• Numerical Simulation Of Single Phase And Boiling Microjet Impingement

      Ragunathan, Srivathsan (2008)
      This work presents results from the numerical simulation of single phase and boiling microjets primarily for high density electronics cooling. For the single phase microjets, numerical simulation results for the flow fields and heat transfer characteristics in a laminar, confined microjet (76 mum in diameter) impingement arrangement are presented. The parameters varied included the jet Reynolds Number, the fluid Prandtl Number and the ratio of the nozzle-to-plate distance to the jet diameter. Primary and secondary recirculation zones were observed in the stagnation region and the radial outflow region which had a significant impact on the local Nusselt Number distribution on the heated surface. The location and the displacement of the primary and secondary recirculation zones are of particular importance and are associated with secondary peaks in the Nusselt Number similar to those observed for turbulent jet impingement in larger conventional jets. Numerical simulation results are presented for boiling microjet impingement in a confined arrangement. The Rensselaer Polytechnic Institute (RPI) model was modified for laminar flow boiling for simulating these types of flows. The model primarily proposes three different heat transfer components, the single phase heat transfer, the quenching heat transfer and the evaporative heat transfer. The model was first validated with experimental results from the literature and then extended to study the effects of liquid subcooling, microjet Reynolds Number based on the nozzle inlet, and heat flux levels. The simulation results were in good agreement with results from comparable experiments in the literature. The average wall temperature increases as the applied wall heat flux is increased. The slopes of the temperature curves in the radial direction flatten out at higher heat fluxes and lower levels of subcooling indicating the effectiveness of boiling heat transfer. For the cases considered in this study, the single phase heat transfer component dominates the other two modes of heat transfer The liquid velocity profile has a considerable impact on the vapor bubble nucleation, vapor drag and the bubble departure diameter. Lower levels of subcooling are associated with boiling inception and more vigorous boiling in the vicinity of the stagnation zone rather than those with higher levels of subcooling. The degree of subcooling emerged as the single largest factor controlling the lateral temperature rise in an electronic chip cooled by a single, confined impinging microjet. Increases in the jet inlet Reynolds Number for the same heat flux and subcooling levels increased the dominance of forced convection heat transfer over the boiling heat transfer. Lower Reynolds Number flows are marked by partial nucleate boiling in contrast to higher Reynolds Number flows marked by forced convection boiling. For all the cases considered in this work, the single phase heat transfer component dominated the other two modes of heat transfer. The evaporative mode dominates the quenching heat transfer mode, an observation that is markedly different from those observed for turbulent evaporative jets found in the literature.
    • Numerical Simulation of Snow Deposition Around living Snow Fences

      Petrie, John; Zhang, Kun; Shehata, Mahmoud (2019-09-13)
      In this study, computational fluid dynamics (CFD) was used to investigate the air flow around porous snow fences to gain insight into snow transport and deposition in the vicinity of fences. Numerical simulations were performed to validate the CFD approach using experimental data from a wind tunnel study. Subsequent simulations were used to test the use of a porosity model to represent fence geometry and determine the effect of fence spacing for fences comprised of multiple rows. The results demonstrate that CFD simulations can reproduce the aerodynamics around porous fences. Additionally, the flow field generated with a porosity model is in close agreement with that from a model with explicit representation of fence porosity. Simulations of fences comprised of two rows spaced at various distances demonstrate that when the row spacing is small the fence behaves as a single row.
    • Numerical simulation of thermo-mechanical behavior of gypsum board wall assembly

      Quan, Zhili; Hulsey, J. Leroy; Ahn, Il Sang; Chen, Cheng-fu; Xiang, Yujiang (2019-05)
      Fire safety has become a significant concern to public safety; especially in the aftermath of 9/11 attack where, according to official reports, three World Trade Center buildings collapsed because of fire. Therefore, the level of thermal insulation required from building material and structural elements has increased. In recent years, gypsum board wall assemblies have been increasingly used as compartmentation for high-rise residential and commercial buildings. The increasing popularity of gypsum board wall assemblies is due to their relatively high strength-to-weight ratio, ease of prefabrication, fast erection and good thermal insulation. Before implementation of any building material or structural element, its Fire Resistance Rating must be determined by subjecting the material or element to a standard furnace fire test. Over the years, a large database has been collected for the Fire Resistance Rating of building materials and structural elements. However, due to the expensive and time-consuming nature of the standard fire tests, determining an accurate Fire Resistance Rating can be a difficult task. In this study, the author numerically evaluated the Fire Resistance Rating of a new gypsum board wall assembly. Composite steel-EPS (Expanded Polystyrene) insulation is added to a traditional gypsum board wall assembly. The author first did numerical simulation of an experiment on the thermal response of a non-load-bearing gypsum board wall assembly to verify the thermal modeling methodology. The author then did numerical simulation of an experiment on the mechanical response of a load-bearing gypsum board wall assembly to verify the mechanical modeling methodology. Finally, the author used the verified thermal and structural modeling methodology to simulate the new composite steel-EPS gypsum board wall assembly and obtained its numerical Fire Resistance Rating. This Fire Resistance Rating should be compared with future experimental results of the new wall assembly. All modeling was done with ABAQUS V6.14.
    • Numerical simulation study to evaluate recovery performance of miscible displacement and WAG process

      Wu, Xingru (2002-08)
      Several factors including gravity segregation, solvent types, injection methods, and production/injection well constraints are known to impact the performance of Water-Alternate-Gas (WAG) process and miscible displacement. This thesis studies well completions to optimize the miscible displacement and WAG processes through numerical simulation of a pattern model with stochastic permeability distribution. To study the impact of well placement and completions on miscible performance in heterogeneous media, we injected various solvents and examined the effect of gravity segregation, permeability distribution and anisotropy, horizontal well lengths, orientation of vertical and horizontal wells on oil recovery. Also, we conducted simulations with various WAG ratios and cycle lengths to understand the WAG processes. Performance of miscible gas flooding and WAG process are compared to that of waterflooding.
    • Numerical study of an exhaust heat recovery system using corrugated tubes and twisted tape inserts

      Mokkapati, Vamsi Krishna Sarma; Peterson, Rorik; Das, Debendra; Kim, Sun Woo; Lin, Chuen-Sen (2014-12)
      Diesel engine generators are the major power source for small communities in cold regions. Diesel generators waste about 1/3 of their fuel energy in the form of heat through exhaust gas. The primary goal of this work is to capture part of the heat from the exhaust and improve the efficiency of the system. A gas to liquid heat transfer performance of a concentric tube heat exchanger with corrugated tubes and twisted tape inserts is investigated by considering its effects on engine performance and economics. This type of heat exchanger is expected to be inexpensive to install and effective in heat transfer, with minimal effect on exhaust emissions of diesel engines. Most previous research has investigated liquid to liquid heat transfer in corrugated tubes at low Reynolds, not gas to liquid heat transfer. The SolidWorks Flow Simulation computer program was used to perform these studies. The program is first validated by comparing simulation results with renowned correlations and field measurements. Simulations are then conducted for a concentric tube heat exchanger with corrugated tubes and twisted tapes of different configurations to determine the optimal design. The maximum enhancement in the rate of heat transfer was found in an annularly corrugated tube heat exchanger with twisted tape inserts. This exchanger transfers about 235.3% and 67.26 % more heat compared to plain tube and annularly corrugated tube heat exchangers without twisted tapes, respectively. Based on optimal results, for a 120 kWe diesel generator, the application of an annularly corrugated tube heat exchanger with twisted tape inserts can save 2,250 gallons of fuel annually (a cost of approximately $11,330) expected payback of initial cost in one month. In addition, saving heating fuel also reduces CO₂ emissions by 23 metric tons per year.
    • Nutrient chemistry of a large, deep lake in subarctic Alaska

      LaPerriere, J. D.; Tilsworth, T.; Casper, L. A. (University of Alaska, Institute of Water Resources, 1977-08)
      The primary objective of this project was to assess the state of the water quality of Harding Lake, and to attempt to predict the effects of future development within its watershed. Since the major effect of degradation of water quality due to human activity is the promotion of nuisance growths of plants, the major emphasis was placed on measurements of plant growth and concentrations of the major nutrients they require. Planktonic algal growth was found to be low, below 95.6 gm/m2/year, and the growth of submerged rooted plants was found to be relatively less important at approximately 1.35 gm/m2/year. Measurements of the growth of attached algae were not conducted, therefore the relative importance of their growth is currently unknown. A model for predicting the effect of future real estate development in the watershed was modified and applied to this lake. This model adequately describes current water quality conditions, and is assumed to have some predictive ability, but several cautions concerning application of this model to Harding Lake are discussed. A secondary objective was to study the thermal regime of a deep subarctic lake. Intensive water temperature measurements were made throughout one year and less intensive measurements were conducted during two additional years. The possibility that this lake may occasionally stratify thermally under the ice and not mix completely in the spring was discovered. The implications of this possibility are discussed for management of subarctic lakes. Hydrologic and energy budgets of this lake are attempted; the annual heat budget is estimated at 1.96 x 104 ± 1.7 x 103 cal/cm2. The results of a study of domestic water supply and waste disposal alternatives in the watershed, and the potential for enteric bacterial contamination of the lake water are presented. Limited work on the zooplankton, fishes, and benthic macroinvertebrates of this lake is also presented.
    • Obfuscation fingerprinting in Android binaries

      Van Veldhuizen, Matthew Philip (2015-04)
      There are many way to protect code from reverse engineering. One such way is to obfuscate either the source code, machine code or bytecode. Obfuscating Android applications not only makes it harder to reverse engineer, it can also speed up execution by reducing the size of the application and removing unnecessary code. One method of obfuscation is to do it manually and the other method is to use an obfuscation program. However, it may become necessary to reverse obfuscation, because of the loss of source code or when investigating malware, trojans, or other harmful applications. This process is called deobfuscation. Once an application has been obfuscated performing deobfuscation is a tedious task, and knowing how the application was obfuscated would increase the probability of correctly reversing the obfuscation. By examining four Android application obfuscators I successfully identified distinct fingerprints within each of the obfuscated binaries by building a simple Android application, obfuscating it, and then comparing obfuscated and unobfuscated bytecode. Using these fingerprints I was able to associate each obfuscator with an approximate probability that it was used to perform the obfuscation.
    • Observation and analysis of whistler mode echoes received by RPI on IMAGE at high latitudes

      Chen, Xiangdong (2001-05)
      Whistler-mode wave-injection experiments with Radio Plasma Imager (RPI) on IMAGE offer an opportunity to observe the whistler-mode echoes. We have performed raytracing studies to investigate accessibility of whistler-mode waves injected from IMAGE to various regions of the magnetosphere and also to other satellites such as Akebono. RPI detected both discrete and diffuse whistler-mode echoes during our observing period (April 21 to August 28, 2000) when IMAGE was at a low altitude (1̃000-7000 km) and mid-to-high latitudes (>25 - 40S̊) near its perigee. We believe that the discrete echoes are the result of RPI signals reflected at the Earth-ionosphere boundary and the diffuse echoes are the result of scattering of RPI signals by meter-scale irregularities. Raytracing analysis shows that both ducted and nonducted ray propagation are needed to explain the observed whistler-mode dispersion. Comparison of electron densities obtained from our raytracing analysis of dispersion with the electron densities obtained by Kletzing et al. in the Auroral Zone shows that these density values deduced from RPI data were about ten times higher. This may be because the antenna radiation efficiency is higher at higher electron densities.
    • Observation and analysis on the characteristics of strain induced by frost heave for a full-scale buried, chilled gas pipeline

      Yang, Kun; Huang, Scott; Chen, Gang; Darrow, Margaret (2013-12)
      This thesis examines the strain characteristics of a large-scale, buried chilled gas pipeline in the discontinuous permafrost region. A full-scale chilled pipeline gas experiment was conducted in Fairbanks, Alaska. The test pipeline had a length of 105 m and a diameter of 0.9 m. One-third of the pipeline was located in permafrost and the rest was in non-permafrost. The monitoring data were collected from December 1999 to January 2005 including both freezing and thawing phases. In the transition zone between frozen and unfrozen soil, the foundation experienced a vertical movement caused by differential frost heave. The test results indicated that the bending action was the main factor for the pipeline for the circumferential and longitudinal strain distribution of the pipeline. Moreover, linear relationships were developed between frost heave and the longitudinal strain at the top and the bottom (i.e., 0� and 180�) of the pipe. The developed equations can be used to predict the strain of the pipe caused by differential frost heave for future tests with similar site conditions.
    • Obstacle detection with Kinect V2 on a ground robot

      Fisher, Laurin; Lawlor, Orion; Hartman, Chris; Genetti, Jon (2018-12)
      This paper is about determining whether using a Kinect V2 (Xbox One Kinect) mounted on a LAYLA ground robot can be used to detect obstacles, by generating a heightmap with the depth data. We take several factors into consideration including: framerate, power consumption, field of view, and data noise.
    • Occurrence and distribution of barite in the permo-triassic siksikpuk formation along the Brooks Range haul road

      Payne, M.W. (University of Alaska Mineral Industry Research Laboratory, 1980-03)
      Barite commonly occurs in Permian to Triassic age rocks along the north flank of the Brooks Range. The Siksikpuk Formation (Wolfcampian to lowest Guadalupian age) is noted for its barite and is well exposed in the vicinity of Galbraith Lake along the pipeline haul road (Figure 1). The proximity of these barite deposits to an existing road made them a logical selection for investigation. The study was designed to provide detailed stratigraphic information on barite quantity and quality, associated clay mineralogy, and relationship of barite to environments of deposition.
    • Occurrence patterns of whistler mode (WM) echoes observed by RPI/IMAGE and their relation to geomagnetic activity

      Reddy, Amani (2007-12)
      This thesis presents an analysis of whistler mode (WM) echoes observed at altitudes less than 5,000 km by the Radio Plasma Imager (RPI) on the IMAGE satellite. WM echoes are generated either by specular reflection (SR) of RPI signals at the Earth-ionosphere boundary (~90 km) or by magnetospheric reflection of RPI signals [...] at altitudes greater than 1,000 km [Sonwalkar et al., 2004; Sonwalkar et al., 2006]. These echoes are further influenced by field aligned irregularities (FAI) and are categorized into discrete, multipath or diffuse SR- and MR- WM echoes, based on their characteristic spectral forms. A survey of WM echoes observed during January 2004- December 2005 showed that WM echoes occurred at all latitudes and under moderate geomagnetic conditions. Occurrence patterns of WM echoes observed in August-December 2005 during geomagnetically quiet and disturbed periods indicate that geomagnetic storms lead to significant changes in FAI that affect the propagation of WM echoes. Our results help (1) in better understanding propagation and generation mechanisms of naturally occurring WM waves, and (2) in planning future WM wave injection experiments in space.
    • On the detection of virtual machine introspection from inside a guest virtual machine

      Marken, Brandon Ashlee; Lawlor, Orion; Price, Channon; Barry, Ronald; Hartman, Christopher; Genetti, Jon (2015-12)
      With the increased prevalence of virtualization in the modern computing environment, the security of that technology becomes of paramount importance. Virtual Machine Introspection (VMI) is one of the technologies that has emerged to provide security for virtual environments by examining and then interpreting the state of an active Virtual Machine (VM). VMI has seen use in systems administration, digital forensics, intrusion detection, and honeypots. As with any technology, VMI has both productive uses as well as harmful uses. The research presented in this dissertation aims to enable a guest VM to determine if it is under examination by an external VMI agent. To determine if a VM is under examination a series of statistical analyses are performed on timing data generated by the guest itself.
    • Operational Safety of Gravel Roads in Rural and Tribal Communities: Vulnerability to Structural Failures and GeoHazards

      Ibrahim, Ahmed; Sharma, Sunil; Kassem, Emad; Nielsen, Richard; Nasrin, Sabreena (2020-04-20)
      Of the 4.1 million miles of federal and state highways in the U.S., 2.2 million miles (or 54%) are unpaved, gravel roads. In the Pacific Northwest and Alaska, unpaved gravel roads provide critical transportation access, with some communities relying on just a single highway for access into and out of town. In such cases, these highways become a critical component of the infrastructure, and there is a need to ensure that safe access is always available to the communities. The Idaho highway database has been used to identify unpaved, gravel roads in Idaho that are critical for access to rural communities. Once identified, information regarding their existing condition has been used to assess their vulnerability and other impacts. The results of this study are considered an initial evaluation that relies on information that is readily available in the database. The project outcomes include a comprehensive literature review of unpaved roads including data produced from field visits. In addition, a questionnaire survey was sent to local jurisdictions authorities for investigating locations, reasons of road closures, and population size of the affected communities. Finally, 37 responses have been received by the research team indicating five rural communities that have experienced closures and isolation. The reasons for the closure of the unpaved roads were due to the lack of funding for snow removal, excessive dirt, unstable gravel roads, tornados, and heavy rains. The location of those communities was spread across the state of Idaho with corresponding populations range from 25 to 8,500 people.
    • Optimization of oilfield power distribution through installation of underground transmission lines applied to the Alaskan North Slope

      Mielke, Robert (2004-05)
      An analytical model is developed to evaluate economic feasibility of installing new underground segments to the power transmission system maintained and operated by Greater Prudhoe Bay Central Power Station. Installation of underground segments is considered for intersections of power lines and roadways. Old materials and equipment are abandoned in favor of new technological infrastructure additions to transmission systems. This installation is progressive in its approach; it aims to eliminate superfluous oilfield operations via implementation of technological innovation. Results indicate that installation of underground segments of transmission line is an economically feasible project. Installation sites are chosen that optimize the economics of this investment. Project impact to power reliability, idle rig time, and streamlined rig operations far outweighs the investment associated with this project. Additionally, this project's effect on Prudhoe Bay oil production shows great potential for additional power line burial projects. Hence, it is hoped that this research be considered a pilot project, that future power line burial projects be considered for implementation, and that economic modeling of future projects be accomplished via revision of this work to include comparison of actual vs. predicted economics of this pilot project.
    • Optimum transportation systems to serve the mineral industry north of the Yukon basin in Alaska

      Wolff, E.N.; Lambert, C.; Johansen, N.I.; Rhodes, E.M.; Solie, R.J. (University of Alaska Mineral Industry Research Laboratory, 1972)
      In 1972 the U. S . Bureau of Mines awarded a grant (No. G 01 22096) to the Mineral Industry Research Laboratory, University of Alaska, for a research project to determine optimum transportation systems to serve the mineral industry north of the Yukon River basin in Alaska. The study was conducted during the period May 1 - November 1, 1972. The study assesses the mineral potential of the region and selects two copper deposits: a known one at Bornite, and a potential one on the upper Koyukuk River. Two possible mining sites within the extensive coal bearing region north of the Brooks Range are also selected. A computer model was developed to perform an economic analysis of technically feasible transportation modes and routes from these four sites to Alaskan ports from which minerals could be shipped to markets. Transport modes considered are highway, rail, cargo aircraft, river barge, winter haul road and air cushion vehicles (A.C.V.). The computer program calculates the present worth of tax benefits from mining and transportation and revenues based on the value of minerals at the port, as well as the auxillary benefits derived from the anticipated use of the routes by the tourist industry. Annual and fixed costs of mining and transportation of minerals are calculated, and benefit-cost ratios determined for each combination of routes and modes serving the four mineral sites. The study concludes that the best systems in terms of a high benefit-cost ratio are those utilizing a minimum of new construction of conventional highways or railroads. The optimum system as derived from this study is one linking together existing transportation systems with aircraft or A.C.V. These modes are feasible only for the shipment of a high value product, namely blister copper produced by a smelter at the mining site, Of the several alternatives considered for the shipment of coal, only a slurry pipeline to an as yet undeveloped port on the Arctic coast showed significant promise. The study recommends that: 1. More government support should be given to mineral exploration in Alaska. 2. Potential mineral industry development should be considered in transportation planning at state and federal levels. 3. Additional research pertinent to mining and processing of minerals in the North should be conducted, and the feasibility of smelting minerals within Alaska explored. 4. Alternatives for providing power to Northwestern Alaska should be investigated.
    • Order reduction and eigenstructure assignment for nonsmooth vibrating systems: a nonlinear normal modes approach

      Lu, Rongdong (2002-08)
      Two related problems are addressed in this thesis. The first one is for order reduction of conservative vibrating systems with piecewise linear nonsmooth nonlinearities of arbitrary dimension. Linear-based, PMM-based and LELSM-based order reduction transformations are applied. The technique is applied to multi-degree-of-freedom systems with nonsmooth clearance, deadzone, bang-bang, and saturation nonlinearities. The resulting approximate frequencies are compared with those obtained from numerical simulations. The second technique is eigenstructure assignment of n-degree-of-freedom conservative vibrating systems with nonsmooth nonlinearities. Three distinct control strategies which utilize methods for approximating the NNM frequencies and mode shapes are employed. First, PMM for approximating NNM frequencies is used to determine n constant actuator gains for eigenvalue placement. Second, an approximate single-degree-of-freedom reduced model is found with one actuator gain for the mode to be controlled. The third strategy allows the frequencies and mode shapes (eigenstructure) to be placed by using a full n x n matrix of actuator gains and employing LELSM for approximating NNM frequencies and mode shapes.
    • Organic and Color Removal from Water Supplies by Synthetic Resinous Adsorbents: Completion Report

      Tilsworth, Timothy (University of Alaska, Institute of Water Resources, 1974-01)
    • Outreach and Technology Transfer on the Effectiveness of Wildlife Fences and Wildlife Crossing Structures in a Multifunctional Landscape

      Huijser, Marcel P. (2018-04)
      This project undertook outreach and technology transfer tasks on the effectiveness of wildlife fences and wildlife crossing structures in a multifunctional landscape. The tasks accomplished included (1) publication of an article in an international peer-reviewed journal on the effectiveness of wildlife mitigation measures along U.S. Highway 93 North; (2) submitting an abstract to, presenting at, and attending the 2017 International Conference on Ecology and Transportation in Salt Lake City, Utah; and (3) updating the website and outreach material of the People’s Way Partnership (http://www.peopleswaywildlifecrossings.org/).