The influence of the stagnation zone on the fluid dynamics at the nozzle exit of a confined and submerged impinging jet

The influence of the stagnation zone on the fluid dynamics at the nozzle exit of a confined and... 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 $$0.25 < {{ H}{/}{ D}} < 8.75$$ 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 $$1350 < Re < 17{,}300$$ 1350 < R e < 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 $$0 < {{ H}{/}{ D}} < 1$$ 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 $${{ L}{/}{ D}} > 0.5$$ L / D > 0.5 —where D is the inner diameter of the jet—in order to minimise modelling uncertainty. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

The influence of the stagnation zone on the fluid dynamics at the nozzle exit of a confined and submerged impinging jet

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Publisher
Springer Berlin Heidelberg
Copyright
Copyright © 2015 by Springer-Verlag Berlin Heidelberg
Subject
Engineering; Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-015-2092-6
Publisher site
See Article on Publisher Site

Abstract

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 $$0.25 < {{ H}{/}{ D}} < 8.75$$ 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 $$1350 < Re < 17{,}300$$ 1350 < R e < 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 $$0 < {{ H}{/}{ D}} < 1$$ 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 $${{ L}{/}{ D}} > 0.5$$ L / D > 0.5 —where D is the inner diameter of the jet—in order to minimise modelling uncertainty.

Journal

Experiments in FluidsSpringer Journals

Published: Jan 20, 2016

References

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