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Three Dimensional Control of High-Speed Cavity Flow Oscillations

Cavity structures, like weapons bays and landing gear wells on aircraft, suffer from severe oscillations under high speed flow
conditions. These oscillations are associated with intense surface pressure/velocity fluctuations inside the cavity which can radiate strong
acoustic waves and cause structural damage. The physics of cavity flows have been studied for several decades with much of the effort put
towards flow controls to reduce these oscillations. Geometric modifications of the cavity structure are usually only effective for
suppressing the oscillations within the designed flow conditions. Therefore, active flow control is more attractive for a wider application
range. Previous research have proven that mass/momentum injection at the cavity leading edge can effectively suppress the pressure/velocity
fluctuations. Due to the limited control authorities of current actuators, a steady actuation which introduces three-dimensional disturbances
is studied to reduce the energy requirements of the actuator and improve the suppression of the oscillations over a wide range of free-stream
Mach numbers. Surface fluctuating pressure measurements are acquired to determine the control performances of a number of 3-D actuation
configurations. Flow fields, including velocity fields and density gradient fields, are measured to reveal the flow features with and without
the flow control. Mathematical methods, including modal decomposition analysis, are further applied to study the dynamics of the flow field.
All of these analyses together elucidate the effective 3-D actuation mechanism in the cavity flow control. The suppression of pressure
fluctuations are obtained in both full-span and finite-span cavities. The successful flow control is found to be the redistribution of the
energy in the shear layer by the counter-rotating-vortex pairs, which are introduced by the 3-D actuation in the cross-flow. In addition, a
design guide for the actuator geometry is given based on the observations. / A Dissertation submitted to the Department of Mechanical Engineering in partial fulfillment of the
requirements for the degree of Doctor of Philosophy. / Fall Semester 2017. / August 16, 2017. / Active flow control, Cavity flow, Steady blowing, Subsonic, Three-dimensional / Includes bibliographical references. / Louis N. Cattafesta, III, Professor Directing Dissertation; Christopher Tam, University Representative;
Kunihiko Taira, Committee Member; Emmanuel G. Collins, Committee Member.
ContributorsZhang, Yang (author), Cattafesta, Louis N. (professor directing dissertation), Tam, Christopher K. W. (university representative), Taira, Kunihiko (committee member), Collins, E. (Emmanuel) (committee member), Florida State University (degree granting institution), College of Engineering (degree granting college), Department of Mechanical Engineering (degree granting departmentdgg)
PublisherFlorida State University
Source SetsFlorida State University
LanguageEnglish, English
Detected LanguageEnglish
TypeText, text, doctoral thesis
Format1 online resource (147 pages), computer, application/pdf

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