ID 368

Volumetric Displacement Effects of Dispersed Phase on the Prediction of a Dense Spray

 

Abstract:

Accurate prediction of a dense spray flow using an Euler-Lagrange approach is challenging because of high volume loading of dispersed phase. In reality the presence of liquid droplets would displace the corresponding mass portion of carrier phase which is not enforced in typical Euler-Lagrange numerical approaches. To accurately model the dense sprays, one needs to capture this effect by taking into account the spatio-temporal changes in the volume fraction of carrier phase due to presence of dispersed phase. This leads to zero-Mach number, variable density governing equations which are commonly neglected in the standard two-way coupling spray simulations. Using pressure-based solvers, this gives rise to a source term in the pressure Poisson equation and a non-divergence free velocity field. To validate the predictive capability of such an approach, an experimental relatively dilute particulate round jet is first examined using Direct Numerical Simulation coupled with Point-Particle approach and then higher volume loadings up to 40% are investigated with and without taking into account the volumetric displacement effects. It is shown that for volume loadings above 5%, the volumetric displacement effects enhance dynamics of the flow resulting in a higher stream-wise mean and rms velocities particularly near field of jet where local volume fraction is relatively high. This enhancement is conjectured through the modified continuity equation which increases the carrier phase velocity in the regions of high void fraction due to conservation of mass.