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Title: Generation of laminar streaks in a Rankine-body boundary layer by free-stream vortical disturbances
Author: Zincone, Eva
ISNI:       0000 0004 6494 0579
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2017
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It is known that friction due to boundary layer disturbances can affect the performances of many engineering systems and there are many works on the suppression of the transitional boundary layer. Most of the results on the velocity and pressure in the literature are for the flat-plate boundary layer, but it is interesting to see how the velocity and pressure change with the curvature. This work aims to extend the results of the flat-plate boundary layer to a Rankine-body boundary layer. A small amplitude, unsteady, three-dimensional perturbation of a mean base flow is considered. The flow is assumed incompressible and the Reynolds number high. The analysis is performed in an optimal coordinate system, where the streamwise coordinate is replaced by the velocity potential and the wall normal coordinate by the streamfunction associated to the inviscid mean flow given by a uniform flow which encounters a source flow. The perturbation flow around and far from the body is solved analytically. In the viscous region near the body, the base flow satisfies the steady mean flow equations in optimal coordinates with no similarity. Boundary region equations in optimal coordinates for the perturbation flow are derived and numerically solved by imposing no-slip conditions at the wall for the three velocity components and appropriate boundary conditions at a large distance from the body. The latter are found by matching with the outer solution. The boundary region equations are parabolic in the streamwise coordinate therefore a marching procedure along this coordinate will be used in the code. Initial conditions to start the code are derived. The results suggest that the mean pressure gradient modifies the shape of the streamwise velocity profile compared to the one of the flat-plate boundary layer and the inner perturbation pressure matches the outer one at a large distance from the body. It is observed that the streamwise wavenumber of the perturbation plays a key role in the development of streaks.
Supervisor: Ricco, Pierre Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available