Gordon Atanga - Academia.edu (original) (raw)

Papers by Gordon Atanga

Research paper thumbnail of Direct numerical simulation of turbulent flames on parallel computers

Last but not the least, I appreciate and count it a privilege being part of the CMFI Germany Chri... more Last but not the least, I appreciate and count it a privilege being part of the CMFI Germany Christian community. You have been exceedingly encouraging. Thank you.

Research paper thumbnail of Direct numerical simulation of turbulent flames on parallel computers

Last but not the least, I appreciate and count it a privilege being part of the CMFI Germany Chri... more Last but not the least, I appreciate and count it a privilege being part of the CMFI Germany Christian community. You have been exceedingly encouraging. Thank you.

Research paper thumbnail of Vented hydrogen deflagrations in containers: effect of congestion for homogeneous mixtures

This paper presents results from an experimental study of vented hydrogen deflagrations in 20-foo... more This paper presents results from an experimental study of vented hydrogen deflagrations in 20-foot ISO containers. The scenarios investigated include 14 tests with explosion venting through the doors of the containers, and 20 tests with venting through openings in the roof. The parameters investigated include hydrogen concentration, vent area, type of venting device, and the level of congestion inside the containers. All tests involved homogeneous and initially quiescent hydrogen-air mixtures. The results demonstrate the strong effect of congestion on the maximum reduced explosion pressures, which typically is not accounted for in current standards and guidelines for explosion protection. The work is a deliverable from work package 2 (WP2) in the project "Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations", or HySEA (www.hysea.eu), which receives funding from the Fuel Cells and Hydrogen Joint Undertaking (FCH JU) under grant agreement no. 671461.

Research paper thumbnail of Structural response for vented hydrogen deflagrations: coupling CFD and FE tools

Zenodo (CERN European Organization for Nuclear Research), Sep 11, 2017

This paper describes a methodology for simulating the structural response of vented enclosures du... more This paper describes a methodology for simulating the structural response of vented enclosures during hydrogen deflagrations. The approach adopted entails full spatial mapping of explosion loads predicted with the computational fluid dynamics (CFD) tool FLACS-Hydrogen to the non-linear finite element (FE) IMPETUS Afea solver. The modelling involves one-way coupling of pressure loads taken from either experiments or CFD simulations to the FE solver. The performance of the combined model system is evaluated for vented hydrogen deflagrations in 20-foot ISO containers. The work is part of work package 3 (WP3) in the project 'Improving hydrogen safety for energy applications through prenormative research on vented deflagrations' (HySEA).

Research paper thumbnail of Simulating vented hydrogen deflagrations: Improved modelling in the CFD tool FLACS-hydrogen

International Journal of Hydrogen Energy, Mar 1, 2021

This paper describes validation of the computational fluid dynamics tool FLACS-Hydrogen. The vali... more This paper describes validation of the computational fluid dynamics tool FLACS-Hydrogen. The validation study focuses on concentration and pressure data from vented deflagration experiments performed in 20-foot shipping containers as part of the project Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations (HySEA), funded by the Fuel Cells and Hydrogen Joint Undertaking (FCH 2 JU). The paper presents results for tests involving inhomogeneous hydrogen-air clouds generated from realistic releases performed during the HySEA project. For both experiments and simulations, the peak overpressures obtained for the stratified mixtures are higher than those measured for lean homogeneous mixtures with the same amount of hydrogen. Using an in-house version of FLACS-Hydrogen with the numerical solver Flacs3 and improved physics models results in significantly improved predictions of the peak overpressures, compared to the predictions by the standard Flacs2 solver. The paper includes suggestions for further improvements to the model system.

Research paper thumbnail of Assessing the influence of real releases on explosions: Selected results from large-scale experiments

Journal of Loss Prevention in The Process Industries, Sep 1, 2021

The research activities in the project Assessing the Influence of Real Releases on Explosions (AI... more The research activities in the project Assessing the Influence of Real Releases on Explosions (AIRRE) included a unique series of large-scale explosion experiments with ignited high-momentum jet releases directed into congested geometries. The primary objective for the AIRRE project was to gain improved understanding of the effect realistic releases and turbulent flow conditions have on the consequences of accidental gas explosions in the petroleum industry, to develop methodology that can facilitate safe and optimal design of process facilities. This paper presents selected results from experiments involving ignition of a highly turbulent gas cloud, generated by a large-scale, pressurised release of natural gas. The paper gives an overview of the effect on maximum explosion overpressures of varying the ignition position relative to the release point of the jet and a congested region placed inside the flammable cloud, with either a high or medium level of congestion. For two of the tests involving a jet release and the medium congestion rig, the maximum overpressures significantly exceeded those obtained in a quiescent reference test. The paper presents detailed results for selected tests in the campaign. The effects on the relevant explosion phenomena from introducing initial turbulence, initial flow momentum and concentration gradients, as generated by the realistic release, are discussed.

Research paper thumbnail of CFD modelling of gas explosions: Optimising sub-grid model parameters

Journal of Loss Prevention in The Process Industries, Jul 1, 2019

Validation of the surrogates at the overall optimal parameter values.. . C.4 Validation of the ov... more Validation of the surrogates at the overall optimal parameter values.. . C.4 Validation of the overall optimised model, separately for each campaign. C.5 Maximum overpressure across the rig for BFETS Phase 2 experiments for the standard and overall optimised model and experimental data.. . C.6 Overpressure-time histories for BFETS Phase 2 experiments for the standard model, overall optimised model and experimental data.. .. .

Research paper thumbnail of Assessing the influence of real releases on explosions : motivation and previous work

Gas explosions represent a severe hazard in industry - a majority of the 100 largest property los... more Gas explosions represent a severe hazard in industry - a majority of the 100 largest property losses in the hydrocarbon industries from 1974 to 2017 involved fires and explosions (Marsh, 2018). Most accidental gas explosions entail a chain of events that include loss of containment of gaseous or liquid fuel, dispersion and mixing to form a flammable fuel-air cloud, ignition, turbulent combustion, local pressure build-up and propagation of blast waves in the surroundings. The positive feedback between expansion of combustion products, generation of turbulence in the unreacted mixture, especially in wakes behind obstacles, and enhanced rate of turbulent combustion causes flame acceleration in congested geometries (Bjerketvedt et al., 1997). However, it is also clear that pre-ignition turbulence and various instability phenomena can play a significant role in explosion scenarios, and that deflagrations may undergo transition to detonations (DDT) under certain conditions (Moen, 1993). S...

Research paper thumbnail of Turbulence in real flammable gas releases

International audienceThe research activities in AIRRE project (Assessing the Influence of Real R... more International audienceThe research activities in AIRRE project (Assessing the Influence of Real Releases on Explosions) include a unique series of large-scale explosion experiments with ignited high-momentum jet releases of natural gas directed into congested geometries. The primary objective for the AIRRE project is to gain improved understanding of the effect realistic releases and turbulent flow conditions have on the course and consequences of accidental gas explosions in the petroleum industry, and thereby develop and commercialize technology and methodology that can facilitate safe and optimal design of process facilities. A few tests were performed in open air without any congestion. The mean velocity and turbulence flow fields are presented herein. Flameproof turbulence sensors were purposely designed for the project and calibrated at small scale. These are Pitot probes connected to fast differential pressure sensors. This paper describes the turbulence measurement technique...

Research paper thumbnail of Assessing the influence of real releases on explosions: Selected results from large-scale experiments

Journal of Loss Prevention in the Process Industries, 2021

The research activities in the project Assessing the Influence of Real Releases on Explosions (AI... more The research activities in the project Assessing the Influence of Real Releases on Explosions (AIRRE) included a unique series of large-scale explosion experiments with ignited high-momentum jet releases directed into congested geometries. The primary objective for the AIRRE project was to gain improved understanding of the effect realistic releases and turbulent flow conditions have on the consequences of accidental gas explosions in the petroleum industry, to develop methodology that can facilitate safe and optimal design of process facilities. This paper presents selected results from experiments involving ignition of a highly turbulent gas cloud, generated by a large-scale, pressurised release of natural gas. The paper gives an overview of the effect on maximum explosion overpressures of varying the ignition position relative to the release point of the jet and a congested region placed inside the flammable cloud, with either a high or medium level of congestion. For two of the tests involving a jet release and the medium congestion rig, the maximum overpressures significantly exceeded those obtained in a quiescent reference test. The paper presents detailed results for selected tests in the campaign. The effects on the relevant explosion phenomena from introducing initial turbulence, initial flow momentum and concentration gradients, as generated by the realistic release, are discussed.

Research paper thumbnail of Validating, Documenting And Qualifying Models Used For Consequence Assessment Of Hydrogen Explosion Scenarios

This paper was presented at the Eleventh International Symposium on Hazards, Prevention, and Miti... more This paper was presented at the Eleventh International Symposium on Hazards, Prevention, and Mitigation of Industrial Explosions (11 ISHPMIE) in Dalian on 24-29 July 2016. This paper explores a systematic methodology for validating, documenting and qualifying models used for consequence assessment of accidental explosion scenarios. To demonstrate the advantages of implementing and maintaining an integrated framework, example validation cases relevant for the modelling of vented hydrogen deflagrations are presented. Simulations were performed using the computational fluid dynamics (CFD) tool FLACS-Hydrogen. The main focus of this study is on the definition and application of a model evaluation protocol (MEP), building on recent advances from the hydrogen safety community. Particular emphasis is put on the classification of experiments in the validation database. The present methodology is found to be highly useful for qualifying a model system for specific applications as well as for...

Research paper thumbnail of Influence Of Congestion On Vented Hydrogen Deflagrations In 20-Foot Iso Containers: Homogeneous Fuel-Air Mixtures

This paper was presented at Twenty-Sixth International Colloquium on the Dynamics of Explosions a... more This paper was presented at Twenty-Sixth International Colloquium on the Dynamics of Explosions and Reactive Systems (26 ICDERS) in Boston, 30 July – 4 August 2017. Further progress in the field of hydrogen safety is a prerequisite for widespread acceptance and use of hydrogen as an energy carrier in society. Fires and explosions represent a significant hazard for hydrogen installations, and specific measures are generally required for reducing the risk to an acceptable level. It is common practice in industry to install electrolysers, refuelling stations, fuel cell backup systems and other equipment for hydrogen energy applications in containers or smaller enclosures, and explosion venting is a frequently used measure for reducing the consequences of hydrogen deflagrations in confined systems. Whereas most enclosures used for hydrogen applications in industry are inherently congested, the empirical correlations in international standards for design of venting devices, such as EN 14...

Research paper thumbnail of Simulating vented hydrogen deflagrations: Improved modelling in the CFD tool FLACS-hydrogen

International Journal of Hydrogen Energy, 2021

This paper describes validation of the computational fluid dynamics tool FLACS-Hydrogen. The vali... more This paper describes validation of the computational fluid dynamics tool FLACS-Hydrogen. The validation study focuses on concentration and pressure data from vented deflagration experiments performed in 20-foot shipping containers as part of the project Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations (HySEA), funded by the Fuel Cells and Hydrogen Joint Undertaking (FCH 2 JU). The paper presents results for tests involving inhomogeneous hydrogen-air clouds generated from realistic releases performed during the HySEA project. For both experiments and simulations, the peak overpressures obtained for the stratified mixtures are higher than those measured for lean homogeneous mixtures with the same amount of hydrogen. Using an in-house version of FLACS-Hydrogen with the numerical solver Flacs3 and improved physics models results in significantly improved predictions of the peak overpressures, compared to the predictions by the standard Flacs2 solver. The paper includes suggestions for further improvements to the model system.

Research paper thumbnail of CFD modelling of gas explosions: Optimising sub-grid model parameters

Journal of Loss Prevention in the Process Industries, 2019

Validation of the surrogates at the overall optimal parameter values.. . C.4 Validation of the ov... more Validation of the surrogates at the overall optimal parameter values.. . C.4 Validation of the overall optimised model, separately for each campaign. C.5 Maximum overpressure across the rig for BFETS Phase 2 experiments for the standard and overall optimised model and experimental data.. . C.6 Overpressure-time histories for BFETS Phase 2 experiments for the standard model, overall optimised model and experimental data.. .. .

Research paper thumbnail of Structural response for vented hydrogen deflagrations: Coupling CFD and FE tools

International Journal of Hydrogen Energy, 2019

This paper describes a methodology for simulating the structural response of vented enclosures du... more This paper describes a methodology for simulating the structural response of vented enclosures during hydrogen deflagrations. The approach adopted entails full spatial mapping of explosion loads predicted with the computational fluid dynamics (CFD) tool FLACS-Hydrogen to the non-linear finite element (FE) IMPETUS Afea solver. The modelling involves one-way coupling of pressure loads taken from either experiments or CFD simulations to the FE solver. The performance of the combined model system is evaluated for vented hydrogen deflagrations in 20-foot ISO containers. The work is part of work package 3 (WP3) in the project 'Improving hydrogen safety for energy applications through prenormative research on vented deflagrations' (HySEA).

Research paper thumbnail of Blind-prediction: Estimating the consequences of vented hydrogen deflagrations for homogeneous mixtures in 20-foot ISO containers

International Journal of Hydrogen Energy, 2019

This paper summarises the results from a blind-prediction study for models developed for estimati... more This paper summarises the results from a blind-prediction study for models developed for estimating the consequences of vented hydrogen deflagrations. The work is part of the project Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations (HySEA). The scenarios selected for the blind-prediction entailed vented explosions with homogeneous hydrogen-air mixtures in a 20-foot ISO container. The test program included two configurations and six experiments, i.e. three repeated tests for each scenario. The comparison between experimental results and model predictions reveals reasonable agreement for some of the models, and significant discrepancies for others. It is foreseen that the first blind-prediction study in the HySEA project will motivate developers to improve their models, and to update guidelines for users of the models.

Research paper thumbnail of Vented hydrogen deflagrations in containers: Effect of congestion for homogeneous and inhomogeneous mixtures

International Journal of Hydrogen Energy, 2018

This paper summarises the results from 66 vented hydrogen deflagration experiments performed in 2... more This paper summarises the results from 66 vented hydrogen deflagration experiments performed in 20-foot shipping containers: 42 tests with initially homogeneous and quiescent mixtures, and 24 tests with inhomogeneous mixtures. Other parameters investigated include hydrogen concentration, vent area, type of venting device, ignition position, and the level and type of congestion inside the container. The results confirm that internal congestion can increase the maximum reduced explosion pressure in vented deflagrations significantly, compared to vented deflagrations in empty enclosures. As such, it is important to incorporate the effect of congestion in the theoretical and/or empirical correlations recommended in standards and guidelines for explosion protection. The work reported here is a deliverable from work package 2 (WP2) in the project "Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations" (HySEA). The project received funding from the Fuel Cells and Hydrogen Joint Undertaking (FCH JU).

Research paper thumbnail of Consequence models for vented hydrogen deflagrations: CFD vs. engineering models

International Journal of Hydrogen Energy, 2018

This paper compares two approaches for predicting the consequences of vented hydrogen deflagratio... more This paper compares two approaches for predicting the consequences of vented hydrogen deflagrations: empirical engineering models (EMs) and computational fluid dynamics (CFD) simulations. The study is part of the project 'Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations' (HySEA), funded by the Fuel Cells and Hydrogen 2 Joint Undertaking (FCH JU) under grant agreement No 671461. The HySEA project focuses on vented hydrogen deflagrations in containers and smaller enclosures with internal congestion representative of industrial applications. Data from experiments conducted as part of the HySEA project are used to evaluate predictions from a selection of EMs and the CFD tool FLACS. The experiments involve various obstacle and venting configurations, and initially quiescent homogeneous hydrogen-air mixtures with hydrogen concentrations in the range 15e24 vol%. There is a significant scatter in the maximum reduced overpressures predicted by the different EMs in the present study. For certain configurations, there is an order of magnitude difference between the different EM predictions. Two versions of the CFD tool FLACS are used in the present study: i) the standard commercial release FLACS v10.7r2, and ii) an in-house development version termed FLACS-beta. The commercial release generally over-predicts the maximum overpressures measured in the experiments, while the development version of FLACS gives improved results for several configurations.

Research paper thumbnail of 13th International Symposium on Hazards, Prevention and Mitigation of Industrial Explosions, Proceedings

It is our pleasure to present the proceedings of the 13th International Symposium on Hazards, Pre... more It is our pleasure to present the proceedings of the 13th International Symposium on Hazards, Prevention, and Mitigation of Industrial Explosions (ISHPMIE). The publication of these proceedings was heavily affected by the global situation. In light of these challenges, we are happy to compile proceedings consisting of 84 high-quality papers that reflect the scientific state-of-the-art in the following topical categories: Advances in explosion protection: Strategies, measures, and protective equipment; Detonations and DDT; Electro-chemical energy carriers; Explosion modelling and simulation; Explosion prevention; Explosion properties of substances and mixtures; Explosion testing; Explosions of sprays and vapors; Flame propagation and acceleration; Gas, dust, and hybrid mixture explosions; Hydrogen safety and Ignition phenomena. All articles in this volume have been subject to a peer review process administered by the proceeding editors.

Research paper thumbnail of Direct numerical simulation of turbulent flames on parallel computers

Last but not the least, I appreciate and count it a privilege being part of the CMFI Germany Chri... more Last but not the least, I appreciate and count it a privilege being part of the CMFI Germany Christian community. You have been exceedingly encouraging. Thank you.

Research paper thumbnail of Direct numerical simulation of turbulent flames on parallel computers

Last but not the least, I appreciate and count it a privilege being part of the CMFI Germany Chri... more Last but not the least, I appreciate and count it a privilege being part of the CMFI Germany Christian community. You have been exceedingly encouraging. Thank you.

Research paper thumbnail of Vented hydrogen deflagrations in containers: effect of congestion for homogeneous mixtures

This paper presents results from an experimental study of vented hydrogen deflagrations in 20-foo... more This paper presents results from an experimental study of vented hydrogen deflagrations in 20-foot ISO containers. The scenarios investigated include 14 tests with explosion venting through the doors of the containers, and 20 tests with venting through openings in the roof. The parameters investigated include hydrogen concentration, vent area, type of venting device, and the level of congestion inside the containers. All tests involved homogeneous and initially quiescent hydrogen-air mixtures. The results demonstrate the strong effect of congestion on the maximum reduced explosion pressures, which typically is not accounted for in current standards and guidelines for explosion protection. The work is a deliverable from work package 2 (WP2) in the project "Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations", or HySEA (www.hysea.eu), which receives funding from the Fuel Cells and Hydrogen Joint Undertaking (FCH JU) under grant agreement no. 671461.

Research paper thumbnail of Structural response for vented hydrogen deflagrations: coupling CFD and FE tools

Zenodo (CERN European Organization for Nuclear Research), Sep 11, 2017

This paper describes a methodology for simulating the structural response of vented enclosures du... more This paper describes a methodology for simulating the structural response of vented enclosures during hydrogen deflagrations. The approach adopted entails full spatial mapping of explosion loads predicted with the computational fluid dynamics (CFD) tool FLACS-Hydrogen to the non-linear finite element (FE) IMPETUS Afea solver. The modelling involves one-way coupling of pressure loads taken from either experiments or CFD simulations to the FE solver. The performance of the combined model system is evaluated for vented hydrogen deflagrations in 20-foot ISO containers. The work is part of work package 3 (WP3) in the project 'Improving hydrogen safety for energy applications through prenormative research on vented deflagrations' (HySEA).

Research paper thumbnail of Simulating vented hydrogen deflagrations: Improved modelling in the CFD tool FLACS-hydrogen

International Journal of Hydrogen Energy, Mar 1, 2021

This paper describes validation of the computational fluid dynamics tool FLACS-Hydrogen. The vali... more This paper describes validation of the computational fluid dynamics tool FLACS-Hydrogen. The validation study focuses on concentration and pressure data from vented deflagration experiments performed in 20-foot shipping containers as part of the project Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations (HySEA), funded by the Fuel Cells and Hydrogen Joint Undertaking (FCH 2 JU). The paper presents results for tests involving inhomogeneous hydrogen-air clouds generated from realistic releases performed during the HySEA project. For both experiments and simulations, the peak overpressures obtained for the stratified mixtures are higher than those measured for lean homogeneous mixtures with the same amount of hydrogen. Using an in-house version of FLACS-Hydrogen with the numerical solver Flacs3 and improved physics models results in significantly improved predictions of the peak overpressures, compared to the predictions by the standard Flacs2 solver. The paper includes suggestions for further improvements to the model system.

Research paper thumbnail of Assessing the influence of real releases on explosions: Selected results from large-scale experiments

Journal of Loss Prevention in The Process Industries, Sep 1, 2021

The research activities in the project Assessing the Influence of Real Releases on Explosions (AI... more The research activities in the project Assessing the Influence of Real Releases on Explosions (AIRRE) included a unique series of large-scale explosion experiments with ignited high-momentum jet releases directed into congested geometries. The primary objective for the AIRRE project was to gain improved understanding of the effect realistic releases and turbulent flow conditions have on the consequences of accidental gas explosions in the petroleum industry, to develop methodology that can facilitate safe and optimal design of process facilities. This paper presents selected results from experiments involving ignition of a highly turbulent gas cloud, generated by a large-scale, pressurised release of natural gas. The paper gives an overview of the effect on maximum explosion overpressures of varying the ignition position relative to the release point of the jet and a congested region placed inside the flammable cloud, with either a high or medium level of congestion. For two of the tests involving a jet release and the medium congestion rig, the maximum overpressures significantly exceeded those obtained in a quiescent reference test. The paper presents detailed results for selected tests in the campaign. The effects on the relevant explosion phenomena from introducing initial turbulence, initial flow momentum and concentration gradients, as generated by the realistic release, are discussed.

Research paper thumbnail of CFD modelling of gas explosions: Optimising sub-grid model parameters

Journal of Loss Prevention in The Process Industries, Jul 1, 2019

Validation of the surrogates at the overall optimal parameter values.. . C.4 Validation of the ov... more Validation of the surrogates at the overall optimal parameter values.. . C.4 Validation of the overall optimised model, separately for each campaign. C.5 Maximum overpressure across the rig for BFETS Phase 2 experiments for the standard and overall optimised model and experimental data.. . C.6 Overpressure-time histories for BFETS Phase 2 experiments for the standard model, overall optimised model and experimental data.. .. .

Research paper thumbnail of Assessing the influence of real releases on explosions : motivation and previous work

Gas explosions represent a severe hazard in industry - a majority of the 100 largest property los... more Gas explosions represent a severe hazard in industry - a majority of the 100 largest property losses in the hydrocarbon industries from 1974 to 2017 involved fires and explosions (Marsh, 2018). Most accidental gas explosions entail a chain of events that include loss of containment of gaseous or liquid fuel, dispersion and mixing to form a flammable fuel-air cloud, ignition, turbulent combustion, local pressure build-up and propagation of blast waves in the surroundings. The positive feedback between expansion of combustion products, generation of turbulence in the unreacted mixture, especially in wakes behind obstacles, and enhanced rate of turbulent combustion causes flame acceleration in congested geometries (Bjerketvedt et al., 1997). However, it is also clear that pre-ignition turbulence and various instability phenomena can play a significant role in explosion scenarios, and that deflagrations may undergo transition to detonations (DDT) under certain conditions (Moen, 1993). S...

Research paper thumbnail of Turbulence in real flammable gas releases

International audienceThe research activities in AIRRE project (Assessing the Influence of Real R... more International audienceThe research activities in AIRRE project (Assessing the Influence of Real Releases on Explosions) include a unique series of large-scale explosion experiments with ignited high-momentum jet releases of natural gas directed into congested geometries. The primary objective for the AIRRE project is to gain improved understanding of the effect realistic releases and turbulent flow conditions have on the course and consequences of accidental gas explosions in the petroleum industry, and thereby develop and commercialize technology and methodology that can facilitate safe and optimal design of process facilities. A few tests were performed in open air without any congestion. The mean velocity and turbulence flow fields are presented herein. Flameproof turbulence sensors were purposely designed for the project and calibrated at small scale. These are Pitot probes connected to fast differential pressure sensors. This paper describes the turbulence measurement technique...

Research paper thumbnail of Assessing the influence of real releases on explosions: Selected results from large-scale experiments

Journal of Loss Prevention in the Process Industries, 2021

The research activities in the project Assessing the Influence of Real Releases on Explosions (AI... more The research activities in the project Assessing the Influence of Real Releases on Explosions (AIRRE) included a unique series of large-scale explosion experiments with ignited high-momentum jet releases directed into congested geometries. The primary objective for the AIRRE project was to gain improved understanding of the effect realistic releases and turbulent flow conditions have on the consequences of accidental gas explosions in the petroleum industry, to develop methodology that can facilitate safe and optimal design of process facilities. This paper presents selected results from experiments involving ignition of a highly turbulent gas cloud, generated by a large-scale, pressurised release of natural gas. The paper gives an overview of the effect on maximum explosion overpressures of varying the ignition position relative to the release point of the jet and a congested region placed inside the flammable cloud, with either a high or medium level of congestion. For two of the tests involving a jet release and the medium congestion rig, the maximum overpressures significantly exceeded those obtained in a quiescent reference test. The paper presents detailed results for selected tests in the campaign. The effects on the relevant explosion phenomena from introducing initial turbulence, initial flow momentum and concentration gradients, as generated by the realistic release, are discussed.

Research paper thumbnail of Validating, Documenting And Qualifying Models Used For Consequence Assessment Of Hydrogen Explosion Scenarios

This paper was presented at the Eleventh International Symposium on Hazards, Prevention, and Miti... more This paper was presented at the Eleventh International Symposium on Hazards, Prevention, and Mitigation of Industrial Explosions (11 ISHPMIE) in Dalian on 24-29 July 2016. This paper explores a systematic methodology for validating, documenting and qualifying models used for consequence assessment of accidental explosion scenarios. To demonstrate the advantages of implementing and maintaining an integrated framework, example validation cases relevant for the modelling of vented hydrogen deflagrations are presented. Simulations were performed using the computational fluid dynamics (CFD) tool FLACS-Hydrogen. The main focus of this study is on the definition and application of a model evaluation protocol (MEP), building on recent advances from the hydrogen safety community. Particular emphasis is put on the classification of experiments in the validation database. The present methodology is found to be highly useful for qualifying a model system for specific applications as well as for...

Research paper thumbnail of Influence Of Congestion On Vented Hydrogen Deflagrations In 20-Foot Iso Containers: Homogeneous Fuel-Air Mixtures

This paper was presented at Twenty-Sixth International Colloquium on the Dynamics of Explosions a... more This paper was presented at Twenty-Sixth International Colloquium on the Dynamics of Explosions and Reactive Systems (26 ICDERS) in Boston, 30 July – 4 August 2017. Further progress in the field of hydrogen safety is a prerequisite for widespread acceptance and use of hydrogen as an energy carrier in society. Fires and explosions represent a significant hazard for hydrogen installations, and specific measures are generally required for reducing the risk to an acceptable level. It is common practice in industry to install electrolysers, refuelling stations, fuel cell backup systems and other equipment for hydrogen energy applications in containers or smaller enclosures, and explosion venting is a frequently used measure for reducing the consequences of hydrogen deflagrations in confined systems. Whereas most enclosures used for hydrogen applications in industry are inherently congested, the empirical correlations in international standards for design of venting devices, such as EN 14...

Research paper thumbnail of Simulating vented hydrogen deflagrations: Improved modelling in the CFD tool FLACS-hydrogen

International Journal of Hydrogen Energy, 2021

This paper describes validation of the computational fluid dynamics tool FLACS-Hydrogen. The vali... more This paper describes validation of the computational fluid dynamics tool FLACS-Hydrogen. The validation study focuses on concentration and pressure data from vented deflagration experiments performed in 20-foot shipping containers as part of the project Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations (HySEA), funded by the Fuel Cells and Hydrogen Joint Undertaking (FCH 2 JU). The paper presents results for tests involving inhomogeneous hydrogen-air clouds generated from realistic releases performed during the HySEA project. For both experiments and simulations, the peak overpressures obtained for the stratified mixtures are higher than those measured for lean homogeneous mixtures with the same amount of hydrogen. Using an in-house version of FLACS-Hydrogen with the numerical solver Flacs3 and improved physics models results in significantly improved predictions of the peak overpressures, compared to the predictions by the standard Flacs2 solver. The paper includes suggestions for further improvements to the model system.

Research paper thumbnail of CFD modelling of gas explosions: Optimising sub-grid model parameters

Journal of Loss Prevention in the Process Industries, 2019

Validation of the surrogates at the overall optimal parameter values.. . C.4 Validation of the ov... more Validation of the surrogates at the overall optimal parameter values.. . C.4 Validation of the overall optimised model, separately for each campaign. C.5 Maximum overpressure across the rig for BFETS Phase 2 experiments for the standard and overall optimised model and experimental data.. . C.6 Overpressure-time histories for BFETS Phase 2 experiments for the standard model, overall optimised model and experimental data.. .. .

Research paper thumbnail of Structural response for vented hydrogen deflagrations: Coupling CFD and FE tools

International Journal of Hydrogen Energy, 2019

This paper describes a methodology for simulating the structural response of vented enclosures du... more This paper describes a methodology for simulating the structural response of vented enclosures during hydrogen deflagrations. The approach adopted entails full spatial mapping of explosion loads predicted with the computational fluid dynamics (CFD) tool FLACS-Hydrogen to the non-linear finite element (FE) IMPETUS Afea solver. The modelling involves one-way coupling of pressure loads taken from either experiments or CFD simulations to the FE solver. The performance of the combined model system is evaluated for vented hydrogen deflagrations in 20-foot ISO containers. The work is part of work package 3 (WP3) in the project 'Improving hydrogen safety for energy applications through prenormative research on vented deflagrations' (HySEA).

Research paper thumbnail of Blind-prediction: Estimating the consequences of vented hydrogen deflagrations for homogeneous mixtures in 20-foot ISO containers

International Journal of Hydrogen Energy, 2019

This paper summarises the results from a blind-prediction study for models developed for estimati... more This paper summarises the results from a blind-prediction study for models developed for estimating the consequences of vented hydrogen deflagrations. The work is part of the project Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations (HySEA). The scenarios selected for the blind-prediction entailed vented explosions with homogeneous hydrogen-air mixtures in a 20-foot ISO container. The test program included two configurations and six experiments, i.e. three repeated tests for each scenario. The comparison between experimental results and model predictions reveals reasonable agreement for some of the models, and significant discrepancies for others. It is foreseen that the first blind-prediction study in the HySEA project will motivate developers to improve their models, and to update guidelines for users of the models.

Research paper thumbnail of Vented hydrogen deflagrations in containers: Effect of congestion for homogeneous and inhomogeneous mixtures

International Journal of Hydrogen Energy, 2018

This paper summarises the results from 66 vented hydrogen deflagration experiments performed in 2... more This paper summarises the results from 66 vented hydrogen deflagration experiments performed in 20-foot shipping containers: 42 tests with initially homogeneous and quiescent mixtures, and 24 tests with inhomogeneous mixtures. Other parameters investigated include hydrogen concentration, vent area, type of venting device, ignition position, and the level and type of congestion inside the container. The results confirm that internal congestion can increase the maximum reduced explosion pressure in vented deflagrations significantly, compared to vented deflagrations in empty enclosures. As such, it is important to incorporate the effect of congestion in the theoretical and/or empirical correlations recommended in standards and guidelines for explosion protection. The work reported here is a deliverable from work package 2 (WP2) in the project "Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations" (HySEA). The project received funding from the Fuel Cells and Hydrogen Joint Undertaking (FCH JU).

Research paper thumbnail of Consequence models for vented hydrogen deflagrations: CFD vs. engineering models

International Journal of Hydrogen Energy, 2018

This paper compares two approaches for predicting the consequences of vented hydrogen deflagratio... more This paper compares two approaches for predicting the consequences of vented hydrogen deflagrations: empirical engineering models (EMs) and computational fluid dynamics (CFD) simulations. The study is part of the project 'Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations' (HySEA), funded by the Fuel Cells and Hydrogen 2 Joint Undertaking (FCH JU) under grant agreement No 671461. The HySEA project focuses on vented hydrogen deflagrations in containers and smaller enclosures with internal congestion representative of industrial applications. Data from experiments conducted as part of the HySEA project are used to evaluate predictions from a selection of EMs and the CFD tool FLACS. The experiments involve various obstacle and venting configurations, and initially quiescent homogeneous hydrogen-air mixtures with hydrogen concentrations in the range 15e24 vol%. There is a significant scatter in the maximum reduced overpressures predicted by the different EMs in the present study. For certain configurations, there is an order of magnitude difference between the different EM predictions. Two versions of the CFD tool FLACS are used in the present study: i) the standard commercial release FLACS v10.7r2, and ii) an in-house development version termed FLACS-beta. The commercial release generally over-predicts the maximum overpressures measured in the experiments, while the development version of FLACS gives improved results for several configurations.

Research paper thumbnail of 13th International Symposium on Hazards, Prevention and Mitigation of Industrial Explosions, Proceedings

It is our pleasure to present the proceedings of the 13th International Symposium on Hazards, Pre... more It is our pleasure to present the proceedings of the 13th International Symposium on Hazards, Prevention, and Mitigation of Industrial Explosions (ISHPMIE). The publication of these proceedings was heavily affected by the global situation. In light of these challenges, we are happy to compile proceedings consisting of 84 high-quality papers that reflect the scientific state-of-the-art in the following topical categories: Advances in explosion protection: Strategies, measures, and protective equipment; Detonations and DDT; Electro-chemical energy carriers; Explosion modelling and simulation; Explosion prevention; Explosion properties of substances and mixtures; Explosion testing; Explosions of sprays and vapors; Flame propagation and acceleration; Gas, dust, and hybrid mixture explosions; Hydrogen safety and Ignition phenomena. All articles in this volume have been subject to a peer review process administered by the proceeding editors.