Browse Author: Wojciech Sołowski

E-Unsat 2020 presentation and Young Invited Lecture

The E-Unsat 2020 has been excellently organised and a resound success, despite being fully online. Even though I must say I did miss the chats with friends and informal, but often illuminating discussions with the attendees, I still have seen many great presentations and learnt much.

Silo filling comparison, CPDI vs Granular CPDI. Simulation done by inserting points on top, and letting them settle under gravity. Lines denotes the domain of the material points, with significant deformations and lack of density recovery in CPDI simulation, while with granular extension the particles settle down at much more realistic density. We used Mohr-Coulomb model for the simulation, (c) Seyedan & Sołowski

I was also presenting the paper authored by Dr Abed and me on validation of gas transport couplings in our THMC coupled Finite Element Method code Thebes (presentation here, and paper here). We have much more to do in relation to gas transport – my doctoral student Abhishek Gupta is responsible for that, and we hope to deliver ambitious simulations of gas transport of a generic nuclear waste repository in a year or two.

I was delighted to deliver the Young Invited Lecture on Granular Material Point Method, something we are working on with Seyed Mohammad Javad Seyedan. We will aim to publish full paper based on the presentation, but for now, the presentation is here.

Many more exciting things has happened and is happening with the research in my group – I will try to update you on that soon!

Long-delayed update

Hi, I have been very busy recently, leading to lack of updates for a very long time. During past few months I delivered a plenary lecture during the 32nd Nordic Seminar on Computational Mechanics in Oulu (slides), Quoc Anh Tran graduated with a doctoral degree (thesis), and we have a new journal paper published, “A convected particle least square interpolation material point method” in IJNME. That one is not currently freely available, so in case you need a copy, contact me at my Aalto email.

Spectacular train station in Liège, architect Santiago Calatrava

So, what the future holds? SMJ Seyedan should graduate relatively soon with another doctoral degree related to MPM, Tito Adibaskoro is slowly progressing towards the same goal. To continue the research I applied for research related to MPM both at national level (Academy of Finland proposal) and international one (Marie-Curie ITN network), and let’s keep fingers crossed.

On the THMC modelling of clays, a new student has started in January, more update on that later!

Few more presentations…

A statue of a mermaid sitting on a rock, surrounded by water.
Photo: CreativeCommons (author AVDA Berlin), see more

Last month I had a pleasure to give presentations on MPM and modelling of clays at Chalmers University, Technical University of Denmark (DTU) and Hamburg University of Technology (TUHH). The presentations are here for MPM and Clay

Hopefully the cooperation with those universities will be successful and we will get some grants together in the future!

Papers, papers…


Much is happening at Aalto and I have been late with much what should be posted. Just to update things quickly, recently SMJ Seyedan has published a paper detailing a small strain enhancement for constitutive models for soils. The paper is here (open access). The idea is to have a thermodynamically consistent enhancement in the initial part of the stress-strain curve, which can be applied to any model using constant shear modulus. We tested it for Mohr-Coulomb and Modified Cam Clay, but it should work for other constitutive models too. Unfortunately, we have no such neat way to adjust the bulk modulus yet, but hopefully in the future… The paper comes with a Matlab code, so it is easy to try it out!


On another front, QA Tran has published a paper related to the null space errors in the Material Point Method. The paper is here and is also open access. The paper discusses null space errors and show how to filter them out efficiently. Such filtering is recommended when we have a problem with large deformations, in which number of material points in some grid cells increases above the initial value. That creates a problem when the data is tranferred from the nodes back to the material points – we have less nodes than the points and as such the transfer uses extra assumptions leading to errors. For example, having 4 nodes transferring data to 9 points, we need to create 9 values at the points from 4 values at the node – that is impossible without extra assumptions which may lead to errors.
The same paper also shows that use of a generalised-alpha integration scheme in the Material Point Method helps to damp out high frequency vibrations, without affecting the total energy and total momentum balance much. Very useful when we need a solution without high frequency noise – and much better than using an overall damping coefficient which alters the solution significantly.

References:
S. Seyedan and W. T. Sołowski, “Enhancing Constitutive Models for Soils: Adding the Capability to Model Nonlinear Small Strain in Shear,” Advances in Civil Engineering, vol. 2019, Article ID 6016350, 11 pages, 2019. https://doi.org/10.1155/2019/6016350.
Tran, Q‐A, Sołowski, W. Temporal and null‐space filter for the material point method. Int J Numer Methods Eng. 2019; 1– 33. https://doi.org/10.1002/nme.6138

Dragan Grgic public lecture at Aalto, 8th April 2019

Microstructural characterization and numerical evaluation of the effective elastic properties of oolitic rocks

Aalto University has had the pleasure to host a public lecture of Professor Dragan Grgic (GeoRessources Laboratory, Université de Lorraine). Professor Grgic visited Finland due to cooperation with VTT and GTK. During the visit, he kindly agreed to held a lecture at Aalto.

Professor Grgic presentation can be downloaded here.

MPM 2019 Conference in Cambridge and presentation at Imperial College London

We have attended the 2019 MPM conference in Cambridge in numbers. I had a presentation on Uintah software and a keynote, while other members of the research group presented their research. You can find the proceedings here: http://mpm2019.eu/papers

In particular there are some presentations available:

And the conference papers:

On the way back, I have been given opportunity to present my research at Imperial College London. In particular, you can download the abridged presentation related to our research with Dr Abed in project THEBES: THMC Behaviour of the Swelling Clay Barriers

New Journal Paper: GIMP modelling of large deformation problems including strain-rate effects – Application to penetration and progressive failure problems

Quoc Anh Tran, doctoral student working in the Academy of Finland project on landslide modelling, managed to get a journal paper published in Computers & Geotechnics. The paper shows number of improvements in landslides modelling with the Material Point Method. Those include strain rate dependent, structure dependent Mohr-Coulomb model for undrained analysis. We also  used a simple non-local formulation for the shear-band thickness (Pinyol et al. 2017), which reduces mesh dependence. After validation, the paper shows some – I dare to say – rather nice simulation of a Saint-Monique landslide.

The paper is open access, download it from here:

https://www.sciencedirect.com/science/article/pii/S0266352X18302738

Enjoy!

Conferences, conferences…

Last several months have been really busy, with me having really no time to catch my breath (but well, we have now 5 journal papers under review, keep fingers crossed). Recently, SeyedMohammadJavad Seyedan presented in the beautiful city of Porto in the NUMGE 2018 conference. He was explaining how to enrich the constitutive model for soil with capability to model the small strain shear nonlinearity. It is a neat expansion, which has also thermodynamical consistency (note: full paper under review)…   Then, Dr Ayman Abed presented on chemical coupling (download paper) in UNSAT Conference in Hong Kong. That is a nice effort with cooperation from UPC BarcelonaTech. Finally, I have been presenting in Vienna Dr Yang Xiujuan paper on water retention behaviour of MX-80 bentonite, when partially saturated with saline solution, as unfortunately Xiujuan could not come to Vienna.

Hong Kong – photo from the conference dinner (yay, my new camera)

Presentations in Milan 12-13 Sep 2017 (seminar and keynote)

Hey,

Today in the beautiful city of Milan, I had a seminar at the Politecnico di Milano on the bentonite behaviour modelling, related to THEBES project. The slides are here. Also, the keynote lecture in the IV ECCOMAS YOUNG INVESTIGATOR CONFERENCE – YIC2017 entitled “MPM or FEM / PFEM / SPH /… Insights on the Material Point Method future” is here. In case you need more information or the movies (sorry, no movies in the .pdf), please do not hesitate to contact me! We are always happy to share!

Enjoy!

Paper published and available for download!

The new paper in Computers & Geotechnics:

 A study on how to couple thermo-hydro-mechanical behaviour of unsaturated soils: Physical equations, numerical implementation and examples

 is now on-line!

For the paper please follow https://authors.elsevier.com/a/1VXgy,63b~gd8H  to get the free copy (link valid until 30th of September). Afterwards, please contact me for the copy if you need one… The paper is summing up the developments of the coupled Finite Element code for the THEBES project at Aalto.

 
Thanks for reading!
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