Dr. Matteo Angelino

De Montfort University, United Kingdom


Talk Title
Progress in the new theory of turbulent rectangular free jets with experimental and numerical evidence
Talk Abstract

The evolution of turbulent submerged rectangular free jets has been described for decades as defined by two distinct regions of flow, resulting from the interaction of the jet with the stagnant fluid: the potential core region, PCR, or zone of flow establishment, with vortical shear layers surrounding an inner flow, where the velocity remains equal to the exit one; and the zone of established flow, or fully developed region, FDR, further downstream. The experiments carried out at the University of Rome Tor Vergata by Gori and coworkers in the last two decades showed that turbulent jets with moderate Reynolds numbers can present an initial region with minimal change in velocity and turbulence. This region has been called Undisturbed Region of Flow (URF) in the average representation of the flow. The URF can be further subdivided into two types of flow: the Negligible Disturbance Flow (NDF) and the Small Disturbance Flow (SDF) in the instantaneous representation of the flow. The development of rectangular submerged free jets has been investigated in the wind tunnels of the Laboratory of Thermo-Fluid Dynamics and Energy Engineering of the University of Rome “Tor Vergata”, with hot wire/film anemometry, shadowgraph visualizations and Particle Image Velocimetry (PIV). The URF, and the NDF plus SDF, showed to have laminar-like shear layers even for turbulent Reynolds numbers. The axial length of the URF, NDF and SDF, decreases with the increasing Reynolds number. The new types of flows were also investigated in heat transfer applications, where the rectangular jet was used to cool a heated cylinder. In order to confirm the experimental findings, large-eddy simulations (LES) were carried out in a certain range of Reynolds numbers (2000 to 35,000). The high level of accuracy of the solutions allowed for a detailed theoretical analysis of the momentum budget in the average representation of the flow. The mathematical interpretation confirmed the two self-similar behaviors of the PCR and FDR, following previous theories by Tollmien and Görtler. Most importantly, it helped identify a new self-similar law for the URF, thus refining our understanding of the physics governing this region. More recent simulations expanded on these studies by analyzing the mass transfer in the three regions, URF, PCR and FDR, and by comparing them to the concentration visualizations obtained with Particle Image Velocimetry. The concentration, treated as a passive scalar in the numerical simulations, was shown for the first time to follow a self-similar behavior, and to be a function of the self-similar variables of the momentum equation, for a large range of Schmidt numbers (1 to 100).

Short Biography

Matteo Angelino was awarded the PhD in Energy and Environmental Engineering from the University of Rome “Tor Vergata” in 2015. He spent a year at the University of Minnesota and four years at Loughborough University. He is now a Lecturer in Aeronautical Engineering at De Montfort University.

Talk Keywords
Turbulent rectangular free jet. Undisturbed Region of Flow (URF). Negligible Disturbance Flow (NDF). Small Disturbance Flow (SDF). Self-similarity. Particle Image Velocimetry (PIV). Large Eddy Simulations (LES).
Target Audience
Students, Post doctoral, Industry, Doctors and professors
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