- Author
- Persson, B. | Dahlberg, M.
- Title
- Simple Model of Foam Spreading on Liquid Surfaces.
- Coporate
- Swedish National Testing and Research Institute, Boras, Sweden
- Report
- SP REPORT 1994:27, 1994, 28 p.
- Keywords
- foam extinguishing systems | mathematical models | liquid surfaces | experiments
- Identifiers
- foam flow; oil slicks; foam spread; foam layer; one dimensional foam flow without radiation; rotationally symmetric flow without radiation; one dimensional foam flow exposed to radiation; one dimensional foam flow on a solid surface
- Abstract
- An approximate theoretical model of foam spreading on liquids has been formulated. The model is analogous to the spreading of oil slicks on water surfaces. Viscous friction is assumed to be the dominating mechanism in opposing the foam spread. The spreading process is decoupled from the mass transport due to evaporation and drainage of water contained in the foam. The evaporation is assumed to be caused by external radiation, thus simulating the important case of foam spreading on a burning surface. The reduction of the foam layer thickness is accounted for by including a prescribed rate of decrease fixed by the radiation intensity. The decrease rate has been determined in a separate experiment. In the present formulation it is assumed that the foam layer has a triangular shape which presumably is a poor approximation for the initial phase of the spread. More work is needed to find out if this assumption needs to be modified. Preliminary experiments have been carried out with foam spreading in a long water channel and in a circular basin without external heating. Foam application rates in the circular basin have been in the order of 1 - 4 1/m² min. The theory fits reasonably well with the experimental results. Thus it can be concluded that the model correctly describes the basic phenomena of the foam spread. The model has also been applied to predict the spreading when the foam is exposed to radiation. The predictions agree qualitatively well with experimental results reported in the literature.