nature Journals

This talk will give an overview of Nature Portfolio journals and the editorial process involved in publishing.The discussions will especially cover the aims and scope of Nature Computational Science,the editorial process,and our vision for this journal in the growing field of computational science.I will also discuss what editors do,what they look for,and how they make decisions,together with some practical tips for writing and submitting a paper to a Nature Portfolio journal.
18

2023.08

Electronic Excitations in Materials: A First-Principles Perspective

Understanding excited state phenomena is at the heart of many important materials problems,such as photovoltaics,photocatalysis,plasmonics and quantum information.In this talk,I will first give an overview of my recent research in computational materials science.I will then highlight our recent progress in developing accurate and efficient first-principles methods that enable us to probe electronic excitations in emerging materials. Among them,a subspace time-dependent density functional theory method is developed which can compute both excitation energy and excited state forces accurately for systems containing up to a few thousand electrons.We have also developed a time-dependent orbital-free DFT method with which tens of thousands of electrons can be treated fairly accurately in metals.
08

2023.08

Multiscale Modelling and Simulation of Graphene-basedNanomaterials: Understanding and Predicting theMechanics of Reinforcement

We have connected together single-scale simulations to understand and predict the behaviour of graphene-based nanoma- terials on long length and time scales,while still capturing the important interactions at the nano-scale.To ensure our methods are reliable and reproducible,we have developed methods that endow our approaches with validation,verification and uncertainty quantification (WUQ).Coarse-grained molecular dynamics allows us to determine the tendency of GO to disperse or aggregate,which can severely affect the mechanical performance of nanocomposite materials.We find the aggregation depends upon the two-phase nature of oxidised and un-oxidised graphene domains on the GO surface.

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