Numerical Experiments on Turbulent Entrainment

Boga, Gabriele (2020) Numerical Experiments on Turbulent Entrainment. [Laurea magistrale], Università di Bologna, Corso di Studio in Aerospace engineering / ingegneria aerospaziale [LM-DM270] - Forli'
Documenti full-text disponibili:
[img] Documento PDF (Thesis)
Disponibile con Licenza: Salvo eventuali più ampie autorizzazioni dell'autore, la tesi può essere liberamente consultata e può essere effettuato il salvataggio e la stampa di una copia per fini strettamente personali di studio, di ricerca e di insegnamento, con espresso divieto di qualunque utilizzo direttamente o indirettamente commerciale. Ogni altro diritto sul materiale è riservato

Download (10MB)


The aim of this thesis work is the study of the turbulent entrainment phenomenon in jets through numerical experiments. More specifically, an attempt to study the effect of engulfment and nibbling mechanisms separately was made. The flow chosen for the numerical experiments is the temporal planar jet. The idea behind these experiments is to study the spreading and the mixing of a passive scalar under the effect of two modified velocity fields. The first is a large-scale velocity field obtained through a filtering operation, while the second is a small-scale velocity field obtained subtracting the large-scale velocity field from the total one and then adding the mean velocity. Initially, the post-processing of a spatially developing planar jet, performed by Doctor Andrea Fregni and Professor Andrea Cimarelli, has been carried out in order to analyse the main features of spatially evolving jets compared with the temporal ones. A co-flow and a passive scalar are present in the simulation. The Reynolds number is set to Re = 3000 and the Schmidt number is Sc = 1. After this first step, a benchmark DNS of a temporal planar jet with Re = 3000 and Sc = 1 has been performed in order to evaluate the main differences with respect to the spatially evolving jet. Once the settings were validated, the numerical experiments with large and small scale velocity fields have been performed. The filter used in all the experiments is the box filter. The results of two different filter lengths are presented, the first is Δ = 1.5λcl and the second is Δ = 3λcl. Since λcl is function of time, the two filter lengths are themselves varying in time. The results of the experiments were then compared with those of the unfiltered solution. The passive scalar spread approximatively the same amount under the effect of the large-scale velocity fields and under the effect of the unfiltered velocity. On the other hand, the small-scale fluctuations have been proved to be important in the mixing process.

Tipologia del documento
Tesi di laurea (Laurea magistrale)
Autore della tesi
Boga, Gabriele
Relatore della tesi
Correlatore della tesi
Corso di studio
Ordinamento Cds
Parole chiave
Turbulent entrainment, turbulent jets, CFD, DNS
Data di discussione della Tesi
19 Marzo 2020

Altri metadati

Statistica sui download

Gestione del documento: Visualizza il documento