TY - JOUR

T1 - On the interaction of turbulent shear layers with harmonic perturbations

AU - Lifshitz, Yuli

AU - Degani, David

AU - Tumin, Anatoli

N1 - Funding Information:
Acknowledgements This work was supported by Grant No. 2002021 from the United States–Israel Binational Science Foundation (BSF).

PY - 2008/1

Y1 - 2008/1

N2 - The problem of coherent perturbations in a turbulent shear layer is considered for the purpose of developing a mathematical model based on a triple decomposition that extracts the coherent components of random fluctuations. The governing equations for the mean and the coherent parts of flow are derived, assuming the eddy-viscosity equivalence for the random part of flow, and solved by iterations to provide a coupled solution of the problem as a whole. Calculations agree well with experimental data in the upstream part of the layer where the mean-coherent flow interaction is the most important. In this region, the interaction changes the mean flow velocity distribution in such a manner that the neutral stability curve is shifted upstream relative to its position in the undisturbed layer and the perturbation intensity decreases further downstream. Experiments show that the coherent waves suppress the turbulent Reynolds stress production downstream of this region, but the model fails to predict the layer spreading correctly probably due to an inadequate turbulence closure of the mean flow. For the case of a turbulent mixing layer, we suggest a new closure relation that takes into account this coherent-random interaction.

AB - The problem of coherent perturbations in a turbulent shear layer is considered for the purpose of developing a mathematical model based on a triple decomposition that extracts the coherent components of random fluctuations. The governing equations for the mean and the coherent parts of flow are derived, assuming the eddy-viscosity equivalence for the random part of flow, and solved by iterations to provide a coupled solution of the problem as a whole. Calculations agree well with experimental data in the upstream part of the layer where the mean-coherent flow interaction is the most important. In this region, the interaction changes the mean flow velocity distribution in such a manner that the neutral stability curve is shifted upstream relative to its position in the undisturbed layer and the perturbation intensity decreases further downstream. Experiments show that the coherent waves suppress the turbulent Reynolds stress production downstream of this region, but the model fails to predict the layer spreading correctly probably due to an inadequate turbulence closure of the mean flow. For the case of a turbulent mixing layer, we suggest a new closure relation that takes into account this coherent-random interaction.

KW - Periodic excitation

KW - Turbulent shear layers

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U2 - 10.1007/s10494-007-9085-3

DO - 10.1007/s10494-007-9085-3

M3 - Article

AN - SCOPUS:37549055409

VL - 80

SP - 61

EP - 80

JO - Flow, Turbulence and Combustion

JF - Flow, Turbulence and Combustion

SN - 1386-6184

IS - 1

ER -