1	Modeling Aqueous Film Forming Foam (AFFF) Brian Y. Lattimer 410.737.8677 www.haifire.com
2	Topics Background Modeling approach Modeling Results Experimental Results Model input data
3	Background Alternative foam formulations being developed Environmentally friendly Performance evaluation impeding progress Full-scale test required Lack of understanding of foam extinguishment mechanism Current small-scale tests not measuring all important parameters Performance a function of multiple parameters
4	Background Goals of study Accelerate the evaluation process of foam Develop model Predict full-scale performance of a foam Use / develop small-scale tests Measure performance of specific aspects of foam Drainage, evaporation, spreading characteristics Model input data Near term goal of predicting MIL-SPEC test 28 and 50 ft² MOGAS pool fires
5	Previous Work Swedish National Laboratory and Research Institute (SP) Small-scale tests Drainage and evaporation rates Viscosity of foam Large-scale foam spread tests With and without fire Nozzle characterization Some velocity and mass distribution Modeling Simplified 1-D cases (channel and axisymmetric) Meshing of 1-D cases for 2-D case
6	Previous Work SP (continued) Conclusion Modeling approach not capable of predicting very large scale tests with hose line application Several studies on modeling foam drainage and evaporation Perssons et al. (1992, 1996, 1997), Magrabi, et al. (1997) Ablation model for Hi-Ex foams Boyd and Di Marzo (1998) Rheology of foam Gardiner et al. (1998) Persson et al. (1998)
7	Suppression Process
8	Modeling Approach Field model Model foam spreading Unsteady shallow water equations Hydraulics / hydrology of river flows Divide space above fuel into a single layer of cells Cell thickness varies Average properties over height of foam Source terms from small-scale test data Solution drainage Solution evaporation Foam addition from nozzle Momentum from nozzle spray Shear force between foam and fuel
9	Modeling Approach Thermal modeling Radiation from fire to foam Emissive power of fire and configuration factors Evaporation of foam dependent on predicted incident flux onto foam No predictions of foam temperatures in initial versions Small-scale testing shows no heat transfer to fuel until foam less than 25 mm (1.0 in.) thick
10	Equations of Motion
11	Equations of Motion Other body forces Shear between foam and fuel Shear from external air currents Wind Air entrainment into fire Momentum from foam application Surface tension Various boundary conditions Effects of obstructions
12	1-D Shallow Water Equation Assumptions No source terms Constant density Verification Compared against exact solutions to Riemann problem
13	Dry Bed Problem
14	Dry Bed Problem
15	Wet Bed Problem
16	Spill
17	Wave Reflection
18	Next Steps in Modeling Adding in source terms Frictional shear between the flow and the bed Mass losses and gains Validation 2-D solutions Validation Foam flows
19	Evaporation, Drainage and Suppression Models Evaporation Heat balance at surface Effective absorptivity Drainage Foam mass to predict drainage rate Develop a reference curve 75 mm thick foam layer Moderate irradiance level (20 kW/m²) Suppression Critical foam mass 0.90 kg/m²
20	Validation of Drainage and Evaporation Models
21	Validation of Drainage and Evaporation Models
22	Validation of Drainage and Evaporation Models
23	Summary Solved and verified 1-D shallow water equations Developed and validated models for foam solution mass drained and evaporated Developed model for suppression Implementing source terms and multiple dimensions into model Conducting test to support model input data development