Doctor of Philosophy, The Ohio State University, 2019, Aero/Astro Engineering

Impinging oblique shockwaves are commonplace in both external and internal flow paths on high-speed vehicles, and their prevalence will only increase with the continued pursuit of readily deployable flight vehicles. These shockwaves cause sharp pressure rises that create intense localized structural loads. Recently, impinging shocks waves have been identified as a mechanism to induce panel flutter, which presents a major concern for fatigue failure and increased noise generation. Critical to this is the fact that loss of panel stability occurs at different operating conditions and panel stiffness compared to classical panel flutter. To date, research on shock-induced panel flutter has been limited to a two-dimensional, semi-infinite assumption. Additionally, most existing simulations on the topic are restricted to inviscid flow. This dissertation documents expanded understanding of shock-induced panel flutter phenomena by exploring the effects of three-dimensionality and viscosity on the aeroelastic system. The analysis is carried out numerically using the Air Force Research Laboratory FDL3DI code. The first configuration considered is Mach 2 inviscid flow over a square panel. The panel is simply supported on all four edges, and the shockwave is set to impinge along the mid-chord. A parametric sweep is performed over non-dimensional dynamic pressure and incident shock angle. Mean, standard deviation, and time history of the panel response are presented. Additionally, the panel response is projected onto the natural mode shapes in order to gain deeper insight into the characteristics of the structural response. Fluid pressure snapshots are also provided. In general, the panel flutter response is qualitatively similar to previous studies on the semi-infinite configuration. Flutter amplitude is slightly lower and flutter frequency slightly higher for the three-dimensional configuration in all cases. Additionally, the critical non-dimensional dynamic pressure is i (open full item for complete abstract)

Committee: Jack McNamara Ph.D. (Advisor); Datta Gaitonde Ph.D. (Advisor); Miguel Visbal Ph.D. (Committee Member); Jen-Ping Chen Ph.D. (Committee Member) Subjects: Aerospace Engineering; Mechanical Engineering

Bachelor of Sciences, Ohio University, 2017, Physics and Astronomy

Core collapse supernovae are an important class of objects in stellar evolution research as they are the final life stage of high mass stars. Supernovae in general are classified into several spectral types; this paper explores SN 2005da, classified as a Type Ic, meaning it lacks hydrogen and helium lines. The supernova was originally classified as a broad-lined Type Ic (Type Ic-BL), with expansion velocities near maximum light greater than or approximately equal to 15000 km/s. However, some of the elements present in the spectrum, namely carbon and oxygen, have narrower lines (FWHM approximately equal to 2300 km/s) than other elements, indicating an interaction with a previously ejected envelope. The supernova is also found to have a decay time, with a change in magnitude over 15 days following maximum light of about 1.4 magnitudes, that is significantly faster than typical Type Ic or Ic-BL. This is more akin to a rarer object type known as a Type Ibn, although it lacks the characteristic narrow helium lines of this type. Therefore, SN 2005da appears to be unlike known examples of Type Ic supernovae.

Committee: Ryan Chornock (Advisor) Subjects: Astronomy; Astrophysics; Physics

MS, University of Cincinnati, 2011, Engineering and Applied Science: Aerospace Engineering

Mixed compression inlets offer a potential increase in pressure recovery compared to conventional external compression inlets at Mach numbers above two. However, these inlets suffer from problems with shock boundary layer interactions which cause flow instabilities and severe performance reductions. Previous experiments conducted at the University of Michigan used a wind tunnel with glass side walls and an extensive test section to measure the shock boundary layer interaction associated with a single oblique shock. This work presents an investigation of possible improvements to the current single shock experiment. A 10° oblique shock generator was designed by researchers at the University of Michigan and simulated at the University of Cincinnati. The 10° design did not start in the actual wind tunnel, but was successfully simulated by bypassing the transients from quiescent flow with the help of an initial solution generated from one dimensional inviscid nozzle theory. The residuals from the simulation leveled off at higher levels than expected in some mesh blocks, which indicates unsteadiness. The same case was then simulated in a time accurate manner, and showed very small variations in the solution over time. The magnitude of these variations were large enough to prevent the residuals in the steady simulation from dropping, but small enough that an averaged solution could be used for analysis. A grid dependency study was conducted and found that the 24 million node grid is very close to being grid independent. A new design was desired that would allow the actual tunnel to start, and this resulted in a 6° oblique shock generator. This geometry allows the tunnel to start, and produces a more benign shock boundary layer interaction than the 10° oblique shock generator. A follow up experiment has been designed where the oblique shock is followed by a normal shock and a subsonic diffuser. This new configuration will provide insights into the effects that combined ob (open full item for complete abstract)

Committee: Mark Turner ScD (Committee Chair); Shaaban Abdallah PhD (Committee Member); Paul Orkwis PhD (Committee Member) Subjects: Aerospace Materials

MS, University of Cincinnati, 2010, Engineering and Applied Science: Aerospace Engineering

The presented work shows that Prandtl-Meyer expansion can be used as a foundation to predict bleed rate for a single bleed hole oriented normal to a supersonic freestream. A CFD study was used to explore flowfield phenomena that can be used in conjunction with Prandtl-Meyer expansion theory to improve model accuracy. Of these phenomena, the shear layer and barrier shock were the best defined and their geometric placement within the bleed hole were the basis for the bleed rate model. Coefficients of variation of the root mean square error between data and predictions were between 0.10 and 0.15 for all but the highest of freestream Mach numbers evaluated. Development of an analytical bleed rate model and recommendations for follow-on activity are presented.

Committee: Awatef Hamed PhD (Committee Chair); Prem Khosla PhD (Committee Member); John Slater PhD (Committee Member) Subjects: Aerospace Materials