TURBULENT LINE MOMENTUM PUFFS

The time evolution of a line puff-a turbulent element with momentum-is studied by numerical simulation of the flow and mixing using a two-eq uation turbulence model, and by experimental measurements of the scala r concentration field in an advected line puff. The numerical solution reveals a distinct double-vortex flow with a loss of initial impulse due to pressure interaction, and mixing at the front of the puff. The added mass coefficient associated with the loss of impulse is found to be approximately 1. The computed flow and puff characteristics suppor t the concept of self-similarity beyond a dimensionless time of 25-30. The predicted puff now features and mixing rates are well-supported b y experimental observations.