FLOW AND MIXING FIELDS OF TURBULENT BLUFF-BODY JETS AND FLAMES

The mean structure of turbulent bluff-body jets and flames is presente d. Measurements of the flow and mixing fields are compared with predic tions made using standard turbulence models. It is found that two vort ices exist in the recirculation zone; an outer vortex close to the air coflow and an inner vortex between the outer vortex and the jet. The inner vortex is found to shift downstream with increasing jet momentum flux relative to the coflow momentum Bur and gradually loses its circ ulation pattern. The momentum Bur ratio of the jet to the coflow in is othermal Bows is found to be the only scaling parameter for the Bow fi eld structure. Three mixing layers are identified in the recirculation zone. Numerical simulations using the standard k-epsilon and Reynolds stress turbulence models underpredict the length of the recirculation zone. A simple modification to the C-1 constant in the dissipation tr ansport equation fixes this deficiency and gives better predictions of the flow and mixing fields. The mixed-is-burnt combustion model is fo und to be adequate for simulating the temperature and mixing field in the recirculation zone of the bluff-body flames.