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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
Research Student Awards

PhD Thesis: The disturbance field generated by a periodic jet


Year: 2005

Supervisor(s): Mike Gaster

The investigation of the evolution of Tollmein-Schlichting waves generated by a periodic jet in a laminar boundary layer will be discussed. More specifically the waves originating from a three-dimensional jet, of various amplitudes creating disturbances in the boundary layer. Parameters of the point jet, such as the diameter of the jet, the frequency and the orientation of the jet were varied with different results at each time. The measurements obtained are compared with computations generated by a simple analytical method. The analytical method was fast and various parameters of the flow could be altered and the resulting flow field calculated quickly. Comparisons showed good agreement with the analytical method for small amplitudes, but the comparison failed at larger amplitudes where the motion becomes nonlinear. This was expected as the analytical method was linear did not take into consideration the nonlinear behaviour of the excitation. Some experiments were carried out at much larger amplitudes where breakdown of the flow occurred. Throughout the experiments the amplitude of the exciter was measured in terms of the mass flow rate and the nozzle velocity.