TY - GEN

T1 - Statistics of the turbulent/non-turbulent interface in a spatially evolving mixing layer

AU - Attili, Antonio

AU - Cristancho, Juan C.

AU - Bisetti, Fabrizio

PY - 2013

Y1 - 2013

N2 - The thin interface separating the inner turbulent region from the outer irrotational fluid is analyzed in a direct numerical simulation of a spatially developing turbulent mixing layer. A vorticity threshold is defined to detect the interface separating the turbulent from the non-turbulent regions of the flow and to calculate statistics conditioned on the distance from this interface. The statistics of the position of the two interfaces in the mixing layer, i.e., on the low- and high-speed sides, are characterized by a Gaussian distribution and evolve in the streamwise direction coherently with the self-similar behavior of the flow. A strong vorticity jump is observed at the interfaces, in agreement with the results for other free shear flows, such as turbulent jets and wakes. Far from the interfaces, the conditional vorticity recovers the value observed for the classical turbulent statistics in the middle of the layer. The thickness of the interfaces are found to be of the order of the Taylor's microscale, similarly to other shear flows. Finally, the local velocity of the interfaces with respect to the flow is of the order of the Kolmogorov velocity, confirming that entrainment is governed by the dynamics of the smallest scales.

AB - The thin interface separating the inner turbulent region from the outer irrotational fluid is analyzed in a direct numerical simulation of a spatially developing turbulent mixing layer. A vorticity threshold is defined to detect the interface separating the turbulent from the non-turbulent regions of the flow and to calculate statistics conditioned on the distance from this interface. The statistics of the position of the two interfaces in the mixing layer, i.e., on the low- and high-speed sides, are characterized by a Gaussian distribution and evolve in the streamwise direction coherently with the self-similar behavior of the flow. A strong vorticity jump is observed at the interfaces, in agreement with the results for other free shear flows, such as turbulent jets and wakes. Far from the interfaces, the conditional vorticity recovers the value observed for the classical turbulent statistics in the middle of the layer. The thickness of the interfaces are found to be of the order of the Taylor's microscale, similarly to other shear flows. Finally, the local velocity of the interfaces with respect to the flow is of the order of the Kolmogorov velocity, confirming that entrainment is governed by the dynamics of the smallest scales.

UR - http://www.scopus.com/inward/record.url?scp=85034043106&partnerID=8YFLogxK

M3 - Conference contribution

AN - SCOPUS:85034043106

T3 - International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2013

BT - International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2013

PB - TSFP-8

T2 - 8th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2013

Y2 - 28 August 2013 through 30 August 2013

ER -