A. James Clark School of Engineering
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item VERIFICATION AND VALIDATION OF A CANDIDATE SOOT DEPOSITION MODEL IN FIRE DYNAMICS SIMULATOR VERSION 5.5.1(2010) Cohan, Brian David; Sunderland, Peter B; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Deposition of soot generated from fires is important for tenability, smoke management, detector response, and fire forensics. Previous versions of Fire Dynamics Simulator (FDS) did not account for soot deposition, but FDS 5.3.1 includes an optional soot deposition model based on thermophoresis and turbulent deposition. This thesis analyzes the implementation of these deposition mechanisms independently. Predictions using FDS 5.5.1 are compared with measurements from three existing test series that involve small-scale hood tests, corridors, and large compartments, with heat release rates of 2 kW - 2 MW. Predictions of optical densities for well ventilated compartments generally agreed with experimental data. FDS over predicted optical density for small fires in large compartments and under predicted the mass deposition on surfaces in the small-scale hood test. Compartments without vents indicate that decreased smoke production rates or increased deposition rates would improve the agreement.Item THE EFFECT OF STAIR WIDTH ON OCCUPANT SPEED AND FLOW OF HIGH RISE BUILDINGS(2010) Blair, Alyson Janna; Milke, James A.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This research investigates the influence of stairwell width on velocity and specific flow of occupants descending stairs during building evacuations. It examines data collected by the National Institute of Standards and Technology taken from eight different stairwells during unannounced fire drills in four buildings. Based on the raw data given by NIST the velocity, density, and specific flow were calculated for each occupant on every floor in which data was collected. Though data was noisy, results demonstrate that there is a linear trend between density of occupants in a stairwell and the velocity they descend at. There is also a parabolic trend between density and specific flow rate of occupants on stairs. While no direct correlation was found, stairwell width does seem to influence the speed and specific flow of occupants since the stairwell with the smallest effective width found occupants traveling slower. As well, the correlations in the SFPE Handbook, developed by Nelson and Mowrer concerning velocity and specific flow rate, were found to be an upper limit on the data that was analyzed.Item Simulating the Fuel Mass Loss Rate in Fire Dynamics Simulator (FDS) Using a New Furniture Calorimeter(2010) McKeever, Meghan Allison; Trouve, Arnaud; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Fire Dynamics Simulator (FDS) is widely used in the fire community to simulate and understand in detail enclosure fire dynamics. Fire models require accurate descriptions of the fuel sources to simulate the fire behavior. One approach in FDS is to describe the fuel mass loss rate from furniture calorimeter tests. Unfortunately furniture calorimeter tests do not account for enclosure effects on the fuel sources (i.e. the thermal feedback of the smoke layer and the air vitiation). This work explores a simple pyrolysis model that uses furniture calorimeter data and applies a correction to the data to represent enclosure effects. The study includes: (1) the development of a database which compiles furniture calorimeter data, (2) the development of a modified version of FDS that incorporates a simple pyrolysis model proposed by Professor Quintiere and (3) a performance evaluation of the model by detailed comparisons between FDS results and experimental data from two studies performed at the University of Canterbury.Item BAYESIAN BELIEF NETWORK AND FUZZY LOGIC ADAPTIVE MODELING OF DYNAMIC SYSTEM: EXTENSION AND COMPARISON(2010) CHENG, PING DANNY; MODARRES, MOHAMMAD; Reliability Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The purpose of this thesis is to develop, expand, compare and contrast two methodologies, namely BBN and FLM, which are used in the modeling of the dynamics of physical system behavior and are instrumental in a better understanding on the POF. The paper begins with an introduction of the proposed approaches in the modeling of complex physical systems, followed by a quick literature review of FLM and BBN. This thesis uses an existing pump system [3] as a case study, where the resulting NPSHA data obtained from the applications of BBN and FLM are compared with the outputs derived from the implementation of a Mathematical Model. Based on these findings, discussions and analyses are made, including the identification of the respective strengths and weaknesses posed by the two methodologies. Last but not least, further extensions and improvements towards this research are discussed at the end of this paper.Item CHARACTERIZING SMOKE DISPERSION ALONG BEAMED CEILINGS USING SALT-WATER MODELING(2010) Chan, Chau Siang; Marshall, Andre W.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The study successfully validated the use of salt-water analog modeling as an effective diagnostic, predictive and scaling tool for understanding fire dispersion in a beam-ceiling complex compartment using the Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) techniques. Dimensionless dispersion signatures and front arrival times were compared between the fire and salt-water experiments which showed excellent agreement. Prediction of the detector lag times using fire and saltwater data agreed with that of fire experiments.Item An Integrated Methodology for Assessing Fire Simulation Code Uncertainty(2010) Ontiveros, Victor Luis; Milke, James A.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Fire simulation codes are powerful tools for use in risk-informed and performance-based approaches for risk assessment. Given increasing use of fire simulation code results, accounting for the uncertainty inherent in fire simulation codes is becoming more important than ever. This research presents a "white-box" methodology with the goal of accounting for uncertainties resulting from simulation code. Uncertainties associated with the input variables used in the codes as well as the uncertainties associated with the sub-models and correlations used inside the simulation code are accounted for. A Bayesian estimation approach is used to integrate all evidence available and arrive at an estimate of the uncertainties associated with a parameter of interest being estimated by the simulation code. Two example applications of this methodology are presented.Item Preference Based Fair Allocation of Limitted Resources(2009) Vakili Pourtaklo, Nasim; Marcus, Steven; Ball, Michael; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The fair division of scarce resources among agents is a challenging issue across a range of applications, especially when there is competition among agents. One application of resource division is in Air Traffic Management (ATM). This dissertation is motivated by the fairness issues that arise in the resource allocation procedures that have been introduced under Collaborative Decision Making (CDM). Fair rationing and allocation of available en-route time slots are two major challenges that we address in this research. The first challenge, fair rationing, is about how to compute a fair share of available resources among agents, when the available resources fall below the total demand. Since the demand, (flights), are time dependent, we introduce a new rationing method that includes the time dependency of demand. The new procedure gives every flight that is disrupted by an AFP a share of available resources. This is in contrast to Ration-By-Schedule (RBS), the allocation method currently in use, where later scheduled flights do not receive any slots. We will discuss and prove the fairness properties of our novel rationing procedure. The second challenge, allocation of en-route resources, is about how to allocate resources among competitive agents, (flight operators), when each agent has different preferences over resources, (time slots). We design four randomized procedures for allocating scarce resources when the airlines' preferences are included. These procedures use an exogenous fair share, which can be computed using the method described above, as a fairness standard for the allocation of slots among airlines. The first two procedures, Preference Based Proportional Random Allocation (PBPRA) and Modified-PBPRA, implicity assume equal weight for each time slot. Compared to RBS, PBPRA and M-PBPRA reduce the total internal cost of airlines and also assign each airline a number of slots close (in expectation) to their fair share. The fairness, efficiency and incentive properties of PBPRA and M-PBPRA are evaluated. The value (or cost of delay) an airline associates with a particular flight may vary substantially from flight to flight. Airlines who wish to receive priority for certain flights usually are willing to pay more for specific time slots. To address the need to express varying priorities, we propose two procedures, Dual Price Proportional Random Allocation (DP-PRA) and Modified-DP-PRA (MDP-PRA) , that assign dual prices to resources, i.e. time slots, in order to capture the airlines' preferences over delays, rerouting and cancelations. We explore the fairness, efficiency and incentive properties of DP-PRA and MDP-PRA.Item AN INTEGRAL MODEL FOR TURBULENT FLAME RADIAL LENGTHS UNDER A CEILING(2010) Ding, Haiwen; Quintiere, James G; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)An analytical study using an integral model for turbulent flame radial lengths under a ceiling is presented. Dimensionless equations give results in terms of Q* -- dimensionless firepower, and D/H -- the ratio of fire diameter to ceiling height. The model used an empirical relationship for the mixing ratio of air entrained to stoichiometric air needed for the ceiling jet flame. This value varies from 9.6 for short radial flames to 1 for long flames that tend to become laminar. Predictions from the model are in good agreement with the experimental data from previous work found in the literature. They span a range that contains data where the fire plume flame just touches the ceiling to the case where long ceiling flames become laminar. An alternative empirical fit of the theoretical results finds that the radial flame length is independent of ceiling height once the flame hits the ceiling.Item Analysis of the Effects of Temperature and Velocity on the Response Time Index of Heat Detectors(2010) Pomeroy, Andrew Tom; Milke, James A; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recent revisions to NFPA 72, the National Fire Alarm Code, have specified the response time index (RTI) as the sensitivity listing for heat detectors. Originally derived as a sprinkler sensitivity rating, there has been little work performed to validate the use of the RTI rating for heat detectors. RTI values are determined by plunging the devices into a hot wind tunnel at 200 C (392 F) and 1.5 m/s (4.9 ft/s). These test conditions are unrealistically severe for the majority of expected ceiling jet profiles. While the RTI correlation is purported to be independent of temperature and velocity, data from previous studies indicates otherwise. This study examined the effects of low temperature and low velocity plunge test conditions on the constancy of the RTI for several common heat detectors. The RTI correlation was found to be inconsistent across temperature and velocity test conditions.Item NUMERICAL MODELING OF BALCONY SPILL PLUMES USING FIRE DYNAMICS SIMULATOR (FDS)(2010) Lim, Johnson Meng Kee; Trouvé, Arnaud C; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Trends in modern architectural design have led to the proliferation of large atrium buildings. Fires in such buildings can result in significant loss of life and property damage as the propagation of smoke is unimpeded. The design of effective smoke management systems for atrium buildings requires reliable calculation methods to predict the quantity of smoke produced. Numerical modeling using FDS is performed in this research to examine the entrainment processes as the smoke flows from a compartment, through a balcony before discharging into an atrium. Different fire sizes and geometrical configurations are analyzed and empirical correlations are proposed for the mass flow rate of smoke at the spill edge and for the entrainment as the smoke rotates upwards around the spill edge. These correlations show good agreement with experimental data from previous work.