Using FDS to Simulate Smoke Layer Interface Height in a Simple Atrium

Abstract

This study examines the possible effects of various make-up air supply arrangements and velocities in an atrium smoke management system. Variations include velocities ranging from 0.5 to 3.0 m/s. The arrangement of make-up air supply injection points include symmetrically located vents placed low in the spaced, an array of vents distributed from the floor to the ceiling, and asymmetrically located vents. Fire Dynamic Simulator version 4.06 is applied to simulate ten scenarios in a 30.5 m cubical domain with a fire source simulating a stack of pallets with an approximate peak heat release rate of 5 MW. Results show that make-up air supply velocities should be diffused such that little to no velocity effects reach the fire. Make-up air should be supplied to the fire symmetrically for the best chance of not disturbing the fire plume. Disturbing the fire and smoke plume results in a significant increase in the smoke production rate, as evidenced by a deeper smoke layer.

Fire Experiments and Simulations in a Full-scale Atrium Under Transient and Asymmetric Venting Conditions

“…The least-square method [13,27] as well as the npercent (N = 30%) method [14,26] have been assessed by means of absolute and relative discrepancies, the latter being calculated with respect to the total atrium height (20 m). These two methods have been used to assess their accuracy in representing the smoke layer height.…”

“…-Wall A. Twelve thermocouples were installed in three thermocouple trees to measure the temperature at 30 cm from the wall A (sensors [14][15][16][17][18][19][20][21][22][23][24][25] as can be observed in Figure 2c. These measurements are used to study the smoke temperature at the far field and the smoke layer drop.…”

“…On one hand, the make-up air supply velocity is reported on the norms [2,11], to be limited to values below 1 m/s in the flame proximity. However, some studies confirmed that upper values can perturb the flame, increasing the smoke production and reducing the smoke layer interface height, especially for atria heights below 20 m [12][13][14][15]. On the other hand, an excessive exhaust flow rate can remove clean air throughout the smoke layer reducing the effectiveness of the smoke exhaust system, effect known as plugholing, which was studied under different smoke exhaust rates and outlet locations by Lougheed et al [4].…”

On the fluid dynamics of the make-up inlet air and the prediction of anomalous fire dynamics in a large-scale facility

“…As it has been commented before, some works [12,[16][17][18] have shown that make-up air velocities of the order or larger than 1 m/s can disturb considerably both the fire and plume and, thus, can have a significant influence on the fire-induced conditions. However, in a previous work [12], different venting conditions were analyzed, including make-up velocities larger than 1 m/s, not finding any significant influence of these velocities on the inner conditions' evolution, for the specific cases studied.…”

“…In the recent years, some researchers have dealt with this make-up air issue, such as the studies from Hadjisophocleous and Lougheed [14], Yi et al [15] or Kerber and Milke [16] on the influence of the vents location and arrangement, as well as inlet velocities, on the fire-induced conditions. These works were conducted considering different shaped and sized atria and gave guidance on these matters, finding advisable to supply the fresh air below the theoretical smoke layer height, within a symmetric venting topology and at velocities lower than 1 m/s, to avoid plume perturbations, which reinforced the requirements and goals of the abovementioned fire codes.…”