Background
In 2019, Southwest Research Institute (SwRI) initiated an internal research program to investigate our ability to predict results in the Steiner Tunnel test, standardized in ASTM E84. The main goal of this project was to simulate the full-scale (24 ft. 20 in specimen) material flammability test most commonly used in the U.S. with Fire Dynamics Simulator (FDS), a Computational Fluid Dynamics (CFD) code developed at the National Institute of Standards and Technology (NIST) specifically to simulate fires, and to predict the test performance for a wide range of materials to within the test method’s documented precision obtained from intra- and inter-laboratory studies. The fire test that was modeled in this IR&D is the ASTM E84 tunnel test. The IR&D project had both experimental and modelling components. The experimental data for the non-combustible materials (heat flux and temperature) were used to validate the FDS simulation results. Experiments were also successfully completed to obtain ignition, heat release rate and smoke production rate data for two plywood materials at different heat fluxes in the Cone Calorimeter. The FDS simulations provided good agreement with the experimental results (measured heat flux) for the non-combustible materials.
Approach
Both CFD modeling and experimental design was used to achieve the objectives of the project. The project was able to complete the full range of experiments for non-combustible materials and two plywood materials with different substrates and with/without support systems (steel rods and/or wire mesh). Experiments were also successfully completed to obtain ignition, heat release rate and smoke production rate data for two plywood materials at different heat fluxes in the Cone Calorimeter. Full-scale simulations were carried out for the ASTM E84 tests for two different types of non-combustible specimens (Marinite I and Duraboard LD), the computational results were validated with experimental data for predicted specimen surface heat flux, and specimen exposed surface temperature. Subsequently, simulations were carried out to predict the flame spread rate over the surface of the thin and thick plywood materials backed with an air gap.
Accomplishments
The goal of the IR&D project was to develop a validated methodology based on FDS to predict performance in the ASTM E84 tunnel test based on fire and flammability properties derived from small-scale fire test data, other measurable properties and generic characteristics of the test material. The CFD-based methodology was able to successfully simulate the ASTM E84 tunnel test and address the limitations of the existing models and correlations. In addition to the simulations, the project was able to develop a new method for determining the required FDS input parameters from small-scale fire test data, other measurements and general material characteristics. This was also a significant accomplishment of the project. Considering the complexity of the problem, FDS did a reasonable job in predicting the thermal field.