Recent Advances in Skin Biomechanics and Mechanobiology – Convergence of Physical Experiments, Imaging and Modelling Techniques
by Georges Limbert, Adrian Buganza-Tepole, Michel Destrade, Cormac Flynn and Aisling Ní Annaidh

Besides the brain, no other organ of the human body plays such a central role in our everyday biological, physical and social life than the skin. The skin is the first line of defence of our body against the external environment, and therefore, acts as an essential physical interface. This interface controls many types of exchanges between our inner and outside worlds which take the form of mechanical, thermal, biological, chemical and electromagnetic processes.

To unravel some of the secrets of such a complex organ new integrated experimental, imaging and multiphysics computational techniques are needed and novel constitutive theories explaining particular mechanobiological processes need to be formulated and put to the test.

The first objective of this mini-symposium is to present the latest experimental, imaging and modelling techniques to characterise and predict the biomechanics, mechanobiology and biophysics of the skin in health, disease, ageing and trauma. The second objective is to provide a forum for open discussions and for identifying current and future research challenges. Special emphasis will be placed on papers demonstrating how integration of multiple techniques (e.g. physical testing and in situ imaging, physical testing and physics-based numerical simulations) can be pivotal in unveiling fundamental aspects of skin physiology and biophysics.

We expect presentations from academia and industry, and therefore the event should also provide excellent networking opportunities. The mini-symposium will be of particular interest to interdisciplinary researchers and engineers working in the medical devices, consumer goods, cosmetics, pharmaceutical, numerical simulation, sport equipment, tissue engineering and regenerative medicine sectors.

Cellular Mechanics and Mechanobiology
by Muhammad H. Zaman, Ben Fabry and Thomas Franz

Models based on partial differential equations arise in a number of applications in science and engineering. These models often present significant mathematical and numerical challenges: for example, questions of a mathematical nature such as those pertaining to the quantitative and qualitative analysis (existence of solutions, their structure, regularity, etc.) and numerically related issues such as convergence of approximate solutions, the consistency of the numerical schemes, and the development and implementation of algorithms.

The objective of this mini-symposium is to bring together researchers working on theoretical and numerical aspects of models based on partial differential equations for the purpose of sharing ideas on the well-posedness of problems, the behavior of solutions, and on the design of reliable numerical schemes. We are interested in various approaches, which can include finite elements, finite differences, boundary elements, spectral methods, least-squares methods, and non-standard discretization techniques.

Models for Computational Analyses of Cardiovascular Biomechanics
by Daniel Balzani, Gerhard A. Holzapfel, Alexey Kamenskiy, Igor Kars̆aj, and Michele Marino

Advances in modeling and simulation of the cardiovascular system enable improvements in our understanding of cardiovascular mechanics and mechanobiology. They also provide novel approaches to optimize medical device design, patient risk stratification, and surgical planning that are increasingly relevant to clinical practice. The goal of this minisymposium is to bring together researchers to develop computational methods for the analysis of the cardiovascular system in health and disease with experimental and clinical researchers in these areas and thereby foster multidisciplinary interaction and collaboration. Contributions are invited that present recent advances in a broad range of topics, including:

• constitutive models and algorithms for cardiovascular tissues in health and disease;
• computational methods to simulate interventional treatments, such as angioplasty and stenting, or the deployment of stent-grafts and transcatheter valve prostheses;
• cardiovascular fluid/solid mechanics and fluid-structure interaction;
• modeling approaches to characterize the interrelations between mechanics and biological/biochemical processes such as aging, growth, remodeling, adaptation, repair, and smooth-muscle activation;
• computational models of vascular pathologies, including aneurysms, dissections, pediatrics, etc.;
• multiscale modeling approaches that bridge the scales from the sub-cellular level to the tissue level;
• optimization methods for the identification of material properties or surgical and device design;
• image processing methods for the construction of three-dimensional anatomical geometries;
• approaches to uncertainty quantification and sensitivity analysis.

Topology Optimization of Micro-/Nano-structures
by Yongbo Deng, Zhenyu Liu, Weihong Zhang, Jihong Zhu and Jan G. Korvink

Topology optimization can determine the topology, shape, and size of a structure, simultaneously. It has been regarded to be one of the most powerful approaches for the inverse design of structures in several scientific areas, including elasticity, fluid dynamics, thermodynamics, electromagnetics, etc. Currently, development of micro-/nano-technology, numerical computation and manufacturing processes brings new opportunities and challenges to the topology optimization community. On the one hand, there is a scaling effect of structures at the micro-/nano-scale which increases the physics behind the structural design; on the other hand, lithography-like reductive manufacturing and 3D printing-like additive manufacturing processes have been extended downward to the nanoscale. Therefore, micro-/nano-technology provides attractive and challenging opportunities for the topology optimization community, because the optimization procedure of the micro-/nano-structures requires to synthetically include scaling effects and manufacturability.

For this minisymposium, contributions dealing with topology optimization and the corresponding applications in micro-/nano-technology for elasticity and fluidic mechanics are highly encouraged. The topics include but not limit to engineering structures, metamaterials, hierarchical structures, interfacial textures, combination of shape and topology optimization, topology optimization combined with optimal control, optimization combined with model reduction, smart structure and material considerations. The related application areas can include but are not limited to mechanical engineering, mechanics, numerical computation, manufacturing, aeronautics, astronautics, multiple scales and multiphysics, electronics, bio-medicine, materials design and processing, and methods such as acceleration through single-objective and many-objective optimization, meta-models for high-dimensional problems, uncertainty quantification, etc.

Material Design, Modelling and Applications 
by Georgios E. Stavroulakis, Georgios A. Drosopoulos and Sarp Adali

The purpose of this mini-symposium is to bring together researchers from structural and mechanical engineering fields and investigate a wide range of problems using numerical, analytical and experimental methods. Papers related to modelling, design and optimization of various engineering materials and structures and in particular, composite materials are solicited.

Traditional fibre reinforced composites, sandwich panels, composite laminated beams, shells, plates, woven composites and nanocomposite materials will be part of the symposium. Papers on different failure types, on mechanical behaviors of structures and on material properties are welcome. The microscopic structure of the materials may be assessed using multi-scale techniques. Papers on homogenization, hierarchical and multi-scale approaches connecting the length scales of composite materials are encouraged.

Emphasis is on the solution of special problems, such as buckling/post-buckling, nonsmooth effects like contact and friction or vibration including carbon nanotube or graphene reinforced nanocomposites. Papers on smart and functionally graded structures are welcome. Load types include but not limited to statics and dynamics, thermal effects and acoustic applications. Studies on novel meta materials and including auxetics may be presented.

Experimental, Theoretical and Numerical Investigations of Sea Ice in the Marginal Ice Zone of Antarctica
by Carina Nisters, Jörg Schröder, Doru C. Lupascu, Tim Ricken and Marcello Vichi

The steady long-term decline in Arctic sea ice and the sudden recent decrease of ice extent in the Southern Hemisphere have manifold impacts on the Earth system, and they are of eminent public and scientific interest. Discussions about hemispheric trends, the variability of sea ice cover, and its relation to global climate change often ignore the fact that sea ice has high regional variability and that the regions where the ice retreats or develops in a given year can be very different. The satellite-based remote sensing data that document such changes in ice thickness are collected on coarse spatial scales and typically cannot resolve finer details. However, many of the processes that make sea ice such an essential aspect of the polar oceans take place at much smaller scales, which range from sub-millimeters to meters.

Understanding how the large-scale behavior of satellite-monitored sea ice relates to and depends on the processes that drive the growth and decay of ice requires an understanding of the evolution of ice structure and its properties on these smaller scales. Besides, the ice structure is temperature-dependent and exhibits considerable spatial and temporal variability. Other properties of sea ice, such as its light transmission and reflexion, a complex microstructure consisting mainly of ice, brine, and air inclusions, and the integration of biota and particles in the ice, must be understood to describe the characteristics of sea ice entirely. At the same time, the interactions at the boundary layers between the atmosphere and sea ice, as well as between wave and sea ice, are crucial components to describe the dynamics of sea ice fully. Sea ice has a significant influence on the interaction between air and sea, both the outgoing long-wave radiation and the heat exchange are reduced, and the oceanic absorption of the short-wave radiation is modulated. Shearing between the ice and the underlying ocean often occurs in response to wind, ocean currents, and waves. This makes the understanding of ice dynamics on large (spatial and temporal) scales equally essential and underlines the need for a sufficient rheological description and numerical approximations.

This mini-symposium invites new ideas and concepts, which will lead to progress in the development of efficient, reliable, and robust solution methods for the simulation of sea ice dynamics, growth and melting processes, and biogeochemical activities in ice.

Extended Continua: Computational Challenges
by Andrew McBride, Ali Javili and Paul Steinmann

Many important engineering and natural materials possess an underlying sub-scale structure that requires extended continuum descriptions (non-local, gradient, micromorphic, etc) to predict their response.

This presents numerous computational challenges including, among others,

• the correct functional setting;
• implementation and efficiency issues;
• model and parameter identification
• verification/calibration and validation.

Potential approaches include:

• properly balanced Ansatz spaces in Galerkin methods;
• collocation methods;
• automatic and symbolic differentiation;
• error estimation;
• adaptivity and parallelization;
• machine learning and inverse methods; and
• experimental data.

Given these challenges, the objective of this minisymposium is to share expert knowledge on recent developments in computational methods tailored to extended continua and thereby significantly advance the field.

Discrete Element Modelling: Calibration and Validation
by Corné J. Coetzee and Daniel N. Wilke

The Discrete Element Method (DEM) was introduced 40 years ago by Cundall and Strack. At the time, modelling large industrial scale applications was not possible, but as computation capabilities increased over the years, DEM has become the numerical method of choice for analysing granular materials in all kinds of industries. Examples include bulk materials handling in the mining and agricultural sectors such as belt conveying and transfer chutes, mixing, crushing, screening, tumbling mills as well as bin, hopper and silo filling and discharge. In the pharmaceutical industry it is used to analyse coating processes, die filling and granulation. Other industries include food handling, chemical engineering, geotechnical and civil engineering, oil and gas, mineral processing and powder metallurgy.

DEM can only be used as an effective design and predictive tool if the results are accurate and obtained in a reasonable time frame. The material is modelled as individual or discrete particles and in large scale applications this can range from billions to trillions. These large numbers of particles cannot be modelled and simplifications need to be made, especially in terms of particle shape and size. More effective algorithms, faster computers and the use of (multi) graphics processing units (GPUs) can also speed up the simulations. The bulk behaviour of the material is driven by the model parameters such as inter-particle coefficients of friction, contact stiffness and damping. These parameter values should be carefully selected in a process often referred to as DEM calibration. Over the years, a broad approach for the calibration of cohesionless (dry) materials has emerged. This includes a number of laboratory experiments for measuring the bulk response, which are then modelled while the parameter values are adjusted until the predicted bulk response is accurate. This can also be combined with optimisation and design of experiment techniques to find the calibrated parameter set more efficiently . Recent calibration approaches also include uncertainty quantification through Bayesian parameter estimation . Cohesive (wet) materials can also be modelled by introducing cohesive forces acting at the contacts. However, it is still not possible to accurately model the bulk behaviour of such materials and more research is needed in selecting appropriate contact models, including calibration and validation.

The aim of this mini-symposium is to bring together experts in this field to present their latest developments and results. Researchers, academics and practising engineers are all welcome to submit abstracts on any of the following topics:

•  Calibration of cohesionless (dry) granular materials including particle scale and shape
• Calibration of cohesive (wet) granular materials including validation
• Speed-up of computation time through the use of more effective algorithms and GPUs
• The modelling of unique, challenging and interesting applications in all industries
• Industry case studies

Numerical Methods for Partial Differential Equations
by Daniele Boffi and Lucia Gastaldi

Models based on partial differential equations arise in a number of applications in science and engineering. These models often present significant mathematical and numerical challenges: for example, questions of a mathematical nature such as those pertaining to the quantitative and qualitative analysis (existence of solutions, their structure, regularity, etc.) and numerically related issues such as convergence of approximate solutions, the consistency of the numerical schemes, and the development and implementation of algorithms.

The objective of this mini-symposium is to bring together researchers working on theoretical and numerical aspects of models based on partial differential equations for the purpose of sharing ideas on the well-posedness of problems, the behavior of solutions, and on the design of reliable numerical schemes. We are interested in various approaches, which can include finite elements, finite differences, boundary elements, spectral methods, least-squares methods, and non-standard discretization techniques.

Novel Simulation Techniques for Deforming-Domain Problems
by Marek Behr and Stefanie Elgeti

The mini-symposium will focus on computational methods and flow simulations that involve deforming domains, and in particular, fluid-structure, fluid-object, and solid-solid interaction, as well as fluid-air and melt-solid interfaces.

Both major mesh-based approaches, that of interface-tracking and interface-capturing, will be represented. An interface-tracking method places computational nodes at the moving interface and adjusts the computational mesh to the movement of those nodes. An interface-capturing method allows the computational mesh to be stationary, and records which computational cells, or elements, are filled with fluid, empty, or contain the interface.

The challenges associated with interface-tracking methods include: robust interface-tracking methodology, general algorithms for displacing the nodes at the interface, compatibility of fluid and structural representation, and adjustment of the computational mesh away from the interface.

The interface-capturing methods will benefit from: improved accuracy of the predicted position of the interface, control over mass conservation errors, representation of interfacial phenomena such as surface tension, and adaptive refinement at the interface.

Our goal is to provide a forum for exchange of ideas, latest developments, and comparison of various methods, as well as discussion of applications of these methods.

Emerging general approaches relevant to the above mentioned engineering problems are especially welcome, including space-time meshing, model-order reduction, uncertainty quantification, hybrid modeling, and data driven techniques.

Model Order Reduction in Computational Mechanics and Mechatronics
by Tamara Bechtold and Jan G. Korvink

The availability of mathematical models is essential for the design, analysis and control of modern technical systems. With the increase of computational power, the complexity of these mathematical descriptions increases as well, which maintains the computational needs above the available possibilities. This is especially true for mechatronic systems, which operation is determined by multiple energy domains and their respective couplings. Modeling these features on continuum level (by partial differential equations) and numerically simulating them by, e.g., the finite element method, requires a time integration of large scale nonlinear ordinary differential equation systems. Mathematical methods of Model Order Reduction (MOR) offer the possibility to replace such high dimensional model with a lower dimensional surrogate, such that the computational time can be significantly reduced while preserving the accuracy of the original numerical model [1]. Reduced order models can be used at the system-level for prediction, analysis and control.

Whereas MOR for single-domain linear systems is considered as state of the art and is already available within industrial finite element simulators [2], considerable research effort is still being dedicated to model order reduction of multiphysical, parameterized and nonlinear systems [3].

Over the past decades, the discipline of model order reduction has seen tremendous advancements in the underlying theory, leading to a wider range of applicability of the ideas of “real-time simulation” and recently “digital twins”. Similarly, applications of model order reduction to real mechatronic problems arising in industry and academia have further fed the development of theory to make the technique more practicable. This minisymposium at the AFRICOMP 2020 will bring together theorists and practitioners working in the area of model order reduction in computational mechanics and mechatronics.

Advanced Strategies for Numerical Simulations in the Presence of Polymorphic Uncertain Data
by Michael Kaliske, Wolfgang Graf, Sigrid Leyendecker, Stefanie Reese, Wolfgang Wall

Numerical simulations (analysis and design) of structures or systems are currently often characterised by deterministic methods. Deterministic modelling of the reality indicates preciseness and safety, while, on contrary all available data and information are characterized by various types of uncertainty (variability, imprecision, incompleteness), which cannot be neglected.
The main focus is the presentation of methods for the numerical simulation of structures under consideration of polymorphic data uncertainty. With the help of the mini-symposium, the opportunities of interand transdisciplinary shall be used for the generation of synergies between mathematics and engineering sciences.

Engineering solutions are characterized by inherent robustness and flexibility as essential features for a faultless life of structures and systems under uncertain and changing conditions. An implementation of these features in a structure or system requires a comprehensive consideration of uncertainty in the model parameters and environmental and man imposed loads as well as other types of intrinsic and epistemic uncertainties. Numerical design of structures should be robust with respect to (spatial and time dependent) uncertainties inherently present in resistance of materials, boundary conditions etc. This requires in turn the availability of a reliable numerical analysis, assessment and prediction of the lifecycle of a structure taking explicitly into account the effect of the unavoidable uncertainties.

Challenges in this context involve, for example, limited information, human factors, subjectivity and experience, linguistic assessments, imprecise measurements, dubious information, unclear physics etc. Due to the polymorphic nature and characteristic of the available information both probabilistic and set-theoretical approaches as well as newly developed joint approaches are relevant for solutions.

This mini-symposium aims at bringing together researchers, academics and practicing engineers concerned with the various forms of advanced engineering designs. Recent developments of numerical methods in the field of engineering design which include a comprehensive consideration of uncertainty and associated efficient analysis techniques, such as advanced Monte Carlo simulation, meta-model approximations, and High Performance Computing strategies are explicitly invited. These may involve imprecise probabilities, interval methods, Fuzzy methods, and further concepts.

Furthermore, methods for interacting and interdependent uncertain variables as well as uncertainty models for spatial and temporal dependent quantities are addressed. The contributions may address specific technical or mathematical details, conceptual developments and solution strategies, individual solutions, and may also provide overviews and comparative studies. Particular attention should be paid to practical applicability in engineering. Besides the applications of the involved engineering sciences, “real world” scenarios should be presented.