Oscillatory thermal structures in a reattaching jet flow

Abstract

Spatially varying surface temperature oscillations in a nominally steady reattaching slot jet at a Reynolds number (Re) of 5000 are analyzed using Proper Orthogonal Decomposition (POD) for two nozzle-to-surface spacings, and three exit openings of the nozzle. The surface temperature data in these experiments were recorded using infrared thermography at a frequency of 20 Hz along two selected lines on the impingement surface corresponding to geometrically similar and dissimilar regions within the reattachment curtain. The magnitude of temperature oscillations were found to increase with an increase in exit opening for the larger nozzle spacing. The POD analysis results indicate that a majority of the temperature flucutations are well captured by 15 dominant modes. In many cases, the three dominant modes accounted for approximately 60 percent of the variance in surface temperature fluctuation.

An experimental method to investigate coherent spiral vortices in the boundary layer over rotating bodies of revolution

“…Recent investigations show that the potential of IRT can be dramatically enhanced by filtering the measurement data sets using proper orthogonal decomposition (POD). For example, Narayanan (2007) applied this methodology to study the modes of temperature fluctuations of slot jet impingement by filtering IRT data with first 15 POD modes. Ranc et al (2015) demonstrated improvements in the signalto-noise ratio of IRT measurements of a thermomechanical phenomenon by selecting physically admissible thermal modes from POD.…”