“…It should be noted that, while spectra of velocity fluctuations measured a t one point in space may fail to detect quasiperiodicity of the flow, two-point statistics, such as the coherence Coh,, between Fourier components of u obtained at two different locations in space, could be a more effective detector. I n this context, Keffer (1979) noted that, in the turbulent wake of a heated cylinder, the temperature spectrum at x/d = 40 (d is the cylinder diameter) did not exhibit a peak a t the vortex-shedding frequency, but the coherence between temperature fluctuations measured a t x/d = 6 and x/d = 40 did exhibit a significant peak a t the Strouhal frequency. Krothapalli et al (1981) presented autocorrelations and spectra of u on the centreline of a plane jet over the range 2…”