L. Környei

25625214100

Publications - 16

Prediction model of performance–energy trade-off for CFD codes on AMD-based cluster

L. Környei Łukasz Szustak Marcin Lawenda

Publication Name: Future Generation Computer Systems

Publication Date: 2025-08-01

Volume: 169

Issue: Unknown

Page Range: Unknown

Description:

This work explores the importance of performance–energy correlation for CFD codes, highlighting the need for sustainable and efficient use of clusters. The prime goal includes the optimisation of selecting and predicting the optimal number of computational nodes to reduce energy consumption and/or improve calculation time. In this work, the utilisation cost of the cluster, measured in core-hours, is used as a crucial factor in energy consumption and selecting the optimal number of computational nodes. The work is conducted on the cluster with AMD EPYC Milan-based CPUs and OpenFOAM application using the Urban Air Pollution model. In order to investigate performance–energy correlation on the cluster, the CVOPTS (Core VOlume Points per TimeStep) metric is introduced, which allows a direct comparison of the parallel efficiency for applications in modern HPC architectures. This metric becomes essential for evaluating and balancing performance with energy consumption to achieve cost-effective hardware configuration. The results were confirmed by numerous tests on a 40-node cluster, considering representative grid sizes. Based on the empirical results, a prediction model was derived that takes into account both the computational and communication costs of the simulation. The research reveals the impact of the AMD EPYC architecture on superspeedup, where performance increases superlinearly with the addition of more computational resources. This phenomenon enables a priori the prediction of performance–energy trade-offs (computing-faster or energy-save setups) for a specific application scenario, through the utilisation of varying quantities of computing nodes.

Open Access: Yes

DOI: 10.1016/j.future.2025.107810

Estimating the air quality standard exceedance areas and the spatial representativeness of urban air quality stations applying microscale modelling

F. Martín V. Rodrigues J. Bartzis I. Sakellaris Zoltán Horváth X. Jurado N. Reiminger P. Thunis C. Cuvelier S. Janssen J. Sousa E. Rivas L. Tarrason M. G. Villani N. Masey S. Hamilton J. L. Santiago F. Russo J. Stocker R. Jackson G. Tinarelli L. Környei R. San José J. L. Pérez-Camanyo G. Sousa Santos D. Barbero

Publication Name: Science of the Total Environment

Publication Date: 2025-08-01

Volume: 988

Issue: Unknown

Page Range: Unknown

Description:

This study builds upon the findings of a FAIRMODE intercomparison exercise conducted in a district of Antwerp, Belgium, where a comprehensive dataset of air pollutant measurements (air quality stations and passive samplers) was available. Long-term average NO2 concentrations at very high spatial resolution were estimated by several dispersion modelling systems (Martín et al., 2024) to investigate the ability of these to capture the detailed spatial distribution of NO2 concentrations at the microscale in urban environments. In this follow-up research, we extend the analysis by evaluating the capability of these modelling systems to predict the NO2 annual limit value exceedance areas (LVEAs) and spatial representativeness areas (SRAs) for NO₂ at two reference air quality stations. The different modelling approaches used are based on CFD, Lagrangian, Gaussian, and AI-driven models. The different modelling approaches are generally good at predicting the LVEA and SRAs of urban air quality stations, although a small SRA (corresponding to low concentration tolerances or the traffic station) is more difficult to predict correctly. However, there are notable differences in performance among the modelling systems. Those based on CFD models seem to provide more consistent results predicting LVEAs and SRAs. Then, lower accuracy is obtained with AI-based systems, Lagrangian models, and Gaussian models with street canyon parameterizations. The Gaussian models with street-canyon parametrizations show significantly better results than models using simply a Gaussian dispersion parametrization. Furthermore, little differences are observed in most of the statistical indicators corresponding to the LVEA and SRA estimates obtained from the unsteady full month CFD simulations compared to those from the scenario-based CFD simulation methodologies, but there are some noticeable differences in the LVEA or SRA (traffic station, 10 % tolerance) sizes. The number of scenarios does not seem to be relevant to the results. Different bias correction methodologies are explored.

Open Access: Yes

DOI: 10.1016/j.scitotenv.2025.179824

Comparison of different geometry trees in fire simulation

L. Környei Csaba Hajdu F. Hajdu Rajmund Kuti Dóra Beke

Publication Name: Pollack Periodica

Publication Date: 2024-10-16

Volume: 19

Issue: 3

Page Range: 34-39

Description:

Wildfire simulations can help to better understand the dynamics and effects of forest fires. The basis of wildfire simulation is the tree-burning simulation. In this paper, the fire simulation of 7 different geometry Hungarian trees in the case of arson is presented. It was observed that the trees were burned down fast. The maximum mass loss rate and maximum heat release rate were larger as the tree was larger. The largest intensity fire could be observed in the case of the smallest tree. The maximum temperature was higher in the case of a large crown diameter. The maximum aerosol reached high pollutant concentrations. In the case of large crown height, the maximum CO2 concentration was higher. The results presented in this paper can be the basis of the following forest fire simulations.

Open Access: Yes

DOI: 10.1556/606.2024.01022

Using dispersion models at microscale to assess long-term air pollution in urban hot spots: A FAIRMODE joint intercomparison exercise for a case study in Antwerp

F. Martín Ákos Kovács V. Rodrigues Bence Liszkai J. Bartzis I. Sakellaris Zoltán Horváth X. Jurado N. Reiminger P. Thunis C. Cuvelier S. Janssen J. Sousa E. Rivas M. G. Villani J. L. Santiago F. Russo J. Stocker R. Jackson G. Tinarelli L. Környei R. San José J. L. Pérez-Camanyo G. Sousa Santos D. Barbero

Publication Name: Science of the Total Environment

Publication Date: 2024-05-15

Volume: 925

Issue: Unknown

Page Range: Unknown

Description:

In the framework of the Forum for Air Quality Modelling in Europe (FAIRMODE), a modelling intercomparison exercise for computing NO2 long-term average concentrations in urban districts with a very high spatial resolution was carried out. This exercise was undertaken for a district of Antwerp (Belgium). Air quality data includes data recorded in air quality monitoring stations and 73 passive samplers deployed during one-month period in 2016. The modelling domain was 800 × 800 m2. Nine modelling teams participated in this exercise providing results from fifteen different modelling applications based on different kinds of model approaches (CFD – Computational Fluid Dynamics-, Lagrangian, Gaussian, and Artificial Intelligence). Some approaches consisted of models running the complete one-month period on an hourly basis, but most others used a scenario approach, which relies on simulations of scenarios representative of wind conditions combined with post-processing to retrieve a one-month average of NO2 concentrations. The objective of this study is to evaluate what type of modelling system is better suited to get a good estimate of long-term averages in complex urban districts. This is very important for air quality assessment under the European ambient air quality directives. The time evolution of NO2 hourly concentrations during a day of relative high pollution was rather well estimated by all models. Relative to high resolution spatial distribution of one-month NO2 averaged concentrations, Gaussian models were not able to give detailed information, unless they include building data and street-canyon parameterizations. The models that account for complex urban geometries (i.e. CFD, Lagrangian, and AI models) appear to provide better estimates of the spatial distribution of one-month NO2 averages concentrations in the urban canopy. Approaches based on steady CFD-RANS (Reynolds Averaged Navier Stokes) model simulations of meteorological scenarios seem to provide good results with similar quality to those obtained with an unsteady one-month period CFD-RANS simulations.

Open Access: Yes

DOI: 10.1016/j.scitotenv.2024.171761

One-at-a-Time sensitivity study of a tree burning simulation

L. Környei F. Hajdu Rajmund Kuti

Publication Name: Pollack Periodica

Publication Date: 2024-03-22

Volume: 19

Issue: 1

Page Range: 53-59

Description:

The aim of the research was to carry out the One-at-a-Time sensitivity analysis of a tree burning experiment simulation with a novel fuzzy logic-based method. It was observed that the precent of the remaining tree is sensitive to the moisture content, the crown-base diameter and the tree height. The other variables, which are maximum mass loss rate, maximum heat release rate, and maximum temperature at the top of the tree are moderately sensitive or not sensitive to the selected parameters. The presented results can be used in sensitivity studies and wildfire simulations.

Open Access: Yes

DOI: 10.1556/606.2023.00850

Correction to: A 4‑year study of bovine reproductive hormones that are induced by pharmaceuticals and appear as steroid estrogenic pollutants in the resulting slurry, using in vitro and instrumental analytical methods (Environmental Science and Pollution Research, (2023), 30, 60, (125596-125608), 10.1007/s11356-023-31126-y)

Pál Szakál Judit Plutzer Renato Kalocsai L. Környei Richárd Gubó Eduard Gubó Tamás Szakál Dora Pordan-Haber Tibor Molnar Ákos Bede‑Fazekas Zoltán Szalai Lili Szabó

Publication Name: Environmental Science and Pollution Research

Publication Date: 2024-02-01

Volume: 31

Issue: 6

Page Range: 9868

Description:

The correct Author affiliations is shown in this paper.

Open Access: Yes

DOI: 10.1007/s11356-024-31992-0

A physics-based reduced order model for urban air pollution prediction

L. Környei Gianluigi Rozza Giovanni Stabile Moaad Khamlich Zoltán Horváth

Publication Name: Computer Methods in Applied Mechanics and Engineering

Publication Date: 2023-12-01

Volume: 417

Issue: Unknown

Page Range: Unknown

Description:

This article presents an innovative approach for developing an efficient reduced-order model to study the dispersion of urban air pollutants. The need for real-time air quality monitoring has become increasingly important, given the rise in pollutant emissions due to urbanization and its adverse effects on human health. The proposed methodology involves solving the linear advection–diffusion problem, where the solution of the Reynolds-averaged Navier–Stokes (RANS) equations gives the convective field. At the same time, the source term consists of an empirical time series. However, the computational requirements of this approach, including microscale spatial resolution, repeated evaluation, and low time scale, necessitate the use of high-performance computing facilities, which can be a bottleneck for real-time monitoring. To address this challenge, a problem-specific methodology was developed that leverages a data-driven approach based on Proper Orthogonal Decomposition with regression (POD-R) coupled with Galerkin projection (POD-G) endorsed with the discrete empirical interpolation method (DEIM). The proposed method employs a feedforward Neural Network (NN) to non-intrusively retrieve the reduced-order convective operator required for online evaluation. The numerical framework was validated on synthetic emissions and real wind measurements. The results demonstrate that the proposed approach significantly reduces the computational burden of the traditional approach and is suitable for real-time air quality monitoring. Overall, the study advances the field of reduced order modeling and highlights the potential of data-driven approaches in environmental modeling and large-scale simulations.

Open Access: Yes

DOI: 10.1016/j.cma.2023.116416

A 4-year study of bovine reproductive hormones that are induced by pharmaceuticals and appear as steroid estrogenic pollutants in the resulting slurry, using in vitro and instrumental analytical methods

Pál Szakál Judit Plutzer Renato Kalocsai L. Környei Ákos Bede-Fazekas Richárd Gubó Eduard Gubó Tamás Szakál Dora Pordan-Haber Tibor Molnar Zoltán Szalai Lili Szabó

Publication Name: Environmental Science and Pollution Research International

Publication Date: 2023-12-01

Volume: 30

Issue: 60

Page Range: 125596-125608

Description:

The main objective of the research was to study the environmental "price" of the large-scale, milk production from a rarely known perspective, from the mapping of the estrogenic footprint (the amount of oestrus-inducer hormonal products, and the generated endoestrogens) in the resulting slurry in a dairy cow farm. These micropollutants are endocrine-disrupting chemicals (EDCs) and can be dangerous to the normal reproductive functions even at ng/kg concentration. One of them, 17ß-estradiol, has a 20,000 times stronger estrogenic effect than bisphenol-A, a widely known EDC of industrial origin. While most studies on EDCs are short-term and/or laboratory based, this study is longitudinal and field-based. We sampled the slurry pool on a quarterly basis between 2017 and 2020. Our purpose was testing the estrogenic effects using a dual approach. As an effect-based, holistic method, we developed and used the YES (yeast estrogen screen) test employing the genetically modified Saccharomyces cerevisiae BJ3505 strain which contains human estrogenic receptor. For testing exact molecules, UHPLC-FLD was used. Our study points out that slurry contains a growing amount of EDCs with the risk of penetrating into the soil, crops and the food chain. Considering the Green Chemistry concept, the most benign ways to prevent of the pollution of the slurry is choosing appropriate oestrus-inducing veterinary pharmaceuticals (OIVPs) and the separation of the solid and liquid parts with adequate treatment methods. To our knowledge, this is the first paper on the adaptation of the YES test for medicine and slurry samples, extending its applicability. The adapted YES test turned out to be a sensitive, robust and reliable method for testing samples with potential estrogenic effect. Our dual approach was successful in evaluating the estrogenic effect of the slurry samples.

Open Access: Yes

DOI: 10.1007/s11356-023-31126-y

Complex-Geometry 3D Computational Fluid Dynamics with Automatic Load Balancing

József Bakosi L. Környei Marc Charest Jacob Waltz Aditya Pandare Mátyás Constans Paula Rutherford Ákos Kovács Zoltán Horváth

Publication Name: Fluids

Publication Date: 2023-05-01

Volume: 8

Issue: 5

Page Range: Unknown

Description:

We present an open-source code, Xyst, intended for the simulation of complex-geometry 3D compressible flows. The software implementation facilitates the effective use of the largest distributed-memory machines, combining data-, and task-parallelism on top of the Charm++ runtime system. Charm++’s execution model is asynchronous by default, allowing arbitrary overlap of computation and communication. Built-in automatic load balancing enables redistribution of arbitrarily heterogeneous computational load based on real-time CPU load measurement at negligible cost. The runtime system also features automatic checkpointing, fault tolerance, resilience against hardware failure, and supports power- and energy-aware computation. We verify and validate the numerical method and demonstrate the benefits of automatic load balancing for irregular workloads.

Open Access: Yes

DOI: 10.3390/fluids8050147

Numerical Examination of a Forest Area Fire

L. Környei Csaba Hajdu F. Hajdu Rajmund Kuti Dóra Beke

Publication Name: Chemical Engineering Transactions

Publication Date: 2023-01-01

Volume: 107

Issue: Unknown

Page Range: 61-66

Description:

An important task of sustainability is the protection of Earth's forests and the prevention of forest fires. In this paper, the numerical examination of a typical Hungarian ash forest fire is presented. The connection between sustainability and forest fire simulations is also discussed. For the simulation, a Fire Dynamics Simulator was selected, and a particle-based model was used. The simulation setup, which includes a random location of trees following Poisson distribution, is also explained. Then, the simulation of a 10x10 m area of ash forest is presented. It was found that in case of arson, the fire spreads rapidly among the trees, and there will be a high-intensity fire in which the forest area burns down in 4 min. The mass loss rate, the temperature, and the heat release rate also increased fast (above 50 kg/s, above 2,000 °C and above 800,000 kW). The aerosol concentration reached a high pollutant concentration (1.3x10-6), and the carbon dioxide concentration also increased significantly (above 14,000 ppm). These changes have a direct effect on climate change. Therefore, it is important to examine them in a simulation environment. The simulation was compared to a pine tree forest simulation, and it could be observed that in the case of the pine tree, the values are similar, but phenomena occur faster. With the computer simulation, it is easier to determine the areas affected by the fire, which also helps fire prevention and firefighting. The aim of the research is to contribute to the prevention and more efficient extinguishment of wildfires and the sustainability of the Earth.

Open Access: Yes

DOI: 10.3303/CET23107011

Examination of effects of indoor fires on building structures and people

L. Környei Csaba Hajdu F. Hajdu Geza Zolyomi Rajmund Kuti Gabriella Lászlo

Publication Name: Heliyon

Publication Date: 2023-01-01

Volume: 9

Issue: 1

Page Range: Unknown

Description:

The scientific study of the harmful effects of indoor fires on building structures and on the environment is a top issue today. Indoor fires frequently occur all over the world. The goal of our research is to examine the effects of an average room fire on the survival possibility of a trapped person and on the building structure, taking into account features of the Eastern European architecture. First, a computational fluid dynamics (CFD) simulation was performed to examine the change of temperature, oxygen, and carbon monoxide concentration in a selected room in a vacant building used for military training. Based on the results, a 1:1 scale fire experiment was carried out with the parameters used in the simulation. The experiment was repeated once with the same settings. It was observed that without the intervention of firefighters, the temperature in the experiment could have rapidly reached 400 °C, as suggested by the simulation, which could have caused structural damage to the building. Furthermore, after 3 min the carbon monoxide concentration reached 400 ppm in both experiments and the simulation, which is a harmful level to people trapped inside the room. Also, in the experiment there was sufficient oxygen at the ground level with what people can survive 3 min.

Open Access: Yes

DOI: 10.1016/j.heliyon.2022.e12720

Phase-field modeling of eutectic structures on the nanoscale: the effect of anisotropy

L. Környei László Rátkai Tamás Pusztai László Gránásy Gyula I. Tóth

Publication Name: Journal of Materials Science

Publication Date: 2017-05-01

Volume: 52

Issue: 10

Page Range: 5544-5558

Description:

A simple phase-field model is used to address anisotropic eutectic freezing on the nanoscale in two (2D) and three dimensions (3D). Comparing parameter-free simulations with experiments, it is demonstrated that the employed model can be made quantitative for Ag–Cu. Next, we explore the effect of material properties and the conditions of freezing on the eutectic pattern. We find that the anisotropies of kinetic coefficient and the interfacial free energies (solid–liquid and solid–solid), the crystal misorientation relative to pulling, the lateral temperature gradient play essential roles in determining the eutectic pattern. Finally, we explore eutectic morphologies, which form when one of the solid phases are faceted, and investigate cases, in which the kinetic anisotropy for the two solid phases is drastically different.

Open Access: Yes

DOI: 10.1007/s10853-017-0853-8

Integrated urban air pollution dispersion modelling framework and application in air quality prediction of the city of győr

É V.P. Rácz L. Környei Balázs Szintai István Harmati György Istenes Bence Liszkai Péter Zsebők Zoltán Horváth

Publication Name: Harmo 2016 17th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes Proceedings

Publication Date: 2016-01-01

Volume: 2016-May

Issue: Unknown

Page Range: 410-414

Description:

Model accuracy versus model running time - urban air pollution dispersion modellers have to balance between them when selecting models to be implemented. CFD based models seem to be the best candidates for an accurate model that can be validated at urban scale at highest level on the price of a longer running time. In this paper we shall introduce 3DAirQC software framework which addresses a portable and validated CFD model for air quality prediction and control.

Open Access: Yes

DOI: DOI not available

Phase-field modeling of polycrystalline solidification: From needle crystals to spherulites - A review

Attila Szállás L. Környei László Rátkai Bálint Korbuly Tamás Pusztai László Gránásy Gyula I. Tóth

Publication Name: Metallurgical and Materials Transactions A Physical Metallurgy and Materials Science

Publication Date: 2014-01-01

Volume: 45

Issue: 4

Page Range: 1694-1719

Description:

Advances in the orientation-field-based phase-field (PF) models made in the past are reviewed. The models applied incorporate homogeneous and heterogeneous nucleation of growth centers and several mechanisms to form new grains at the perimeter of growing crystals, a phenomenon termed growth front nucleation. Examples for PF modeling of such complex polycrystalline structures are shown as impinging symmetric dendrites, polycrystalline growth forms (ranging from disordered dendrites to spherulitic patterns), and various eutectic structures, including spiraling two-phase dendrites. Simulations exploring possible control of solidification patterns in thin films via external fields, confined geometry, particle additives, scratching/piercing the films, etc. are also displayed. Advantages, problems, and possible solutions associated with quantitative PF simulations are discussed briefly. © 2013 The Minerals, Metals & Materials Society and ASM International.

Open Access: Yes

DOI: 10.1007/s11661-013-1988-0

Parallel implementation of a combustion chamber simulation with MPI-OpenMP hybrid techniques

L. Környei

Publication Name: Mipro 2012 35th International Convention on Information and Communication Technology Electronics and Microelectronics Proceedings

Publication Date: 2012-08-22

Volume: Unknown

Issue: Unknown

Page Range: 356-361

Description:

The parallelization techniques utilized in a study of gas flow in a combustion chamber are described and discussed in this paper. Models of compressible fluid dynamics are solved with the finite volume method, and an additional algorithm, called "snapper" that handles piston and valve movement. In order to achieve an acceptable scaling on a CPU cluster with 240 cores, a two-stage parallelization with MPI in conjecture with OpenMP is implemented. For some types of physical investigations, the actual spatial region of interest is somehow changing, deforming, or moving in time in a predefined fashion. Handling gas dynamics with piston motion, even with the simplest models requires precaution. Apart from numerical and physical corrections, there are challenges, where multiple types of unstructured, and specially generated deforming grids are handled in a computer system with distributed memory. In the present work the results of the first implementations and benchmarks are presented, which prove to be well scaling for this modest-sized cluster. © 2012 MIPRO.

Open Access: Yes

DOI: DOI not available

Local Scale Wind Regime Changes and their Consequences on Sustainability in the Carpathian Basin (Hungary)

É V.P. Rácz L. Környei

Publication Name: Chemical Engineering Transactions

Publication Date: 2023-01-01

Volume: 107

Issue: Unknown

Page Range: 475-480

Description:

The Carpathian basin is facing significant threats to its unique biogeography and the sustainability of its human society due to climate change. While studies have extensively analyzed temperature and precipitation changes, little attention has been given to the analysis of wind regime changes despite their potential correlation with diverse climatic effects. This paper presents a comprehensive analysis of long-term observational wind data at both local and regional scales of the basin. The study aims to identify trends in wind speed and direction and raises some implications for sustainability aspects such as forest health, agricultural potential, and availability of wind energy. To track the decadal trends in wind speed, two indexes were utilized: the number of calm days and the number of windy days. In addition to traditional wind roses, fine changes in wind direction distribution were visualized using heat maps. The dominance of local winds was also examined through aggregated wind roses. Our research findings reveal that contrary to predictions and reanalysis data, there has been a noteworthy rise in wind resources in the Hungarian Great Plain, accompanied by a decrease in the number of calm days. It is evident that there are variations among different geographical regions within Hungary regarding changes in wind regimes. These trends have the potential to impact current dominant climatic influences, leading to possible modifications in climate change patterns and necessitating a reassessment of main forest and agricultural species.

Open Access: Yes

DOI: 10.3303/CET23107080