TY - JOUR
T1 - LES study of the combined effects of groups of vortices generated by a pulsating turbulent plane jet impinging on a semi-cylinder
AU - Kharoua, Nabil
AU - Khezzar, Lyes
AU - Nemouchi, Zoubir
AU - Alshehhi, Mohamed
N1 - Publisher Copyright:
© 2016 Elsevier Ltd
PY - 2017
Y1 - 2017
N2 - The present work is a numerical study of a submerged pulsating plane turbulent jet impinging on a convex semi-cylinder placed at a distance equal to twice the nozzle-exit width, using the Large Eddy Simulation approach. The temperature of the jet is higher than that of the surrounding air and the impingement wall. The Reynolds number, based on the nozzle-exit width and the time-averaged velocity is equal to 5600. The inflow is forced at a frequency of 600 Hz by imposing a sinusoidal velocity profile at the nozzle exit. The study focuses on the effects of the organized structures, shed from the free-shear layer, on the boundary layer developing along the curved surface and the corresponding heat transfer. In particular, the present contribution is an investigation, in an unexplored research field, namely, the simultaneous time-dependent responses of the Nusselt number, the friction coefficient and the pressure profiles to the passage of the coherent structures along the curved wall. The passage of the primary coherent vortices induces secondary vortices within the boundary layer and entrains both the hot air, from the jet, and the cold air, from the surroundings, which is undesirable in heating applications. The primary vortices, the induced vortices and their pairing have a major effect on the heat and fluid flow. Thus, air is entrained towards the wall immediately downstream of the induced vortices (downwash) and ejected away from the wall just upstream (upwash). It is shown that the dynamic field can be uncorrelated with the thermal field and may not be sufficient for a good prediction of the expected heat transfer.
AB - The present work is a numerical study of a submerged pulsating plane turbulent jet impinging on a convex semi-cylinder placed at a distance equal to twice the nozzle-exit width, using the Large Eddy Simulation approach. The temperature of the jet is higher than that of the surrounding air and the impingement wall. The Reynolds number, based on the nozzle-exit width and the time-averaged velocity is equal to 5600. The inflow is forced at a frequency of 600 Hz by imposing a sinusoidal velocity profile at the nozzle exit. The study focuses on the effects of the organized structures, shed from the free-shear layer, on the boundary layer developing along the curved surface and the corresponding heat transfer. In particular, the present contribution is an investigation, in an unexplored research field, namely, the simultaneous time-dependent responses of the Nusselt number, the friction coefficient and the pressure profiles to the passage of the coherent structures along the curved wall. The passage of the primary coherent vortices induces secondary vortices within the boundary layer and entrains both the hot air, from the jet, and the cold air, from the surroundings, which is undesirable in heating applications. The primary vortices, the induced vortices and their pairing have a major effect on the heat and fluid flow. Thus, air is entrained towards the wall immediately downstream of the induced vortices (downwash) and ejected away from the wall just upstream (upwash). It is shown that the dynamic field can be uncorrelated with the thermal field and may not be sufficient for a good prediction of the expected heat transfer.
KW - Forcing frequency
KW - Impinging jet
KW - Large Eddy Simulation
KW - Pulsating jet
KW - Steady jet
UR - http://www.scopus.com/inward/record.url?scp=85007240254&partnerID=8YFLogxK
U2 - 10.1016/j.applthermaleng.2016.12.047
DO - 10.1016/j.applthermaleng.2016.12.047
M3 - Article
AN - SCOPUS:85007240254
SN - 1359-4311
VL - 114
SP - 948
EP - 960
JO - Applied Thermal Engineering
JF - Applied Thermal Engineering
ER -