PARTICLE DISPERSION IN A TRANSITIONAL AXISYMMETRICAL JET - A NUMERICAL-SIMULATION

Numerical simulations are used to study the dynamics and dispersion of particles in the near field of a high velocity transitional axisymmetric jet. A time-dependent finite-difference approach that employs a fourth-order, phase-accurate flux-corrected transport algorithm is used to simulate the flow. Extensive flow visualization and analysis based on numerical simulation are employed to analyze the influence of large-scale vortical structures on the particle dynamics and dispersion. The simulations provide evidence of the existence of three distinct dispersion mechanisms, namely, the vortex, centrifugal, and inertial mechanisms, and the prominent role of vortex merging in the dispersion process. Whereas small particles get caught in the vortical structures and large particles pass through them, the intermediate size particles ride over them and tend to be flung out of the shear layer. Quantified dispersion results also show the higher dispersion of intermediate size particles (Stokes number near unity), that has been reported by previous investigators for lower velocity jets. The effects of particle density, injection location, and injection velocity on dispersion have also been studied. The predictions are also compared with previous experimental and numerical results.