Fire Investigation - Essay Example

Fire Investigation Name Course Lecturer Date Introduction This paper is going to focus on the topic of fire investigation. Under this topic, the paper will shed light on a number of aspects related to fire investigation. In the first case, the paper will discuss the potential limitations and applications of computer modeling to explosion and fire investigations. This means that the paper will outline the possible consequences of computer modeling when used to investigate a fire or an explosion. Still under computer modeling, the paper will outline how fire modeling can be applied in fire investigation. The next item that will be focused on in this paper is that involving the discussion of the different types of modeling that can be applied in fire investigation. Under this item, such models as the numerical models will be highlighted. These kinds of models are those that involve the use of mathematical calculations because of the presence of numbers. The other kind of model to be highlighted is the full scale building model. This kind of model resembles a pinch experiment that is built in a full size. The paper will also highlight the various options for modeling fires. Under this item, the paper will explain the way they can be utilized in the investigation of fire to not only aid fire investigation but also to serve as a tool for fire investigation. The paper will also provide a description of how these modeling options can be used in fire investigation. Among the example of a model that will be given in this paper is the one in which the fire investigation comes up with a theory that explains the place where the fire begun or started and the way it developed and spread. With this modeling, the fire investigators can have an opportunity of making proper decision, which will outline whether their theory was really correct. Computer Modeling in Fire Investigation According to Gregory Gorbett, there are two broad categories of fire modeling. These categories are mathematical and physical fire modeling. The existence of physical fire modeling can be traced back to as long as the dawn of man. It involves a simple act of setting fire on objects to investigate their effects. The use of mathematical modeling techniques to study fire phenomena started in the early 1940’s. There are three categories that can be obtained from the mathematical fire modeling. The bases of these categories are the calculations being performed. These categories therefore, are computational fluid dynamic models, zone models and hand calculations. The place of computer fire modeling has been in the designing and analysis of such fire protection systems as detection systems and sprinkler systems, evaluation of the consequences of fire on property and people, estimation of risk and assessment of post fire reconstruction. The main focus of this paper however, is on the utilization of computer fire models for purposes of fire investigation (Gorbett, 2008). Physical fire modeling This type of modeling involves actual combustion of fuels and examination of their results. The physical fire modeling methods are still applied today in fire protection profession. For instance, there are standard tests such as E603, D2859, D1230 and ASTM that are used to show the hazards linked with different fuels. Physical fire modeling is therefore the first main category that models fire dynamics. It basically involves the demonstration and testing of fire given various scenarios and fuels. There are two broad categories of these types of physical demonstrations and tests. These are small-scale tests and full-scale tests. In full scale tests, a fire scenario is replicated through the creation of an item or scenario with same or similar geometric dimensions and trying to reproduce the particular fire phenomena. In small scale physical fire modeling, the fire scenario is replicated through the creation of an item or structure with a scaled-down or reduced geometric dimension as well as other variables when trying to reproduce the fire phenomena (KRAUSE, et al., 2011). Mathematical models It is from the physical models that mathematical models begun. The mathematical models are that consists of a number of mathematical equations that help in explaining the behavior of a given physical system. This means that scientists take time to observe physical models and try to come up with equations based on fundamentals of thermal science so as to match the physical behavior observed. These kinds of mathematical equations vary from simple algebraic equations that help in the prediction of such basic fire phenomena as flame height calculations to complex partial differentiation equations that help in the prediction of the fire phenomena in an enclosure (RASBASH, 2004). Types of models The first model is called basic hand calculation. This model involves algebraic equations designed mainlu on experimental correlations used to estimate the consequences of simple fire phenomena. Despite the fact that these hand calculations are basic, they can offer a reliable method for predicting fire phenomena. The user can get a quick estimate or calculation for predicting fire phenomena in a given scenario. At a more advanced level, the upper level mathematical equations can be used. This involves the use of such more advanced computer fire models as zone and field. The zone and field computer models are based on experimental correlations and hand calculations. The hand calculations are in most cases fed into a Microsoft Excel as a group of calculations for repetition and ease of use. The U.S. Nuclear Regulatory Commission came up with the Fire Dynamic Tools as a popular example of this. An example of basic hand calculation physical fire model is Heskestad Flame Height Correlation. According to this model, the area of the fire source=22/7D2/4= Area Equivalent (BISWELL, 1999). Computer modeling Zone Fire Model 1975 marked the year in which fire investigation underwent transition from basic hand calculation models to computer fire models. One of the examples of computer fire model is called the Zone fire model. In this model computer software is used to evaluate enclosure fire dynamics. The zone fire model that is more common is the one in which compartments under fire are separated into two zones. These zones are commonly termed lower and upper zones or layers. The basis of these zones is the dynamics and physics of the fire inside a given enclosure. These zones include air entertainment, combustion products and fire plume. Consequently, the upper zone consists of fire plume as well as the resulting hot gases collection and combustion products. They constitute the upper layer of the fire burning in an enclosure. The lower zone constitutes the entrained air outline as well as the ambient air. As the collection of hot gases increases in the upper layer, the height of the interface between the lower and the upper zone changes constantly. When the hot gases in the upper zone increase, the upper layer increases downwards. From the mathematical point of view therefore, the zone models can be seen to be distinguished into two distinct control volumes, the upper zone and the lower zone. Consequently, the upper zone is seen as a control volume. This zone gets both energy and mass from the fire. At the same time, it loses energy by mass movement of hot gases through openings, convection, and radiation to the floor and by conduction and radiation when it comes in contact with a surface (Gorbett, 2008). Computational Fluid Dynamics The other name of this model is field models. In field models, a compartment under fire is separated into hundreds or thousands of tiny calculation cells or cubes based on the user inputs. There are more intensive calculations in field models than in zone models. Higher level mathematics is used in the field models to calculate each cell so as to bring specific relationship of energy transfer as well as the flow of fluids to each cell. In each cell, the calculations apply the basic laws of energy conservation, momentum and mass. These are then balanced with the other adjacent cells (COTE, 2003). Applications of Computer Fire Modeling There are various ways in which computer fire modeling can be of help in fire investigation. The first way is that it helps in understanding the fire. In this case, computer fire modeling can help a fire investigator to understand the way a fire has evolved. Computer fire modeling, in this case, will, more specifically help by assessing the relationship or the correlation between the rate of heat released by burning fuel and other variables like the radiant ignition or CO production. It is possible to have multiple runs in complex scenarios using a range of ventilation variables so that the user can have a range of results to investigate or analyze their effects. The models also provide the ability to determine the minimum energy needed for a compartment to change through flashover and the timing issues for flashover as well as full-room involvement. Modeling may also help in analyzing whether fuels are sufficient for flashover. It can also help in evaluating the damage that comes after the fire because of the heat flux from a burning object (Gorbett, 2008). Computer modeling can also help in timeline analysis. This is because it can offer a range of timing issues that may help in understanding the accounts of eyewitness, fire progression in relation to other variables, possibility of egress, survivability of occupants, comparison of injuries resulting from fire development, interaction and activation of fire protection elements as well as the evaluation of the time to ignition and ignition issues.This application is of great value in providing an objective analysis for analyzing the progression of fire events (KRAUSE, et al., 2011). Survivability analysis Different fire by-products affect people in adverse ways. The fire by-products in this case include visibility reduction, heat and flame, toxic gases and temperature. There are tenability limits for these various by products. A computer fire model can analyze these tenability limits. Therefore, fire investigators can use these models to help in their analysis of escape and egress issues (NATO et al., 2007). The computer fire models can also be used to analyze post-fire indicators. In this case, the fire investigators can use computer fire models in comparing the physical evidence or post-fire damage to the outcomes of the different models. Majority of the models can offer insight into the heat transfer as well as the subsequent consequences of this heat transfer on materials (JONES, 2009). The computer fire modeling can also be used to visualize the fire phenomena. This is because most of the computer fire models have a feature that involves the transfer of mathematical result into 3-dimensional computer graphics. For instance CFAST and FDS have companion animation software that offers fire animation that can be used for visualizing fire phenomenon (ROBY & CARPENTER, 2002). The last application of computer fire modeling is in multiple hypotheses. In this case, a computer fire modeling is very useful when it comes to scientific method. This is because computer fire models may offer an objective way of testing a given hypothesis. The computer fire modeling allows a fire investigator to test their hypothesis or the hypotheses of others for refutation or validation (YEOH & YUEN, 2009). Limitation of Computer Fire Models The limitation of the computer fire models is that they have to be chosen well for the above purposes so as to ensure that there is appropriate selection of the models as well as proper use of the models within their assumptions and limitations. Conclusion In conclusion, computer fire modeling should be used as a tool by a fire investigator to analyze fire. It is easier to use computer fire modeling in fire investigations than to use it in design engineering. This is because of the presence of other information such as fire department reports, forensic evidence and eyewitness accounts. In this context, the computer fire model is often utilized in supplementing the other information so as to demonstrate that a given hypothesis is plausible or is not plausible. References: BISWELL, H. H. (1999). Prescribed burning in California wildlands vegetation management. Berkeley ;London, University of California Press. COTE, A. E. (2003). Operation of fire protection systems: a special edition of the Fire Protection Handbook. Quincy, Mass, National Fire Protection Association. Gorbett, G.E. (2008). Computer Fire models for fire investigation and reconstruction. International Symposium on Fire Investigation Science and Technology. INTERNATIONAL WORKSHOP ON STRUCTURES IN FIRE, KODUR, V., & FRANSSEN, J.-M. (2010). Structures in fire: proceedings of the Sixth International Workshop. Lancaster, Penn, DEStech Publications. JONES, A. M. (2009). Fire protection systems. Clifton Park, NY, Delmar Cengage Learning. KRAUSE, E., SHOKIN, Y., RESCH, M., KRÖNER, D., & SHOKINA, N. (2011). Computational Science and High Performance Computing IV the 4th Russian- German Advanced Research Workshop, Freiburg, Germany, October 12 to 16, 2009. Berlin, Heidelberg, Springer Berlin Heidelberg. http://dx.doi.org/10.1007/978-3-642- 17770-5. NATO ADVANCED RESEARCH WORKSHOP ON COMPUTATIONAL MODELS OF RISKS TO INFRASTRUCTURE, SKANATA, D., & BYRD, D. M. (2007). Computational models of risks to infrastructure. Amsterdam, Netherlands, IOS Press. RASBASH, D. (2004). Evaluation of fire safety. Chichester, West Sussex, England, J. Wiley. ROBY, R., & CARPENTER, D. (2002). Fire investigation: analysis and reconstruction. London, McGraw-Hill. YEOH, G. H., & YUEN, K. K. (2009). Computational fluid dynamics in fire engineering theory, modelling and practice. Burlington, MA, Butterworth-Heinemann. http://search.ebscohost.com/login.aspx?direct=true&scope=site&db=nlebk&db=nlabk&A N=249 286. Read More