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PublisherThe University of Arizona.
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AbstractBetter understanding of the behavior of compressible turbulent mixing layer is desirable for its active flow control by actuators which can be applied in many different fields. In order to generate large coherent structures in the downstream out of small energy entrainment, the instability and receptivity of free mixing layers with respect to three-dimensional spatially growing disturbances are considered. The triple decomposition method is utilized for the flow field, which leads to the conventional stability equations applying closure models for coherent and incoherent perturbations. The biorthogonal eigenfunction system (BES) is developed and applied with normal modes considered for perturbations, and the eigenvalue problem for the system of ordinary differential equations of coherent perturbations is solved numerically. Analyses address receptivity of the mixing layer to a localized energy deposition and instability of coherent perturbations downstream including the nonparallel flow effect. Influence of different frequencies, Mach numbers, and locations of energy deposition on the receptivity and amplification of perturbations is discussed, concluding that dominant frequency of perturbations depends on downstream locations and perturbations with lower frequency are more unstable further downstream but less receptive. A high Mach number can suppress both the overall instability and receptivity of a mixing layer and it also has effect on location for the most receptive region when compressibility effect is taken into account.
Degree ProgramGraduate College