Mechanical Engineering
GRADUATE SEMINAR
NOTICE OF 2nd PhD SEMINAR PRESENTATION
CANDIDATE: Jerry Adjei Adjetey
DEGREE SOUGHT: PhD
DATE: 9/18/2026
TIME: 11:30am
LOCATION: Room 1101 CEI
TITLE: Flow organisation and turbulence in moderately and severely confined axisymmetric jets
Abstract
The present study investigates the influence of geometric confinement on the development and organisation of moderately (D/d = 5) and severely (D/d = 3) confined axisymmetric turbulent jets using large eddy simulation, where D is the chamber diameter and d is the nozzle exit diameter. The Reynolds number, based on nozzle exit conditions (Uj, d), is 30 000. To quantify deviations from canonical behaviour, the confined cases are compared with a free jet at the same Reynolds number. Confinement is shown to fundamentally alter jet development by suppressing radial expansion, accelerating centerline decay, and promoting confinement-controlled recirculation and momentum redistribution. Azimuthal analysis of the wall shear stress in the post-attachment region reveals that both confined cases are dominated by a first azimuthal mode, indicating a preferred large-scale asymmetry. In the moderately confined case, the first mode manifests as a sustained wall attachment and slow circumferential wandering in the jet-wall interaction region, whereas in the severely confined case, it appears only as weak and intermittent modulation without sustained large-scale organisation. Further distinction between the confined and free jets is obtained through analysis of an enstrophy-based identification of the jet-background interface. The free jet exhibits a classical turbulent/non-turbulent interface, whereas under stronger confinement, the interface evolves into a marker of localised, high-intensity turbulent activity embedded within a fully turbulent environment.
All Graduate Students are invited to attend