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@article{Rigas:2017:10.1017/jfm.2017.32,
author = {Rigas, G and Morgans, AS and Morrison, JF},
doi = {10.1017/jfm.2017.32},
journal = {Journal of Fluid Mechanics},
pages = {570--591},
title = {Weakly nonlinear modelling of a forced turbulent axisymmetric wake},
url = {http://dx.doi.org/10.1017/jfm.2017.32},
volume = {814},
year = {2017}
}

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TY  - JOUR
AB  - A theory is presented where the weakly nonlinear analysis of laminar globally unstableflows in the presence of external forcing is extended to the turbulent regime. The analysisis demonstrated and validated using experimental results of an axisymmetric bluff bodywake at high Reynolds numbers,ReD∼1.88×105, where forcing is applied using aZero-Net-Mass-Flux actuator located at the base of the blunt body. In this study wefocus on the response of antisymmetric coherent structures with azimuthal wavenumbersm=±1 at a frequencyStD= 0.2, responsible for global vortex shedding. We foundexperimentally that axisymmetric forcing (m= 0) couples nonlinearly with the globalshedding mode when the flow is forced at twice the shedding frequency, resulting inparametric subharmonic resonance through a triadic interaction between forcing andshedding. We derive simple weakly nonlinear models from the phase-averaged Navier-Stokes equations and show that they capture accurately the observed behaviour forthis type of forcing. The unknown model coefficients are obtained experimentally byproducing harmonic transients. This approach should be applicable ina variety ofturbulent flows to describe the response of global modes to forcing.
AU  - Rigas,G
AU  - Morgans,AS
AU  - Morrison,JF
DO  - 10.1017/jfm.2017.32
EP  - 591
PY  - 2017///
SN  - 0022-1120
SP  - 570
TI  - Weakly nonlinear modelling of a forced turbulent axisymmetric wake
T2  - Journal of Fluid Mechanics
UR  - http://dx.doi.org/10.1017/jfm.2017.32
UR  - http://hdl.handle.net/10044/1/43589
VL  - 814
ER  -

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