EFFECTS OF BOUNDARY-LAYER DISPLACEMENT AND SEPARATION ON OPPOSED-FLOWFLAME SPREAD

An analysis is presented of the viscous-inviscid interaction region ar ound the tip of a flame spreading over the surface of a solid fuel in a forced laminar high Reynolds number air stream that opposes the flam e propagation. Through the interaction, the vaporization of the solid and the thermal expansion of the gas originate an adverse pressure gra dient upstream of the flame tip, which leads to a decrease of the shea r acting on the small region controlling the flame spread rate. Under certain realistic conditions this adverse pressure gradient may separa te the boundary layer upstream of the vaporizing region of the solid, leading to a new mode of flame spread with a higher spread rate determ ined by the Bow in the whole interaction region.