Approved for public release, distribution unlimited / Investigating the effect of steam ingestion into an aircraft jet engine is necessary to improve understanding of stall and surge in transonic axial compressors. Specifically, to understand the "pop stall" phenomenon experienced by naval fighter jet aircraft during steam catapult launches. Steam leakage from an aircraft carrier catapult system can be ingested into the intake and cause stall or surge in a jet engine upon takeoff. It is important to understand the conditions under which this occurs as the Navy prepares for the fielding of the single engine F- 35C, the aircraft carrier variant of the Joint Strike Fighter. This project prepares the structure and instrumentation to investigate the inlet distortion and effects of steam ingestion on a transonic axial compressor. A compressor test facility, including mechanical equipment, data acquisition system, and remote digital control system, was configured to test a transonic compressor rotor, similar to what will be used in the Joint Strike Fighter. Rotor inlet and exit velocity profiles were measured with a three-hole probe to obtain a set of baseline data before future experiments.

This thesis analyzes performance of the vision-based target-tracking system developed at the Naval Postgraduate School using the Monte Carlo method. Specifically, sensitivities of the target position estimation algorithm to various sensor errors are computed and analyzed. Furthermore, dependence of this algorithm on the performance of the target-tracking control system is established.

E) requirements for the lead ship of each new construction shock-hardened ship class. While those trials are necessary in order to evaluate the vunerability and survivability of the ship, they are very expensive, require extensive time for planing and coordination, and pose serious danger to the crew, ship and marine environment. Thus, computer modeling of the ship structure, surrounding fluid, and virtual shock environment by utilizing finite element method offers a valuable design tool and an alternative to these tests. This thesis investigates the response of a catamaran-hull ship subjected to an underwater explosion by creating a virtual UNDEX environment based on the modeling and simulation methodology established by the Shock and Vibration Computational Laboratory at the Naval Postgraduate School (NPS). In previous works, all of the structural models were monohull ships and there have been concerns about the feasibility of creating the coupled fluid and catamaran-hull model. This thesis studies the effect of an additional hull and gap between two hulls on the dynamic response of the ship as well as the effect of the charge location.

Birds are very graceful creatures that fly effortless through the air. Many of their maneuvers and capabilities are unmatched by current man-made airplane technology. To investigate the fundamental unsteady fluid dynamics and force production of the flapping wings of birds, two types of idealized wing motions with combined linear translation and pitching were considered in a two-dimensional context, one for characteristic pitching and the other for perch landing. Two validation cases were first carried out to verify the model and assess accuracy of the COMSOL Multiphysics software package. After successful verification, the pitch rate in each type of wing motion was systematically varied. The force production, pressure distribution, velocity field, and vorticity field were examined in detail in each case. For the pitching-only motion, as the pitch rate goes from the slowest (K=1/64) to the fastest (K=1/2), the peak lift increases by about four times; while for the perching maneuver, the peak lift increases about ten times. Associated with the force enhancement are significantly improved stability of the boundary layer on the dorsal side of the wing and delay of flow separation. In actual bird flight, such great force enhancement could be critical for the animals to perform highly controlled maneuvers. The present study thus confirms the significant role of pitch rotation in the unsteady aerodynamics of flapping wings.

Otology and neurotology are surgical specialties focusing on the treatment of ear diseases. A key component of many otologic and neurotologic surgical procedures is the removal of a portion of the skull behind the ear to gain access to subsurface anatomy. This process, called a mastoidectomy, is performed manually with a high speed surgical drill. Many vital structures, including nerves and blood vessels, are embedded within the temporal bone near the region of bone that must be removed, which makes the procedure difficult, time consuming, and in some cases, overly invasive. Image-guided and robotic systems have the potential to improve otologic procedures using medical imaging to guide their interventions, enabling patient-specific treatments that reduce invasiveness and save valuable operating room time. However, since damage to the complex vital structures within the surgical field could result in severe consequences to the patient, any image-guided or robotic surgical system must be extremely safe and accurate. These requirements, along with the small surgical workspace and difficulty integrating systems into the current clinical workflow, have limited the adoption of such systems in otologic surgery to date. This dissertation presents the design, experimentation, and analyses of image-guided, robotic systems under development for otologic surgery in an effort to bring these systems closer to clinical realization. The specific goals of the work are to better understand the technical requirements of various otologic surgical procedures, to improve the safety and efficiency of image-guided and robotic surgery by incorporating system modeling and medical image data into the surgical planning process, and to show feasibility and provide insights into practical issues through experimentation. Two image-guided otologic procedures are explored in this work: (1) robotic mastoidectomy and (2) minimally invasive cochlear implantation. The technical requirements of robotic mastoidectomy are first explored to determine the necessary robot workspace and the required milling forces. Using these design requirements, a bone-attached robotic system is developed and tested in temporal bone specimens and fresh human cadaver heads. Next, planning algorithms to improve the safety and efficiency of robotic mastoidectomy are described. A method for building patient-specific safety margins around vital anatomy based on probabilistic error models of the robotic system, required safety rates, and simulations of the surgery is provided. A second planning algorithm is presented, which improves robot trajectory generation for milling porous bone in close proximity to vital anatomy by using CT image-based force modeling to optimize tool orientation and velocity. The focus then shifts to minimally invasive, image-guided cochlear implantation. Two key safety issues are investigated: the positional accuracy of drilling a narrow tunnel towards the cochlea for electrode insertion and the heat rise near vital nerves during drilling. A method for pre-operative, patient-specific risk assessment utilizing the CT scan, modeling of the bone drilling process, and anatomical conditions is presented, followed by an improved surgical drilling approach. Finally, an experimental setup enabling direct temperature measurement of the bone near the facial nerve in cadavers is developed and used to validate the modeling and surgical approach.

<p>This dissertation documents the results of a theoretical and numerical study of time dependent storage of energy by melting a phase change material. The heating is provided along invading lines, which change from single-line invasion to tree-shaped invasion. Chapter 2 identifies the special design feature of distributing energy storage in time-dependent fashion on a territory, when the energy flows by fluid flow from a concentrated source to points (users) distributed equidistantly on the area. The challenge in this chapter is to determine the architecture of distributed energy storage. The chief conclusion is that the finite amount of storage material should be distributed proportionally with the distribution of the flow rate of heating agent arriving on the area. The total time needed by the source stream to ‘invade’ the area is cumulative (the sum of the storage times required at each storage site), and depends on the energy distribution paths and the sequence in which the users are served by the source stream. Chapter 3 shows theoretically that the melting process consists of two phases: “invasion” thermal diffusion along the invading line, which is followed by “consolidation” as heat diffuses perpendicularly to the invading line. This chapter also reports the duration of both phases and the evolution of the melt layer around the invading line during the two-dimensional and three-dimensional invasion. It also shows that the amount of melted material increases in time according to a curve shaped as an S. These theoretical predictions are validated by means of numerical simulations in chapter 4. This chapter also shows that the heat transfer rate density increases (i.e., the S curve becomes steeper) as the complexity and number of degrees of freedom of the structure are increased, in accord with the constructal law. The optimal geometric features of the tree structure are detailed in this chapter. Chapter 5 documents a numerical study of time-dependent melting where the heat transfer is convection dominated, unlike in chapter 3 and 4 where the melting is ruled by pure conduction. In accord with constructal design, the search is for effective heat-flow architectures. The volume-constrained improvement of the designs for heat flow begins with assuming the simplest structure, where a single line serves as heat source. Next, the heat source is endowed with freedom to change its shape as it grows. The objective of the numerical simulations is to discover the geometric features that lead to the fastest melting process. The results show that the heat transfer rate density increases as the complexity and number of degrees of freedom of the structure are increased. Furthermore, the angles between heat invasion lines have a minor effect on the global performance compared to other degrees of freedom: number of branching levels, stem length, and branch lengths. The effect of natural convection in the melt zone is documented.</p> / Dissertation

The overall objective of this work is to develop a computational fluid-structure interaction (FSI) model of vocal fold vibration for its future applications in clinical care of voice disorders. One example of such applications is computer model based planning for implant insertion in medialization thyroplasty, i.e., a surgical procedure designed to restore voice for patients with unilateral vocal fold paralysis. <p> We have investigated several fundamental and practical issues involved in the accurate and efficient modeling of the vocal fold dynamics, three-dimensional (3D) flow simulations, and the development as well as validation of patient-specific FSI models. <p> We first studied the significant role of nonlinear strains in the vocal fold vibration using a simple two-dimensional (2D) vocal fold model. Then, we combined an in vivo experimental study using rabbit subjects with 3D FSI modeling to develop an advanced subject-specific model. This model incorporates the anatomical geometry obtained from micro-magnetic resonance imaging of the larynx and also the 3D simulation of both flow and tissue deformation; furthermore, a reduced-order FSI model with simplified flow was developed to identify the unknown elastic properties of the tissue. As a result, the overall model was able to capture the individual-specific characteristics of vocal fold vibration. Finally, application and limitation of the reduced-order FSI model were further studied using a simple vocal fold model.

Turbulent combustion, as seen in practical combustors, is highly complex and beyond current numerical means to accurately simulate. Simplifying assumptions commonly used in computational models approximate the complexity of small scale reaction and mixing to reduce computational cost, but these estimates cost accuracy. It is a necessity to understand fundamental aspects of combustion and what approximations do not sacrifice accuracy while reducing computational expenses. The study of laminar flames allows full simulation of chemical kinetics and transport, and evaluation of combustion phenomena. The experimental work to follow presents characterization of partially premixed tubular flames containing premixed hydrogen-air streams imposed on fuels diluted by carbon dioxide. The tubular flame structures are novel, containing distinct zones of premixed and diffusion flames. Flames have resemblance to turbulent flames, - local extinction zones, varying curvature, and zones of enhancement, - while existing in a steady-state and allowing detailed laser diagnostics of flame structure. Due to the novelty of partially premixed tubular flames, the objectives of the research to follow are: 1) parametrically survey and analyze stable flame geometry via chemiluminescence and 2) perform non-intrusive Raman spectroscopy on select cases to develop a fundamental understanding of flame composition as a foundation for numerical comparison and validation.

<p> The demand for miniature devices has increased the application of hydroforming process in various micro-scale applications. This research ascertain the material properties of 0.2 mm thick AISI 304 stainless steel using hydraulic bulge test, and it also analyze the surface characteristics of the same material. The work pieces for this work consist of circular and elliptical work pieces. The circular work pieces were formed using dies of cavity diameters 5 mm and 11 mm, while the elliptical work pieces were formed using elliptical cavity dies with aspect ratio of 0.5, 0.8, and 0.67. Analytical methods proposed by Chakrabarty, Ekineev-Kruglov, Jovane, and Marciniak for the determination of the flow curve of sheet metal were compared to the experimental result. The outcome indicates that the Ekineev - Kruglov method has the best correlation with the experiment. An improved approach of the Banabic method was developed for the elliptical workpieces, and the results showed shows considerable improvement on the method. Surface characteristics of the 5 mm and 11 mm die work pieces were tested using the atomic force microscope; the outcome demonstrates that most of the surface parameters exhibit a linear relation with the strain. The roughness increase with increasing strain.</p>

<p> When tracking a target, a crane must move from its initial position to the target area. This point-to-point move results in residual vibration due to the dynamics of the system. Once tracking is initiated, it is possible that the vibration caused by the initial move is amplified by the tracking input. This thesis focuses on the tracking of an Autonomous Surface Vehicle by blending of these two phases in order to increase tracking accuracy. Fuzzy Logic Control (FLC) is employed to blend an Input Shaper and Zero Phase Error Tracking Controller (ZPETC) together. The FLC is comprised of membership functions based on position and velocity error that is mapped to a gain. This gain determines whether or not tracking should be used based on the error. Using this control scheme, tracking is improved.</p>