Vibration reduction of helicopter tail shaft by using dry friction dampers

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2017

Author

Özaydın, Onur

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Condensation in grooved heat pipes involves several simultaneous phenomena including vapor-liquid boundaries whose shapes are unknown a priori, fluid flow due to capillary and dispersion pressure gradients and condensation over ultra thin films. In grooved heat pipes, the majority of condensation occurs on fin tops due to the thinner liquid film, having a lower thermal resistance, compared to inside the groove where the fluid is substantially thicker. Majority of the studies in the literature assume an approximate profile for the liquid film surface and apply an integral balance for conservation laws, including the effect of the capillary pressure only. In addition, this approximate profile is matched with the liquid profile inside the groove, which serves as a boundary condition. In the current study, the effect of a slope dependent disjoining pressure and the matching conditions with the groove are investigated using a comprehensive model. The results suggest that for small temperature differences and small slopes, the effect of dispersion pressure is non negligible and beyond limiting values of edge slope angles, the disjoining effect precludes solutions where the fin top film matches the groove in a smooth transition. In addition bifurcation manner is found for the results. Their physical availability is examined in this study. This analysis results suggested that the second set of answers which is found because of bifurcation, despite its mathematical validity, could not be physically valid.

Subject Keywords

Helicopters., Shafting., Vibration., Friction.

URI

http://etd.lib.metu.edu.tr/upload/12621655/index.pdf
https://hdl.handle.net/11511/26882

Collections

Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

O. Özaydın, “Vibration reduction of helicopter tail shaft by using dry friction dampers,” M.S. - Master of Science, Middle East Technical University, 2017.