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Numerical forcing scheme to generate passive scalar mixing on the centerline of turbulent round jets in a triply periodic box

Rah, Kyupaeck Jeff and Blanquart, Guillaume (2019) Numerical forcing scheme to generate passive scalar mixing on the centerline of turbulent round jets in a triply periodic box. Physical Review Fluids, 4 (12). Art. No. 124504. ISSN 2469-990X.

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Numerical studies of passive scalars in three-dimensional (3D) periodic box turbulence have often used arbitrary scalar forcing schemes to sustain the variance. These existing methods represent certain flow configurations, but they have not been derived using specific velocity and scalar profiles. In this work, a forcing technique is devised to generate centerline scalar mixing of round jets in a triply periodic box. It is derived from the scalar transport equation using a Reynolds-like decomposition of the scalar field. The equation is closed by applying the known mean velocity and scalar profiles of axisymmetric jets. The result is a combination of a mean gradient term and a linear scalar term. Direct numerical simulations at different Reλ have been performed with these source terms for unity Schmidt numbers. Scalar flux values and scaling exponents of energy spectra from simulations are comparable to experimental values. In addition, a dimensional analysis shows that the normalized scalar statistics, such as variance, flux, and dissipation rate, should only be a function of Reynolds number; indeed, such quantities computed from our simulations approach constant values as the Reynolds number increases. The effects of velocity forcing on scalar fields are also investigated; changing velocity forcing terms may result in unstable scalar fields even under the same scalar forcing. It may indicate that an appropriate relation between the velocity and scalar forcing schemes can help producing a proper scalar mixing environment.

Item Type:Article
Related URLs:
URLURL TypeDescription
Rah, Kyupaeck Jeff0000-0003-1898-2930
Blanquart, Guillaume0000-0002-5074-9728
Additional Information:© 2019 American Physical Society. Received 2 May 2019; published 30 December 2019. The authors gratefully acknowledge funding from the National Science Foundation (CBET No. 1512771 and No. 1761690) and from the Air Force Office of Scientific Research (No. FA9550-16-1-0510) under the supervision of Dr. Chiping Li. In addition, K.J.R. acknowledges the financial support from the Samsung Scholarship Foundation.
Funding AgencyGrant Number
Air Force Office of Scientific Research (AFOSR)FA9550-16-1-0510
Samsung Scholarship FoundationUNSPECIFIED
Issue or Number:12
Record Number:CaltechAUTHORS:20200102-100023911
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:100448
Deposited By: Tony Diaz
Deposited On:02 Jan 2020 19:37
Last Modified:02 Jan 2020 19:37

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