67th Annual Meeting of the APS Division of Fluid Dynamics (November 23, 2014 — November 25, 2014)

V0011: Submerged laminar jet impingement: A textbook case for vortex-wall interaction influencing heat transfer

Authors

• Wilko Rohlfs, Institute of Heat and Mass Transfer, RWTH Aachen University
• Claas Ehrenpreis, Institute of Heat and Mass Transfer, RWTH Aachen University
• Jörg Johannes, Institute of Heat and Mass Transfer, RWTH Aachen University
• Reinhold Kneer, Institute of Heat and Mass Transfer, RWTH Aachen University

DOI: https://doi.org/10.1103/APS.DFD.2014.GFM.V0011

This contribution provides a comprehensible visualization of vortex structures influencing local and instantaneous transport processes, such as heat or mass transfer. The video demonstrates the impingement of a laminar submerged jet, which is a phenomenon often seen in daily life, as for instance hair dryers or air conditioners. But also in industry jets are commonly used for cooling or drying applications.

Using conventional ink, the flow field of a single laminar jet is visualized from different angles, providing a general impression of the investigated flow phenomenon. Important features of the flow field are large scale vortices, which travel along the impingement wall and influence heat and mass transfer.

For a detailed view of the convective transport processes, fully-resolved numerical simulations are conducted. The results show vortices, which emerge at the shear layer of the jet and travel towards the wall - where they get deflected and accelerated in radial direction. In the vicinity of the wall, a secondary vortex is formed, such that a pair of large-scale counter-rotating vortices travels in radial direction. Examining the heat transfer capability by the instantaneous Nusselt number, the influence of the hydrodynamic flow structures (with velocities pointing towards or away from the wall) on the scalar transport becomes evident. To the end, the time-averaged Nusselt number is shown, demonstrating the contribution of vortices on the overall heat transfer. For a more detailed description see Rohlfs et al., IJHMT, 55, 7728-36, 2012.