Toggle Main Menu Toggle Search

Open Access padlockePrints

Effects of Lewis number on the reactive scalar gradient alignment with local strain rate in turbulent premixed flames

Lookup NU author(s): Professor Nilanjan ChakrabortyORCiD

Downloads

Full text for this publication is not currently held within this repository. Alternative links are provided below where available.


Abstract

The effects of Lewis number Le on the reactive scalar gradient alignment with the local strain rate have been studied using Direct Numerical Simulation data of freely propagating statistically planar turbulent premixed flames with Le ranging from 0.34 to 1.2. The alignment characteristics of the reaction progress variable gradient are explained using the statistics of dilatation rate, and flame normal and tangential strain rates. The strength of dilatation rate is shown to increase with decreasing Le and this effect becomes particularly strong for the flames with Le < 1 because of thermo-diffusive instability. The dilatation rate is shown to be responsible for the preferential alignment of the reactive scalar gradient with the most extensive principal strain rate in the reaction zone for flames with Le close to unity, contrary to the alignment of scalar gradient with the most compressive principal strain rate in turbulent passive scalar transport. However, stronger dilatation rate effects in Le ≪ 1 flames (e.g. Le = 0.34) gives rise to the preferential alignment of the reactive scalar gradient with the most extensive principal strain rate for the major portion of the flame-brush. The scalar gradient alignment with local strain rate plays an important role in the transport of scalar dissipation rate and the flame surface density. The observed alignment with the most extensive principal strain rate destroys the scalar gradient and the magnitude of this sink is found to increase with decreasing Lewis number for a given turbulent Reynolds number and Damköhler number.


Publication metadata

Author(s): Chakraborty N, Klein M, Swaminathan N

Publication type: Article

Publication status: Published

Journal: Proceedings of the Combustion Institute

Year: 2009

Volume: 32

Issue: 1

Pages: 1409-1417

ISSN (print): 1540-7489

ISSN (electronic): 1873-2704

Publisher: Elsevier Inc

URL: http://dx.doi.org/10.1016/j.proci.2008.06.021

DOI: 10.1016/j.proci.2008.06.021


Altmetrics

Altmetrics provided by Altmetric


Share