A Spectral Study of a Moderately Loaded LPT Airfoil: Part 2—Effects of Turbulence Intensity and Reynolds Number on Frequencies Affecting By-Pass Transition

Abstract

A single wire, hot-wire, probe is used to examine the airflow in, and in close vicinity to, the shearlayer of a Low-Pressure Turbine (LPT) airfoil. The experiment was performed with varying turbulence intensities (Tu) and Reynolds numbers (ReBx); in this work, Re is based on the cascade inflow velocity and axial chord length. In part 1 of the present study [1], the methodology used to identify the key frequencies in the free shearlayer using a combination of statistical and spectral measures of the airflow was first discussed. Here, the focus is on the effects of ReBx and Tu on the spectral results. The frequencies and location in the shearlayer of the Tollmien-Schlichting (TS) waves and Kelvin-Helmholtz (KH) instabilities are shown to be affected by both Tu and ReBx. Additionally, the KH instabilities are shown to undergo pairing.