Amplitude and frequency modulation in wall turbulence

Abstract

In this study we examine the impact of the strength of the large-scale motions on the amplitude and frequency of the small scales in high-Reynolds-number turbulent boundary layers. Time series of hot-wire data are decomposed into large-and small-scale components, and the impact of the large scale on the amplitude and frequency of the small scales is considered. The amplitude modulation effect is examined by conditionally averaging the small-scale intensity (u2/S2) for various values of the large-scale fluctuation (uL). It is shown that u2/ S increases with increasing value of (uL) in the near-wall region, whereas, farther away from the wall, u2*S decreases with increasing uL. The rate of inc..