<p> Numerical simulations of waterjet inlets have been conducted in order to understand inlet performance during ship turning maneuvers. During turning maneuvers waterjet systems may experience low efficiency, cavitation, vibration, and noise. This study found that during turns less energy arrived at the waterjet pump relative to operating straight ahead, and that the flow field at the entrance of the waterjet pump exhibited a region of both low pressure and low axial velocity. The primary reason for the change in pump inflow uniformity is due to a streamwise vortex. In oblique inflow the hull boundary layer separates when entering the inlet and wraps up forming the streamwise vortex. These changes in pump inflow during turning maneuvers will result in increased unsteady loading of the pump rotor and early onset of pump rotor cavitation.</p><p> Simulations covered drift angles from 0&deg; to 30&deg;, pump velocities relative to free stream speed of 0.6 to 1.0 for inlet geometries with ramp angles of 25&deg; and 30&deg; with inlet-hull fairing radii relative to pump diameter of 0.1 to 0.2. The following observations were made: 1) the onset of the streamwise vortex occurred between drift angles of 5&deg; and 10&deg;; 2) increasing drift angle increased the strength of the streamwise vortex and lowered the energy of the flow entering the pump; 3) increasing the flow rate through the waterjet system increased the strength of the streamwise vortex; 4) increasing ramp angle tended to increase the strength of the streamwise vortex; and 5) increasing the fillet radius decreases the strength of the streamwise vortex.</p><p> Simulations of steady ahead operation of the waterjet propelled <i> R.V. Athena</i> were also conducted for Froude numbers of 0.34 to 0.84. From these simulations it was found that the pump inflow can be effectively approximated at a new ship speed from a known ship speed by scaling only the mean component of the axial velocity by the relative change in waterjet flow rate. Additionally, waterjet pump operating point and rotor blade inflow angles were found to independent of ship speed.</p>

<p> In the aspect of electric-ship grounding, the time-domain behavior of the ship hull is needed. The grounding scheme impacts the nature of voltage transients during switching events and faults, identifiability and locatability of ground faults, fault current levels, and power quality. Due to the large size of ships compared with the wavelengths of the desired signals, time-domain measurement or simulation is a time-consuming process. Therefore, it is preferred that the behavior be studied in the frequency-domain. In the frequency-domain one can break down the whole ship hull into small blocks and find the frequency behavior of each block (scattering parameters) in a short time and then con- nect these blocks and find the whole ship hull scattering parameters. Then these scattering parameters should be transferred to the time-domain. The problem with this process is that the measured frequency-domain data (or the simulated data) is band-limited so, while calculating time-domain solutions, due to missing DC and low frequency content the time-domain response encounters causality, passivity and time-delay problems. Despite availability of several software and simulation packets that convert frequency-domain information to time-domain, all are known to suffer from the above mentioned problems. This dissertation provides a solution for computing the Time-Domain Impulse-Response for a system by using its measured or simulated scattering parameters. In this regard, a novel wavelet computational approach is introduced.</p>

<p> The Systems Engineering community spends considerable effort developing system specifications during the design phase. Yet during the operational and support phase, there is a potential degradation of those specifications in the form of delayed, missed, or insufficient maintenance (i.e., maintenance that does not restore the system to the design specifications), which are commonly called departures (e.g., Structure/Weld Joint - Incorrect Electrode Usage, Valve Timing, etc.). While the impact of each departure on the system is reviewed as part of the current approval process, there is no evaluation to the equipment and/or personnel from the accumulated number of departures. </p><p> The impact of these accumulated departures is analyzed to determine if there is a correlation between these accumulated departures and casualties to equipment (documented on casualty reports that impact system availability and operational readiness) and/or mishaps to document a safety event and/or damage to property. The analysis required the development of a framework to systematically store and catalog U.S. Navy data on a select set of hulls from 2004 to 2016 specifically addressing data on 6,810 departures, 4,808 casualty reports, and 6 mishaps. A series of analyses were conducted to include (1) ensuring the hulls met the criteria of in-service (i.e., operational ready for deployment), (2) test for trends together as a class followed by this same analysis on a per hull basis, which helped define the correct correlation method, (3) Spearman&rsquo;s rank-order correlation analyses as a class followed by this same analysis on a per hull basis and (4) regression analysis to determine if departures could be used to predict future casualties. The correlations and regression results suggested meaningful, statistically significant at the 0.01 level, for a majority of the relationships between the accumulated number of departures determined at the class level and for each individual hull. The framework and process that is described in this paper can be used to track and influence the number of casualty reports that are predicted to occur by controlling the number of accumulated departure from specifications. There also was no correlation determined between the accumulated departures from specifications and subsequent Mishaps and thus there was no regression analysis conducted.</p><p>

No description available.

<p> The United States Coast Guard does not adequately perform a Level of Repair Analysis and Business Case Analysis to align vessel maintenance requirements with available resources during the development of an Integrated Logistics Life Cycle Plan (ILSP) which leads to increased vessel sustainment costs and reduced workforce proficiency. The ILSP&rsquo;s maintenance philosophy dictates the designed supportability and maintainability of a vessel throughout its life cycle yet existing ILSPs fail to prescribe the required balance of Coast Guard (internal employees) and non-Coast Guard (contracted) technicians for the execution of hull, mechanical, and electrical depot maintenance. This research develops a standard model to enhance the balance of maintenance resources using a Business Case Analysis (BCA) extension of a Level of Repair Analysis (LORA) informed by Activity-Based Costing Management (ABC/M) theory. These analyses are integral to a complete Life Cycle Cost Analysis (LCCA) and will contain a simplified LORA framework that provides an analysis of alternatives, a decision analysis, and a sensitivity analysis for the development of a maintenance philosophy. This repeatable analysis can be used by engineering managers to develop and sustain cost-effective maintenance plans through all phases of a vessel&rsquo;s life cycle (acquisition, sustainment, and disposal).</p><p>

<p> Increased activity at ports is an indication of economic development and growth; however, it also puts public health, regional air quality and global climate at risk because the exhaust from the marine diesel engines is not subjected to the stringent regulations as on-road engines. This dissertation characterizes the effectiveness of strategies and technologies to mitigate criteria pollutants and the long-lived greenhouse gas, carbon dioxide (CO₂) from marine diesel engines. The dissertation also provides insight into the current state-of-art of gaseous and particulate matter portable emission measurement system (PEMS). Results from a project show how to determine the measurement allowance for PEMS in order to provide accurate measurements for the development of emission inventories and subsequently, air pollution mitigating regulations. </p><p> In-use gaseous emissions from the two main engines were measured at sea for the first time in order to evaluate the performance of a Code of Federal Regulations (CFR) compliant PEMS against instruments meeting the simplified measurement method (SMM) complaint with International Maritime Organization (IMO). </p><p> For the first time, emissions were measured from a modern container vessel with newest engine technologies. The vessel was operated on marine gas oil, a cleaner fuel, in regulated waters and on heavy fuel oil in unregulated waters. Impact of cleaner fuel and newest technologies on the engine was assessed. A simple equation was developed to estimate time required to completely switch fuels which can be used by vessel owners to comply with regional/international fuel regulations. </p><p> Vessel speed reduction (VSR), which is a worldwide acceptable strategy for ocean-going vessels (OGVs), was evaluated. The study showed that putting a speed limit on a container OGVs as they sail near ports and coastlines could cut emissions of air pollutants by up to 70%. This study also found that by reducing the vessel speed by a mere 3-6 knots from cruise speed will result in significant reductions of criteria pollutants and carbon dioxide. </p><p> Towards the goal of reducing emissions and dependency on fossil fuels, this dissertation explores benefits of consuming hydrotreated algae biofuel in small marine diesel engines for the first time. Significant particulate matter (PM2.5) and nitrogen oxides (NOx) benefits were reported with slight improve in fuel economy when fuel was switched from ultra low sulfur diesel (ULSD) to 50:50 blend of ULSD and algae fuels. </p><p> The dissertation investigates the benefits associated with the hybridization of the tugboat. A conventional tugboat was retrofitted with one auxiliary engine, shaft generators, addition of lithium polymer batteries and an energy management system. Up to 30% reduction in NO_x, PM_2.5 and CO₂ was found. The energy management system in the hybrid tugboat allows the use of the auxiliary engine for propulsion as opposed to the only main engines during transit mode, thus leading to the significant reductions. </p><p> Another section of this dissertation provides an evaluation of latest PM-PEMS under different environmental and in-use conditions and features performance, accuracy and precision of PM-PEMS compared to the gravimetric reference method. The research from this study shows current PM-PEMS typically underreport the PM emissions compared to the reference method, with the exception of PEMS with photo-acoustic technology which incorporated a gravimetric filter. All PM-PEMS under evaluation performed poorly when encountered with sulfate laden PM during diesel particulate filter (DPF) regeneration.</p>

<p> Noise generated by flow over rough surfaces is an important issue in naval applications and in aeronautical engineering. This work numerically investigates roughness-induced noise from low-Mach-number turbulent boundary layers. The computational approach is based on Lighthill's acoustic analogy with acoustic sources obtained from large-eddy simulation. An acoustic formulation is derived, which shows that each roughness element acts as an individual in-plane dipole source strengthened by its image in the wall. Flow configurations investigated include boundary-layer flows over a single hemispherical roughness element, a pair of streamwisely aligned hemispherical elements and three roughness fetches consisting of 10 &times; 4 hemispherical, cuboidal and cylindrical roughness elements, respectively.</p><p> Results for a single hemispherical roughness element and a pair of hemispherical elements show that the spanwise dipole, which has been overlooked before, is of larger or similar strength compared to the streamwise dipole. The viscous contribution to the dipoles is negligible compared to the pressure contribution. The main sound sources arise from the impingement of incoming turbulence and the unsteady horse-shoe vortices generated around the element. The roughness-induced unsteady wake motions are unimportant as a source of self noise. However, they significantly enhance sound radiation from a downstream hemisphere.</p><p> The effects of multi-element interactions and the roughness shape are investigated with arrays of 10 &times; 4 sparsely distributed hemispheres, cuboids and short cylinders. The dipole strength, orientation and spatial distribution show strong dependence on the roughness shape. Correlations between dipole sources associated with neighboring elements are found to be small for these sparsely distributed roughness arrays. Correlations and coherence between roughness dipoles and surface pressure fluctuations are analyzed, which reveals the importance of the impingement of upstream turbulence and surrounding vortical structures to dipole sound radiation, especially in the streamwise direction. For roughness shapes with sharp frontal edges, the edge-induced unsteady separation and reattachment also play important roles in sound generation. Large-scale turbulent structures in the boundary layer have a relatively low influence on roughness dipoles, except for the first row of elements.</p>

The customer service within the United States Coast Guard Naval Engineering department has increased significantly in the past decade. Many areas of the naval engineering departments have adopted a customer service policy in part or in whole. However, the naval engineering community is persistently working to reduce costs and operational liabilities generated through their support practices. Financial and operational liabilities have also grown in the past decade, and the United States Coast Guard Naval Engineering department has failed to aggressively address this issue until recently. This leaves naval engineering communities who use their own version of customer service policies to adopt a standard that is compliant toward the Coast Guard’s Naval Engineering force management goals. This paper looks at the history of Coast Guard Naval Engineering customer service issues, how the engineering community has managed the issues in the past and how improvements can be made. / text

abstract: An optimal energy scheduling procedure is essential in an isolated environment such as naval submarines. Conventional naval submarines include diesel-electric propulsion systems, which utilize diesel generators along with batteries and fuel cells. Submarines can charge the batteries by running diesel-electric generators only at the surface or at snorkeling depth. This is the most dangerous time for submarines to be detectable by acoustic and non-acoustic sensors of enemy assets. Optimizing the energy resources while reducing the need for snorkeling is the main factor to enhance underwater endurance. This thesis introduces an energy management system (EMS) as a supervisory tool for the officers onboard to plan energy schedules in order to complete various missions. The EMS for a 4,000-ton class conventional submarine is developed to minimize snorkeling and satisfy various conditions of practically designed missions by optimizing the energy resources, such as Lithium-ion batteries, Proton-exchange membrane fuel cells, and diesel-electric generators. Eventually, the optimized energy schedules with the minimum snorkeling hours are produced for five mission scenarios. More importantly, this EMS performs deterministic and stochastic operational scheduling processes to provide secured optimal schedules which contains outages in the power generation and storage systems. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2020

No description available.