Background Metaballs is a method that can be applied to multiple areas, for example creating clouds and water drop simulations. This thesis looks in into thepossibility of using metaballs as a technique for fire propagation.Objectives The aim of this thesis is to investigate if metaballs can be used asa method for fire propagation in comparison to a method that has been used inmultiple games already, a grid method. The comparison was categorized into two;degree of realism in each methods spreading pattern, and how well they performregarding execution time in different scenarios.Methods A user study was conducted to determine how realistic each method isaccording to the users. The study consisted of a survey, remotely done from home,in which the participants were asked to rate the degree of realism on different clips ofthe methods of fire propagation. As a point of reference for judging fire propagation,the participants also watched two videos of actual fires spreading. To evaluate theperformance of the methods they were exposed to different scenes containing differentamounts of objects the methods had to process.Results The user study concluded that there was no significant difference in themethods spreading regarding its realism. In total, 32 participants with the age rangeof 19 to 77 volunteered for the study. The performance tests concluded that theproposed method did not perform as good as the grid method, with an average often times the execution time.Conclusion The conclusion from the user study is that the results from the userstudy did not show any significant difference between the two methods. Performancewise however, the grid was proven to be a better alternative.

The mechanism of flame propagation in fuel beds of wildland fires is important to understand and quantify fire spread rates. Fires spread by radiative and convective heating and often require direct flame contact to achieve ignition. The flame interface in an advancing fire is unsteady and turbulent, making study of intermittent flames in complex fuels difficult. This thesis applies the one-dimensional turbulence (ODT) model to a study of flame propagation by simulating a lab-scale fire representative of the flame interface in a fuel bed and incorporating solid fuel particles into the ODT code. The ODT model is able to resolve individual flames (a unique property of this model) and provide realistic turbulent statistics. ODT solves diffusion-reaction equations on a line-of-sight that is advanced either in time or in one spatial direction (perpendicular to the line-of-sight). Turbulent advection is modeled through stochastic domain mapping processes. A vertical wall fire, in which ethylene fuel is slowly fed through a porous ceramic, is modeled to investigate an unsteady turbulent flame front in a controlled environment. Simulations of this configuration are performed using a spatial formulation of the ODT model, where the ODT line is perpendicular to the wall and is advanced up the wall. Simulations include radiation and soot effects and are compared to experimental temperature data taken over a range of fuel flow rates. Flame structure, velocities, and temperature statistics are reported. The ODT model is shown to capture the evolution of the flame and describe the intermittent properties at the flame edge, though temperature fluctuations are somewhat over predicted. A solid particle devolatilization model was included in the ODT code to study the convective heating of unburnt solid fuels through direct flame contact. Here the particles are treated as sweet gum hardwood and a single-reaction, first order decomposition model is used to simulate the devolatilization rates. Only preliminary results were presented for a simple case, but this extension of the ODT model presents new opportunities for future research.

Engineered timber products are becoming increasingly popular in the construction industry due to their attractive aesthetic and sustainability credentials. Cross-laminated timber (CLT) is one such engineered timber product, formed of multiple layers of timber planks glued together with adjacent layers perpendicular to each other. Unlike traditional building materials such as steel and concrete, the timber structural elements can ignite and burn when exposed to fire, and thus this risk must be explicitly addressed during design. Current design guidance focusses on the structural response of engineered timber, with the flammability risk typically addressed by encapsulation of any structural timber elements with the intention of preventing their involvement in a fire. Exposed structural timber elements may act as an additional fuel load, and this risk must be adequately quantified to satisfy the intent of the building regulations in that the structure does not continue burning. This can be achieved through timber’s natural capacity to auto-extinguish when the external heat source is removed or sufficiently reduced. To address these issues, a fundamental understanding of auto-extinction and the conditions necessary to achieve it in real fire scenarios is needed. Bench-scale flammability studies were undertaken in the Fire Propagation Apparatus to explore the conditions under which auto-extinction will occur. Critical conditions were determined experimentally as a mass loss rate of 3.48 ± 0.31 g/m2s, or an incident heat flux of ~30 kW/m2. Mass loss rate was identified as the better criterion, as critical heat flux was shown by comparison with literature data to be heavily dependent on apparatus. Subsequently, full-scale compartment fire experiments with exposed timber surfaces were performed to determine if auto-extinction could be achieved in real fire scenarios. It was demonstrated that auto-extinction could be achieved in a compartment fire scenario, but only if significant delamination of the engineered timber product could be prevented. A full-scale compartment fire experiment with an exposed back wall and ceiling achieved auto-extinction after around 21 minutes, at which point no significant delamination of the first lamella had been observed. Experiments with an exposed back and side wall, and experiments with an exposed back wall, side wall, and ceiling underwent sustained burning due to repeated delamination, and an increased quantity of exposed timber respectively. Firepoint theory was used to predict the mass loss rate as a function of external heat flux and heat losses, and was successfully applied to the bench-scale experiments. This approach was then extended to the full-scale compartment fire experiment which achieved auto-extinction. A simplified approach based on experimentally obtained internal temperature fields was able to predict auto-extinction if delamination had not occurred – predicting an extinction time of 20-21 minutes. This demonstrates that the critical mass loss rate of 3.48 ± 0.31 g/m2s determined from bench-scale experiments was valid for application to full-scale compartment fire experiments. This was further explored through a series of reduced-scale compartment fire experiments, demonstrating that auto-extinction can only reliably be achieved if burnout of the compartment fuel load is achieved before significant delamination of the outer lamella takes place. The quantification of the auto-extinction phenomena and their applicability to full-scale compartment fires explored herein thus allows greater understanding of the effects of exposed timber surfaces on compartment fire dynamics.

Simulating fire propagation in games can be problematic since it requires immense computational power if the fire is portrayed physically accurate. To decrease the computational power required, simplifications and approximations must be made. The aim of this thesis is to evaluate possible methods for simulating fire spread in a networked game environment. More specifically, a level set and a node graph method are implemented and investigated. A vector field was created with the different level properties, which the two methods used as a base for the fire behavior. The performance and overall behavior of the methods were evaluated and tested in order to create an optimized simulation suited for games. Two implementations were made in the Frostbite game engine. The level set propagates the fire with two different level set operators; the normal advection operator and the vector field operator. The normal advection operator spreads the fire outwards in the normal direction. The vector field operator spreads the fire front according to the vector field. The node graph implementation uses a semi-connected bi-directed graph with nodes as starting positions for the fire. The fire spreads through the nodes via their connections. This implementation also depends on the vector field which was translated to the nodes through scalar projection. The vector field represents the properties of fire dynamics and can be adjusted to move the level set and node graph implementation according to wind, slope and fuel. The node graph implementation was further developed with networked capabilities, a heat grid which translates the heat of the node graph making it possible to sample the heat at a position within the level, and also basic interaction with vegetation. / <p>Examensarbetet är utfört vid Institutionen för teknik och naturvetenskap (ITN) vid Tekniska fakulteten, Linköpings universitet</p>

This report covers the creation of a dynamic fire propagation method for a real-time environment. The purpose is to see if it is possible to create a system that can control fire propagation behaviour and visual design based on some sort of simple parametrization, the purpose stems from the lack of a system to control and design a fire propagation scenario. To attain the results, a fire propagation method is devised based on the purpose of having a parameter based system, this method is created through the use of scripting in a real-time game engine to control visuals and behaviour of built in particle systems. Results show fire propagation through an example scenario where the fire behaves differently based on the material that is burning, based on parameters set by an artist. These results conclude that is it possible to create a parameter based fire propagation system and that it can be used to change the visual design and behaviour and be expanded to provide better artist input and control. The report suggests further research in the area of simplified controlled fire simulation in real-time engines, and usability. / Den här rapporten täcker skapandet av en metod för dynamisk eldspridning i en realtidsmiljö. Syftet är att se om det är möjligt att skapa ett system som kan kontrollera spridningsbeteendet och den visuella designen av elden baserat på någon sorts simplifierad parametrisering, Syftet härstammar ifrån att det saknas system där man kan kontrollera och designa ett eldspridningsscenario. För att nå resultat så skapas en metod som är baserad på syftet att använda ett parameterbaserat system, denna metoden skapas med hjälp av programmering i en realtidsmotor genom att kontrollera det visuella samt beteendet hos inbyggda partikelsystem. Resultatet visar eldspridning genom ett exempelscenario där elden beter sig olika baserat på vilket material som brinner, baserat på parametrar som är satta av en artist. Slutsatsen av resultatet visar att det är möjligt att skapa ett parameterbaserat eldspridningssystem och att det kan användas för att kontrollera den visuella designen och beteende samt att det kan expanderas för att förse artister med bättre kontroll över systemet. Rapporten föreslår fortsatta studier inom området simplifierade kontrollerade eldsimulationer inom realtidsmotorer, och användarvänlighet.