Numerical particle tracking studies in a turbulent round jet

This paper discusses numerical particle tracking of a 3D cloud of monodisperse particles injected within a steady incompressible free round turbulent jet. The presented modelling is adequate for particle-turbulence interaction in dilute suspensions

The Reynolds numbers of environmental concern are generally high, and here the turbulence closure is a traditional k-epsilon model á la Launder and Spalding with an ad hoc correction of Pope’s to the epsilon equation to account for circumferential vortex stretching in a round jet. The resulting mean-flow and Reynolds-stress fields are discussed in the light of the LDA measurements by Hussein et al. (1994) with Re∼10^5

The carrier fluid’s unresolved turbulence is modelled as a Markovian process. We particularly refer to the reviews of Wilson, Legg and Thomson (1983) and McInnes and Bracco (1992). Clouds of marked fluid particles, rather than trajectories, are used for visualising the dispersing power of fluctuations

As fluctuations in inhomogeneous turbulence are known to entail sizeable spurious effects, the consistency of the Eulerian and Lagrangian statistics are checked by comparing the first- and second-order moments of the particle velocity with the mean flow and Reynolds stresses of the Eulerian solution, as well as the concentration fields from either solution

Surprisingly, our tests failed to confirm the full effectiveness of the corrections proposed in either model. The particle spurious mean-velocity vanishes towards the jet edge, thus abating the nonphysical migration towards low-turbulence regions. However, because of a residual disagreement between the Lagrangian and Eulerian mean velocities, mass conservation entails concentration profiles that do not follow the anticipated scaling. Possible reasons for this are discussed.