• Experimental and numerical simulation of hydraulic fracturing

      Hoveidafar, Mohammad; Chen, Gang; Metz, Paul; Ahn, Il Sang; Zhang, Yin (2017-12)
      Hydraulic Fracturing (HF) has many applications in different fields such as stimulation of oil and gas reservoirs, in situ stress measurements, stress relief for tunneling projects as well as in underground mining applications such as block caving mining. In the HF process, high pressure fluid is injected into a well to generate fractures in tight rock formations. This technique is particularly suitable for developing hydrocarbon energy resources in tight rock formations such as shale with very low permeability. An experimental setup was designed and developed to simulate the HF process in the laboratory. Cubic plaster specimens were molded and HF experiments were conducted with simulated plaster models. Five laboratory tests were performed on cubic specimens under different stress conditions. Because the uniaxial compressive strength of the plaster was about 1600 psi, in all experiments the applied vertical stress was 1000 psi to avoid breaking the specimens before injection of fluid. The differential horizontal stress varied from 100 to 500 psi. These stress levels are related to shallow formations in a real environment. It was observed that increasing the differential horizontal stress by 100 psi, the minimum pressure required to initiate HF decreases about 100 psi. These results were in agreement by 2D failure criterion of HF. All in all, the small scale HF experiments were conducted successfully in the rock mechanics lab. It was observed that vertical hydraulic fractures would propagate along maximum horizontal stress, which is in agreement with propagation of HF theory. Three-dimensional (3D) numerical models were developed and computer simulations were conducted with ABAQUS, a commercially available finite element analysis (FEA) software. The numerical simulation results compared favorably with those from the laboratory experiments, and verification and analysis were carried out. Since the results obtained from the numerical model were in agreement with the results of experiments and verified the correctness of the model, further investigation was carried out with developed computer models. Several scenarios with different vertical stresses and different levels of horizontal stress were simulated. A statistical software, R, was used to generate a 3D failure criterion for the HF in shallow formations.... It can be stated that in shallow formations, vertical stress has the least effect among stress components on the minimum pressure required to initiate HF.
    • Experimental And Numerical Study Of Sonic Wave Propagation In Freezing Sand And Silt

      Li, Hui (2009)
      A numerical model for delineating the temperature-velocity relationship of freezing porous media and soil is developed in Matlab based on Leclaire's Biot-type three-phase theory. Leclaire's theory gives lower sonic velocities than the experimental results because it does not take into consideration the effect of the solid-ice frame when water is freezing. To take the solid-ice effective frame into account, the average bulk and shear moduli estimation are modified with a proposed procedure. The modification gives higher P-wave and S-wave velocities that fit experimental data well. A comprehensive suite of physical and acoustic laboratory experiments are conducted on artificial sands, sand-clay mixtures and Fairbanks silts to investigate the temperature-velocity relationship during the freezing process and the effects of grain size and fine clay content. A Multi-channel ultrasonic scanning system (MUSS) is designed, installed and programmed for the experimental computerized ultrasonic tomography (CUST) study. The inward and outward freezing process and freezing front development in Fairbanks silt samples are observed using computerized ultrasonic tomography (CUST) in the laboratory. The experiments generate sonic wave velocity and temperature distribution during the freezing process. The freezing front is clearly identified in the CUST as a function of time and temperature. Comprehensive numerical finite element method (FEM) simulations, which account for the conduction in porous media, the latent heat effect and the nonlinear thermal properties of soil, are performed on the inward and outward freezing process of Fairbanks silt based on the experimental conditions. In conjunction with the temperature-velocity model developed in the study, sonic wave velocity tomograms are generated. The results are comparable with those obtained by CUST. The study indicates that CUST is an effective method for studying freezing processes and has potential for indirect measurement of unfrozen water content variations in the soil without interfering with the freezing process.
    • Experimental investigation of fiber-reininforced polymer composite bridge deck panel in cold regions

      Choppali, Usha (2005-08)
      To build highway bridges in cold regions like Alaska, cast-in-place concrete has been found to be difficult and expensive, especially in winter seasons. Decked Bulb-Tee bridge members can be heavy and the deck cannot be replaced. On the other hand, fiber-reinforced plastic (FRP) composite materials offer a great opportunity in this area. The primary technical barrier to the use of composite materials in infrastructure applications is lack of data on environmental durability. The present study presents experimental load and strain results of a FRP composite panel that was subjected to cold temperatures. The FRP panel consists of an upper and a bottom laminate tied by a honeycomb core, which was produced by sequentially bonding a flat sheet to a corrugated sheet. Specifically, the objective of this research was to understand the effects of low temperature and low-temperature thermal cycling on the performance of FRP composite bridge deck panels in cold regions. This was achieved by analyzing static tests and results for a FRP deck panel. The research results reported herein showed an increase in stiffness as temperature was lowered up to a certain point, and a reverse trend at a further lower temperature.
    • Experimental investigation of low salinity enhanced oil recovery potential and wettability characterization of Alaska North Slope cores

      Patil, Shivkumar B. (2007-12)
      Rock wettability and the chemical properties of the injection water influence fluid distribution and multiphase fluid flow behavior in petroleum reservoirs and hence it consequently affects the final residual oil saturation. Many researchers have proven that oil recovery is increased by decreasing the salinity of water used for waterflooding process. Three sets of experiments were conducted on representative Alaska North Slope (ANS) core samples to experimentally ascertain the influence of injected brine/fluid composition on wettability and hence on oil recovery in secondary oil recovery mode. All the sets of experiments examined the effect of brine salinity variation on wettability and residual oil saturation of representative core samples. The core samples used in the first and third set were new (clean) while in the second set core samples were oil aged. For first and second sets laboratory reconstituted 22,000 TDS, 11,000 TDS and 5,500 IDS (total dissolved solids) brines were used while for the third set ANS lake water was used. Oil aging of core decreased the water wetting state of cores slightly. This observation could be attributed to adsorption of polar compounds of crude oil. The general trend observed in all the coreflood experiment was reduction in Sor (up to 20%) and slight increase in the Amott-Harvey Wettability Index with decrease in salinity of the injected brine at reservoir temperature.
    • Experimental investigation of low salinity water flooding to improve viscous oil recovery from the Schrader Bluff Reservoir on Alaska North Slope

      Cheng, Yaoze; Zhang, Yin; Dandekar, Abhijit; Awoleke, Obadare; Chen, Gang (2018-05)
      Alaska's North Slope (ANS) contains vast resources of viscous oil that have not been developed efficiently using conventional water flooding. Although thermal methods are most commonly applied to recover viscous oil, they are impractical on ANS because of the concern of thawing the permafrost, which could cause disastrous environmental damage. Recently, low salinity water flooding (LSWF) has been considered to enhance oil recovery by reducing residual oil saturation in the Schrader Bluff viscous oil reservoir. In this study, lab experiments have been conducted to investigate the potential of LSWF to improve heavy oil recovery from the Schrader Bluff sand. Fresh-state core plugs cut from preserved core samples with original oil saturations have been flooded sequentially with high salinity water, low salinity water, and softened low salinity water. The cumulative oil production and pressure drops have been recorded, and the oil recovery factors and residual oil saturation after each flooding have been determined based on material balance. In addition, restored-state core plugs saturated with viscous oil have been employed to conduct unsteady-state displacement experiments to measure the oil-water relative permeabilities using high salinity water and low salinity water, respectively. The emulsification of provided viscous oil and low salinity water has also been investigated. Furthermore, the contact angles between the crude oil and reservoir rock have been measured. It has been found that the core plugs are very unconsolidated, with porosity and absolute permeability in the range of 33% to 36% and 155 mD to 330 mD, respectively. A produced crude oil sample having a viscosity of 63 cP at ambient conditions was used in the experiments. The total dissolved solids (TDS) of the high salinity water and the low salinity water are 28,000 mg/L and 2,940 mg/L, respectively. Softening had little effect on the TDS of the low salinity water, but the concentration of Ca²⁺ was reduced significantly. The residual oil saturations were reduced gradually by applying LSWF and softened LSWF successively after high salinity water flooding. On average, LSWF can improve viscous oil recovery by 6.3% OOIP over high salinity water flooding, while the softened LSWF further enhances the oil recovery by 1.3% OOIP. The pressure drops observed in the LSWF and softened LSWF demonstrate more fluctuation than that in the high salinity water flooding, which indicates potential clay migration in LSWF and softened LSWF. Furthermore, it was found that, regardless of the salinities, the calculated water relative permeabilities are much lower than the typical values in conventional systems, implying more complex reactions between the reservoir rock, viscous oil, and injected water. Mixing the provided viscous oil and low salinity water generates stable water-in-oil (W/O) emulsions. The viscosities of the W/O emulsions made from water-oil ratios of 20:80 and 50:50 are higher than that of the provided viscous oil. Moreover, the contact angle between the crude oil and reservoir rock in the presence of low salinity water is larger than that in the presence of high salinity water, which may result from the wettability change of the reservoir rock by contact with the low salinity water.
    • An experimental investigation of natural freezing and biopolymers for permeability modification to reduce the volume of dense non-aqueous phase liquids in groundwater

      D'Cunha, Neil John (2004-12)
      Dense Non-Aqueous Phase Liquid (DNAPL) contamination is one of the major environmental concerns today. DNAPL can remain in significant quantities as residual contaminants in the low permeability zones even after the bulk phase has been removed. As the drive fluid sweeps through the aquifer it follows the path of least resistance, which is the high permeability zone. Thus the contaminants trapped in the low permeability zones remain as residuals and serve as a source for prolonged contamination. Conventional remediation techniques are ill-equipped to deal with the heterogeneities of the aquifers. Various techniques to enhance the efficiency of the conventional methods are tried without significant success. Reducing the temperature of soil formations can modify aquifer flow paths. The natural freezing of soils in winter may be used effectively to modify the flow paths. In summer, permeability modification can be accomplished by emplacement of microbial polymer gels. In this thesis, we have investigated using a laboratory scale one dimensional column experiment, a novel technique to reduce the volume of residual DNAPL using a combination of natural freezing in winter and biopolymer in summer.
    • Experimental investigation of the influence of various nanoparticles on water-based mud

      Dhiman, Paritosh (2016-12)
      In the oil and gas industry, drilling fluids play an important role in the success of drilling operations. Hence, it is vital to predict accurately and maintain drilling fluid properties. Drilling fluids have multitude of functions, including but not limited to balancing the formation pressure, transporting cuttings, lubricating the bit, minimizing formation damage and maintaining well stability. Efficient completion of any drilling operation is governed by the selection of the proper drilling fluid. Growing hydrocarbon demand is driving the industry to explore unconventional resources such as shale formations and deep water and ultra-deep water areas where high temperature high pressure (HTHP) conditions persist. Generally, oil-based muds have been widely used in HTHP operations, as they can withstand high temperatures while offering high lubricity, but they are expensive and have an environmental impact. Water-based muds offer a cost-effective and environment-friendly option, but they have limited HTHP application, as they tend to break down, resulting in increased fluid loss and viscosity reduction. Also, upon exposure to high temperatures, they also face the issue of gelation and degradation of weighing materials and additives. Due to these issues with both oil-based muds and water-based muds, new drilling fluids are formulated regularly and the existing systems are tailored to curtail drilling operation costs. Most recently, nanoparticles have been recognized as an effective additive to improve the performance of drilling fluids, having the potential to overcome the limitations of current drilling fluid systems in challenging conditions. In this study, experiments have been conducted to investigate the impact of different nanoparticles on various drilling fluid properties, including rheology, filtration, and lubricity, considering a wide range of influence factors, such as nanoparticle concentration, particle size, nanoparticle type, temperature, and aging. The effect of nanoparticle concentrations (0.01 wt% ~ 1wt%) on drilling fluid properties has been first investigated using SiO₂ nanoparticles with and without coating. Then the effect of nanoparticle size (5 nm ~ 50 nm) on drilling fluid properties has been examined using TiO₂ nanoparticles. Subsequently, the impact of nanoparticle type, including four different nanoparticles, on drilling fluid properties has been tested. Moreover, the effects of temperature and aging on the nanoparticle-based drilling fluid properties have been investigated.
    • Experimental investigation on the transportation of commingled blends of gas-to-liquid (GTL) products and Alaskan heavy crude oil through the Trans-Alaska Pipeline System (TAPS)

      Igbokwe, Chidiebere G. C.; Dandekar, Abhijit Y.; Chukwu, Godwin A.; Patil, Shirish L.; Khataniar, Santanu (2006-08)
      Heavy oil deposits in the West Sak and Ugnu formations are currently considered as potential resources to address the issue of declining oil production on Alaska's North Slope (ANS). Similarly, an estimated proven and recoverable ANS gas reserve of 38 trillion cubic feet (TCF) can be converted to high premium Gas-to-Liquid products which may be commingled with Alaskan heavy oil products. These commingled blends of GTL and Alaska heavy oil can be transported through the Trans Alaska Pipeline System (TAPS). The primary operational issues that could affect the transportation of these fluids through TAPS are: pump ability of the heavy oil, cold restart following a prolonged shut down, and solid deposition in the pipeline. Since TAPS was originally designed to carry light to medium, low viscosity crude oil, transporting heavy or viscous oil may cause problems with the overall hydraulics. In this study, ANS crude oil was distilled and the heavy fraction cuts (~18° API gravity) were commingled with ANS crude oil and GTL samples for evaluation. Density and viscosity results showed that addition of GTL significantly reduced heavy oil viscosity to present TAPS conditions. However, solid deposition was observed to be a potential problem.
    • Experimental Investigations Of Fluid Dynamic And Thermal Performance Of Nanofluids

      Kulkarni, Devdatta Prakash; Das, Debendra K. (2007)
      The goal of this research was to investigate the fluid dynamic and thermal performance of various nanofluids. Nanofluids are dispersions of metallic nanometer size particles (<100 nm) into the base fluids. The choice of base fluid is an ethylene or propylene glycol and water mixture in cold regions. Initially the rheological characterization of copper oxide (CuO) nanofluids in water and in propylene glycol was performed. Results revealed that higher concentrations of CuO nanoparticles (5 to 15%) in water exhibited time-independent pseudoplastic and shear-thinning behavior. Lower concentrations (1 to 6%) of CuO nanofluids in propylene glycol revealed that these nanofluids behaved as Newtonian fluids. Both nanofluids showed that viscosity decreased exponentially with increase in temperature. Subsequent correlations for viscosities as a function of volume concentration and temperature were developed. Effects of different thermophysical properties on the Prandtl number of CuO, silicon dioxide (SiO2) and aluminum oxide (A12O 3) nanofluids were investigated. Results showed that the Prandtl number increased with increasing volume concentrations, which in turn increased the heat transfer coefficients of the nanofluids. Various nanofluids were compared for their heat transfer rates based on the Mouromtseff number, which is a Figure of Merit for heat transfer fluids. From this analysis, the optimal concentrations of nanoparticles in base fluids were found for CuO-water nanofluids. Experiments were performed to investigate the convective heat transfer enhancement and pressure loss of CuO, SiO2 and A12O 3 nanofluids in the turbulent regime. The increases in heat transfer coefficient by nanofluids for various volume concentrations compared to the base fluid were determined. Pressure loss was observed to increase with nanoparticle volume concentration. It was observed that an increase in particle diameter increased the heat transfer coefficient. Calculations showed that application of nanofluids in heat exchangers in buildings could result in volumetric flow reduction, reduction in the mass flow rate and size, and pumping power savings. Experiments on a diesel electric generator with nanofluids showed a reduction of cogeneration efficiency due to the decrease in specific heat compared to the base fluids. However, it was found that the efficiency of the waste heat recovery heat exchanger increased for nanofluids.
    • Experimental Study Of Adsorbed Cation Effects On The Frost Susceptibility Of Natural Soils

      Darrow, Margaret Marie; Huang, Scott; Shur, Yuri (2007)
      Frost heaving is ubiquitous throughout cold regions, causing damage to building foundations, roads, airfields, railways, utilities, and pipelines. Out of the voluminous body of research conducted over the last 80 years, few studies investigated the mineral surface effects on frost heaving. These previous studies were conducted nearly 50 years ago with rudimentary equipment and on homogeneous and artificial soils that have limited applicability to actual field conditions. The purpose of the research presented here is to investigate the adsorbed cation effects on the frost susceptibility of natural soils through experimental testing. A comprehensive suite of laboratory experiments was conducted on five natural heterogeneous soils, including the preparation of divalent and monovalent cation-treated samples. Experimental testing included measurements of engineering index properties, chemical properties, clay content and mineralogy, soil-moisture characteristic curves, unfrozen water content, zeta potential, and frost heave testing. Frost heave tests were conducted using a state-of-the-art laboratory system that demonstrates high repeatability. Soil-moisture characteristic---soil freezing characteristic (SMC-SFC) relations were developed for the five natural soils over an unprecedented range of measurements and using a new approach, which can be related to the Clausius-Clapeyron equation. The SMC-SFC relations yield a new variable, eta, which describes the water retention properties of soil at increasing matric potentials and decreasing temperatures. The five untreated soils demonstrated significantly different frost heave ratios, ranging from 0.7 percent to 49.2 percent. Statistical analysis indicates that the frost susceptibility of the five untreated soils is most dependent on adsorbed cations, eta, amount of microaggregates smaller than 2 mum, and clay content. For the entire body of untreated and cation-treated samples, statistical analysis indicates that the frost susceptibility is most dependent on adsorbed cations, unfrozen water content, and amount of smectite, kaolinite, and chlorite present in the soil. The results from each cation treatment indicate that the frost susceptibility of (1) Ca2+-saturated soil is most dependent on zeta potential and unfrozen water content; (2) Mg2+-saturated soil is most dependent on zeta potential and amount of chlorite; and (3) Na +-saturated soil is most dependent on zeta potential, unfrozen water content, and amount of chlorite.
    • Experimental study of multiphase flow of viscous oil, gas and sand in horizontal pipes

      Hulsurkar, Panav; Awoleke, Obadare; Ahmadi, Mohabbat; Patil, Shirish (2017-05)
      The oil and gas industry relies on multiphase flow models and correlations to predict the behavior of fluids through wells and pipelines. Significant amount of research has been performed on the multiphase flow of different types of liquids with gases to extend the applicability of existing models to field-specific fluid conditions. Heavy oil and gas flow research commenced in the past decade and new correlations have been developed that define their flow behavior/regimes. This study aims to plant a foot in the quite deficient area of multiphase flow research that focuses on a sufficiently common situation faced by many heavy oil producing fields: the presence of sand in wells and pipelines. This study will be the first recorded attempt to understand the multiphase flow of heavy oil, gas, and sand. A 1.5" diameter multiphase flow loop facility capable of handling solids was designed and constructed for the study. Data logging instruments were calibrated and installed to be able to withstand the erosive effects of sand. The flow loop was leak and pressure tested with water and air. Three oils of 150, 196 and 218 cP viscosities were utilized to gather 49 single phase liquid, 227 two-phase liquid- air and 87 three-phase liquid, air and solid multiphase flow data points which included differential and absolute pressures, fluid flow rates, temperatures, liquid and composite liquid- solid hold- up data and photo and videotaping of the observed flow regimes. Validation of the setup was performed using single phase flow of oil and two-phase flow of oil and air. Sand was added in three different concentrations to the 218 cP oil and three-phase oil, gas and sand multiphase flow tests were performed. Flow patterns were identified and flow pattern maps were created using acquired data. No change was observed on flow pattern transitions by changing oil viscosities. Liquid hold- up and differential pressures were compared to observe the effect of changing oil viscosity and the presence of sand in varying concentrations on the two-phase flow of oil and gas and the three-phase flow of oil, gas and sand respectively. An increase in differential pressures was observed with increasing viscosities and the addition of sand. No changes in hold-up were seen with changing oil viscosities rather flow patterns impacted liquid hold-up significantly. The slug flow pattern was analyzed. Composite liquid-solid hold-up in slug flow were physically measured and predicted. Liquid slug lengths were predicted and compared with observed lengths using photo and videography techniques. Differential pressures and liquid hold-up were compared with existing multiphase flow models in the PIPESIM multiphase flow simulator to test model predictions against observed flow data. The dependence of differential pressure gradients and liquid hold-up on dimensionless variables was realized by performing normalized linear regressions to identify the most significant dimensionless groups and the results were given a mathematical form by proposing correlations for differential pressure and hold-up predictions. To the best of our knowledge, this study is the first attempt at systematically measuring pressure drop and liquid hold up during the three-phase flow of oil, gas and sand.
    • Experimental study of solid deposition and vapor pressure in gas-to-liquid and crude oil mixtures for trasportation through the Trans Alaska Pipeline System

      Amadi, Samuel Uche (2003-08)
      Chemical conversion of Alaska North Slope (ANS) gas to liquid and subsequently transporting it through the Trans Alaska Pipeline System (TAPS) is a means of bringing the ANS gas to the market. However, transporting the gas-to-liquid (GTL) product with ANS crude oil through the Trans Alaska Pipeline System (TAPS) may pose some operational challenges. The major issue of concern relates to the asphaltene and wax deposition problems in the pipeline, as well as the vapor pressure of GTL and GTL/crude oil blends. In this study, experiments were carried out to determine the degree to which GTL is a flocculant of asphaltene. The stability/instability of the ANS crude to asphaltene deposition, as well as the wax appearance temperature of various cuts of GTL and GTL/crude oil blends were also determined. The results show that GTL is a possible flocculant of asphaltene, however, ANS is stable to asphaltene deposition. The results also show that GTL has a high wax appearance temperature, which raises a concern under arctic conditions. The Reid vapor pressure test results from this study show no consistent trend. This is because the GTL samples used have been flashed already as a result of sample withdrawal from the container by previous researchers. Thus the sample did not meet both the ASTM and IP requirements for Reid vapor test.
    • Experimental Study of Various Techniques to Protect Ice-Rich Cut Slopes

      Li, Lin; McHattie, Robert; Xhang, Xiong; Zhang, Mingchu (Alaska University Transportation Center, Alaska Department of Transportation and Public Facilities, 2014)
    • Experimental Study of Various Techniques to Protect Ice-Rich Cut Slopes

      Li, Lin; McHattie, Robert; Zhang, Xiong; Zhang, Mingchu (Alaska University Transportation Center, 2014-08)
      Cut slopes are usually required to achieve roadway design grades in the ice-rich permafrost areas in Alaska. However, excavation and exposure of a cut slope destroy the existing thermal balance and result in degradation of ice-rich permafrost. Environmentally acceptable, legal, and economically viable solutions for ice-rich slope protection are still rare. Three potential thermal-erosion mitigation techniques were investigated. Four test sections (Section A: 1 ft wood chips, Section B: coconut blanket, Section C: coconut blanket + Tecco-mesh, and Section D: 1 ft crushed rock as a control section) were constructed at the Dalton Highway 9 Mile Hill during the period of April 17 through April 27, 2013. Temperature and moisture sensors were installed to monitor four test sections and evaluate the effectiveness of the different mitigation techniques. Also, a weather station was built to record climatic information at the test site by April 30, 2013. The filed monitoring period ended on November 11, 2014. No obvious erosion was observed in Sections A and B due to less ice content when compared with Sections C and D which failed one and a half months after construction. The performance of four techniques was discussed in detail.
    • Experimental Study on an Electrical Deicing Technology Utilizing Carbon Fiber Tape

      Yang, Zhaohui “Joey”; Yang, Ting; Song, Gangbing; Singla, Mithun (Alaska University Transportation Center, 2012)
    • An experimental study on the interaction of coaxial and co-rotating vortex rings

      Satti, Jagannadha Reddy (2012-05)
      The study investigated the role of formation time, Reynolds Number, and non-dimensional frequency number, the three most significant parameters in the dynamics of vortex rings, in the interaction between co-axial and co-rotating vortex rings and in the ring behaviors of merging and leapfrogging. To generate and investigate vortex rings with the required characteristics, two laminar vortex rings were generated consecutively from a piston-cylinder apparatus such that the rings propagated in the same direction and that the spatial separation between them decreased until they began merging. Using digital particle image velocimetry to measure the flow fields as well as the trajectory and circulation of the individual rings, a series of experiments were conducted at three formation times, with the experiments at each formation time repeated at different Reynolds Numbers, and the experiments at each Reynolds Number in turn repeated at different non-dimensional frequency numbers. The results indicate that at low Reynolds Numbers, the total circulation in the flow is relatively constant before and after the rings merge. However, at high Reynolds Numbers, the total circulation begins rapidly decreasing upon the contact of two vortex ring cores, indicating a transition to a turbulent vortex ring during merging, before stabilizing at a lower level, indicating that the merged ring has transitioned back to a laminar vortex ring after shedding some circulation.
    • Experiments on the interactions between a rigid plate and vortices

      Milke, Shaun; Peterson, Rorik; Peng, Jifeng; Xiang, Yujiang (2015-08)
      This study provides a quantitative analysis, and subsequent comparison, of flow field behavior under varied experimental parameters for vortex production by, and vortex ring interaction with, a rigid plate. The relationship between the experimental parameters: flapping amplitude and average rotational speed, and flow field characteristics: vorticity, circulation, total kinetic energy, and vortex trajectory, were examined for the cantilevered plate. The relationships between the parameter of plate inclination and the flow field characteristics of vorticity, circulation, and vortex trajectory, were examined for the inclined plate. All experiments involved a particle image velocimetry (PIV) analysis followed by processing of the data to produce quantified flow field data. The cantilevered plate experiments revealed that a flapping cantilevered plate produces two primary vortices: a tip vortex and a plate hugging vortex, and in some cases a stopping vortex above the tip. It was determined that the maximum magnitudes attained, the accumulation rate, and the dissipation rate of both circulation and kinetic energy are speed dependent. However, rate of accumulation and dissipation of either quantity does not vary with total flapping amplitude. It was concluded that flapping amplitude does not influence the shape of vortex trajectory or the trajectory angle relative to the horizontal, though the total distance traveled along the vortex trajectory is dependent on flapping amplitude. In the case of the inclined plate, it was concluded that the levels of vorticity, particularly in the lower part of the vortex ring, and the formation of additional vortices in the flow field are dependent on plate inclination and thus, the degree of asymmetry of the interaction. During the die off phase the circulation of the upper part of the vortex ring is inversely proportional to plate angle, while circulation of the lower part of the vortex ring is proportional to plate inclination. The relationship between plate inclination and vertical displacement of the two parts of the ring was found to be based on the degree of asymmetry.
    • Exploration and estimation of gravel resource potential in southeast Chukchi Sea continental shelf off Kivalina, Alaska

      D'Souza, Abhijith T. (2005-12)
      Frequent storm surges in the Alaskan arctic result in washovers and high erosion of barrier islands. The village council of Kivalina has resolved to relocate from its present location on a barrier island in Northwest arctic Alaska to an adjacent onshore site. The relocation plan envisages excavation of upper 4 meter of the 25 km² onshore permafrost ground and construction of a foundation pad. The objective of this research is to estimate the gravel resource potential in the continental shelf off Kivalina. In this context seismic surveys and sediment sampling were conducted. The seismic surveys were of limited use as they failed to resolve the upper 1-2 m of the seafloor. The lithostratigraphy indicated dominance of the 2.4-3.4 mm size fraction in the region north of Kivalina. The geostatistical analysis indicated an omnidirectional variogram fit to the data with ordinary kriging producing the best kriging estimate of the gravel resource potential. At least 20 x 10⁶ m³ of gravel above the 90 % cut-off is present in the upper 0.5 m of the seafloor. The regional Pleistocene glaciation has affected the lateral variations in gravel abundance in the nearshore southeast Chukchi Sea.
    • Factors affecting costs of mining in Alaska

      Lambert, C.; Taylor, D. (University of Alaska Mineral Industry Research Laboratory, 1982)
      The basic factors which affect the cost of mining in Alaska are discussed herein. Contrary to popular opinion, cold weather is not the major factor. This problem has, for the most part, been solved through experience in Eastern Canada and later efforts in British Columbia and the Yukon. Remoteness and isolation and its effect upon personnel, inventory and services of all kinds are among the more difficult with which to anticipate and cope. Considerable creativity is required to solve these problems, which differ somewhat with the type and location of mineral deposit, and will quite likely require solutions at variance with the current attitudes and practices of the company involved. In Alaska, electric power, transportation and land tenure pose difficulties of a type not experienced when existing mines in Canada were developed.
    • Factors Affecting Water Management on the North Slope of Alaska

      Greenwood, Julian K.; Murphy, R. Sage (University of Alaska, Institute of Water Resources, 1972-02)
      The North Slope of Alaska is undergoing sudden development following the recent discovery of large oil and gas reserves in the area. The water resources of the region should be carefully managed both to ensure adequate supplies of usable water at reasonable cost, and to guard against excessive deterioration of water quality. The likely effects on the environment of man's activities are investigated and found to be poorly understood at the present time. Research priorities are suggested to supply rapid answers to questions of immediate importance. The applicability of a regional management concept to the North Slope waters is considered and the concept is recommended as part of a broad land and water planning philosophy which would emphasize regional control over state and federal control. The use of economic incentives rather than standards for the control of water quality is not recommended at the present time.