On the influence of array size and jet spacing on jet interactions and confluence in round jet arrays
2016 (English)In: Journal of Fluids Engineering - Trancactions of The ASME, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 138, no 8, 081206Article in journal (Refereed) Published
Arrays of unconfined confluent round jets exist in a number of engineering applications, including ventilation supply devices, sewage disposal systems, combustion burners, chemical mixing, and chimney stacks. Interacting confluent round jets are also interesting from a purely scientific point of view, as jet interactions and confluence bring additional complexity to the flow field. Yet little scientific attention has been paid to unconfined confluent round jets and detailed scientific investigations are scarce.
The present work uses computational models to study the effects of confluence and jet-to-jet interactions in four different confluent jet arrangements, reporting on the influence of jet array size and dimensionless jet spacing, 𝑆⁄𝑑0. The results show that both jet spacing and jet array size largely influence the jet-to-jet interactions and flow field development in confluent jet arrays. The jet interactions in the investigated setups result in regions of negative static pressure between jets, jet deformation, high spanwise velocity and jet displacement. Generally smaller jet spacing and larger array size results in stronger influence of jet interactions.
After the jets have combined the confluent jets form a zone with constant maximum streamwise velocity and decay of turbulence intensity, called a Confluent Core Zone (CCZ). During the CCZ the combined jet will have asymmetric spreading rates leading to axisswitching. The entrainment rate of the CCZ is constant, but the volumetric flow of the combined jet is substantially affected by the degree of entrainment before the jets have combined.
Place, publisher, year, edition, pages
2016. Vol. 138, no 8, 081206
Computational Fluid Dynamics (CFD), Confluent jets, Confluent Core Zone (CCZ), Jet interactions, Axis-switching.
IdentifiersURN: urn:nbn:se:liu:diva-117079DOI: 10.1115/1.4033024ISI: 000379589700012OAI: oai:DiVA.org:liu-117079DiVA: diva2:805419
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Funding agencies:The authors gratefully acknowledge the financial support received from the Swedish Research Council (Grant No. 2008-31145-61023-37) and Linkoping University (Sweden). The National Supercomputer Centre (NSC) is acknowledged for providing computational resources. The authors thank Dr. Mark Tummers, Delft University of Technology, and Ph.D. student Shahriar Ghahremanian, Linkoping University, for the fruitful cooperation when conducting the experimental work used for validation.2015-04-152015-04-152016-08-22Bibliographically approved