Phase invariant proper orthogonal decomposition for the study of a compressed vortex

Abstract

We propose here an experimental investigation of a vortex submitted to a radial perturbation while being compressed. This experiment reproduces a model situation of the complex flows that take place in a real engine cylinder. An isolated tumbling flow is first submitted to an injection of fluid and then compressed and measurements are realised by Particle Image Velocimetry (PIV). The Proper Orthogonal Decomposition is known to be an unbiased method to identify the coherent structures of turbulent flows. It is possible to make this decomposition for a given phase or to create a set of basis functions with the whole set of compression stroke velocity fields. First, the experimental set-up will be presented, then the second part provides the POD principle. Results of phased POD decomposition of the compression of the unperturbated vortex will be presented. Finally results from the time invariant POD will be discussed to study the influence of the jet perturbation in the compression of a vortex.

Temporal evolution analysis of in-cylinder flow by means of proper orthogonal decomposition

“…The third (and last) step is the two-dimensional (2D) spline interpolation of the re-scaled data, presently on the re-mapped coordinates, onto the reference grid 13,26,27…”

“…We note three major differences distinguishing the present three-step procedure from similar steps taken in previous phase-invariant POD analyses. 16,17,26–28 These differences are rooted in the disparate purpose of yielding a metric for comparing the directional similarity between a pair of vector fields (for the present analysis) versus generating a set of phase-invariant POD modes that span the tumble flow field over multiple crank angles (in previous studies).…”

A comparative study of turbulent velocity fields in an internal combustion engine with shrouded valve and flat/bowl piston configurations

“…It was concluded that the cyclic variations increase during the compression process and at the end of the compression stage, they may decrease to reach to those obtained during the intake process. Moreau et al [23] studied an experimental investigation of a vortex submitted to a radial perturbation while being compressed. An isolated tumbling flow was first submitted to an injection of fluid and then compressed and measurements were realized by PIV.…”