Primus Research Programme–The interaction of fluids and solids

Dear colleagues,

please notice the following job announcement by Sebastian Schwarzacher. See also the attached leaflet.

Dear friends,

please find attached a job-announcement for my “Primus Research Programme–The interaction of fluids and solids”. Two positions are available for up to three years starting from the 1.1.2019 at the Charles University, Prague.

The deadline of application is the 16th of November.

Please forward this information to any person who might be interested to apply.

Many thanks and best regards,

Sebastian

Marie-Curie PhD Fellows

Dear students,

Martin Řehoř, who is currently working at the University of Luxembourg, would like to draw your attention to the following announcement.

The University of Luxembourg (UL) invites applications for four Marie-Curie PhD Fellows (Doctoral Candidate) positions (m/f) as part of the Rapid Biomechanics and Simulation for Personalised Clinical Design (RAINBOW) MCSA European Training Network. RAINBOW is funded under the European Union’s Horizon 2020 research and innovation programme.

For details please see job announcement webpage.

Viscoelastic transitions exhibited by modified and unmodified bitumen

Dear colleagues,

We would like to invite you to a lecture titled “Viscoelastic Transitions Exhibited by Modified and Unmodified Bitumen” by Murali Krishnan from the Indian Institute of Technology Madras. The lecture will take place on Tuesday, July 24 at 10:00 in K4.

Abstract:
The working temperature of a bituminous pavement can typically range from 75C to -20C. Bitumen shows a wide spectrum of mechanical behaviour in this temperature range and these include those of a viscoelastic fluid, a viscoelastic solid and an elastic solid. Due to the amorphous nature of the material, the transitions between such mechanical responses are gradual. This investigation focuses on the transition between the viscoelastic solid and the viscoelastic fluid state of a wide class of bitumens with regard to unaged and short-term aged conditions. An unmodified binder and three modified binders were subjected to temperature sweep and frequency sweep in the viscoelastic regime across a wide range of temperatures. Depending on the material and the post-processing method followed, one could discern a viscoelastic fluid and a viscoelastic solid regime and a frequency dependent mixture regime consisting of a viscoelastic solid and a viscoelastic fluid, across the tested temperatures and frequencies.
It is shown in this investigation that parameters such as G’–G” crossover and frequency independence of tan(δ) cannot be used to estimate the temperatures corresponding to the onset of either fluid-like or solid-like behaviour of the body as the temperature varies. It is also shown that the time-temperature superposition principle does not hold good in the temperature regime tested (75 to 25C) due to the viscoelastic transitions exhibited by bitumen and modified bitumen.

On a variational model for thick fluids: talk by José Francisco Rodrigues

The seminar will take place on Friday, June 22, 2018 at 10:00 am in K6. José Francisco Rodrigues will give a lecture “On a variational model for thick fluids”.

Abstract: In chemical engineering models, shear-thickening or dilatant fluids converge in the limit case to a class of incompressible fluids with a maximum admissible shear rate, the so-called thick fluids. These non-Newtonian fluids can be obtained, in particular, as the power limit of the shear-thickening fluids, and can be described as a class of evolution variational inequalities, in which the shear rate is bounded by a positive constant or, more generally, by a bounded positive function. It is then possible to establish the existence, uniqueness, and the continuous dependence of solutions to this general class of thick fluids with variable threshold on the absolute value of the deformation rate tensor, the solutions of which belong to a time dependent convex set. For sufficiently large viscosity, the asymptotic stabilization toward a unique steady state can also be proved.

Combinatorial scientific computing and its problems: talk by Miroslav Tůma

The seminar will take place on Monday, May 14, 2018 at 9:00 am in K4. Miroslav Tůma will conclude his lecture on “Combinatorial scientific computing and its problems”.

Abstract:

In this talk we would like to point out some relations between continuous modelling of problems in sciences and engineering and
underlying discrete algorithms. Without going into details we will mention some of these relations and show their use in contemporary computational mathematics.

Hydrodynamic processes during formation of planetary systems Part III: talk by RNDr. Ondrej Chrenko

The seminar will take place on Monday, April 30, 2018 at 9:00 am in K4. Ondrej Chrenko will conclude his lecture on “Hydrodynamic processes during formation of planetary systems”.

Abstract:

Planets form in protoplanetary disks which are rotating structures of gas and dust surrounding young stars. Before a protoplanetary disk disperses, the mass of gas dominates over the mass of solids and thus the evolution of the disk and planets is driven by hydrodynamic phenomena. Although this evolutionary stage does not last longer than several million years, it inevitably predetermines the properties of the emerging planetary system, i.e. the multiplicity of planets, their orbital configuration, distances from the central star, their masses and types (whether they become terrestrial or gas giants). Understanding the impact of hydrodynamic processes on planet formation can help us understand the great diversity among the observed extrasolar planetary systems.

First, I will demonstrate the variety of hydrodynamic processes in protoplanetary disks by reviewing several examples, e.g. instabilities leading to angular momentum transport, instabilities enhancing accretion of solids, and planet-disk interactions leading to planetary migration. Next, I will describe numerical solution of the fluid equations within the framework of so-called FARGO hydrodynamic codes (Masset 2000, Benítez-Llambay & Masset 2016) which are often used to study planet-disk interactions. I will present a recent 2D model focused on interactions of multiple planets with a gas disk and a coupled disk of pebbles (Chrenko et al. 2017). Finally, I will outline a more advanced 3D model which is currently under development and I will discuss the implementation of radiative diffusion and stellar irradiation.

Hydrodynamic processes during formation of planetary systems Part II: talk by RNDr. Ondrej Chrenko, Ph.D.

The seminar will take place on Monday, April 16, 2018 at 9:00 am in K4. Ondrej Chrenko will continue with a second lecture on “Hydrodynamic processes during formation of planetary systems”.

Abstract:

Planets form in protoplanetary disks which are rotating structures of gas and dust surrounding young stars. Before a protoplanetary disk disperses, the mass of gas dominates over the mass of solids and thus the evolution of the disk and planets is driven by hydrodynamic phenomena. Although this evolutionary stage does not last longer than several million years, it inevitably predetermines the properties of the emerging planetary system, i.e. the multiplicity of planets, their orbital configuration, distances from the central star, their masses and types (whether they become terrestrial or gas giants). Understanding the impact of hydrodynamic processes on planet formation can help us understand the great diversity among the observed extrasolar planetary systems.

First, I will demonstrate the variety of hydrodynamic processes in protoplanetary disks by reviewing several examples, e.g. instabilities leading to angular momentum transport, instabilities enhancing accretion of solids, and planet-disk interactions leading to planetary migration. Next, I will describe numerical solution of the fluid equations within the framework of so-called FARGO hydrodynamic codes (Masset 2000, Benítez-Llambay & Masset 2016) which are often used to study planet-disk interactions. I will present a recent 2D model focused on interactions of multiple planets with a gas disk and a coupled disk of pebbles (Chrenko et al. 2017). Finally, I will outline a more advanced 3D model which is currently under development and I will discuss the implementation of radiative diffusion and stellar irradiation.

Hydrodynamic processes during formation of planetary systems: talk by RNDr. Ondrej Chrenko, Ph.D.

The seminar will take place on Monday, April 9, 2018 at 9:00 am in K4. Ondrej Chrenko will give a lecture “Hydrodynamic processes during formation of planetary systems”.

Abstract:

Planets form in protoplanetary disks which are rotating structures of gas and dust surrounding young stars. Before a protoplanetary disk disperses, the mass of gas dominates over the mass of solids and thus the evolution of the disk and planets is driven by hydrodynamic phenomena. Although this evolutionary stage does not last longer than several million years, it inevitably predetermines the properties of the emerging planetary system, i.e. the multiplicity of planets, their orbital configuration, distances from the central star, their masses and types (whether they become terrestrial or gas giants). Understanding the impact of hydrodynamic processes on planet formation can help us understand the great diversity among the observed extrasolar planetary systems.

First, I will demonstrate the variety of hydrodynamic processes in protoplanetary disks by reviewing several examples, e.g. instabilities leading to angular momentum transport, instabilities enhancing accretion of solids, and planet-disk interactions leading to planetary migration. Next, I will describe numerical solution of the fluid equations within the framework of so-called FARGO hydrodynamic codes (Masset 2000, Benítez-Llambay & Masset 2016) which are often used to study planet-disk interactions. I will present a recent 2D model focused on interactions of multiple planets with a gas disk and a coupled disk of pebbles (Chrenko et al. 2017). Finally, I will outline a more advanced 3D model which is currently under development and I will discuss the implementation of radiative diffusion and stellar irradiation.

Up to the boundary Lipschitz regularity for variational problems: talk by Erika Maringová

The seminar will take place on Monday, March 19, 2018 at 9:00 am in K4. Erika Maringová will give a lecture “Up to the boundary Lipschitz regularity for variational problems”.

Abstract: We prove the existence of a regular solution to a wide class of convex, variational integrals. Via technique of construction of the barriers we show that the solution is Lipschitz up to the boundary. For the linear growth case [1], we identify the necessary and sufficient condition to existence of solution; in the case of superlinear growth [2], we provide the sufficient one. The result is not restricted to any geometrical assumption on the domain, only its regularity plays the role. The talk will be based on two works,

[1] L. Beck, M. Bulíček, and E. Maringová.  Globally Lipschitz minimizers for variational problems with linear growth, accepted to ESAIM: COCV in 2017.

[2] M. Bulíček, E. Maringová, B. Stroffolini and A. Verde. A boundary regularity result for minimizers of variational integrals with nonstandard growth, accepted to Nonlinear Analysis in 2018.