P. B. MacCready Jr’s scientific contributions

Predicting the transport and decay of the organized vortex system for various aircraft types, flight modes, and meteorological conditions requires clear identification of the various significant factors and mechanisms involved in the transport/decay process. Outside of the ground effect, the dominant factors include the cir­culation and core characteristics of the vortices, the turbulence in the wake and in the environment, and the thermal stability of the environment. The environmental factors are sometimes dominant; the vortex wakes from an airplane operating in two different meteorological regimes can differ by an order of magnitude in decay and by an order of magnitude in descent distance. Thus any theory of vortex-wake decay in the real atmosphere must consider the meteorological factors, and field observations on decay must be interpreted with consideration of these factors.