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Publications

Articles in Refereed Journals

  • L. Schmeller, D. Peschka, Gradient flows for coupling order parameters and mechanics, SIAM Journal on Applied Mathematics, 83 (2023), pp. 225--253, DOI 10.1137/22M148478X .
    Abstract
    We construct a formal gradient flow structure for phase-field evolution coupled to mechanics in Lagrangian coordinates, present common ways to couple the evolution and provide an incremental minimization strategy. While the usual presentation of continuum mechanics is intentionally very brief, the focus of this paper is on an extensible functional analytical framework and a discretization approach that preserves an appropriate variational structure as much as possible. As examples, we first present phase separation and swelling of gels and then the approach of stationary states of multiphase systems with surface tension and show the robustness of the general approach.

  • D. Peschka, Partial and complete wetting of thin films with dynamic contact angle, Physics of Fluids, 35 (2023), pp. 041705/1--041705/6, DOI 10.1063/5.0146538 .
    Abstract
    The wetting of thin films depends critically on the sign of the spreading coefficient S. We discuss the cases S<0, S=0, and S>0 for transient models with contact line dissipation and find that the use of a dynamic contact angle solves problems for S>0 that models might otherwise have. For initial data with a non-zero slope and S>0, we show that there exists a finite time at which the contact angle of the thin film goes to zero. Then, a molecular precursor emerges from the thin film and moves outward at a constant velocity.

  • R. Shiri, L. Schmeller, R. Seemann, D. Peschka, B. Wagner, Impact of noise on spinodal dewetting of liquid-liquid films, communications physics, 6 (2023), pp. 109/1--109/11, DOI 10.1038/s42005-023-01208-x .
    Abstract
    We investigate the spinodal dewetting of a thin liquid polystyrene (PS) film on a liquid polymethylmethacrylate (PMMA) subtrate. Following the evolution of the corrugations of the PS film via in situ measurements by atomic force microscopy (AFM) and those of the PS-PMMA interface via ex situ imaging, we provide a direct and detailed comparison of the experimentally determined spinodal wavelengths with the predictions from linear stability analysis of a thin-film continuum model for the bilayer system. The impact of rough interfaces and fluctuations is studied theoretically by investigating the impact of different choices of initial data on the unstable wavelength and on the rupture time. The key factor is the mode selection by initial data perturbed with correlated colored noise in the linearly unstable regime, which becomes relevant only for liquid bilayers to such an extent. By numerically solving the mathematical model, we further address the impact of nonlinear effects on rupture times and on the morphological evolution of the interfaces in comparison with experimental results.

  • A. Zafferi, K. Huber, D. Peschka, J. Vrijmoed, T. John, M. Thomas, A porous-media model for reactive fluid-rock interaction in a dehydrating rock, Journal of Mathematical Physics, 64 (2023), pp. 091504/1--091504/29, DOI 10.1063/5.0148243 .
    Abstract
    We study the GENERIC structure of models for reactive two-phase flows and their connection to a porous-media model for reactive fluid-rock interaction used in Geosciences. For this we discuss the equilibration of fast dissipative processes in the GENERIC framework. Mathematical properties of the porous-media model and first results on its mathematical analysis are provided. The mathematical assumptions imposed for the analysis are critically validated with the thermodynamical rock data sets.

  • L. Giacomelli, M. Gnann, D. Peschka, Droplet motion with contact-line friction: Long-time asymptotics in complete wetting, Proceedings of The Royal Society of London. Series A. Mathematical, Physical and Engineering Sciences, 479 (2023), pp. 20230090/1--20230090/23, DOI 10.1098/rspa.2023.0090 .
    Abstract
    We consider the thin-film equation for a class of free boundary conditions modelling friction at the contact line, as introduced by E and Ren. Our analysis focuses on formal long-time asymptotics of solutions in the perfect wetting regime. In particular, through the analysis of quasi-self-similar solutions, we characterize the profile and the spreading rate of solutions depending on the strength of friction at the contact line, as well as their (global or local) corrections, which are due to the dynamical nature of the free boundary conditions. These results are complemented with full transient numerical solutions of the free boundary problem.

Preprints, Reports, Technical Reports

  • M. Thomas, S. Tornquist, Ch. Wieners, Approximating dynamic phase-field fracture in viscoelastic materials with a first-order formulation for velocity and stress, Preprint no. 3002, WIAS, Berlin, 2023, DOI 10.20347/WIAS.PREPRINT.3002 .
    Abstract, PDF (493 kByte)
    We investigate a model for dynamic fracture in viscoelastic materials at small strains. While the sharp crack interface is approximated with a phase-field method, we consider a viscous evolution with a quadratic dissipation potential for the phase-field variable. A non-smooth constraint enforces a unidirectional evolution of the phase-field, i.e. material cannot heal. The viscoelastic equation of motion is transformed into a first order formulation and coupled in a nonlinear way to the non-smooth evolution law of the phase field. The system is fully discretized in space and time with a discontinuous Galerkin approach for the first-order formulation. Based on this, existence of discrete solutions is shown and, as the step size in space and time tends to zero, their convergence to a suitable notion of weak solution of the system is discussed.

  • L. Schmeller, D. Peschka, Sharp-interface limits of Cahn--Hilliard models and mechanics with moving contact lines, Preprint no. 2990, WIAS, Berlin, 2023, DOI 10.20347/WIAS.PREPRINT.2990 .
    Abstract, PDF (5979 kByte)
    We construct gradient structures for free boundary problems with moving capillary interfaces with nonlinear (hyper)elasticity and study the impact of moving contact lines. In this context, we numerically analyze how phase-field models converge to certain sharp-interface models when the interface thickness tends to zero. In particular, we study the scaling of the Cahn--Hilliard mobility with certain powers of the interfacial thickness. In the presence of interfaces, it is known that the intended sharp-interface limit holds only for a particular range of powers However, in the presence of moving contact lines we show that some scalings that are valid for interfaces produce significant errors and the effective range of valid powers of the interfacial thickness in the mobility reduces.

Talks, Poster

  • D. Peschka, Moving contact lines for sliding droplets, 93rd Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM 2023), Session 11 ``Interfacial Flows'', May 30 - June 2, 2023, Technische Universität Dresden, June 1, 2023.

  • D. Peschka, Multiscale limits of thin-film models with moving support, In Search of Model Structures for Non-equilibrium Systems, April 24 - 28, 2023, Westfälische Wilhelms-Universität Münster, April 27, 2023.

  • D. Peschka, Multiscale limits of thin-film models with moving support, Kolloquium des SFB 1114, Freie Universität Berlin, April 20, 2023.

  • D. Peschka, Sharp-interface limit of models with mechanics and contact lines, 10th International Congress on Industrial and Applied Mathematics (ICIAM 2023), Session 00247 ``Interfaces and Free Boundaries in Fluid Mechanics and Materials Science'', August 20 - 25, 2023, Waseda University, Tokyo, Japan, August 24, 2023.

  • L. Schütz, M. Heida, M. Thomas, Materials with discontinuities on many scales, SCCS Days 2023 of the Collaborative Research Center -- CRC 1114 ``Scaling Cascades in Complex Systems'', November 13 - 15, 2023.

  • M. Thomas, Approximating dynamic phase-field fracture with a first-order formulation for velocity and stress, Annual Workshop of the GAMM Activity Group on Analysis of PDEs, September 18 - 20, 2023, Katholische Universität Eichstätt-Ingolstadt, September 20, 2023.

  • M. Thomas, Damage in viscoelastic materials at finite strains, Workshop ``Variational Methods for Evolution'', December 3 - 8, 2023, Mathematisches Forschungsinstitut Oberwolfach, December 7, 2023.

  • M. Thomas, Some aspects of damage in nonlinearly elastic materials: From damage to delamination in nonlinearly elastic materials, Variational and Geometric Structures for Evolution, October 9 - 13, 2023, Università Commerciale Luigi Bocconi, Levico Terme, Italy, October 10, 2023.

  • M. Thomas, Approximating dynamic phase-field fracture with a first-order formulation for velocity and stress, Nonlinear PDEs: Recent Trends in the Analysis of Continuum Mechanics, July 17 - 21, 2023, Universität Bonn, Hausdorff School for Advanced Studies in Mathematics, July 17, 2023.

  • M. Thomas, Approximating dynamic phase-field fracture with a first-order formulation for velocity and stress, Seminar für Angewandte Mathematik, Technische Universität Dresden, June 5, 2023.

  • M. Thomas, Nonlinear fracture dynamics: Modeling, analysis, approximation, and applications, Presentation of project proposals in SPP 2256 ``Variational Methods for Predicting Complex Phenomena in Engineering Structures and Materials'', Bad Honnef, March 27, 2023.

Flexible Research Platform