Turbulence Filter and POD Analysis for Velocity Fields in Lifted CH 4-Air Diffusion Flames

The turbulence filter and the proper orthogonal decomposition (POD) methods are applied to PIV measurements of lifted CH₄-air diffusion flames at three different Reynolds numbers. Properties such as vorticity and strain rate distributions of the decomposed fields are analyzed in order to assess the physical behavior. The turbulence filter can use relatively less data than the POD method while still providing significant insight about the flow field. The energy activation rates show the first modes (mean flow) account for 85% of the total energy. Reconstruction of the POD modes reveals that the combination of modes yields a complex fluctuating behavior. The averaged Reynolds stress of the mean flow removed parts shows interesting correlation with the mean flow vorticity and strain rate distributions. Selected turbulent properties are calculated and discussed.