The influence of the stagnation zone on the fluid dynamics at the nozzle exit of a confined and submerged impinging jet
| Autor: | Nicholas Jeffers, Edmond J. Walsh, Ciaran Conway, Jason Stafford, Jeff Punch |
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| Rok vydání: | 2016 |
| Předmět: |
Fluid Flow and Transfer Processes
Physics Turbulence Nozzle Computational Mechanics General Physics and Astronomy Laminar flow Escape velocity Mechanics 01 natural sciences 010305 fluids & plasmas 010309 optics Physics::Fluid Dynamics Particle image velocimetry Mechanics of Materials 0103 physical sciences Fluid dynamics Electronics cooling Boundary value problem |
| Zdroj: | Experiments in Fluids. 57(2) |
| ISSN: | 1432-1114 0723-4864 |
| Popis: | Low profile impinging jets provide a means to achieve high heat transfer coefficients while occupying a small quantity of space. Consequently, they are found in many engineering applications such as electronics cooling, annealing of metals, food processing, and others. This paper investigates the influence of the stagnation zone fluid dynamics on the nozzle exit flow condition of a low profile, submerged, and confined impinging water jet. The jet was geometrically constrained to a round, 16-mm diameter, square-edged nozzle at a jet exit to target surface spacing (H/D) that varied between $$0.25 < {{ H}{/}{ D}} < 8.75$$ . The influence of turbulent flow regimes is the main focus of this paper; however, laminar flow data are also presented between $$1350 < Re < 17{,}300$$ . A custom measurement facility was designed and commissioned to utilise particle image velocimetry in order to quantitatively measure the fluid dynamics both before and after the jet exits its nozzle. The velocity profiles are normalised with the mean velocity across the nozzle exit, and turbulence statistics are also presented. The primary objective of this paper is to present accurate flow profiles across the nozzle exit of an impinging jet confined to a low H/D, with a view to guide the boundary conditions chosen for numerical simulations confined to similar constraints. The results revealed in this paper suggest that the fluid dynamics in the stagnation zone strongly influences the nozzle exit velocity profile at confinement heights between $$0 < {{ H}{/}{ D}} < 1$$ . This is of particular relevance with regard to the choice of inlet boundary conditions in numerical models, and it was found that it is necessary to model a jet tube length $${{ L}{/}{ D}} > 0.5$$ —where D is the inner diameter of the jet—in order to minimise modelling uncertainty. |
| Databáze: | OpenAIRE |
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