FDS Modeling of the Sensitivity of the Smoke Potential Values used in Fire Safety Strategies

Andrei-Mircea Corches, Lene Ulriksen, Grunde Jomaas

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Abstract

To investigate the sensitivity of Fire Dynamics Simulator (FDS) with respect to the input parameters that are used to define the optical properties of the smoke, a parametric study was performed for relevant fire scenarios in an open plan office building. The parametric study mainly focuses on the two key parameters in FDS that define the optical properties of the smoke, namely the smoke potential and the effective heat of combustion.
In Denmark, the open source computational fluid dynamics (CFD) program Fire Dynamics Simulator is commonly used to assess the production and transport of the combustion products in performance based fire safety design. The results are used to evaluate the safety level of buildings based on the time comparison between the available safe egress time (ASET) and the required safe egress time (RSET). For a majority of performance based analysis the optical properties of the smoke determine the available safe egress time, as defined based on the acceptance visibility criterion defined in the Danish performance-based fire safety design code. Because there is no uniform test method to measure the optical properties of the smoke and due to the absence of a best practice guide that is widely accepted by the fire engineering community, values from a vast variety of experiments are used in the engineering analysis to express the properties that determine the decrease of visibility from the presence of smoke. The selection of these values, which are used as input parameters in the simulation model, determines to a great extent the results obtained using the CFD simulation tools, and thereby also the fire safety design.
As the majority of combustible materials in buildings are characterized by smoke potential values lower than 2.0 ob∙m³/g, the underestimation of this input parameter may lead to the wrong assessment of the evacuation safety level of the building. In this context, in order to ensure a robust fire safety solution it is recommended that values around 1.0 - 2.0 ob∙m³/g are used to define the optical properties of the smoke in office building fires. Using these values to defining the design fires will reduce the sensitivity of the numerical fire simulation and further reduce the risk of overestimating the evacuation safety level (ESL) of the building.
Original languageEnglish
Title of host publicationProceedings of the 10th International Conference on Performance-Based Codes and Fire Safety Design Methods
Number of pages12
Publication date2014
Publication statusPublished - 2014
Event10th International Conference on Performance-Based Codes and Fire Safety Design Methods - Gold Coast, Australia
Duration: 10 Nov 201412 Nov 2014
Conference number: 10

Conference

Conference10th International Conference on Performance-Based Codes and Fire Safety Design Methods
Number10
CountryAustralia
CityGold Coast
Period10/11/201412/11/2014

Keywords

  • Smoke potential
  • Performance-based fire safety design
  • Optical density
  • Visibility
  • FDS

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