Application of triple decomposition on cylinder wake energy budget

Triple decomposition is a methodology for the analysis of turbulent flow to decompose flow fields into mean, wave, and turbulence components. Triple decomposition is useful when large-scale coherent structures repeatedly appear in a flow. Cylinder wake is a representative flow that contains such coherent structures with a fluctuating frequency.

The data set of the two-dimensional velocity field was acquired from laboratory experiments conducted using particle image velocimetry in a flume. We applied triple decomposition on flow fields behind a circular cylinder by using proper orthogonal decomposition. Then, we estimated the kinetic energy budgets of those three components respectively and investigated the structure of energy transfer among the components.

When we combined the first and second modes, their combinations propagated downstream oscillating with a frequency. The energy transfers from mean shear fields to wake and turbulence in similar amounts, but energy from wake to turbulence did not occur significantly. Therefore, it proves that the wake must be a form of waves as previously pointed out.