Energy transfer mechanisms and resolvent analysis in the cylinder wake

Jin, Bo, Symon, Sean and Illingworth, Simon J. (2020) Energy transfer mechanisms and resolvent analysis in the cylinder wake. Chanson, Hubert and Brown, Richard (eds.) In 22nd Australasian Fluid Mechanics Conference, AFMC 2020. Australasian Fluid Mechanics Society.. (doi:10.14264/8a216b5).

Abstract

Energy transfer mechanisms for vortex shedding behind a 2D cylinder at a Reynolds number of Re=100 are investigated. We first characterize the energy balances achieved by the true cylinder flow-both for the flow as a whole and for each of its most energetic harmonic frequencies. Suitable energy conservation laws reveal the existence of nonlinear energy transfer mechanisms which neither produce nor consume energy overall, but account for an important transfer of energy between temporal frequencies. We then compare the energy balance for DNS to that predicted by resolvent analysis. Although a suitable energy balance is achieved for each harmonic, resolvent analysis does not respect the conservative nature of the nonlinear terms and fails to model nonlinear energy transfer between temporal frequencies. This lack of nonlinear energy transfer helps to explain the excess energy of the leading resolvent mode in the far wake.

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