Class

Palabos Summer School 2020

Dates

8-10 July 2020

Place

University of Geneva

Typical audience

Typical audience are advanced doctoral researchers and postdocs. Note that the class is open to anyone interested, although participants should have previous experience with the Lattice Boltzmann Method. No prior knowledge of Palabos is required.

Price

250 EUR (academic) / 500 EUR (industrial) Updated price for 2020 online version of the class: 40 CHF (academic) / 80 CHF (industrial)

Registration

Registration is closed.

 

COVID-19 Situation (updated 21st April)

Following the global outbreak of the Coronavirus (COVID-19), we will be unable to hold the Palabos Summer School 2020 in physical classrooms at the University of Geneva. Instead, the class will be taught online with the help of a Web conferencing tool.

The format of the class however remains unchanged. The class is limited to registered users. It lasts three days and consists of interactive theory sessions (with the possibility to ask questions) and practice sessions, during which participants receive individual help from the staff for problem solving.

 

 

The Palabos Summer School 2020 covers selected topics in Lattice Boltzmann theory and a practical introduction to the open-source Palabos software library. Participants should have prior exposure to the Lattice Boltzmann Method and Computational Fluid Dynamics. Typical participants could be PhD researchers who are already 1-2 years into their PhD or PostDocs (LB beginners are instead referred to Week 5 of our Mooc). The proposed topics cover

 

LBM:

  • Comparison of algorithms for curved boundary conditions

  • Mesh refinement in LBM

  • Fluid-structure interaction and modeling of deformable immersed bodies

  • Modern collision models: Universal mathematical description and implementation details

  • Compressible lattice Boltzmann models: A collide-and-stream viewpoint

Palabos:

  • Concepts of Palabos at the user level

  • Concepts of Palabos at the application programmer level

  • Fluid-Structure interaction with multiple immersed, deformable bodies

  • Simulation of exterior flow problems with a nested grid hierarchy



Schedule

 

9:00 - 10:30

10:45-12:00

13:30 - 14:30

14:45-17:00                       

Wed 8.7.

Theory: Palabos software architecture

Palabos hands-on

Theory: Curved boundary conditions 

Palabos hands-on

Thu 9.7.

Theory: Palabos software architecture

Palabos hands-on

Theory: Mesh refinement algorithms

Palabos hands-on

Fri 10.7.

Theory: Fluid-structure interaction and simulation of Red Blood Cells

Palabos hands-on

Theory: General framework for modern collision models.

Theory: Compressible LBMs
(School ends at 16:00)

 

Administrative information

Preparation: Hands-on sessions are carried out on the participants’ own laptops, which should be prepared in advance to be equipped with a C++ compiler, MPI, and Paraview. Typical configurations could be (1) a Linux Laptop, (2) a Windows Laptop with a properly configured Linux sub-system, (3) a Mac with a development environment (e.g. through Homebrew). Before attending the class, try to download and compile Palabos.

 

Class contents

Palabos software architecture

Lecturer: Dr. Jonas Lätt

The structure of the Palabos software library is described for two types of target usage, namely the set up new Palabos-based simulations and the development of new algorithms and models in Palabos. The philosophy of Palabos encourages smooth interaction between different aspects of the software, including parallel execution speed, coupling between physical models, execution with different LB collision models or lattice structures, addition of turbulence models, and finally, pre- and post-processing and checkpointing. The class teaches that this interaction is guaranteed by respecting the software model of Palabos, which includes generic collision models (“Dynamics classes”), generic non-local algorithms/couplings (“Data Processors”), and template-driven lattice structures (“Lattice Descriptors”).

Curved boundary conditions

Lecturer: Francesco Marson

During this session, we will cover the main techniques to handle complex curved boundary conditions. We will see how to deal with moving boundaries and the different ways to compute the fluid-solid momentum exchange. At the end of the lecture, you will be able to choose the best fitting off-lattice boundary condition for your application and to use it for a fluid-solid interaction problem.

Mesh refinement algorithms

Lecturer: Dr. Orestis Malaspinas

Mesh refinement is of crucial importance for many engineering applications especially for high Reynolds number flows. In the frame of the lattice Boltzmann method, the transitions are particularly sharp because of the cartesian nature of the mesh and must be handled with great care. In this session, we will discuss the theoretical aspects of mesh refinement in the lattice Boltzmann method and its implementation in Palabos. Finally, we will see how to set up the mesh to perform the simulation of a high Reynolds number flow and then perform an actual simulation.

Fluid-structure interaction and simulation of Red Blood Cells

Lecturer: Christos Kotsalos

Fluid-structure/ solid interaction (FSI) concerns how a fluid understands the existence of an immersed body and vice-versa. A consistent and meticulous handling of the FSI is a very critical factor for stable and accurate simulations that deal with both fluid and solid phases. Main focus of the course will be cellular blood flow simulations, i.e., explicit modeling of the trajectories and deformations of blood cells (red blood cells, platelets) inside the blood plasma. More in detail, Palabos will be used for the simulation of the fluid phase (blood plasma) and the immersed boundary method, while an in-house finite element solver will be used for the resolution of deformable bodies physics. By the end of the session, the users should be able to couple Palabos with external solvers and build FSI simulations of complex systems, other than biomedical applications.

General framework for modern collision models

Lecturer: Dr. Christophe Coreixas

During the past three decades, numerous collision models have been proposed to improve the numerical stability of lattice Boltzmann methods (LBMs). Roughly speaking, they are distinct with regard to the moment space used for the collision step (raw, central, Hermite, central Hermite or cumulants), the computation of the relaxation time (which is dynamic for entropic and subgrid scale model based LBMs), and the non-equilibrium part of populations (that is recomputed for regularized approaches). This lecture is then dedicated to the presentation of a unified framework that ease: (1) the derivation of relationships between collision models, and more importantly, (2) their implementation in an LB code.

Compressible lattice Boltzmann models

Lecturer: Dr. Christophe Coreixas

Over the past three decades, the lattice Boltzmann method (LBM) has emerged as an interesting candidate for computational fluid dynamics and beyond. Despite the wide validity range of standard LBMs, the simulation of fully compressible flows (including discontinuities such as shock waves) remains a tedious task. This talk aims at providing basic notions on how to design compressible LBMs, with a particular emphasis on models based on the stream-and-collide algorithm. Several strategies allowing for the simulation of realistic configurations in an acceptable time frame will also be discussed. Eventually, recent compressible LBMs compliant with best practices originating from discrete velocity models (numerical equilibria and dynamic/static lattice shifts) will be presented.