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-equation turbulence model, and by experimental measurements of the scalar 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 support the concept of self-similarity beyond a dimensionless time of 25–30. The predicted puff flow features and mixing rates are well-supported by experimental observations.