Fire Protection Engineering Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2772
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Item COMPUTATIONAL FLUID DYNAMICS ANALYSIS OF SPATIALLY-RESOLVED SPRAY SCANNING SYSTEM (4S) SPRAY PATTERNS(2023) Bors, Jeffrey; Trouve, Arnaud C; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In computational fluid dynamics (CFD) fire models, sprinkler sprays are represented in complex numerical simulations using Lagrangian particles. These CFD sprays are typically characterized using a combination of experimental data, literature correlations, and estimation. The Spatially-Resolved Spray Scanning System (4S) machine provides high resolution data to characterize sprays for use in CFD analysis, however a quantitative analysis on the effect of this high resolution data with FDS in realistic fire scenarios has not been completed before. 4S spray data is analyzed and compared to a basic spray estimated from literature correlations with and without the presence of fire to analyze trends. In all environments, the basic nozzle overestimated water flux closer to the center of the nozzle and underestimated water flux farther from the center. Differences between the basic and 4S nozzle ranged from 1% to 240% in the enclosure fire scenario. Investigation into the differences showed the polar water distribution to be the most impactful parameter provided by the 4S. Local azimuthal trends were shown to be significant, but non-impactful in the enclosure fire simulation. Global azimuthal trends were apparent but not significant.Item A STUDY OF THE FIRE DYNAMICS SIMULATOR (FDS)- CREATING LIFE-LIKE MOVIES AND STUDYING THE ACCURACY OF THE LAGRANGIAN PARTICLE MODEL(2022) Hussain, Zishanul Haque; Trouve, Arnaud; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Fire Dynamic Simulator (FDS) is a computational fluid dynamics (CFD) model of firedrivenfluid flow. It was first released publicly in February 2000. Using SmokeView or Pyrosim to view the results of FDS simulations provides a powerful non-immersive virtual reality experience. It can be used in fire engineering, fire safety training, and fire investigation. By providing a more engaging and interactive user experience, nonimmersive VR can help improve understanding and develop effective fire safety and prevention strategies. On the other hand, FDS is a powerful tool for modeling the physics of fire behavior in buildings and other structures. It has been shown to produce accurate descriptions of fire behavior under a variety of different conditions. This study touches on very divergent, yet very critical, aspects of the applications of FDS. First, generating life-like simulations of fire and smoke characterized by different growth rates and surroundings (a non-immersive virtual reality application). Human behaviour experiments at Morgan State University will use the simulation videos to assess the accuracy of human estimates of fire growth rates and understand how situational factors impact human response. The second part of the study focuses on the Lagrangian particle representation of water droplets in FDS simulations of fire suppression. This study id is going to look at the fire suppression model in which fire suppression is defined by surface wetting or the mass of water falling in the fire surface. The Lagrangian liquid water droplets tracked by FDS represent a larger number of actual droplets. The number of ‘super drops’ can affect the accuracy of the simulations. The particle insertion rate has a default value and controls the mass of the 'super drop'. FDS allows altering the particle insertion rate and hence the mass of the 'super drop. The goal is to find out how changing particle injection rate and mesh grid size impacts the accuracy of the simulation of water sprays.Item DEVELOPMENT OF A COUPLED FDS MODELING AND VIDEO ANALYSIS APPROACH TO ESTIMATE THE BURNING CHARACTERISTICS OF A THIN-WALLED HUMANITARIAN SHELTER(2022) Tan, Genevieve Claire; Milke, James A.; Trouve, Arnaud; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Large fires in humanitarian settlements lead to enormous losses in material, time, and resources that organizations allocate toward supporting refugee camps and displaced persons. In the absence of full-scale shelter fire experiments in humanitarian settlements, a combination of video analysis and fire modeling can be used to estimate burning characteristics of the shelter fire. A MATLAB-based image binarization method is developed to measure the flame height and structure loss over the course of fire development in footage from a shelter burn test conducted in Cox’s Bazar, Bangladesh. The conditions of the shelter fire are recreated in Fire Dynamics Simulator (FDS). Diagnostics in the FDS models provide estimates for the flame height, heat release rate, heat flux, and radiant integrated intensity in and around the shelter. The FDS models exhibit a 10-25 second delay in matching key events in the fire development timeline of the original shelter fire. Otherwise, measurements from the FDS simulations show good agreement to measurements from image processing. Based on results from image processing and FDS models, the steady burning HRR is approximately 900 kW for a shelter fire with a flame height range of approximately 4.1-4.5 m.Item Feasibility Analysis of Coupling FDS Modeling with Machine Learning for Situational Awareness in Aircraft Hangars(2022) Davis, Alison Marie; Milke, James A; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Situational awareness is a critical factor in maintaining the safety of firefighters and can be largely improved in buildings using distributed sensors that provide real-time data. A two-phase approach is used to increase situational awareness in aircraft hangars. Phase I consists of modeling a hangar with an open door in Fire Dynamics Simulator (FDS), with a high density of smoke, temperature, CO and CO2 sensors located at the ceiling. Fuels of interest including Douglas fir, polyethylene, paper, JP-8, and propane are modeled in six potential fire locations, with five locations along the centerline of the hangar and one in the corner of the hangar. Additionally, wind and beams at the ceiling are added to the simulation to determine the impact on the products of combustion that the sensors pick up. Phase II uses the data acquired from the FDS simulations to inform and build machine learning models that utilize supervised learning techniques to identify the location of the fire, the magnitude of the fire and the composition of the fuel that is burning. It is determined that temperature and smoke are the key products of combustion needed for these analyses. The location of the fire is identified within a circular area with a 5 m radius by using temperature measurements, thus reducing the amount of input data needed for the machine learning models. The magnitude of the fire is predicted using temperature as inputs to a heat release rate (HRR) model using a fully connected, three-layer, feed forward neural network. The composition of the fuel is predicted using a linear support vector machine that supports multi-class classification, using products of temperature and smoke obscuration as inputs. The location model is 80% accurate, the HRR model is 85% accurate and the fuel composition model varies between 62% and 91% accuracy depending on the classification goals. These results prove the feasibility of machine learning applications in an aircraft hangar setting.Item IDENTIFYING SMOKE DETECTION BIASES WITHIN DIFFERING ROOM CONFIGURATIONS FOR ZONE AND COMPUTATIONAL FLUID DYNAMIC MODELS(2022) Lee, Adam; Milke, James A; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This research project aims to identify room configuration conditions in which FDS, a CFD model, and CFAST, a zone model, may differ in detector activation time. A total of four configurations, with varying aspect ratios, were explored. Additionally, a range of four ceiling heights were also modeled. Furthermore, a total of three statistically significant models were developed to relate the differences between detection times within CFAST and FDS. It was found that FDS and CFAST discrepancies were a result of the compartment volume to doorway area ratios. Larger volumes compared to the doorway area resulted in better agreement between FDS and CFAST. Additionally, for larger ceilings in FDS, larger variability in activation times were present. Furthermore, for higher ceilings, FDSs’ ability to account for thermal buoyancy within the smoke plume resulted in quicker activation within FDS.Item Predicting the Temperature Increase of Residential Siding and Decking Materials in the WUI Due to External Heat Flux(2022) Harris, Matthew; Milke, James A; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The wildland urban interface (WUI), which is the area where houses meet or intermingle with undeveloped wildland vegetation, has more than doubled over the last 50 years. The frequency and intensity of wildfires occurring in these areas has also increased. To advance the understanding of WUI heat transfer, a multi-phase experimental series was conducted to study the impact of radiant heating on materials common in WUI wildfire scenarios. In the first phase, thermophysical properties of decking and siding materials were measured and a thermal decomposition model derived. In the second phase, the decking and siding materials were cut into 100 mm x 100 mm samples and exposed to a radiant panel at constant heat fluxes of 5 kW/m^2 and 15 kW/m^2 to mimic the incident heat flux from a wildfire. In the third phase, the materials were constructed into larger 280 mm x 410 mm assemblies and exposed to the same heat fluxes to mimic full scale exterior walls and decks in the WUI. During both the second and third phases, the back and sides of the assemblies were insulated, and the back side temperature of the assemblies was measured throughout each experiment using a 24-gauge thermocouple. In addition to the experiments, numerical simulations were performed using Fire Dynamics Simulator (FDS) to assess the utility of the model for predicting the temperature rise of materials in WUI exposure scenarios. The experimental configuration from the second phase of testing was simulated, using the thermophysical properties of materials determined from the first phase. A simplified one-dimensional model was adopted, in which materials were assumed to be homogenous and isotropic, and heat transfer was assumed to occur only in the depth of the sample. The temperature increase for each of the studied materials were compared as to provide recommendations on the safest choice for siding and decking materials in the WUI.Item Simulations of Fire Smoke Movement in High-rise Buildings with FDS(2021) Xu, Hongda; Trouve, Arnaud AT; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Fire Dynamics Simulator (FDS) developed by the National Institute of Standards and Technology (NIST) solves a form of the Navier-Stokes equations appropriate for low-speed (Ma < 0.3), thermally-driven flow with an emphasis on smoke and heat transport and has been shown to be capable of simulating the flow and temperature conditions in the vicinity of a fire [1]. In the present study, we evaluate the ability of FDS to simulate pressure dynamics in high-rise buildings, a pre-requisite to the correct simulation of smoke transport far from the fire.The objective of this study is to test the accuracy of FDS for determining the conditions throughout the entire expanse of a 40-story high-rise building featuring an elevator shaft and four stairwells. The output from FDS is first compared to the results generated by a network model called COSMO. The comparison of the two outputs shows that correct results are predicted by FDS. Additionally, more realistic scenarios are simulated with FDS and the results are compared with those of a network model called CONTAM and an in-house MATLAB program. The network model CONTAM and the MATLAB program do not represent the time-dependent thermal mixing process taking place inside the elevator shaft and the stairwells whereas FDS does. The comparison shows the importance of this thermal mixing process that impacts the pressure dynamics and smoke movement inside the building, with implications for the evacuation capability provided by the stairwells.Item Feasibility Analysis and FDS Modeling of Water Mist Fire Suppression Systems for Protection of Aircraft Hangars(2021) Steranka, Karolyn; Milke, James; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Concern about PFAS containing foam fire suppression agents’ negative environmental impact motivated the U.S. Air Force to perform a two-phase feasibility analysis of water mist systems for protection of aircraft hangars. Phase I involved a feasibility analysis of COTS water mist technologies based on manufacturer specifications, literature, and previous test data. Phase I identified seven manufacturers who have developed systems with potential for successful protection of aircraft hangars. Phase II used FDS to model two low pressure and one high pressure system identified in Phase I. Phase II completed an analysis and validation simulations of the Lagrangian particle, extinction, and evaporation model in FDS. Following validation simulations each nozzle was tested in a full-scale hangar configuration for protection of a JP-8 spill fire. The results found the high-pressure mist system was able to extinguish the fire and earlier activation times lead to less damage to the aircraft and hangar compartment.Item A Generalized Model for Wall Flame Heat Flux During Upward Flame Spread on Polymers(2015) Korver, Kevin; Stoliarov, Stanislav; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A current model accurately predicts flame to surface heat flux during upward flame spread on PMMA based on a single input parameter, the mass loss rate. In this study, the model was generalized to predict the heat flux for a broad range of polymers by adding the heat of combustion as a second input parameter. Experimental measurements were conducted to determine mass loss rate during upward flame spread and heat of combustion for seven different polymers. Four types of heat of combustion values were compared to determine which generated the most accurate model predictions. The complete heat of combustion yielded the most accurate predictions (± 4 kW/m2 on average) in the generalized model when compared to experimental heat flux measurements collected in this study. Flame heat flux predictions from FDS direct numerical simulations were also compared to the generalized model predictions in an exploratory manner and found to be similar.Item ASSESSMENT OF NATURAL VERTICAL VENTILATION FOR SMOKE AND HOT GAS LAYER CONTROL IN A RESIDENTIAL SCALE STRUCTURE(2012) Opert, Kelly; Milke, James; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In firefighting, ventilation tactics are used to increase visibility for firefighter rescue and fire suppression operations, to increase survivability of the occupants of the structure, and to decrease property damage. Improperly implemented ventilation tactics or unplanned, fire-induced ventilation can lead to rapid changes in fire behavior creating fatal conditions inside a building for occupants and firefighters. In this set of experiments, measurements were made within a single, full scale compartment varying the fire size and the ceiling vent conditions between no vents, one 1.2 m by 1.2m (4' by 4') vent, and two combined 1.2 m by 1.2m (4' by 4') vents. The objective was to assess the vents' ability to relieve smoke and the hot gas layer. Thirty-two experiments were conducted using natural gas. These fires were allowed to burn until conditions within the enclosure reached steady state. With one open vent, the hot gas layer was not fully vented. With two open vents, the hot gas layer was fully vented for all three fires sizes. Simulations of the natural gas experiments were produced using the National Institute of Standards and Technology's Fire Dynamics Simulator in order to explore how well the experiments were simulated based on the same fire sizes and vent conditions. The simulated steady state hot gas layer depths were significantly less than the experimental depths in the doorway when both vents were open, due to a discrepancy in whether or not a hot gas layer existed. The steady state hot gas layer temperatures were significantly under-predicted near the burner when both vents were open (meaning the simulated temperatures were cooler than the measured temperatures) and over-predicted in the doorway when one vent was open and two vents were open (meaning the simulated temperatures were hotter than the measured temperatures). Two additional experiments were conducted using sleeper sofas as fuel, in order to evaluate the differences between controlled natural gas fires and furniture. Neither one open vent nor two open vents was enough to raise the hot gas layer interface height. In the experiment with two sofas, two open vents did reduce the hot gas layer temperature at the doorway by as much as 300 °C (600 °F), but the temperature was still in excess of 200 °C (400 °F). In conclusion, the minimum vertical vent size of one 1.2 m by 1.2m (4' by 4') that firefighters are instructed to use does not remove all hazards, even in a 0.5 MW fire. More discussion is needed in the fire service to define the goals of vertical ventilation and how to best address each goal. More validation of the Fire Dynamics Simulator is needed before vertical ventilation can be accurately simulated in a multi-room structure fire.