Andrea Lani

KU Leuven | ku leuven · Center for Mathematical Plasma Astrophysics

Avoiding radio communication blackouts during atmospheric entry is crucial to a space mission and can be lifesaving. A novel ray-tracing algorithm, called Blackout Ray Tracer (BORAT), based on a Snell’s law solver, is introduced to analyze the signal behavior during reentry using geometrical optics for nonmagnetized and magnetized plasma. The ray-t...

This paper investigates the role of magnetohydrodynamics (MHD) on the aerothermodynamics (ATD) of a representative entry vehicle while flying into the Martian atmosphere. By strategically placing a flight-ready superconducting magnet at varied positions in the Schiaparelli reentry capsule of the ExoMars mission, we discern its impact on essential f...

This paper focuses on the validation and verification of the implicit thermochemical non-equilibrium (TCNEQ) solver in the COOLFluiD platform along with the multiphysics models for atmospheric entry applications. The solver is based on the finite volume framework and can handle two and three-dimensional unstructured grids. The solver is coupled wit...

Context. Coronal mass ejections (CMEs) are rapid eruptions of magnetized plasma that occur on the Sun. They are known to be the main drivers of adverse space weather. The accurate tracking of their evolution in the heliosphere in numerical models is of the utmost importance for space weather forecasting. Aims. The main objective of this paper is to...

The present paper addresses the coupling of an Uncertainty Quantification (UQ) toolkit, MultilevelEstimators, and the open-source platform COOLFLuiD. A Multi-Level Monte Carlo (MLMC) method, used for UQ, constructs levels using isotropic p-refinement instead of isotropic h-refinement, therefore requiring, ideally, just one initial "coarse" mesh whi...

Context. Coronal mass ejections (CMEs) are rapid eruptions of magnetized plasma that occur on the Sun, which are known as the main drivers of adverse space weather. Accurately tracking their evolution in the heliosphere in numerical models is of utmost importance for space weather forecasting. Aims. The main objective of this paper is to implement...

In this study, a significant emphasis is placed on the extension of high-order Flux Reconstruction (FR) schemes to cater to high-speed flows, specifically those involving high Mach numbers. The paper delves into the development and implementation of these FR schemes on both straight and curved-edged 2D and 3D simplex elements within the open-source...

Context. The global coronal model COCONUT (COolfluid COronal uNstrUcTured) was originally developed to replace semi-empirical models such as the Wang-Sheeley-Arge model in space weather forecasting chains in order to improve the physical accuracy of the predictions. This model has, however, several simplifications implemented in its formulation to...

The global coronal model COCONUT was originally developed to replace models such as the WSA model in space weather forecasting to improve the physical accuracy of the predictions. This model has, however, several simplifications implemented in its formulation to allow for rapid convergence, one of which includes a single-fluid treatment. In this pa...

As part of the EU New Horizon 2020 project on a Magnetohydrodynamic (MHD) Enhanced Entry System for Space Transportation (MEESST) superconducting magnetic coils will be exposed within an MHD probe to a high enthalpy air plasma. This study assesses key parameters for MHD flow manipulation experiments with the aid of emission spectroscopy measurement...

Atmospheric re-entry is a critical mission phase for crewed spaceflight and sample return missions, which requires careful study of the plasma behavior around the vehicle. This paper describes a numerical rebuilding approach for high-enthalpy plasma flows in PWT experiments with the CFD code URANUS-2D. Therefore, test conditions with high enthalpie...

Context. COolfluid COrona uNstrUcTured (COCONUT) is a global coronal magnetohydrodynamic (MHD) model that was recently developed and will soon be integrated into the ESA Virtual Space Weather Modelling Centre (VSWMC). In order to achieve robustness and fast convergence to a steady state for numerical simulations with COCONUT, several assumptions an...

COCONUT is a global coronal magnetohydrodynamic model recently developed. In order to achieve robustness and fast convergence to steady-state, several assumptions have been made during its development, such as prescribing filtered photospheric magnetic maps for representing the magnetic field in the lower corona. This filtering leads to smoothing a...

In recent years multiple studies on the manipulation of argon plasma flows with magnetohydrodynamic (MHD) forces have been conducted. The principal observations of increasing shock-standoff distances and decreasing surface temperatures, have motivated among other things the initialization of the MEESST project. As part of this EU New Horizon 2020 p...

Context. The text has been edited to adhere to American English based on the spelling style used in the text. In order to anticipate the geoeffectiveness of coronal mass ejections (CMEs), heliospheric simulations are used to propagate transient structures injected at 0.1 AU. Without direct measurements near the Sun, the properties of these injected...

The aim of this paper is to demonstrate the possible use of the new coronal model COCONUT to compute a detailed representation of a numerical CME at 0.1~AU, after its injection at the solar surface and propagation in a realistic solar wind, as derived from observed magnetograms. We present the implementation and propagation of modified Titov-D\'emo...

Computational Fluid Dynamics (CFD)-based global solar coronal simulations are slowly making their way into the space weather modeling toolchains to replace the semi-empirical methods such as the Wang-Sheeley-Arge (WSA) model. However, since they are based on CFD, if the assumptions in them are too strong, these codes might experience issues with co...

This paper is dedicated to the new implicit unstructured coronal code COCONUT, which aims at providing fast and accurate inputs for space-weather forecasting as an alternative to empirical models. We use all 20 available magnetic maps of the solar photosphere covering the date of 2019 July 2, which corresponds to a solar eclipse on Earth. We use th...

We developed a novel global coronal COCONUT (Coolfluid Corona Unstructured) model based on the COOLFluiD code. The steady-state model is predetermined by magnetograms set as boundary conditions, while inside the numerical domain the corona is described by MHD equations. This set of equations is solved with the use of an implicit solver on unstructu...

Atmospheric entries are a crucial part of space missions involving the possible loss of goods, data, and life in case of malfunctions. The cutoff of communication, also known as a radio communication blackout, is caused by the plasma surrounding the hypersonic (entry) vehicle in case the critical electron number density exceeds the radio frequency...

This paper outlines the initial development of a novel magnetohydrodynamic (MHD) plasma control system which aims at mitigating shock-induced heating and the radio-frequency communication blackout typically encountered during (re-)entry into planetary atmospheres. An international consortium comprising universities, SMEs, research institutions, and...

In recent years, global coronal models have experienced an ongoing increase in popularity as tools for forecasting solar weather. Within the domain of up to 21.5 Re, magnetohydrodynamics (MHD) is used to resolve the coronal structure using magnetograms as inputs at the solar surface. Ideally, these computations would be repeated with every update o...

This paper is dedicated to the new implicit unstructured coronal code COCONUT, which aims at providing fast and accurate inputs for space weather forecast as an alternative to empirical models. We use all 20 available magnetic maps of the solar photosphere covering the date of the 2nd of July 2019 which corresponds to a solar eclipse on Earth. We u...

Heat flux mitigation for spacecraft during re-entry is of fundamental importance for the success of a mission. In order to exploit magnetohydrodynamic (MHD) effects as protection system, numerical tools to predict the behaviour of atmospheric entry plasma flows in thermochemical non-equilibrium (TCNEQ) under the influence of externally applied magn...

In the recent years, global coronal models have experienced an ongoing increase in popularity as tools for forecasting solar weather. Within the domain of up to 21.5Rsun, magnetohydrodynamics (MHD) is used to resolve the coronal structure using magnetograms as inputs at the solar surface. Ideally, these computations would be repeated with every upd...

We present a novel global 3D coronal MHD model called COCONUT, polytropic in its first stage and based on a time-implicit backward Euler scheme. Our model boosts run-time performance in comparison with contemporary MHD-solvers based on explicit schemes, which is particularly important when later employed in an operational setting for space-weather...

Heat flux mitigation for spacecraft during re-entry is of fundamental importance for the success of a mission. In order to exploit magnetohydrodynamic (MHD) effects as protection system, numerical tools to predict the behaviour of atmospheric entry plasma flows in thermochemical non-equilibrium (TCNEQ) under the influence of externally applied magn...

Avoiding radio communication blackout during atmospheric re-entry is crucial to a space mission and can be life saving. A novel ray tracing algorithm, called BORAT (BlackOut RAy Tracer), based on a Snell's law solver is introduced to analyse the signal behaviour using geometrical optics for non-magnetized and magnetized plasma. The ray tracing anal...

We present a novel global 3-D coronal MHD model called COCONUT, polytropic in its first stage and based on a time-implicit backward Euler scheme. Our model boosts run-time performance in comparison with contemporary MHD-solvers based on explicit schemes, which is particularly important when later employed in an operational setting for space weather...

This work presents the development of the first high-order Flux Reconstruction (FR) solver for flows governed by the compressible Reynolds-Averaged Navier-Stokes (RANS) equations including Laminar-Turbulent Transition (LTT). The solver is fully implicit and implemented in the open-source COOLFluiD platform. Both the k−ω˜ Shear Stress Transport (SST...

Magnetohydrodynamic (MHD) simulations of the solar corona have become more popular with the increased availability of computational power. Modern computational plasma codes, relying upon computational fluid dynamics (CFD) methods, allow the coronal features to be resolved using solar surface magnetograms as inputs. These computations are carried ou...

The present paper addresses the development and implementation of the first r-adaptive mesh refinement (r-AMR) algorithm for a high-order Flux Reconstruction solver. The r-refinement consists on nodal re-positioning while keeping the number of mesh nodes and their connectivity frozen. The developed algorithm is based on physics-driven spring-analog...

Magnetohydrodynamic (MHD) simulations of the solar corona have become more popular with the increased availability of computational power. Modern computational plasma codes, relying upon Computational Fluid Dynamics (CFD) methods, allow for resolving the coronal features using solar surface magnetograms as inputs. These computations are carried out...

Aside from the launch environment, atmospheric re-entry imposes one of the most demanding environments which a spacecraft can experience. The combination of high spacecraft velocity and the presence of atmospheric particles leads to partially ionised gas forming around the vehicle, which significantly inhibits radio communications, and leads to the...

The chromospheric heating problem is a long-standing intriguing topic of solar physics, and the acoustic wave/shock wave heating in the chromospheric plasma has been investigated in the last several decades. It has been confirmed that acoustic waves, and the shock waves induced by the steepening acoustic waves in the gravitationally stratified chro...

To study acoustic wave propagation and the corresponding energy deposition in partially ionized plasmas, we use a two-fluid computational model that treats neutrals and charged particles (electrons and ions) as two separate fluids. This two-fluid model takes into account the ion–neutral collisions, ionization, and recombination, allowing us to inve...

The present work presents the development of a GPU-enabled high-order finite element-type Flux Reconstruction (FR) solver for hypersonic flows. The focus lies on the porting of the solver to GPUs using the NVIDIA CUDA language in a novel and efficient way. A Localized Laplacian Artificial Viscosity (LLAV) shock capturing method is also ported to GP...

This work presents a numerical methodology to properly characterize and predict the communications blackout phase of the ExoMars Schiaparelli Martian atmospheric re-entry flight. The focus of this work lies on the use of an optical ray tracing technique to describe the electromagnetic waves behaviour within the ionized wake flow of the vehicle. Bi-...

The present paper addresses the development and implementation of the first r-adaptive mesh refinement (r-AMR) algorithm for a high-order Flux Reconstruction solver. The r-refinement consists of nodal re-positioning while keeping their number and connectivity constants. The developed algorithms are based on physics-driven spring-analogies, where th...

To study acoustic wave propagation and the corresponding energy deposition in the partially ionized solar chromosphere, we use a multi-fluid computational model which treats neutrals and charged particles (electrons and ions) as two separate fluids. This two-fluid model takes into account the ion-neutral collisions, ionization and recombination, al...

The computational modeling of high-speed flows (e.g. hypersonic) and space plasmas is characterized by plethora of complex physical phenomena, in particular involving strong bow shocks and/or shock waves boundary layer interactions. The characterization of those flows requires accurate, robust, advanced numerical techniques and well tailored comput...

To study acoustic wave propagation and the corresponding energy deposition in partially ionized plasmas, we use a two-fluid computational model which treats neutrals and charged particles (electrons and ions) as two separate fluids. This two-fluid model takes into account the ion-neutral collisions, ionization and recombination, allowing us to inve...

A new methodology to accurately and efficiently examine the radio frequency blackout phenomenon during the hypersonic reentry process is introduced and validated. The current state-of-the-art thermochemical modelling of CO2 flows is reviewed and one-dimensional stagnation line studies are performed in order to determine a suitable chemical mechanis...

Aims : This paper presents a H2020 project aimed at developing an advanced space weather forecasting tool, combining the MagnetoHydroDynamic (MHD) solar wind and coronal mass ejection (CME) evolution modelling with solar energetic particle (SEP) transport and acceleration model(s). The EUHFORIA 2.0 project will address the geoeffectiveness of impac...

Aims Our goal is to develop and provide an open end-to-end (Sun to Earth) space weather modeling system, enabling to combine ("couple") various space weather models in an integrated tool, with the models located either locally or geographically distributed, so as to better understand the challenges in creating such an integrated environment. Method...

The present paper addresses the development and implementation of the first high-order Flux Reconstruction (FR) solver for high-speed flows within the open-source COOLFluiD (Computational Object-Oriented Libraries for Fluid Dynamics) platform. The resulting solver is fully implicit and able to simulate compressible flow problems governed by either...

This paper describes the main features of a pioneering unsteady solver for simulating ideal two-fluid plasmas on unstructured grids, taking profit of GPGPU (General-purpose computing on graphics processing units). The code, which has been implemented within the open source COOLFluiD platform, is implicit, second-order in time and space, relying upo...

The present paper addresses the development and implementation of the first high-order Flux Reconstruction (FR) solver for high-speed flows within the open-source COOLFluiD (Computational Object-Oriented Libraries for Fluid Dynamics) platform. The resulting solver is fully implicit and able to simulate compressible flow problems governed by either...

When predicting heat fluxes acting on Thermal Protection Systems (TPS) of space vehicles during the hypersonic re-entry phase, state-of-the-art numerical flow solvers do not automatically achieve the required accuracy, even on simple geometries, unless great care is taken when generating the corresponding computational mesh. Within this context, ou...

This paper describes the main features of a pioneering unsteady solver for simulating ideal two-fluid plasmas on unstructured grids, taking profit of GPGPU (General-purpose computing on graphics processing units). The code, which has been implemented within the open source COOLFluiD platform, is implicit, second-order in time and space, relying upo...

The computational modeling of high-speed flows (e.g. hypersonic) and space plasmas is characterized by a plethora of complex physical phenomena, in particular involving strong oblique shocks, bow shocks and/or shock waves boundary layer interactions. The characterization of those flows requires accurate, robust and advanced numerical techniques. To...

We present an innovative numerical method that solves for the multi-fluid plasma equations, including the transport, frictional, and chemical reactions terms, coupled to full Maxwell's equations. The numerical method features a scheme for the electromagnetic field with a proper scaling for the numerical dissipation, a scheme that solves flows at al...

In this paper we present an extension of Residual Distribution techniques for the simulation of compressible flows in non-equilibrium conditions. The latter are modeled by means of a state-of-the-art multi-species and two-temperature model. An entropy-based variable transformation that symmetrizes the projected advective Jacobian for such a thermop...

Recently, shock-fitting methods have been re-gaining popularity as a valid alternative to more standard shock-capturing schemes for tackling simulation of compressible flows including discontinuities, particularly on unstructured grids. This paper presents SF, the first open source framework for developing new-generation shock-fitting methods and c...

In order to investigate the accuracy of the rebuilding code for the free stream conditions and the total enthalpy in the Longshot Hypersonic facility at the von Karman Institute (VKI), a series of unsteady CFD simulations of axisymmetric hypersonic flow over a heat flux probe have been performed. The free stream and the total conditions provided by...

We present a novel numerical model that simulates ideal two-fluid plasmas coupled to the full set of Maxwell’s equations with application to space and laboratory plasmas. We use a fully-implicit finite volume method for unstructured meshes, that uses an advection upstream splitting method (i.e., AUSM+-up) for all speeds to discretize the numerical...

We study magnetic reconnection under chromospheric conditions in five different ionization levels from 0.5% to 50% using a self-consistent two-fluid (ions + neutrals) model that accounts for compressibility, collisional effects, chemical inequilibrium, and anisotropic heat conduction. Results with and without radiation are compared, using two model...

The capability for CFD prediction of hypersonic shock wave laminar boundary layer interaction was assessed for a double wedge model at Mach 7.1 in air and nitrogen at 2.1. MJ/kg and 8. MJ/kg. Simulations were performed by seven research organizations encompassing both Navier-Stokes and Direct Simulation Monte Carlo (DSMC) methods as part of the NAT...

In order to study chromospheric magnetosonic wave propagation including, for the first time, the effects of ion-neutral interactions in the partially ionized solar chromosphere, we have developed a new multi-fluid computational model, accounting for ionization and recombination reactions in gravitationally stratified magnetized collisional media. T...

This work addresses the modeling of non-equilibrium phenomena in inductively coupled plasma discharges. In the proposed computational model, the electromagnetic induction equation is solved together with the set of Navier-Stokes equations in order to compute the electromagnetic and flow fields, accounting for their mutual interaction. Semi-classica...

We present a computational model for the Earth’s magnetosphere that relies on the multi-fluid plasma model. When the multi-fluid equations are coupled to the full Maxwell’s equations, the resulting system is able to tackle non-equilibrium effects that are beyond the magnetohydrodynamics (MHD) description. The multi-fluid model allows for studying r...

We present a Finite Volume scheme for solving Maxwell's equations coupled to magnetized multi-fluid plasma equations for reactive and collisional partially ionized flows on unstructured meshes. The inclusion of the displacement current allows for studying electromagnetic wave propagation in a plasma as well as charge separation effects beyond the s...

The carbuncle phenomenon is a critical numerical instability preventing the accurate simulation of hypersonic flows around blunted configurations. After reviewing the known remedies to handle numerically this instability (designed, all of them, for Finite Volume methods), we present and analyze in depth the only effective cure reported in literatur...

This paper describes the main features of a state-of-the-art Monte Carlo solver for radiation transport which has been implemented within COOLFluiD, a world-class open source object-oriented platform for scientific simulations. The Monte Carlo code makes use of efficient ray tracing algorithms (for 2D, axisymmetric and 3D arbitrary unstructured mes...

In the present contribution we evaluate the heat flux prediction capabilities of second-order accurate Residual Distribution (RD ) methods in the context of atmo- spheric (re-)entry problems around blunt bodies. Our departing point is the computa- tion of subsonic air flows (with air modeled either as an inert ideal gas or as chemically reacting an...

We present a modular shock-fitting algorithm for unstructured grids that can be used in conjunction with virtually any vertex-centred shock-capturing solver. The unstructured, shock-fitting algorithm, originally developed for ideal gases, has here been extended to thermochemical nonequilibrium flows and coupled with COOLFluiD, an in- house shock-ca...

This document summarizes combined efforts to extend an existing pioneering multi-fluid / Maxwell solver in order to enable large 3D simulations of magnetic reconnec-tion with COOLFluiD, the world-class open source multi-physics platform from the Von Karman Institute (VKI). The contributions to this project are threefold. First, the parallel I/O inf...

In the present contribution we evaluate the heat flux prediction capabilities of second- order accurate Residual Distribution methods in the context of atmospheric entry problems around blunt bodies. Our departing point is the computation of subsonic air flows (with air modeled either as an inert ideal gas or as chemically reacting and possibly out...

This paper presents the results of the numerical simulation of plasma flows inside the torch of the VKI inductively coupled plasma facility. The main purpose of this work is the parametric investigation of thermo-chemical non-equilibrium effects on the plasma jet at different operating pressures ranging from 3 to 15 kPa. The test gas is an ionized...

The effects of non-equilibrium in a quasi-one-dimensional nozzle flow are investigated by means of a collisional-radiative model. The gas undergoing the expansion is an air plasma generated by an electromagnetic discharge and consists of atoms, molecules and free electrons. In the present analysis, the electronic excited states of atomic and molecu...

The COOLFluiD (Computational Object Oriented Libraries for Fluid Dynamics) project, officially started in 2002, has lead to the creation of a world-class, extremely modular col- laborative platform for high-performance scientific computing and multi-physics modeling. Target applications include Space Weather modeling, aeroacoustics, turbulence, aer...

An innovative Monte Carlo algorithm for computing the radiative transport in loosely coupled flow-radiation aerothermodynamics calculations is presented. The method makes use of a (1) particle tracking algorithm which relies solely upon vectorial operations and properties, particularly suitable for 2D and 3D unstructured meshes with arbitrary ele-...

This paper addresses the challenges encountered in numerical simulations of a complete hypersonic gun tunnel facility. The computational approach developed within the current work in order to overcome some of these dificulties is described. The simulation is per- formed on the VKI-Longshot free-piston hypersonic wind tunnel. The compression of the...

We present a reduced kinetic mechanism for the modeling of the behavior of the electronic states of the atomic species in air mixtures. The model is built by lumping the electronically excited states of the atomic species and by performing Maxwell- Boltzmann averages of the rate constants describing the elementary kinetic processes of the individua...

The variable high-order multiblock overlapping (overset) grids method of Sjogreen & Yee [CiCP, Vol. 5, 2009] for a perfect gas has been extended to nonequilib- ̈ rium flows. This work makes use of the recently developed high-order well-balanced shock-capturing schemes and their filter counterparts [Wang et al., J. Comput. Phys., 2009, 2010] that ex...

A multi-dimensionally upwind conservative Residual Distribution algorithm for simulating viscous axisymmetric hypersonic flows in thermo-chemical nonequilib- rium on unstructured grids is presented and validated in the case of the complex flow- field over a double cone configuration. The resulting numerical discretization com- bines a state-of-the-...

The COOLFluiD (Computational Object Oriented Libraries for Fluid Dynamics) project, offcially started in 2002, has lead to the creation of a world-class, extremely modular col- laborative platform for high-performance scientific computing and multi-physics modeling. Target applications include Space Weather modeling, aeroacoustics, turbulence, aero...

After presenting a general overview on the capabilities of the COOLFluiD platform for aerothermodynamics appli- cations, a Monte Carlo algorithm for radiative transport, recently developed within the ESA AMOD project, is de- scribed. The method makes use of an innovative ray trac- ing algorithm relying solely upon vectorial operations on arbitrary...

Numerical simulations of hypersonic flows using local correlation based transition (LCTM) model was performed in order to assess the accuracy of the model in hypersonic conditions. Implementation of the model was done in object oriented framework. The governing equa- tions as well as the numerical methods are described. A series of runs were perfor...

Numerical simulation of a moving piston by means of an arbitrary Lagrangian Eulerian solver in a two-dimensional field is performed in order to investigate the flow physics inside a hypersonic ground test facility. The dynamic of the piston is coupled with the fluid throughout a moving boundaries. Rigid mesh strategy was used for the mesh adaptatio...

The aerothermodynamic loadings associated with shock wave boundary layer interactions (shock interactions) must be carefully considered in the design of hypersonic air vehicles. The capability of Computational Fluid Dynamics (CFD) software to accurately predict hypersonic shock wave laminar boundary layer interactions is examined. A series of indep...

A finite volume numerical technique is proposed to solve the compressible ideal MHD equations for steady and unsteady problems based on a quasi-Newton implicit time integration strategy. The solenoidal constraint is handled by a hyperbolic divergence cleaning approach allowing its satisfaction up to machine accuracy. The conservation of the magneti...

A computational model based on a Residual Distribution method for unstructured meshes applied to symmetrizable systems in thermo-chemical nonequilibrium is discussed. At first, a recently developed symmetrization procedure for the convective flux jacobian associated to a two-temperature model describing flows in thermochemical nonequilib- rium is i...

In order to investigate the accuracy of the rebuilding code for the free stream condi- tions and the total enthalpy in the VKI-Longshot facility, a series of unsteady numerical computations of axisymmetric hypersonic flow over a heat flux probe have been performed. The free stream and the total conditions provided by experiments as function of time...

The variable high-order multiblock overlapping (overset) grids method of Sj ̈ ogreen & Yee (CiCP, Vol.5, 2008) for a perfect gas has been extended to nonequilibrium flows. This work makes use of the recently developed high-order well-balanced shock-capturing schemes and their filter counterparts (Wang et al., J. Comput. Phys., 2009, 2010) that exac...

The variable high-order multiblock overlapping (overset) grids method of Sjogreen & Yee (CiCP, Vol.5, 2008) for a perfect gas has been extended to nonequilibrium flows. This work makes use of the recently developed high-order well-balanced shock-capturing schemes and their filter counterparts (Wang et al., J. Comput. Phys., 2009, 2010) that exactly...