TY - JOUR

T1 - Mass and momentum transport in the near field of swirling turbulent jets. effect of swirl rate

AU - Lobasov, Aleksei S.

AU - Alekseenko, Sergey V.

AU - Markovich, Dmitriy M.

AU - Dulin, Vladimir M.

PY - 2020/6

Y1 - 2020/6

N2 - Local transport of the flow momentum and scalar admixture in the near-field of turbulent swirling jets (Re = 5,000) has been investigated by using a combination of the particle image velocimetry and planar laser-induced fluorescence methods. Advection and turbulent and molecular diffusions are evaluated based on the measured distributions of the mean velocity and concentration and the Reynolds stresses and fluxes. As has been quantified from the data, the flow swirl intensifies the entrainment of the surrounding fluid and promotes mass and momentum exchange in the outer mixing layer. A superimposed swirl results in the appearance of a wake/recirculation region at the jet axis and, consequently, the formation of an inner shear layer. In contrast to the scalar admixture, the momentum exchange in the inner shear layer is found to be strongly intensified by the swirl. For the jet with the highest considered swirl rate, a substantial portion of the surrounding fluid is found to enter the unsteady central recirculation zone, where it mixes with the jet that is issued from the nozzle. The contribution of the coherent velocity fluctuations, which are induced by large-scale vortex structures, to the turbulent transport has been evaluated based on triple decomposition, which was based on proper orthogonal decomposition analysis of the velocity data sets. For the considered domain of the jet with the highest swirl rate and vortex breakdown, the contributions of detected helical vortex structures, inducing pressing vortex core, to the radial fluxes of the flow momentum and the scalar admixture are found to locally exceed 65% and 80%, respectively.

AB - Local transport of the flow momentum and scalar admixture in the near-field of turbulent swirling jets (Re = 5,000) has been investigated by using a combination of the particle image velocimetry and planar laser-induced fluorescence methods. Advection and turbulent and molecular diffusions are evaluated based on the measured distributions of the mean velocity and concentration and the Reynolds stresses and fluxes. As has been quantified from the data, the flow swirl intensifies the entrainment of the surrounding fluid and promotes mass and momentum exchange in the outer mixing layer. A superimposed swirl results in the appearance of a wake/recirculation region at the jet axis and, consequently, the formation of an inner shear layer. In contrast to the scalar admixture, the momentum exchange in the inner shear layer is found to be strongly intensified by the swirl. For the jet with the highest considered swirl rate, a substantial portion of the surrounding fluid is found to enter the unsteady central recirculation zone, where it mixes with the jet that is issued from the nozzle. The contribution of the coherent velocity fluctuations, which are induced by large-scale vortex structures, to the turbulent transport has been evaluated based on triple decomposition, which was based on proper orthogonal decomposition analysis of the velocity data sets. For the considered domain of the jet with the highest swirl rate and vortex breakdown, the contributions of detected helical vortex structures, inducing pressing vortex core, to the radial fluxes of the flow momentum and the scalar admixture are found to locally exceed 65% and 80%, respectively.

KW - Coherent structures

KW - Particle image velocimetry

KW - Planar laser-induced fluorescence

KW - Precessing vortex core

KW - Proper orthogonal decomposition

KW - Swirling turbulent jet

KW - Triple decomposition

KW - Turbulent transport

KW - Vortex breakdown

KW - PHASE-RESOLVED CHARACTERIZATION

KW - LARGE-EDDY SIMULATION

KW - DYNAMICS

KW - VORTEX-FLAME INTERACTION

KW - COHERENT STRUCTURES

KW - BREAKDOWN

UR - http://www.scopus.com/inward/record.url?scp=85081200570&partnerID=8YFLogxK

U2 - 10.1016/j.ijheatfluidflow.2020.108539

DO - 10.1016/j.ijheatfluidflow.2020.108539

M3 - Article

AN - SCOPUS:85081200570

VL - 83

JO - International Journal of Heat and Fluid Flow

JF - International Journal of Heat and Fluid Flow

SN - 0142-727X

M1 - 108539

ER -