- Author
-
Carrier, G. F.
|
Fendell, F. E.
|
Hsu, C. T.
- Title
- Modeling of Aspects of Large-Area Fires. Technical Report.
- Coporate
- TRW Electronic and Defense Sector, Redondo Beach, CA
- Report
-
DNA-TR-85-100,
April 30, 1985,
92 p.
- Contract
- DNA-001-83-C-0228
- Keywords
-
buoyant plumes
|
fire spread
|
nuclear winter
- Abstract
- This study continues the theoretical and experimental investigation of aspects of large-area fires initiated earlier and documented in previous reports. The theoretical work seeks to identify the simplest physically reasonable extension (of integral-type theory for the buoyant plume over a finite-area quasisteady fire) that permits description of saturation and condensation of water vapor, if they occur. The plume is subdivided axially into three zones: (1) a low-level fire zone in which entrainment appreciably enhanced over Morton-Taylor-Turner levels occurs, but only that water vapor associated with combustion need be accounted for; (2) a higher zone (lying above the completion-of-burning altitude but below the saturation-of-water-vapor altitude, under the assumption that such saturation occurs prior to updraft stagnation), in which entrainment of water vapor from the ambient occurs; and (3) a still higher zone bounded below by saturation and above by stagnation, in which further entrainment of ambient vapor may be negligible. Condensation of water vapor is of long-standing interest in terms of the possible additional lofting of smoke owing to release of condensational heat, and in terms of the possible self-extinction of fires in moist environments. However, recently the possible role of (condensed) water in enhancing the coagulation of submicron-sized soot is of interest in terms of the nuclear-winter context. Experimentally, improvement is undertaken for flow preparation upwind of the test section in a fire tunnel designed for measuring wind-aided fire spread across a regularly arranged, two-dimensional array of discrete polymeric fuel elements. In particular, hot-wire measurements have quantified the deviations from uniform streaming (in a time-averaged sense) across the leading edge of the fuel matrix and have suggested design alterations.