Within the overarching area of airplane noise, landing gear noise has been proven to be a major contributor to airframe noise. Despite a large focus given to it by past research work, landing gear noise investigations have continuously failed to include landing lights, completely disregarding their potential for seriously altering the landing gear wake structure and overall noise signature. This thesis is one of the first studies to focus on the effect of landing light orientation on landing gear wake and landing gear noise. Pressure fluctuations in the wake of a simplified single light landing gear model are investigated experimentally for several freestream velocities and at various elevations of measurement plane. The effect of the distance between the light and the landing gear strut is also investigated. Three-dimensional flow is found in the wake at the center, or zero elevation, plane. This three-dimensionality is found to be much weaker at the highest elevation from the light, where the wake is found to be primarily two-dimensional. The nature of the transition region between the three-dimensional flow and two-dimensional flow is not investigated, but it is acknowledged that a transition region exists. Complex flow behaviour leading to a wake width larger than twice the size of the light-strut assembly width is found to be present at the zero elevation, and phase-locked PIV imaging is unable to capture any periodic motion within the wake at this elevation. In contrast, the wake at the highest elevation is found to resemble the flow in the wake of circular cylinders, and phase-locked PIV imaging at this elevation clearly captures an alternate vortex shedding scheme. Due to this difference in wake structures, the periodicity at the highest elevation is found to be stronger than that observed at the zero elevation. Changes in light-strut spacing are found to inversely affect the strength of the periodicity in the wake, as larger spacing is linked to greater influence of three-dimensionality, and therefore a weaker periodicity. Changes in light-strut spacing are also found to be inversely related to the oscillation frequency of the periodicity, with the cause for this relationship possibly explained by the wider wake at increased spacing. It is found that the oscillation frequency of periodicity in the single light landing gear wake is consistently in the Strouhal number range of St=0.16-0.18 for all light-strut spacing distances, freestream velocities, and elevations. The flow around the light-strut assembly is therefore characterized as modulated flow around a cylindrical strut because alternate vortex shedding is dominant except for a slight region where the light acts to generate three-dimensionality, and because the oscillation frequency is near that of vortex shedding from a circular cylinder, St=0.19. The wakes of the single light landing gear and two-light landing gear models are compared, but neither design can be supported as quieter than the other at this time due to the unknown amount of vertical radiation from the landing gear wakes. / Thesis / Master of Applied Science (MASc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/23074 |
| Date | 17 November 2017 |
| Creators | Arezina, Marko |
| Contributors | Ziada, Samir, Mechanical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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