噴流火炎における乱れ渦の発生

概要

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The transition from laminar to turbulent modes of an ethylene jet flame was investigated using two-dimensional instantaneous photography of turbulent eddies, by means of a laser-light sheeting method. Observations were made for the eddies around the break point in the fuel flow and the flame. The results show that in the laminar region the fuel flow is bent due to instability in the shear layer, whereas the outer soot layer has little curvature because of the high viscosity in hot layer. In the transient region, eddies generated in the fuel flow deform the outer soot layer. Numerical calculations were performed for predicting fluid motions due to interaction between density and pressure gradients in the flame boundary. The results show that the pressure gradients generate the vorticity in a medium of varying density along the flame. Deformation and stretching of the flame boundary take place once the vorticity becomes stronger than the dissipation due to viscosity.
1993-10-25