DISSIPATION DUE TO PARTICLE TURBULENCE INTERACTION IN A 2-PHASE, TURBULENT, SHEAR-LAYER/

Experimental measurements of particle velocity, size, concentration an d gas velocity have enabled the calculation of additional carrier phas e dissipation due to the Stokes disturbance flow generated by small, h eavy droplets interacting with the coherent large-scale eddies of a tu rbulent shear layer. The flow field was generated by mixing a homogene ous, droplet-laden (volume fraction similar to 10(-5)) high-speed air stream with the ambient atmosphere. Ensemble averaged measurements of the large-scale spanwise vortices through the first pairing event show that the additional dissipation is primarily concentrated into intens e regions located beneath the core of the vortex and extends into the mixing layer close to the free stagnation point. The magnitude of the dissipation is typically on the order of 10% of the rate at which kine tic energy is transferred between the gas and the particles. A simple model based on the steady-state response of heavy particles to an osci llatory forcing qualitatively illustrate the evolution of the dissipat ion and kinetic energy transfer within the freestream outside the mixi ng layer. The comparison also indicates that improved results might be attained by accounting for the unsteady growth of the gas phase veloc ity fluctuation resulting from the evolution of the coherent structure s. Estimates of the single-phase turbulent dissipation indicate that t he additional dissipation due to the presence of the particles is appr oximately 1% of the single-phase dissipation. This is the same order o f magnitude as the mass loading and is in agreement with numerical sim ulation estimates of the increased dissipation in homogeneous turbulen t flows. (C) 1997 American Institute of Physics.