Secondary peak in the Nusselt number distribution of impinging jet flows: A phenomenological analysis

Aillaud, Pierre; Duchaine, Florent; Gicquel, Laurent; Didorally, Sheddia

doi:10.1063/1.4963687

Cited by 39 publications

(48 citation statements)

References 60 publications

(104 reference statements)

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“…where the fluctuations of the radial velocity in the near-wall region are overestimated by 20%. The origin of this difference, which has also been observed in previous LES of the literature (Uddin et al, 2013;Aillaud et al, 2016), is still unclear. Two explanations could be proposed.…”

Section: Dynamical and Thermal Flow Fieldsmentioning

confidence: 71%

“…In the wall-jet region, the meshing strategy enables to meet the wall-resolved constraints of Piomelli and Chasnov (1996) The final mesh, after several design iterations, contains 350 × 10 6 cells, including 100 × 10 6 cells in the pipe only. This mesh size is one order magnitude higher than in the previous LES (Aillaud et al, 2016;Lodato et al, 2009;Hadzȋabdić and Hanjalić, 2008;Uddin et al, 2013), dedicated to lower Reynolds number jet (Re D ∼ 20000).…”

Section: Meshing Strategymentioning

confidence: 83%

“…In the last decade, several LES were carried out on impinging jet configurations. Most of these simulations (Hadzȋabdić and Hanjalić, 2008;Uddin et al, 2013;Aillaud et al, 2016;Natarajan et al, 2016) dealt with a turbulent jet issuing a fully developed pipe at Reynolds number Re D ∼ 20000 and for a nozzle-to-plate distance = H D / 2. Lodato et al (2009) performed a LES for the same nozzle-to-plate distance but a higher Reynolds number = Re 70000…”

Section: Introductionmentioning

confidence: 99%

“…By means of a direct numerical simulation of an impinging jet at = Re 10000 D and = H D / 2, Dairay et al (2015) showed that the hot spots are related to the instability of the secondary structures (unsteady separation). Thanks to an analysis of higher-order statistics from their LES, Aillaud et al (2016) highlighted that the most probable event in the vicinity of the secondary maximum location is a cold fluid flux towards the plate, which leads to heat flux enhancement.…”

mentioning

confidence: 99%

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Large-Eddy simulation of an impinging heated jet for a small nozzle-to-plate distance and high Reynolds number

Grenson

Deniau

2017

International Journal of Heat and Fluid Flow

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This paper reports on the investigation of an original impinging jet configuration through a wall-resolved largeeddy simulation. The heated jet issues from a fully developed pipe flow at temperature of 130°C and a Reynolds number based on the bulk velocity of 60000. The impinged plate is located three diameters downstream of the pipe exit. The CFD results have been validated against a specifically-created experimental database (Grenson et al., 2016). The overall statistical fields are well retrieved by the simulation both in the free jet and the wall jet region. In particular, the secondary maximum at the radial location = r D / 2 in the Nusselt number distribution is well predicted by the simulation. The underlying mechanisms from which the secondary maximum originates has been investigated. This analysis revealed that small-scale hot spots of strong convective heat transfer coefficient are responsible for the emergence of this secondary maximum. It is shown that the hot spots can be associated either to local unsteady "separation" of the flow or streaks-like structures above the impinging plate.

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Section: Dynamical and Thermal Flow Fieldsmentioning

confidence: 71%

Section: Meshing Strategymentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Large-Eddy simulation of an impinging heated jet for a small nozzle-to-plate distance and high Reynolds number

Grenson

Deniau

2017

International Journal of Heat and Fluid Flow

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“…In contrast to the aforementioned compressible numerical investigations, Grenson & Deniau (2017) used a compressible LES code where, despite their low Mach number (M a ≈ 0.064), the molecular viscosity µ and the thermal conductivity κ of the fluid were not assumed constant and varied as a function of the temperature. For such a low Mach number setup, it seems an a-priori a reasonable assumption to neglect these variations in the flow properties (such as in Aillaud et al 2016;Wilke & Sesterhenn 2017), but in this article we show how there are other factors to be considered in addition to the Mach number, which indicate the relevance of flow compressibility. For example, for impinging jet setups with high values of q w , the temperature differences between the jet and the wall will be such that the local values in the thermal conductivity of the flow will be significantly different.…”

Section: Introductionmentioning

confidence: 83%

Compressibility and variable inertia effects on heat transfer in turbulent impinging jets

Otero-Pérez

Sandberg

2020

J. Fluid Mech.

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This article shows the importance of flow compressibility on the heat transfer in confined impinging jets, and how it is driven by both the Mach number and the wall heat-flux. Hence, we present a collection of cases at several Mach numbers with different heat-flux values applied at the impingement wall. The wall temperature scales linearly with the imposed heat-flux and the adiabatic wall temperature is found to be purely governed by the flow compression. Especially for high heat-flux values, the non-constant wall temperature induces considerable differences in the thermal conductivity of the fluid. This phenomenon has to date not been discussed and it strongly modulates the Nusselt number. In contrast, the heat transfer coefficient is independent of the varying thermal properties of the fluid and the wall heat-flux. Furthermore, we introduce the impingement efficiency, which highlights the areas of the wall where the temperature is influenced by compressibility effects. This parameter shows how the contribution of the flow compression to raising the wall temperature becomes more dominant as the heat-flux decreases. Thus, knowing the adiabatic wall temperature is indispensable for obtaining the correct heat transfer coefficient when low heat-flux values are used, even at low Mach numbers. Lastly, a detailed analysis of the dilatation field also shows how the compressibility effects only affect the heat transfer in the vicinity of the stagnation point. These compressibility effects decay rapidly further away from the flow impingement, and the density changes along the developing boundary layer are caused instead by variable inertia effects.

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Turbulent impingement jet heat transfer on concave surfaces for aeronautical applications

Salcedo

Silva

Andrade

2018

J Braz. Soc. Mech. Sci. Eng.

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Turbulent impingement jet heat transfer on concave surfaces has been employed in different engineering applications, e.g., aviation industry. In the aircraft anti-icing systems, hot air from the engine compressor impinges on the inside surface of the leading edge through small drilled holes, configuring the so-called piccolo tube system. A critical aspect in the design of such system is the prediction of heat transfer impinging jets from the piccolo tube. The correct evaluation of the heat transfer rate in such devices is of great interest to optimize both the anti-icing performance and the hot-air bleeding from the high-pressure compressor. Therefore, the present study develops a parametric study of the impingement jet flow on concave surfaces employing the CFD tool. The main goal is to determine the effect of the jet Mach number on this heat transfer mechanism. The present results also showed that at lower H/d conditions, i.e., lower jet-to-impinging surface distances, the temperature field exhibits a more efficient heating process inside the domain, resulting in greater Nusselt number values. A correlation taking into account geometric parameters such as the jet-to-jet spacing and the jet-to-impinging surface distance and jet Mach number is also proposed. Keywords Hot-air anti-icing system • Heat transfer • Turbulent impingement jet • Mach number List of symbols c Sound velocity d Jet diameter H Jet-to-impinging surface distance h(x,y) Local convection heat coefficient h ave Average convection heat coefficient k Air thermal conductivity Ma Mach number = V/c Nu(x,y) Nusselt number = h(x,y)d/k Nu ave Average Nusselt number p Pressure q w Impinging surface local heat flux T w Impinging surface wall temperature T jet Jet inlet static temperature V Jet velocity at the exit of the piccolo tube W Jet-to-jet spanwise distance x x coordinate y y coordinate ρ Air density μ Air dynamic viscosity

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Secondary peak in the Nusselt number distribution of impinging jet flows: A phenomenological analysis

Cited by 39 publications

References 60 publications

Large-Eddy simulation of an impinging heated jet for a small nozzle-to-plate distance and high Reynolds number

Large-Eddy simulation of an impinging heated jet for a small nozzle-to-plate distance and high Reynolds number

Compressibility and variable inertia effects on heat transfer in turbulent impinging jets

Turbulent impingement jet heat transfer on concave surfaces for aeronautical applications

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