VKI Seminar Series 2024
Free registration on https://events.vki.ac.be in respect with the VKI eligibility criteria. You will receive the information to join the seminar of your choice after the registration.
Feedback Control of Liquid Metal Coating (open to public)
Guest Speaker: Dr. Fabio Pino, Université Libre de Bruxelles / von Karman Institute for Fluid Dynamics
Abstract: Hot-dip galvanizing is an industrial process that protects steel products from corrosion. Ensuring a uniform coating remains challenging due to a fluid instability known as undulation. This work presented solutions to this issue, significantly advancing the field of liquid metal coating.
By immersing and then withdrawing a metal sheet from a bath of molten zinc, a liquid film forms on the sheet’s surface, which then solidifies into a protective layer. Controlling the final coating's thickness involves using gas jets to remove excess zinc from the bath. At withdrawal speeds above 2 m/s, the jets oscillate, triggering the undulation instability, which leads to uneven coatings and increased environmental impact due to additional surface treatments.
This research project developed a feedback control strategy to mitigate the undulation using gas jets and magnetic actuators with limited liquid film observations. The project followed a multidisciplinary approach, integrating reduced order modelling, numerical methods, linear stability analysis, model predictive control, and machine learning control. An analytical reduced-order model of the three-dimensional (3D) liquid film was developed, with the observation point location based on linear stability findings. Control methods based on linear stability analysis were tested on two-dimensional (2D) unstable waves, demonstrating strong performance and revealing intricate physical control mechanisms. Expertise was developed in machine learning control by comparing various methods on flow control test cases. Based on this knowledge, reinforcement learning algorithms were applied to the undulating problem, reducing the wave amplitude by 10% with jets pushing the crests and magnets rising the troughs.
These findings pave the way for industrial applications of the feedback regulator to reduce undulation instability and deepen the understanding of the liquid film dynamics. Integrating machine learning control methods into a novel workflow alongside analytical approaches and simulations, this research offered significant advancements in industrial coating processes. Owing to its versatility, this new methodology holds promise for applications in other engineering domains, such as combustion flows or turbulence control.
Biography: Fabio holds a Master’s Degree in Aerospace Engineering from Politecnico di Torino and Politecnico di Milano, as well as a Diplôme d’Ingénieur from École Centrale de Lyon. He continued his education with a 2nd level Master in Space Exploration and the VKI Research Master in Fluid Dynamics. Recently, he earned his Ph.D. from Université Libre de Bruxelles (ULB) in partnership with VKI, with a thesis titled "Feedback Control of Liquid Metal Coating."
Overview of the KRUPS hypersonic re-entry capsule (open to public)
Guest Speaker: Prof. Alexandre Martin, University Research Professor at the University of Kentucky
Biography: Alexandre Martin obtained a B.Sc. in Physics in 1998 from the University of Montréal (Québec, Canada), and a M.Sc.A. (2001) and Ph.D. (2005) from the Department of Mechanical Engineering at École Polytechnique de Montréal (Québec, Canada). He worked primarily on plasma ablation, with an application on industrial high-voltage circuit-breakers. After continuing this work as a Research Associate at École Polytechnique for a year, he then moved to the University of Michigan (Ann Arbor, MI), where he worked on the material response of atmospheric entry vehicles. He is currently a professor in the Mechanical and Aerospace Department at the University of Kentucky (Lexington, KY), where he has been since 2010 and currently hold the EJ Nutter professorship. He has mainly continued his work on the modeling of atmospheric entry vehicles, but also taken other projects such as modeling bourbon barrel toasting. Dr. Martin is an associate-fellow AIAA, a Fellow of St Catherine's College at the University of Oxford, and holds the title of University Research Professor at the University of Kentucky, He has published more than 120 peer-reviewed archival journal and conference papers, and is regularly invited to give presentations on hypersonic ablation.
On the gas-liquid coupling instability in jet wiping using traditional and novel numerical models (open to public)
Guest Speaker: David Barreiro Villaverde, Collaborative PhD VKI and University of A Coruña
Abstract: The jet wiping process is a contactless metering technique implemented in continuous hot-dip galvanizing lines to control the coating mass deposited on a steel strip via high-speed gas jets. The interaction between the gas jets and the liquid film is unsteady, resulting in long-wavelength defects (undulations) in the final product, of great concern in industry for quality standards. This seminar will explore the hydrodynamic mechanisms responsible for these undulations using numerical simulations in OpenFOAM and modal analysis; in particular, the numerical model combines the Volume of Fluid (VOF) and Large Eddy Simulation (LES) techniques, and the dominant flow patterns are extracted via multiscale Proper Orthogonal Decomposition (mPOD). The methodology is validated against laboratory experiments and then applied to investigate the dynamics of jet wiping under various conditions. The goal is to uncover the instability mechanisms in different wiping scenarios and to identify scaling laws that allow extrapolation of the results to industrial configurations, which remain unfeasible with current state-of-the-art techniques. In this sense, the seminar will also introduce a novel hybrid formulation that implements a two-way coupling between an Integral Boundary Layer (IBL) model for the liquid film and a single-phase solver in OpenFOAM for the gas jet, with the objective of simulating the full industrial conditions. Preliminary results are very promising.
Biography: David Barreiro received a Bachelor’s Degree in Industrial Technology Engineering in 2017 and a Master’s Degree in Industrial Engineering in 2019, both from the University of A Coruña. He then enrolled in the PhD program at the same university, collaborating with the von Karman Institute, where he completed a research stay in 2022. The seminar will cover the topic of his PhD thesis, focusing on the numerical investigation of the hydrodynamic mechanisms responsible for defects in the jet wiping process in continuous hot-dip galvanizing lines.
Hypersonic gas-surface interactions (and bourbon) (open to public)
Guest Speaker: Prof. Alexandre Martin, University Research Professor at the University of Kentucky
Abstract: For extra-orbital missions, ablative materials have always been, and still remain, the primary choice for the design of atmospheric entry heat shields. Because of the many uncertainties associated with the usage of such material in complex aerothermal flow environments, it is important to understand and quantify the effects of the phenomena at play. Many specific areas of research can lead to a better understanding of the underlying physics of aerothermodynamic ablation. More specifically, the topics discussed will touch upon the coupling of material response with CFD codes, using a traditional approach, as well as a unified method, as well as the modeling of the spallation phenomenon. Then, an overview of a recent flight mission designed to validate material response models will be presented.
Biography: Alexandre Martin obtained a B.Sc. in Physics in 1998 from the University of Montréal (Québec, Canada), and a M.Sc.A. (2001) and Ph.D. (2005) from the Department of Mechanical Engineering at École Polytechnique de Montréal (Québec, Canada). He worked primarily on plasma ablation, with an application on industrial high-voltage circuit-breakers. After continuing this work as a Research Associate at École Polytechnique for a year, he then moved to the University of Michigan (Ann Arbor, MI), where he worked on the material response of atmospheric entry vehicles. He is currently a professor in the Mechanical and Aerospace Department at the University of Kentucky (Lexington, KY), where he has been since 2010 and currently hold the EJ Nutter professorship. He has mainly continued his work on the modeling of atmospheric entry vehicles, but also taken other projects such as modeling bourbon barrel toasting. Dr. Martin is an associate-fellow AIAA, a Fellow of St Catherine's College at the University of Oxford, and holds the title of University Research Professor at the University of Kentucky, He has published more than 120 peer-reviewed archival journal and conference papers, and is regularly invited to give presentations on hypersonic ablation.
3rd seminar about OpenFOAM - The Espresso Test Case: Simulating Reactor Thermal-Hydraulics in Openfoam (open to public)
Guest Speaker: Dr. Maria Faruoli, Research Engineer, von Karman Institute for Fluid Dynamics
The event aims to bring together OpenFOAM users as well as those interested in potential applications of the code, both for academic and industrial purposes. The seminar will be held in hybrid mode, and it will be organized in the following way:
- 15.00 - Welcome
- 15.35 - Presentation of the development of the modeling of pool type reactors at VKI: MYRRHABELLE, E-SCAPE and MYRRHA
- Session on “The Espresso Test Case: Simulating Reactor Thermal-Hydraulics in Openfoam” by Maria Faruoli
Numerical simulations of the thermal-hydraulic behavior of the cooling system of nuclear reactors are often used to support the design process. This tutorial will lead the participants to perform a complete numerical simulation of a stylized pool-type nuclear reactor (named ESPRESSO) starting from choosing the solver, meshing the geometry, setting up the numerical parameters and the boundary conditions till post-processing. The tutorial will show different approaches to the modelling of the pumps, the heat exchangers and the core. - 16.45 - Survey on interests in research with OpenFOAM
All the material to follow the tutorial will be provided to the participants during the event, and an online platform will be created to share material and create discussions.
The event is organized four times a year and we would like to invite you to share your applications and implementations.
Multi-scale chemically reacting flows: model reduction and machine learning (open to public)
Guest Speaker: Prof. Riccardo Malpica Galassi, assistant professor, Sapienza University of Rome
Abstract: High-fidelity simulations of multi-dimensional turbulent reacting flows at large Reynolds and Karlovitz numbers with detailed chemistry and transport are an essential tool to provide physical insights and to serve as a valuable database for engineering model validation. Despite rapid advances in CPU/GPU high performance computing hardware, the challenge remains due to the large number of reactive scalar variables and the wide spectrum of spatial and temporal scales. Therefore, there are continuing motivations to develop advanced reduced order models (ROM) to improve computational efficiency while preserving the fidelity and predictive capability of the simulations.
In describing the temporal evolution of chemically reacting systems, the large number of characteristic chemical time scales associated with individual reaction pathways cause the stiffness problem, often demanding an unnecessarily large number of time steps to integrate the equations to the desired practical time. In fact, the fastest chemical scales are orders of magnitude smaller than the flow scales of interest.
Model reduction takes effect by recognizing that fast processes constrain the slow dynamics to evolve on a lower-dimensional, invariant manifold. To this end, the computational singular perturbation (CSP) framework employs an eigenvalue decomposition of the local Jacobian matrix to identify the fast/slow spectral gap and projects the system onto the slow invariant manifold (SIM), allowing a significantly accelerated time integration with an efficient explicit algorithm, along with a corrective projection for fast exhausted modes. In fact, the slow dynamics, free of the fast scales, is not stiff anymore and evolves within the SIM at a pace which is orders of magnitude larger than the system's fastest timescale. While the CSP-based solvers have demonstrated effective computational accelerations by orders of magnitude in time steps, a major computational overhead remains in the operation of the large Jacobian matrix to compute the local CSP projection basis. Recently, the renewed interest in CSP-based solvers has been catalyzed by the advent of machine learning techniques. Data-driven approaches may be fruitfully employed to learn projection operators and non-stiff latent spaces, enhancing the efficacy of CSP in capturing the slow system dynamics and reducing computational complexities.
Biography: Riccardo Malpica Galassi is an assistant professor at Sapienza University of Rome. He received his PhD from the Mechanical and Aerospace Department at the University of Rome in 2018, where subsequently, he spent over three years as a post-doctoral fellow. Following this, he spent two years as a Marie Curie post-doctoral Fellow at the Aero-thermo-mechanics department at Université Libre de Bruxelles.He is currently working on the physical understanding of the processes that characterize combustion phenomena, on reduced order models and digital twins, on multi-scale adaptive solvers, on machine learning for combustion, on uncertainty quantification, and reactive flows CFD, with special interest towards turbulent combustion and spray combustion.