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The unsteady lift spectrum for airfoils in turbulent flow has been measured in a water tunnel experiment. The results provide validation data for analytical models that account for the effect of airfoil thickness on the high frequency gust response. A series of four airfoils with elliptical leading edge profiles and thickness-to-chord ratios ranging from 8 to 16 percent were tested in grid-generated turbulence. The turbulent velocity spectrum was measured using Laser Doppler Velocimetry, and was found to be reasonably well approximated by an isotropic, homogeneous turbulence model. The unsteady force measurement setup and calibration procedure were designed to minimize the effect of system resonances, and contamination from facility vibration was reduced using a multiple coherence noise removal technique. Measurements of the unsteady lift spectrum were made at six speeds over the Reynolds number range 0.5 to 1.6 million, and the results were collapsed into a nondimensional force spectrum for the non-dimensional frequency range 1 < f c/U ∞ < 10. The experimental results agree very well with theory and confirm the importance of accounting for thickness to avoid overprediction of the forces in the high frequency range.

Northern resident killer whale pods (Orcinus orca) have distinctive stereotyped pulsed call repertoires that can be used to distinguish groups acoustically. Repertoires are generally stable, with the same call types comprising the repertoire of a given pod over a period of years to decades. Previous studies have shown that some discrete pulsed calls can be subdivided into variants or subtypes. This study suggests that new stereotyped calls may result from the gradual modification of existing call types through subtypes. Vocalizations of individuals and small groups of killer whales were collected using a bottom-mounted hydrophone array in Johnstone Strait, British Columbia in 2006 and 2007. Discriminant analysis of slope variations of a predominant call type, N4, revealed the presence of four distinct call subtypes. Similar to previous studies, there was a divergence of the N4 call between members of different matrilines of the same pod. However, this study reveals that individual killer whales produced multiple subtypes of the N4 call, indicating that divergence in the N4 call is not the result of individual differences, but rather may indicate the gradual evolution of a new stereotyped call.

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