FDS Fire Simulation Models - Thesis Example

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A model of a three-storied building (size 8.4m*6m*9m) is considered in the study having a single compartment on each floor. Each compartment has the same size of 8.4m*6m*3m. The fire scenario is assumed to take place in the ground compartment only. Building size was taken wisely to limit the domain size, which saves computational time and with the assumption that it will not affect the investigating parameters. Research is carried out in two phases: single opening case and double opening case.

A single opening case is modeled by a single window in the compartment. Two beds are occupied in the ground floor compartment, where the fire ignited in one of them. The window is located at a height of 1.5m from the floor and has a size of 1 m*0.5 m. The wind direction is supposed to blow from the window side for proper analysis of wind effect in a compartment fire. Figure 1 shows the detail view of the single opening case.

Different velocities of wind are tested for the fire behavior observation during the compartment fire. Table 1 shows the different sub-cases for single-opening cases having different wind velocities.

The double-opening case has the same compartment with the same window as in a single-opening window. In addition, one door is placed opposite the wall of the window to make the double opening case: one opening the window and the other opening door. The window size is the same as the previous one having a size of 1m*0.5m at the same location. The size of the door is 1m*2m. Figure 2 shows the geometry for the double-opening case.

Wind direction is from the window side and various wind velocities effect on compartment fire is analyzed for this case also. Table 2 shows the cases established.

For this study, a fire source of size 0.3m*0.4m is set to ignite one of the beds. For this ignition purpose, a burner having HRR 4000 kW/m2 is designed at a corner of the bed as shown in figure 3. Two beds are made of up wood (C=3.4 H=6.2 O=2.5) with a soot yield of 0.015 kg/kg (Zhang, 2009). The size of each bed is 3.4m*1.5m*0.7m having a wood thickness of 0.01m.

From figure 3 it is observed that the bed near the window side is ignited. The burner is set up to ignite after 30 seconds after the simulation starts for each case to ensure everything has settled from the previous experiment and allow time for confirmation everything is set. Wind will be blowing from the window side from the beginning and its effect on the fire behavior will be observed. Table 3 shows the FDS code for fire input.

Various material properties should have to be defined in FDS input to model the real objects by assigning their corresponding property value. In this study, two materials are used and they are wood and concrete. Walls are defined as concrete material whereas the beds as wood material as extracted from the SFPE Handbook [47]. The FDS input code for the material property is presented in Table 4.

Timer and temperature thermocouples are two types of devices that are incorporated during this research. A timer device is used to start up the fire ignition after 30 seconds where as other temperature-measuring thermocouples are installed to measure the temperature at a certain location of the compartment to analyze the output result. Table 5 sums up the devices used. Figure 4 shows the device location in the compartment.

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