Applications of stochastic estimation in the axisymmetric sudden expansion

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Abstract
Stochastic estimation was utilized to reconstruct estimates of multipoint conditional averages in an axisymmetric sudden expansion. Application of this technique requires, in addition to the two-point correlation tensor, time series data measured at selected positions simultaneously. One application of this technique yielded estimates of the spatial and temporally evolving velocity field in a given azimuthal plane of the sudden expansion. An application of this technique in the reattachment region clearly shows its unsteady character. The spectra measurements as well as the stochastic estimates utilizing multipoint conditions applied over two directions suggest that coherent structures from the near field shear layer propagate downstream into the reattachment region and cause this unsteadiness.