Fundamentals and applications of multiscale generated vortical structures

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The proposed research program aims at addressing the industrial need to reduce noise, drag and fuel burn (hence CO2 emissions) within the transportation sector (air and road), as well as increase performance of turbine generators (wind and water), by fundamentally understanding the sources of these issues and developing innovative means by which they can be mitigated. Of the various fluid dynamic aspects of the flow field generated by these industrial applications, vortical structures are believed to play a dominant role. Their energy, size and coherence determine the acoustic signature from bluff bodies, the drag force of the body and the velocity deficit in wakes generated by them. Yet our ability to adequately determine their behaviour from initial conditions is lacking, something which would be of upmost importance for the various industrial applications listed above. The proposed research program specifically aims at addressing this by studying the life-cycle of vortical structures. In order to gain a deeper insight, we propose the use of multiscale geometries to systematically change the conditions under which the vortical structures are generated. Two canonical vortical flows will be studied, vortex pairs and vortex rings. Vortex rings are commonly found in jets (for example from jet engines) as well as three-dimensional bluff bodies (for example haulage trucks) and contribute not only to the noise levels but also the drag force. They will be experimentally generated in a water tank and their life-span, from creation to final decay and impact (with a solid surface), will be investigated via particle image velocimetry. To further our understanding of these structures, the manner in which these vortex rings are generated will be modified by using multiscale geometries to generate them. Previous research on flat plates, conducted by the applicant, has suggested that such geometries are able to decrease the intensity of large-scale coherent structures, as well as alter their decay rate.Vortex pairs, which are representative of the vortices created at the tip of aircraft wings, will also be investigated and in a similar fashion to the vortex rings study, it is proposed that multiscale geometries are used to modify the conditions under which these structures are generated. If it can be shown that the strength of these structures can be significantly mitigated upon impact with a wall, this would have substantial benefits not only to the aircraft manufacturer and airline company through added fuel savings, but to the airports as well. Having a shorter separation distance between aircraft would increase the capacity of the airport as more aircraft would be able to land and take-off within a given time period. Alternatively, the same number of aircraft may be able to land within a shorter time period that would reduce aircraft noise experienced by the population in and around the airport.