Research And Application Of The Methods On Fire Numerical Reconstruction For Fire Investigation

Fire is one of the most serious disasters, which often causes some of the greatest losses to property and human life around the world. It had been a trend that numerical simulation method is used in fire science research because fire theory and numerical method was deepened. Fire investigation is a very important work in fire bureau. At present, the cognizance of ignition source, to a great extent, depend on the experience of fire investigator because it lacks of corresponding technical verification. And the abstract conclusion based on professional theory is not easy to be understood and accepted by common people. Full scale fire test costs much and takes long time and small scale fire test is hard to meet all the dimensionless similar requirements. Computer fire numerical test can take less time and cost less. Furthermore, it can easily make contrast tests. So it is a new-emerging and effective method for fire investigation.Based on fire numerical simulation, the fire numerical reconstruction technique and its application on fire investigation were studied here as follows:1) Proposed fire numerical reconstruction orthogonal optimum method. Because the fire scene is often destroyed and complicated, there are many uncertain factors. The common factors in fire were analyzed and several evaluation methods were introduced. Then, the orthogonal optimum method was introduced in experiment design in order to improve the numerical reconstruction efficiency.2) Proposed equivalent parameter method for thin wall modeling. There are thin walls in fire scene, such as ceiling and partition, which change the fire process when they are burning though. The thickness of thin walls is much thinner than grid length used in building fire field simulation. So calculation burden is heavy when the thin wall is modeled directly. An equivalent parameter method was proposed in the paper. In this method while the wall thickness was magnified to fit the normally used grid length in order to reduce the calculation amount, the material properties were changed to make the simulation results unchanged. The analysis on solid phase model and numerical test validated that the method was correct and practical.3) Three typical fire cases, one of which was a real fire test, were numerically reconstructed using the two methods above. The simulation results were compared with site investigation report and photos. The comparing results showed that the simulations were reliable, and so the two methods and the cognizance of ignition source. The intercomparison of fire numerical simulations on different conditions quantified the effects of fire facilities on fire control and people escape.Fire numerical simulation can reconstruction fire development and compare the influences of different settings. It has auxiliary function when cognizing the legal liability, the ignition location and the ignition point. Numerical simulation technique on fire investigation can help to solve many problems and has a broad prospect.