Topi Sikanen - Academia.edu (original) (raw)
Papers by Topi Sikanen
We are very proud to present the abstracts of 62 Nordic and international contributions in the pr... more We are very proud to present the abstracts of 62 Nordic and international contributions in the present book of abstracts. The work demonstrates a significant scientific depth and societal relevance. The conference is a response to the extensive interest in the areas of fire and safety engineering in the Nordic countries in the past decades. As the programme and the abstracts show, the NFSD follow up on challenges with respect to safety dealing with aspects of fire and actions of the rescue service as well as human behavior and risk management. This year there is a special focus on fire safe furniture and the intervention of the rescue service.
In this work, we wanted to study how the construction trends aiming at energy efficient and high-... more In this work, we wanted to study how the construction trends aiming at energy efficient and high-rise buildings are changing the fire modelling practices. Through experiments, FDS validation and a simulation case-study, we investigate the reliability and modelling practices of the mechanical ventilation systems and air-tight building envelopes. The simulation results indicate that the new, very air-tight building envelopes can pose a risk for both occupant and structural safety in fires.
This publication summarizes a three-year research project with a goal to improve and enhance the ... more This publication summarizes a three-year research project with a goal to improve and enhance the capabilities of the NIST Fire Dynamics Simulator to describe water spray dynamics, discharge of large water based fire suppression systems, gas phase cooling by water sprays, flame extinguishment, and the suppression of large complex solid fire loads. Several new features were programmed to the code related to the description of water sprays, flame extinguishment, and suppressability of solid fire loads. Significant emphasis was put on validating the model performance against experimental data. When such data was not readily found in the literature, experiments were conducted to create the data. Due to the code development and validation work, the capability of FDS to predict the performance of fire suppression systems has been significantly improved.
Fire cable risks during plant life cycle Reactive Molecular Dynamics simulations can provide info... more Fire cable risks during plant life cycle Reactive Molecular Dynamics simulations can provide information on the thermal degradation chemistry of fire retardant chemicals and polymeric base materials. Using a model system consisting of ATH embedded in an amorphous PE matrix, we have shown that ATH is chemically promoting the carbonization of PE. FIRED The main objective of the FIRED project is to develop tools for fire risk evaluation and create a new methodology for assessing the defense-in-depth in the context of fire safety. The research concentrates on four main topics: 1. Cable fire risks during plant life cycle, 2. Performance of the fire-barriers, 3. Tool development, maintenance and validation, and 4. Participation and utilization of OECD/NEA PRISME2 and PRISME3 projects.
Numerical simulation of water mist systems is gaining interest among fire safety engineers due to... more Numerical simulation of water mist systems is gaining interest among fire safety engineers due to the increasing range of water mist suppression and protection applications, and the lack of simple and general design rules. The existing Eulerian-Lagrangian framework of FDS can be used for water mist simulations, but the published reports on the s i m u l a t i o n p r o c e s s a n d v a l i d a t i o n s a r e f e w. I n comparison to traditional sprinkler technology, water mist has a wider range of physical suppression and cooling effects. An accurate modeling of such systems requires that all the relevant input parameters can be prescribed. From the modeling viewpoint, an important difference is the stronger exchange of momentum between the gas and liquid phases. The FDS capabilities and improvements concerning the spray dynamics and heat transfer, including the experimental validation, are presented. The experimental work includes the measurements of drop size, drop speed and mist flux profiles, gas phase entrainment speed in a channel geometry and radiative heat flux attenuation.
A new tool is being developed by widening the scope of our earlier platform. In Finland probabili... more A new tool is being developed by widening the scope of our earlier platform. In Finland probability of human fire loss has been higher than in most similar countries. The motivation of the development was to estimate effectiveness of potential measures to improve home fire safety. Constructing a bottom-up system synthetically and modeling the dynamics of the key components and agents realistic enough produces a tool for numerical experiments, where causality is built in. This is an advantage over statistical methods, where distinguishing cause from consequence is difficult, and nonlinear, correlating variables cause confusion. Monte Carlo simulations of realistic agents in home fires were carried out piecewise and iteratively to find out the most important variables. Home was the basic unit of Monte Carlo fire simulations carried out in two phases flaming ignition as the borderline. Pre-flaming simulations used statistical data on population, buildings, households as well as time-us...
Fire Safety Journal, 2017
In this paper we perform predictive simulations of liquid pool fires in mechanically ventilated c... more In this paper we perform predictive simulations of liquid pool fires in mechanically ventilated compartments. We show that steady state burning rates are accurately predicted using a detailed model for the liquid phase heat transfer. The effect of lowered oxygen vitiation on the burning rate of pool fires is correctly captured. Simulations were done using the Fire Dynamics Simulator and the experiments considered were conducted in the OECD PRISME project. The main difference between the present study and previous simulation studies is the use of a detailed liquid evaporation model and the direct calculation of the vitiation and thermal environment interactions through the CFD solver.
Nuclear Engineering and Design, 2017
h i g h l i g h t s Methodology for simulating fires resulting from aircraft impact was developed... more h i g h l i g h t s Methodology for simulating fires resulting from aircraft impact was developed. The methodology was validated using experimental data. Large scale simulations of aircraft impact on a nuclear island were conducted. The fraction of fuel available for subsequent fires was found to be significant. The pooling fraction was strongly affected by impact geometry.
Fire Safety Journal, 2017
Fire-induced pressures have not been considered dangerous in building fires, but the situation ma... more Fire-induced pressures have not been considered dangerous in building fires, but the situation may be changing as building envelopes become increasingly airtight. In this study, we investigate whether this can change the fire development and pose new risks for structural and evacuation safety. We used experiments to validate the numerical models, and models for simulating the fire development in buildings with different airtightness levels. The simulations considered air permeability values typical for traditional, modern and Near-Zero buildings. Three different smoke damper configurations were studied, and the fire growth rates were varied from medium to ultra-fast. The results showed that transitioning from traditional and modern buildings to Near-Zero buildings can sufficiently increase the peak overpressures from fast-growing fires to cause structural damage. Conditions were identified for avoiding excessively high overpressures, while preventing smoke from spreading through the ventilation system.
Nuclear Engineering and Design, 2015
Modelling and analysing fires following aircraft impacts requires information about the behaviour... more Modelling and analysing fires following aircraft impacts requires information about the behaviour of liquid fuel. In this study, we investigated sprays resulting from the impacts of water-filled metal projectiles on a hard wall. The weights of the projectiles were in the range of 38…110 kg, with 8.6…68 kg water, and the impact speeds varied between 96 and 169 m/s. The overall spray behaviour was observed with high-speed video cameras. Ultra-highspeed cameras were used in backlight configuration for measuring the droplet size and velocity distributions. The results indicate that the liquid leaves the impact position as a thin sheet of spray in a direction perpendicular to the projectile velocity. The initial spray speeds were 1.5…2.5 times the impact speed, and the Sauter mean diameters were in the 147…344 mm range. This data can be used as boundary conditions in CFD fire analyses, considering the two-phase fuel flow. The overall spray observations, including the spray deceleration rate, can be used for validating the model.
Computational Methods in Multiphase Flow VII, 2013
Water mists systems are used to protect people and property from fires. They suppress fires by th... more Water mists systems are used to protect people and property from fires. They suppress fires by three main mechanisms: removal of heat from the gases, displacement of oxygen by water vapour and attenuation of radiation by droplets. Correct prediction of these mechanisms hinges on accurate modeling of droplet transport. This paper discusses the modeling and simulation of high speed water mist systems using Large Eddy Simulation and a Lagrangian description of the spray. The focus is on the droplet transport. Particular attention is given to the droplet injection model and sub models for coupling of the dispersed and continuous phases. Effects of turbulence modeling on droplet transport is explored. The modeling results are compared to experimental data from both small and large scale experiments.
Fires in nuclear power plants can be an important hazard for the overall safety of the facility. ... more Fires in nuclear power plants can be an important hazard for the overall safety of the facility. One of the typical fire sources is a pool fire. It is therefore important to have good knowledge on the fire behaviour of pool fire and be able to predict the heat release rate by prediction of the mass loss rate. This final report describes the state of the art within the area of pool fire modelling and the need for further development of pool fire models. As a result of the research in this project two new models are presented: one pyrolysis model and one engineering model. In the project the models were validated and pool fire experiments were included. Also a number of real case studies were incorporated to show the need for the development of pool fire models.
Spotting is an important mechanism of wildland re spread. Burning particles such as twigs and lea... more Spotting is an important mechanism of wildland re spread. Burning particles such as twigs and leaves lofted by the fires boyant plume can be carried by ambient winds anywhere from few meters up to even a kilometer from their source. Firebrands can then start new fires far from the original firefront. This makes it difficult to predict firefronts movements and can cause suprising and life threatening sitsuations for firefighters. Firebrands also pose a signicant fire hazard at Wildland-Urban Interfaces (WUI). Several studies have been conducted into firebrand propagation, most of them theoretical studies aimed at determining the maximum spotting distances for variuous kind of firebrands in dirent ambient conditions. Until late experimental studies of firebrand spotting have been scarce. Considerable amount of work has been done in both combustion of woodland fuel particles and trajectories of particles of various shape. Few studies have combined these two aspects of the problem. The ...
Fire Safety Journal, 2016
We are very proud to present the abstracts of 62 Nordic and international contributions in the pr... more We are very proud to present the abstracts of 62 Nordic and international contributions in the present book of abstracts. The work demonstrates a significant scientific depth and societal relevance. The conference is a response to the extensive interest in the areas of fire and safety engineering in the Nordic countries in the past decades. As the programme and the abstracts show, the NFSD follow up on challenges with respect to safety dealing with aspects of fire and actions of the rescue service as well as human behavior and risk management. This year there is a special focus on fire safe furniture and the intervention of the rescue service.
In this work, we wanted to study how the construction trends aiming at energy efficient and high-... more In this work, we wanted to study how the construction trends aiming at energy efficient and high-rise buildings are changing the fire modelling practices. Through experiments, FDS validation and a simulation case-study, we investigate the reliability and modelling practices of the mechanical ventilation systems and air-tight building envelopes. The simulation results indicate that the new, very air-tight building envelopes can pose a risk for both occupant and structural safety in fires.
This publication summarizes a three-year research project with a goal to improve and enhance the ... more This publication summarizes a three-year research project with a goal to improve and enhance the capabilities of the NIST Fire Dynamics Simulator to describe water spray dynamics, discharge of large water based fire suppression systems, gas phase cooling by water sprays, flame extinguishment, and the suppression of large complex solid fire loads. Several new features were programmed to the code related to the description of water sprays, flame extinguishment, and suppressability of solid fire loads. Significant emphasis was put on validating the model performance against experimental data. When such data was not readily found in the literature, experiments were conducted to create the data. Due to the code development and validation work, the capability of FDS to predict the performance of fire suppression systems has been significantly improved.
Fire cable risks during plant life cycle Reactive Molecular Dynamics simulations can provide info... more Fire cable risks during plant life cycle Reactive Molecular Dynamics simulations can provide information on the thermal degradation chemistry of fire retardant chemicals and polymeric base materials. Using a model system consisting of ATH embedded in an amorphous PE matrix, we have shown that ATH is chemically promoting the carbonization of PE. FIRED The main objective of the FIRED project is to develop tools for fire risk evaluation and create a new methodology for assessing the defense-in-depth in the context of fire safety. The research concentrates on four main topics: 1. Cable fire risks during plant life cycle, 2. Performance of the fire-barriers, 3. Tool development, maintenance and validation, and 4. Participation and utilization of OECD/NEA PRISME2 and PRISME3 projects.
Numerical simulation of water mist systems is gaining interest among fire safety engineers due to... more Numerical simulation of water mist systems is gaining interest among fire safety engineers due to the increasing range of water mist suppression and protection applications, and the lack of simple and general design rules. The existing Eulerian-Lagrangian framework of FDS can be used for water mist simulations, but the published reports on the s i m u l a t i o n p r o c e s s a n d v a l i d a t i o n s a r e f e w. I n comparison to traditional sprinkler technology, water mist has a wider range of physical suppression and cooling effects. An accurate modeling of such systems requires that all the relevant input parameters can be prescribed. From the modeling viewpoint, an important difference is the stronger exchange of momentum between the gas and liquid phases. The FDS capabilities and improvements concerning the spray dynamics and heat transfer, including the experimental validation, are presented. The experimental work includes the measurements of drop size, drop speed and mist flux profiles, gas phase entrainment speed in a channel geometry and radiative heat flux attenuation.
A new tool is being developed by widening the scope of our earlier platform. In Finland probabili... more A new tool is being developed by widening the scope of our earlier platform. In Finland probability of human fire loss has been higher than in most similar countries. The motivation of the development was to estimate effectiveness of potential measures to improve home fire safety. Constructing a bottom-up system synthetically and modeling the dynamics of the key components and agents realistic enough produces a tool for numerical experiments, where causality is built in. This is an advantage over statistical methods, where distinguishing cause from consequence is difficult, and nonlinear, correlating variables cause confusion. Monte Carlo simulations of realistic agents in home fires were carried out piecewise and iteratively to find out the most important variables. Home was the basic unit of Monte Carlo fire simulations carried out in two phases flaming ignition as the borderline. Pre-flaming simulations used statistical data on population, buildings, households as well as time-us...
Fire Safety Journal, 2017
In this paper we perform predictive simulations of liquid pool fires in mechanically ventilated c... more In this paper we perform predictive simulations of liquid pool fires in mechanically ventilated compartments. We show that steady state burning rates are accurately predicted using a detailed model for the liquid phase heat transfer. The effect of lowered oxygen vitiation on the burning rate of pool fires is correctly captured. Simulations were done using the Fire Dynamics Simulator and the experiments considered were conducted in the OECD PRISME project. The main difference between the present study and previous simulation studies is the use of a detailed liquid evaporation model and the direct calculation of the vitiation and thermal environment interactions through the CFD solver.
Nuclear Engineering and Design, 2017
h i g h l i g h t s Methodology for simulating fires resulting from aircraft impact was developed... more h i g h l i g h t s Methodology for simulating fires resulting from aircraft impact was developed. The methodology was validated using experimental data. Large scale simulations of aircraft impact on a nuclear island were conducted. The fraction of fuel available for subsequent fires was found to be significant. The pooling fraction was strongly affected by impact geometry.
Fire Safety Journal, 2017
Fire-induced pressures have not been considered dangerous in building fires, but the situation ma... more Fire-induced pressures have not been considered dangerous in building fires, but the situation may be changing as building envelopes become increasingly airtight. In this study, we investigate whether this can change the fire development and pose new risks for structural and evacuation safety. We used experiments to validate the numerical models, and models for simulating the fire development in buildings with different airtightness levels. The simulations considered air permeability values typical for traditional, modern and Near-Zero buildings. Three different smoke damper configurations were studied, and the fire growth rates were varied from medium to ultra-fast. The results showed that transitioning from traditional and modern buildings to Near-Zero buildings can sufficiently increase the peak overpressures from fast-growing fires to cause structural damage. Conditions were identified for avoiding excessively high overpressures, while preventing smoke from spreading through the ventilation system.
Nuclear Engineering and Design, 2015
Modelling and analysing fires following aircraft impacts requires information about the behaviour... more Modelling and analysing fires following aircraft impacts requires information about the behaviour of liquid fuel. In this study, we investigated sprays resulting from the impacts of water-filled metal projectiles on a hard wall. The weights of the projectiles were in the range of 38…110 kg, with 8.6…68 kg water, and the impact speeds varied between 96 and 169 m/s. The overall spray behaviour was observed with high-speed video cameras. Ultra-highspeed cameras were used in backlight configuration for measuring the droplet size and velocity distributions. The results indicate that the liquid leaves the impact position as a thin sheet of spray in a direction perpendicular to the projectile velocity. The initial spray speeds were 1.5…2.5 times the impact speed, and the Sauter mean diameters were in the 147…344 mm range. This data can be used as boundary conditions in CFD fire analyses, considering the two-phase fuel flow. The overall spray observations, including the spray deceleration rate, can be used for validating the model.
Computational Methods in Multiphase Flow VII, 2013
Water mists systems are used to protect people and property from fires. They suppress fires by th... more Water mists systems are used to protect people and property from fires. They suppress fires by three main mechanisms: removal of heat from the gases, displacement of oxygen by water vapour and attenuation of radiation by droplets. Correct prediction of these mechanisms hinges on accurate modeling of droplet transport. This paper discusses the modeling and simulation of high speed water mist systems using Large Eddy Simulation and a Lagrangian description of the spray. The focus is on the droplet transport. Particular attention is given to the droplet injection model and sub models for coupling of the dispersed and continuous phases. Effects of turbulence modeling on droplet transport is explored. The modeling results are compared to experimental data from both small and large scale experiments.
Fires in nuclear power plants can be an important hazard for the overall safety of the facility. ... more Fires in nuclear power plants can be an important hazard for the overall safety of the facility. One of the typical fire sources is a pool fire. It is therefore important to have good knowledge on the fire behaviour of pool fire and be able to predict the heat release rate by prediction of the mass loss rate. This final report describes the state of the art within the area of pool fire modelling and the need for further development of pool fire models. As a result of the research in this project two new models are presented: one pyrolysis model and one engineering model. In the project the models were validated and pool fire experiments were included. Also a number of real case studies were incorporated to show the need for the development of pool fire models.
Spotting is an important mechanism of wildland re spread. Burning particles such as twigs and lea... more Spotting is an important mechanism of wildland re spread. Burning particles such as twigs and leaves lofted by the fires boyant plume can be carried by ambient winds anywhere from few meters up to even a kilometer from their source. Firebrands can then start new fires far from the original firefront. This makes it difficult to predict firefronts movements and can cause suprising and life threatening sitsuations for firefighters. Firebrands also pose a signicant fire hazard at Wildland-Urban Interfaces (WUI). Several studies have been conducted into firebrand propagation, most of them theoretical studies aimed at determining the maximum spotting distances for variuous kind of firebrands in dirent ambient conditions. Until late experimental studies of firebrand spotting have been scarce. Considerable amount of work has been done in both combustion of woodland fuel particles and trajectories of particles of various shape. Few studies have combined these two aspects of the problem. The ...
Fire Safety Journal, 2016