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Buoyant Turbulent Jets and Flames. Part 1. Adiabatic Wall Plumes. Annual Report.


pdf icon Buoyant Turbulent Jets and Flames. Part 1. Adiabatic Wall Plumes. Annual Report. (3717 K)
Sangras, R.; Dai, Z.; Faeth, G. M.

GDL/GMF-99-01; 67 p. October 1999.

Sponsor:

National Institute of Standards and Technology, Gaithersburg, MD

Keywords:

turbulent jets; turbulent flames; buoyant plumes; buoyant flow

Abstract:

An investigation of the structure and mixing properties of buoyant turbulent plumes is described, motivated by the need to resolve effects of buoyancy/turbulence interactions and to provide data required to benchmark models of buoyant turbulent flows for fire environments. Flows considered in this part of the report include plane adiabatic wall plumes; a second part of the report will consider starting nonbuoyant and buoyant turbulent jets and plumes. Measurements included laser-induced fluorescence (LIF) to find mixture fraction statistics and laser velocimetry (LV) to find velocity statistics, emphasizing conditions far from the source where effects of source disturbances and momentum have been lost. The results show that earlier measurements in the literature were not carried out far enough from the source to provide self-preserving properties and that actual self-preserving adiabatic wall plumes are narrower than previously thought. Adiabatic wall plumes were also found to mix much more slowly than free line plumes because the presence of the wall inhibits access on one side of the flow and the development of large turbulent eddies that dominate the turbulent mixing processes in these flows. This reduced rate of mixing of turbulent wall plumes is a concern in fires because it extends the length of the flame-containing region and reduces the rates of dilution of the flow that is needed to reduce temperatures and toxic gas concentrations in fire plumes.