Trident Scholar Abstracts 2010

            The purpose of this project is to explore several current technologies that can be used to increase the efficiency of small diesel engines for the use in small unmanned aerial vehicles. The specific technologies investigated in this study will be common-rail direct-injection, thermal barrier coatings, and reduction in compression ratio. It is anticipated that these technologies will work together to increase the overall efficiency of a Yanmar L48V diesel engine. Preliminary calculations have shown that due to reduced thermal losses, thermal barrier coatings will not only increase the efficiency of the engine, but will also allow for the investigation of how a reduction in compression ratio on small diesel engines affects their efficiency.

            Reducing the compression ratio of small diesel engines has never fully been explored; however, there is limited data gathered from large, multi-cylinder engines that indicates engine efficiency can be improved using this technique. According to this data, a peak in efficiency occurs at a compression ratio of approximately 16:1. The Yanmar engine will have its compression ratio progressively stepped down from its current value of 20.6:1 to 16:1 in an attempt to validate the hypothesis that efficiency peaks at this lower compression ratio.

            The final part of this study is to incorporate a common-rail fuel injection system onto the Yanmar engine. Common-rail direct-injection is believed to boost the efficiency of the engine due to its high pressure present at its injection nozzles which causes a finer, more efficiently burned spray. Making a finer spray is not the only benefit of the common-rail system. Unlike standard mechanical injection systems that inject fuel at fixed times and apply the entire shot of fuel at once, modern common-rail systems store high pressure fuel in a reservoir that can be injected at times determined by a computer controlled system.

            With all three separate technologies showing potential for an increase in efficiency, the study takes the quest for greater efficiency one step further and investigates how these technologies can work together to increase efficiency even more notably in a small diesel engine.

            With the introduction of the Marshall Plan, policy makers attempted to stimulate post-conflict economic development through the introduction of foreign aid. As time has passed, foreign aid has evolved into a means of humanitarian and development assistance. Nonetheless, post-conflict aid is still of paramount importance to most foreign donors as evidenced by the conclusion of the Cold War, by the myriads of conflicts across the continent of Africa, and most recently by the wars in Iraq and Afghanistan. As nations continue to commit post-conflict aid through both economic and military means, it is important to understand the implications of aid in the post-conflict context. This paper considers the efficacy of aid following the termination of a conflict. By combining elements of conflict models with economic growth models, the research attempts to determine the conditions which inhibit and promote growth. The model considers how different characteristics of conflict zones and the interaction of different types of aid assist in the development process, Using a data set that consists of all acts of political violence from the conclusion of World War II to 2008, the model is empirically tested and then solved using least squares approximation method. The model offers insight into the impact of aid policies in post-conflict situations. The research both assesses the way in which aid is spent and the characteristics of the recipient nation as they apply to economic development. The model provides justification for the inefficacy of some aid programs and the efficacy of others. Finally, using welfare analysis, the researcher determines the optimal aid policy in the post-conflict world. The research offers policy-makers recommendations on future ventures into post-conflict reconstruction and guidance as to the implications of different policy.

            The goal of this project is to measure the production of KS0, Λ, and anti-Λ particles in 19.6 GeV Collisions at RHIC. The research will be presented at the American Physical Society Conference in February 2010 and the Fourteenth International Conference on Strangeness in Quark Matter in September 2009. The measurements in this research will lead to a better understanding of the nuclear matter phase diagram and represent a first step in the search for a nuclear critical point.

            At Brookhaven National Laboratory, the STAR Experiment exists to study Ultra-Relativistic Heavy Ion Collisions, utilizing the relativistic heavy ion collider, RHIC. The experiment is relativistic because we are studying collisions between ions that have been accelerated to nearly the speed of light. It is described as heavy because we use Gold nuclei, which are high in atomic number, for the collisions. It is ionic because the gold has been stripped of all of its electrons before the collision.

            We will use data from collisions that occurred at 19 GeV, meaning the center of mass energy of the collision is 19 GeV. This is a lower energy than much of today’s research is performed at, serving as a first step in the search for the nuclear critical point. From the raw data we will get transverse momentum spectra and yields for KS0, Λ, and anti-Λ’s. We will utilize these spectra to determine the particle to anti particle ratio for Λs as the ratios are important for understanding the amount of strange quarks produced in these collisions.

FACULTY ADVISOR
Assistant Professor Richard Witt
Physics Department

   
Luke P. Finney
Midshipman First Class
United States Navy

An Investigation of Cavity Flow Effects on Store Separation Trajectories

            In recent years, the capability of computational fluid dynamics (CFD) to predict the trajectories of stores falling from an aircraft has greatly expanded. Recently there has been an increased use of internal bays, especially at transonic speeds. However, using CFD to accurately predict the aerodynamic forces in this configuration is both time consuming and problematic. A shear layer exists at the edge of the bay and at transonic speeds the behavior of this shear layer can be unsteady. The flow in the cavity is unsteady as well, but at a much lower velocity. The combined effect has the potential to make the store trajectories unrepeatable; an unacceptable condition for the purposes of providing a flight clearance for a particular configuration. One solution proposed would be to perform a parametric analysis of the release using a time-accurate CFD code but the computational resources required of this approach still make it impossible, even using the best computers available.

            In this study, a cavity previously used as part of the Navy Internal Cavity Study (NICS) will be used in conjunction with the Mark 82 (500 lb class) stores to compare wind tunnel data to CFD results for an internal bay/store configuration. The forces will be calculated along the horizontal traverse of the bay at different depths using flow solvers of increasing complexity in order to better understand the nature of the shear layer. The CFD results will be compared with existing wind tunnel data on the same configurations in order to judge the efficacy of using Euler and Navier-Stokes flow solvers to provide mean force data for the store. If obtainable, time-accurate flow solutions will be used to provide bounds on the unsteady nature of the flow.

            The results of the CFD solutions will serve as input to the Navy Generalized Separation Package (NAVSEP), which combine the aerodynamic forces and moments with ejector and gravitational forces along with the restricted motion properties of the store in order to predict the trajectory of the store after release. The store mass properties will be varied as will the ejector force profiles for the range of aerodynamic forces predicted by the CFD. The family of resulting trajectories will be used to draw conclusions as to the extent to which the unsteady nature of the cavity flow can be expected to adversely affect the trajectory of the store.

            This project is an investigation into the miniaturization of a novel heat transfer enhancement technique that could significantly increase the effectiveness of micro-scale internal flow convective heat transfer. The designs of modern high performance electronic systems, which are often constrained by the large amounts of heat generated, require such advances in the field of heat transfer. The enhancement technique under investigation has been demonstrated effective on conventional scales, yet the increasing demand for localized high heat flux removal motivates its miniaturization. In order to enhance the effectiveness of heat transfer, nanometer-sized magnetically susceptible particles are suspended in a base fluid, and are acted on by alternating external magnetic fields. These external magnetic fields cause the particles to be attracted to, then released from the heat transfer surface. The secondary flows induced by the oscillating motion of these particles, as well as the transfer of thermal energy from the heat transfer surface to the particles themselves, serve as the mechanism of heat transfer enhancement. The enhanced heat transfer effectiveness is quantified by measuring and comparing the coefficient of convective heat transfer between enhanced and non-enhanced trials. The heat transfer fluid is pumped through a stainless steel test section heated under conditions of uniform heat flux. An infrared camera measures the surface temperature of the entire test section. Thermocouples and a differential pressure transducer provide fluid properties data at the inlet and exit of the test section. These measurements provide the data necessary to determine the coefficient of heat transfer. In order to optimize the efficacy of this enhancement technique, several parameters will be varied during experimentation. To determine the effects of scale and flow rate, the enhancement technique will be evaluated on test sections of 1.1 mm, 250 micron and 100 micron hydraulic diameter, and at Reynolds numbers of 100, 340, and 800. Additionally, experimental trials will be conducted utilizing three different particle concentrations and the magnetic parameters of field strength and activation frequency will be optimized. This parametric study will provide insight into the enhancement mechanisms and their optimization.

            The goal of this project is to develop an approach for creating a boundary layer on a ship model that is more closely representative to the actual boundary layer for the ship. Flow within a ship’s boundary layer is virtually all turbulent for the entire length of the ship. For a model’s boundary layer, the flow within the layer can range from completely laminar, to intermittently laminar or turbulent, or fully turbulent. In order to accurately record results from test conducted on a model, the boundary layer of the ship and the model must be “similar”. Currently, the solution to creating similar boundary layers is left up to the experience and scientific justification of the individual Naval Architect or towing tank facility. This project will use analytical predictions and experimental data to develop a set of guidelines to provide a rational approach to replicating a ship’s boundary layer through the use of turbulence stimulation. During the course of this project, the primary focus will be on factors that affect boundary layer flow and transition and how these factors can be used for determining the optimum location turbulence stimulation. A series of tests will be performed on first a flat plate, then a 2-D model, and lastly on a model of the USS Constitution. These tests will consist of using hot film sensors to provide a graphical representation of the flow within the model’s boundary layer. These representations will then be analyzed to determine the most effective means to create a similar model boundary layer. The results obtained will shed light on the current problem of turbulence stimulation. The solution to this problem will help to increase the efficiency and cost of ship design and ship-model testing.

            Current civilian and military power distribution applications are increasingly turning to the utilization of DC power transmission as a high efficiency alternative to traditional AC distribution schemes. A central factor which dominates the performance characteristics of these schemes is the implementation of power converters, which are necessary to modulate voltage and current waveforms within the grid. The dominant form of converter in use in DC distribution applications today is known as the Switched Mode Power Converter (SMPC), which utilizes high frequency semiconductor switches and magnetic components to modulate power. Traditionally, these devices have been constructed using Silicon (Si) and ferrite materials. However, given the increased power and efficiency demands of modern DC distribution design requirements, these materials have reached their upper physical limitations of performance, and undesired trade-offs must made between efficiency, power density and power-throughput to accomplish design goals. This project intends to research two alternative materials for the construction of these components and the benefits which they offer to SMPC design. Silicon Carbide (SiC) and nanocrystalline-structured alloys are currently being researched to supplant Si and ferrite, respectively, within semiconductor switches and magnetic components in SMPCs. The material properties of SiC and nanocrystalline-structured alloys promise to increase efficiency and maximum power throughput while maximizing power density within SMPCs. This project will design SMPCs using a circuit configuration known as a Full-Bridge topology, chosen specifically for its optimal performance characteristics and pertinent naval applications. These converters will be used to study the effects of components using SiC and nanocrystalline alloys upon the design space. Two converters will be built, one as a control converter for comparison utilizing traditional Si components known as Metal Oxide Field Effect Transistors (MOSFETs) and a ferrite transformer core and a second implementing SiC MOSFETs and a nanocrystalline-structured alloy transformer core. Each converter will be evaluated upon the metrics of efficiency, power density and thermal performance for a range of power-throughput levels. The design space will be characterized for each converter using these metrics. It is expected that SiC and nanocrystalline will significantly improve the converter design space, expanding it into regions which were previously unobtainable utilizing Si MOSFETs and ferrite cores without significant trade-offs between the performance parameters under evaluation.

            The Directed Energy Weapons Program at the Office of Naval Research (ONR) is a potential “game changer” of modern naval warfare that will dramatically increase U.S. capability while decreasing the risk of collateral damage. Beam control is one of the five main fields of study in this program and is essential for the development and operation of a directed energy weapon system, especially when operating in the air or on the sea in a combat maritime environment. Directed energy beams are highly susceptible to jitter, the deviation of a light beam from its intended path due to platform induced vibrations and atmospheric effects. The United States Naval Academy (USNA) has developed the Directed Energy Beam Control Laboratory which will be used in this research project to study the correction of jitter in an optical beam. In order to correct jitter caused by mechanical vibrations without feedback from the target, the exact position and orientation of the platform must be determined in real time. The position will be resolved to micrometer precision and the orientation to microradian levels in a time step of 500 microseconds or less. It will be measured by optical sensors and/or accelerometers. The primary objective will be to develop the necessary algorithms and sensor placements that are suitable for predicting the platform induced error in the directed energy beam in real time. This research project will measure the accuracy of the error prediction and how quickly the computer is able to implement these algorithms. Eventually, this error prediction could allow for correction of platform induced jitter without feedback from the target. Knowing this error in real time will improve the aimpoint maintenance on the target and significantly reduce the power required for a directed energy weapon system.

            Optical beam pointing is quickly becoming a topic of importance in areas ranging from laser communications to space applications. One of the main operational concerns with optical beam pointing is the effect of small vibratory motion, defined as jitter. Understanding jitter is important for minimizing the effect it has upon a directed energy beam’s intensity at its target. In this project, Lagrange’s equations of motion are derived for a viscoelastic, point supported plate containing discrete masses, which is representative of an optical platform. The mechanical response of the optical platform is sought for both impact loading and the response imparted by two inertial actuators. A solution of these equations will contain information pertaining to the plate’s amplitude and frequency, analyzed in both time and frequency domains, which together, computes the effect of jitter on the intensity of a directed energy beam at the target. Furthermore, this computed information allows for the use of an optimization approach. By optimizing the placement of the discrete masses on the optical platform, with the goal of minimizing its amplitude, jitter will also be effectively minimized as well. The result of this project’s research is a crucial part of the ongoing research and development of a directed energy weapon currently funded by the Office of Naval Research.

            Radiation can cause the information stored on a digital memory cell to change. As a consequence, these memory cells have the potential to serve as radiation detectors. Since commercially available memory chips are designed to minimize radiation influence, the chips must be modified in order to increase their sensitivity to neutrons. This is accomplished by increasing the probability that an incident neutron will cause a change in the digital information stored on the chip indicating the presence of radiation. The objective of this project is to evaluate both unmodified and modified memory chips for sensitivity to neutrons, comparing them to conventional detection systems, in an effort to establish their potential for general scientific use.

            As part of this project, seven detection systems will be evaluated. This includes four non-powered detectors, namely thermoluminescent dosimeters, foil activation detectors, bubble detectors, and track-etch devices. In addition, a powered 3He proportional counter will be tested. These five conventional detectors will serve as points of comparison for unmodified and modified 4Mb Honeywell memory cells. Each detection system will be exposed to three neutron sources for three variable lengths of time per source. Based on the data obtained from these experiments, statistical analysis will be performed in order to establish each detector’s sensitivity, including a confidence interval and the minimum and maximum sensitivity.

            It is expected that the unmodified memory chip will be fairly insensitive to neutrons at the incident energies available for study. The modified chips, however, are expected to outperform all of the other detection systems. If successful, this project will establish the fact that sensitivity-enhanced memory chips can be used as ultra-sensitive, ultra-low-powered neutron detectors. Memory cell based detection system have the potential to improve existing technologies and enable important new applications—especially use as a system of Nuclear-WMD monitors for cargo containers, capable of detecting the presence of SNM, localizing the cargo container, and communicating the information via satellite.