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Passive scalar diffusion in three-dimensional turbulent rectangular free jets with numerical evaluation of turbulent Prandtl/Schmidt number

Passive scalar diffusion in three-dimensional turbulent rectangular free jets with numerical evaluation of turbulent Prandtl/Schmidt number
Passive scalar diffusion in three-dimensional turbulent rectangular free jets with numerical evaluation of turbulent Prandtl/Schmidt number

The passive scalar spreading of fluids with laminar Prandtl or Schmidt number, Pr, Sc, equal to 1 in turbulent rectangular submerged free jets is analyzed by means of numerical simulation and theoretical analysis in the Reynolds number range 5000–40,000. The numerical investigation is carried out by means of a three-dimensional (3D) Large Eddy Simulation (LES) approach with the dynamic Smagorinsky model. A new mathematical model allows to obtain a simplified description of the passive scalar spreading in the largest area of the flow field, the Fully Developed Region (FDR). The present three-dimensional (3D) investigation shows that the passive scalar spreading follows a self-similarity law in the Fully Developed Region (FDR), as well as in the mean Undisturbed Region of Flow (URF) and in the Potential Core Region (PCR), similarly to what found in the Near Field Region (NFR) of rectangular submerged free jets, investigated with a two-dimensional (2D) approach. The turbulent Prandtl or Schmidt number is evaluated numerically and is found to be inversely proportional to the mean velocity gradient in the PCR. The present 3D numerical results show that the turbulent Prandtl or Schmidt number is zero in most part of the mean URF, and PCR, while it assumes different values outside. In the FDR the turbulent Prandtl or Schmidt number is constant and approximately equal to 0.7, in agreement with the literature, showing that turbulence affects momentum and passive scalar in a different way.

3D turbulent flow and passive scalar, Large eddy simulation, Self-similarity of the fully developed region, Submerged rectangular free jet of fluids with Pr/Sc equal to one, Turbulent Prandtl/Schmidt number evaluation
0735-1933
106-115
Di Venuta, Ivan
c478ec72-9e42-45cd-9afb-147f93b6835b
Boghi, Andrea
54a72da6-c8a2-468c-9773-897efac0638f
Angelino, Matteo
00c795fe-bcaa-439f-bfc9-24cb7907897d
Gori, Fabio
f7e76614-37d8-4c3b-b7b0-8c6603a4515f
Di Venuta, Ivan
c478ec72-9e42-45cd-9afb-147f93b6835b
Boghi, Andrea
54a72da6-c8a2-468c-9773-897efac0638f
Angelino, Matteo
00c795fe-bcaa-439f-bfc9-24cb7907897d
Gori, Fabio
f7e76614-37d8-4c3b-b7b0-8c6603a4515f

Di Venuta, Ivan, Boghi, Andrea, Angelino, Matteo and Gori, Fabio (2018) Passive scalar diffusion in three-dimensional turbulent rectangular free jets with numerical evaluation of turbulent Prandtl/Schmidt number. International Communications in Heat and Mass Transfer, 95, 106-115. (doi:10.1016/j.icheatmasstransfer.2018.03.019).

Record type: Article

Abstract

The passive scalar spreading of fluids with laminar Prandtl or Schmidt number, Pr, Sc, equal to 1 in turbulent rectangular submerged free jets is analyzed by means of numerical simulation and theoretical analysis in the Reynolds number range 5000–40,000. The numerical investigation is carried out by means of a three-dimensional (3D) Large Eddy Simulation (LES) approach with the dynamic Smagorinsky model. A new mathematical model allows to obtain a simplified description of the passive scalar spreading in the largest area of the flow field, the Fully Developed Region (FDR). The present three-dimensional (3D) investigation shows that the passive scalar spreading follows a self-similarity law in the Fully Developed Region (FDR), as well as in the mean Undisturbed Region of Flow (URF) and in the Potential Core Region (PCR), similarly to what found in the Near Field Region (NFR) of rectangular submerged free jets, investigated with a two-dimensional (2D) approach. The turbulent Prandtl or Schmidt number is evaluated numerically and is found to be inversely proportional to the mean velocity gradient in the PCR. The present 3D numerical results show that the turbulent Prandtl or Schmidt number is zero in most part of the mean URF, and PCR, while it assumes different values outside. In the FDR the turbulent Prandtl or Schmidt number is constant and approximately equal to 0.7, in agreement with the literature, showing that turbulence affects momentum and passive scalar in a different way.

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GETTO_LIBERO_3D - Accepted Manuscript
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More information

Accepted/In Press date: 3 February 2018
e-pub ahead of print date: 8 May 2018
Published date: 1 July 2018
Keywords: 3D turbulent flow and passive scalar, Large eddy simulation, Self-similarity of the fully developed region, Submerged rectangular free jet of fluids with Pr/Sc equal to one, Turbulent Prandtl/Schmidt number evaluation

Identifiers

Local EPrints ID: 421763
URI: http://eprints.soton.ac.uk/id/eprint/421763
ISSN: 0735-1933
PURE UUID: eba921f7-34ff-4a3c-ad87-b8e49b448a5b
ORCID for Andrea Boghi: ORCID iD orcid.org/0000-0002-9387-326X

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Date deposited: 26 Jun 2018 16:30
Last modified: 07 Oct 2020 06:44

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