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Collaborating Authors
Reservoir Description and Dynamics
Hydrodynamic Study On Added Resistance By Means of Unsteady Wave Analysis Method
Kashiwagi, Masashi (Department of Naval Architecture and Ocean Engineering, Osaka University) | Sasakawa, Takuma (Department of Naval Architecture and Ocean Engineering, Osaka University) | Wakabayashi, Tomoki (Department of Naval Architecture and Ocean Engineering, Osaka University)
ABSTRACT: It is known that the added resistance in waves can be computed from ship-generated unsteady waves through the unsteady wave analysis method. In order to investigate which component or which part of shipgenerated unsteady waves is dominant in the added resistance, measurements of unsteady waves are carried out for three canonical problems of wave diffraction, forced oscillations in heave and pitch, and free response of ship motions in head waves. With these analyzed results and numerical computations by a unified slendership theory, validity of the linear superposition of component waves is studied. It is found that the added resistance due to local nonlinear wave generation with energy dissipation is rather large when the ship-motion amplitude becomes large and this nonlinearity is prominent near the forefront part of the wave. INTRODUCTION When a ship advances in waves, the resistance on the ship generally increases as compared to that in calm sea. This increase of resistance is called the added resistance which is crucial in predicting the speed loss of a ship in actual seas. Thus a large amount of work on the added resistance has been made so far. Since a pioneering work of Maruo (1960), it has been well recognized that the dominant component in the added resistance is the one due to unsteady disturbance waves by a ship and their interaction with incident waves. Nevertheless, details of the hydrodynamic relation between the added resistance and ship-generated unsteady waves seem to be still unclear, because most comparisons have been made between the total increase in the ship resistance measured by a dynamometer in waves and the calculated value with a simplified potential-flow theory (e.g. Kashiwagi et al., 2010). Ohkusu (1980) proposed a method for measuring ship-generated unsteady waves and then evaluating the wave amplitude function and the added resistance.
Incorporating Turbulent Inflow Conditions In a Blade Element Momentum Model of Tidal Stream Turbines
Togneri, Michael (Marine Energy Research Group (MERG) College of Engineering, Swansea University) | Masters, Ian (Marine Energy Research Group (MERG) College of Engineering, Swansea University) | Orme, James (Swanturbines Ltd)
ABSTRACT: Blade element momentum theory (BEMT) is a well-established method for evaluating the performance of turbines designed to extract energy from a flowing fluid. In this paper, we discuss a modified version of BEMT that allows for greater variation in the permissible inflow conditions, paying particular attention to inflow conditions that model turbulence in coastal waters in order to calculate the power output and other performance parameters of tidal stream turbines (TSTs). In the first part of the paper, we describe the modification we have made to standard BEMT analysis. In the second part, we describe how we create an appropriate representation of a turbulent tidal stream or marine current, and what parameters we can extract from measurements of a real current in order to create this representation. Some preliminary results are presented and their significance discussed. INTRODUCTION The aim of this paper is to discuss some research carried out with the goal of predicting TST performance in turbulent marine currents. There have been many investigations of turbulence in the type of flows likely to be experienced by TSTs (see for instance Lueck and Lu, 1999; Lu et al., 2000; Trevethan and Chanson 2009), but one major difficulty in making these predictions is precisely that detailed measurements of the type described in these investigations are often not available for potential turbine installation sites. Thus, we seek to predict TST performance using not only data from real turbulent flows, but also from artificially created "synthetic" turbulence which will satisfactorily predict the effects of real turbulence without first requiring a lengthy and possibly impractically expensive investigation of flow conditions. As more and more computing power becomes available to a greater number of researchers, the number of fluid dynamics problems amenable to a computational solution is increasing.
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics (0.49)
- Data Science & Engineering Analytics > Information Management and Systems (0.48)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring (0.30)
α to γ Reverse Transformation of Bainite And Martensite Microstructures Under Various Heating Rates
Hara, Takuya (Nippon Steel Corporation Kimitsu R&D Lab) | Yoshioka, I. (Nippon Steel Corporation Steel Research Laboratories) | Shigesato, Genichi (Nippon Steel Corporation Advanced Research Laboratories) | Sugiyama, Masaaki (Nippon Steel Corporation Advanced Research Laboratories) | Koseki, Toshihiko (Department of Materials Engineering, The University of Tokyo)
ABSTRACT: The same coarse austenite (γ) grains as those before austenitizing emerge when a martensite and/or bainite steel with coarse grains is heated to an austenite region at a slow heating rate. This is called γ grain memory. In this study, ferrite (α) to γ reverse transformation behavior is investigated in order to clarify the mechanism of γ grain memory from the viewpoint of the roles of cementite and retained γ. Coarse γ grains and fine globular γ grains, which nucleate along the coarse γ grain boundaries, are formed when bainite and/or martensite steel is heated above the AC3 temperature. The size distribution of γ grain is the same as that before heating. Coarse γ grains are formed by the growth, impingement, and coalescence of acicular γ grains, which corresponds to retained γ between laths. The γ grain memory is suppressed by decreasing the amount of retained γ and by increasing the amount of cementite before heating. These results suggest that α to γ transformation behavior is governed by competition between the nucleation and growth of newly formed γ from the dissolution of cementite and the growth and coalescence of retained γ. γ grain memory occurs when the growth and coalescence of retained γ dominates rather than the nucleation and growth of globular γ grains. INTRODUCTION There are some cases where the same austenite (γ) grains as those before austenitizing emerge when a martensite and/or bainite microstructure in prior γ grains is heated to an austenite region. This is called γ grain memory. Figure 1 shows the schematic diagram of γ grain memory. This phenomenon appears under a slow or rapid heating rate. γ grains are refined and become uniform with an increase in the austenitizing temperature after the same γ grains as those before heating appear.
- Asia > Japan (0.29)
- North America > United States (0.28)
- Well Drilling > Drillstring Design > Drill pipe selection (0.40)
- Reservoir Description and Dynamics (0.32)
Particle And Mechanical Characteristics of Clinker Ash
Wakatsuki, Y. (Geoengineering division, Fukken Co., Ltd) | Yoshioka, I. (Circulation operational headquarters, Chugoku Electric Power Co., Inc) | Nakashita, A. (Engineering division, Energia Eco Materia co., ltd) | Hyodo, M. (Faculty of engineering, Yamaguchi University) | Yoshimoto, N. (Faculty of engineering, Yamaguchi University)
ABSTRACT: The particle and mechanical characteristics for clinker ash to apply to various geomaterial was experimentally investigated in this research. As a result, it was clarified that even though the clinker ash is a friability material, it has a high monotonic shear strength even in loose condition. The secant angle depends upon the effective confining pressure. In other words, it means that the particle crushing has an influence on the secant angle. When the effective confining pressure is less than 200kPa, the secant angle remains secured at more than 35(deg.). INTRODUCTION Clinker ash is generated by crushing coal ash that accumulates in the water tank at the bottom of coal-fired power station boilers into sand and gravel sized pieces. It does not require any special treatment before use. In addition, this material is light in weight and has a high shear strength and coefficient of permeability. Therefore, the use of clinker ash is now spreading. It has been used as a construction material in a variety of applications, such as for embankments, base courses and drainage works, but its overall characteristics have not yet been clarified sufficiently. Clinker ash is one of the specified by-products and is required, according to the Law for the Promotion of Effective Utilization of Resources in Japan, to be put into practice as a recyclable material. The particle and mechanical characteristics of clinker ash for various geomaterials is experimentally investigated in this research. TEST SAMPLES Clinker ash, used as the test samples (C.A. a through f), was collected from six power stations in Western Japan, which are expected to continuously generate a large amount of clinker ash into the foreseeable future. The surface is very angular. This is because solidified clinker ash blocks are mechanically crushed to a size of about 20 mm.
ABSTRACT: This paper presents the mathematical derivation of a new model of speed skate ice friction. The model acronym is FAST, which stands for Friction Algorithm using Speed Skate Thermohydrodynamics. Mutatis mutandis, it is applicable to other ice friction problems in the hydrodynamic friction regime. The paper updates and corrects an earlier publication of the model (FAST 1.0) that omitted the full derivation of the lubrication equation. It also presents a more thorough exploration of the model results and its sensitivity to the variation of physical variables. INTRODUCTION Kietzig et al. (2010) recently reviewed the physics of ice friction. They identified three regimes: boundary friction, where the slider's load is supported primarily by contacting surface asperities; mixed friction, where the load is supported jointly by the asperities and a lubricating layer; and hydrodynamic friction, where the load is supported entirely by the lubricating layer. Penny et al. (2007) presented an earlier review of ice friction and a new model of ice friction based on the assumption of hydrodynamic friction. They incorporated all the aspects of the problem that had been considered by various authors up to that time. These include frictional melting and shear stress, ploughing, heat conduction into the ice and slider and squeeze flow. Prior to this paper, no one had assembled all of these factors into a single model of lubricated ice friction. Furushima (1972) and Bäurle et al. (2007), considered frictional melting and squeeze flow. Evans et al. (1976) and Oksanen and Keinonen (1982) considered frictional melting and heat conduction. Penny et al. (2007) incorporated all of these effects into a single model and verified it against existing measurements (de Koning et al., 1992). However, space limitations precluded incorporating the complete derivation of the model's lubrication equation in that paper.
- North America > Canada > Alberta (0.28)
- North America > Canada > Ontario (0.28)
- Leisure & Entertainment > Sports (0.93)
- Energy > Oil & Gas > Upstream (0.68)
- Reservoir Description and Dynamics (0.68)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring (0.46)
Atomistic Simulations of Semi-Infinite Cracks In Bcc Iron Using an Analytic Bond-Order Potential
Ersland, C.H. (Department of Engineering Design and Materials, Norwegian University of Science and Technology) | Thaulow, C. (Department of Engineering Design and Materials, Norwegian University of Science and Technology) | Østby, E. (SINTEF Materials and Chemistry)
ABSTRACT: Molecular dynamics simulations of a mode I crack in pure _-Fe have been performed, using a fixed boundary moving according to linear elastic displacement equations. An analytic bond-order potential (ABOP) have been used, and the effect of crack orientation in the lattice has been investigated. The different crack-tip behavior due to orientation is studied, and the stress-intensity factors at crack extension/dislocation emission are compared with each other, and with the use of different system sizes and shapes. INTRODUCTION The mechanisms of brittle fracture in materials are, after a century of research, still not fully understood. When a crack extends, the first, critical events leading to extension happens inside the process zone around the crack-tip, where conventional fracture mechanics breaks down. With the emergence of atomistic modeling we can now study details of the complex phenomena taking place inside this zone. An important part of these kind of simulations is the interatomic potential, the force field describing the interactions between the atoms. Cracks in single crystal iron have previously been studied by many other authors during the last decades: Gordon et al. [2007] compared several embedded atom method (EAM) and Finnis- Sinclair (FS) potentials in different crystallographic orientations, while Guo et al. [Guo et al., 2003, Guo and Wang, 2007] studied the effect of temperature and strain rate in various orientations using an FS potential. Machová and Beltz [2004] and Beltz and Machová [2004] have published several studies with cracks under the influence of T-stress with several orientations considered, using an FS potential, while Shastry and Farkas [1996] have studied the competition between cleavage and dislocations in several orientations using molecular statics and an EAM potential. As seen above, most studies of cracks using molecular dynamics/statics use empirical pair potentials like EAM and FS.
- Europe > Norway (0.47)
- North America > United States (0.33)
- Reservoir Description and Dynamics > Reservoir Simulation (0.89)
- Well Completion > Hydraulic Fracturing (0.87)
- Data Science & Engineering Analytics > Information Management and Systems (0.68)
- Reservoir Description and Dynamics > Fluid Characterization > Fluid modeling, equations of state (0.55)
ABSTRACT: The ‘spudcan’ foundations for mobile drilling rigs continue to exhibit a high failure rate in the offshore oil and gas industry. Contributing to this is the more frequent use of larger jack-ups in regions with highly stratified seabeds and continual exploration in deeper and untested environments. The experimental results show that the failure was less severe for a carbonate sand layer sandwiched by soft clay layer compared to that for a silica sand layer, in spite of the higher critical state friction angle of the carbonate sand. INTRODUCTION Progression of Drilling Rigs Most offshore drilling in shallow to moderate water depths throughout the world is performed from independent three leg jack-up rigs with proven flexibility, mobility and cost-effectiveness. Depletion of known reserves in the traditional regions and in shallow waters, is resulting in exploration in deeper, unexplored and undeveloped environments with more complex seabed soil conditions. In emerging provinces and fields, highly layered soils are prevalent (see Fig. 1). Over 75% of the case study data sets forming the basis for the ‘InSafeJIP’ (Osborne et al., 2009) involve stratified seabed profiles, with interbedded layers of clay and sand evincing strong variations in shear strength. The Sunda Shelf, offshore Malaysia, Australia's Bass Strait and North-West Shelf, offshore India and Arabian Gulf are particularly problematic in terms of stratigraphy and soil types. The seabed sediments offshore Australia and Arabian Gulf comprise layered carbonate sediments that range from relatively permeable calcareous sands to fine grained muds, and with varying degrees of intergranular cementation; an example is shown in Fig. 1a (Erbrich, 2005; Watson and Humpheson, 2005). Layered soil profiles result from various geological processes, including previous crustal desiccation, sand channelling and evolving depositional environments associated with changing sea level (Castleberry II and Prebaharan, 1985; Paisley and Chan, 2006).
- Asia (1.00)
- Oceania > Australia > Tasmania > Bass Strait (0.24)
- Oceania > Australia > Western Australia > North West Shelf (0.24)
- Research Report > Experimental Study (0.68)
- Research Report > New Finding (0.66)
- Geology > Mineral > Silicate > Phyllosilicate (0.92)
- Geology > Geological Subdiscipline (0.88)
- Geology > Rock Type > Sedimentary Rock (0.76)
- North America > United States > Wyoming > Hunt Field (0.89)
- North America > United States > Gulf of Mexico > Central GOM > West Gulf Coast Tertiary Basin > Walker Ridge > Block 759 > Jack-St Malo-Big Foot Field > Jack Field > Wilcox Formation (0.89)
- North America > United States > Gulf of Mexico > Central GOM > West Gulf Coast Tertiary Basin > Walker Ridge > Block 758 > Jack-St Malo-Big Foot Field > Jack Field > Wilcox Formation (0.89)
- North America > Canada > Alberta > Smith Field > Am Eagle Et Al Smith 15-7-71-24 Well (0.89)
- Well Drilling > Drilling Equipment > Offshore drilling units (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization (1.00)
Effects of Swirls On Natural Gas Flow In Supersonic Separators
Wen, Chuang (College of Transport & Storage and Civil Engineering, China University of Petroleum) | Cao, Xuewen (College of Transport & Storage and Civil Engineering, China University of Petroleum) | Yang, Yan (College of Transport & Storage and Civil Engineering, China University of Petroleum) | Zhang, Jing (College of Transport & Storage and Civil Engineering, China University of Petroleum)
ABSTRACT: A new swirling device composed of some vanes and an ellipsoid was designed for the supersonic separator. The effects of swirls on natural gas flow were computational simulated with the Reynolds Stress model (RSM). The results show that the strong swirls result in the non-uniform radial distribution of the gas dynamic parameters. The presence of the strong swirls damages the expansion characteristics of the Laval nozzle. With moderate swirls, the low temperature (–60°C) and strong centrifugal field (106 m/s2) are obtained to condense and separate water and heavy hydrocarbons from natural gas in the supersonic separator. INTRODUCTION The concept of supersonic separation is a new technology to condensate and separate water and heavy hydrocarbons from natural gas, working on two major principles of the gas expansion and cyclone separation. The idea was first patented in 1989 by Stork Product Engineering, as the condi-cyclone, a method to remove water from air by forcing it through a tube at supersonic speed, intended for use in air conditioners (Kontt, 2000). The supersonic separator prevents the hydrate problems and eliminates the needs for inhibitor and regeneration systems due to the short residence time in the device, providing an environmentally friendly facility. As a static device, there are no rotating parts to enable high reliability and availability. Alferov, Baguirov, Feygin, Arbatov, Imayev, Dmitriev and Rezunenko(2004) and Betting, Holten and Veen (2003) proposed a method and apparatus for the separation and liquefaction of the gas mixtures, respectively.There are two structures for the supersonic separators. One is called "Twister I", in which a swirl generation device is installed in downstream portion of the supersonic nozzle, and the other is named "Twister II" or "3-S (Super Sonic Separator) separator", where the swirl generation device is installed in the entrance of the nozzle.
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring (1.00)
- Facilities Design, Construction and Operation > Processing Systems and Design (1.00)
- Reservoir Description and Dynamics (0.94)
ABSTRACT: This paper investigates the rubber inclusion effect on the strength and physical characteristics of composite geomaterial (CGM) in which dredged soil, crumb rubber and bottom ash are reused for recycling. Several series of test specimens were prepared at 5 different percentages of rubber content (i.e. 0%, 25%, 50%, 75%, and 100% by weight of the dry dredged soil) and three different percentages of bottom ash content (i.e. 0%, 50% and 100% by weight of the dry dredged soil). The mixed soil specimens were subjected to unconfined compression and elastic wave tests to investigate their unconfined compressive strengths and small strain properties. The test results indicated that the rubber content and bottom ash content were found to influence the strength and stress-strain behavior of CGM. Overall, the bulk unit weight, the unconfined compressive strength, elastic wave velocity, and small strain moduli of CGM were found to decrease with increasing rubber content. The results of elastic wave tests indicate that the higher rubber content, the lower elastic wave velocity and the lower shear modulus. Among the samples tested in this study, those with a lower rubber content exhibited sand-like behavior and a higher shear modulus. INTRODUCTION Due to the large number of vehicles being manufactured, discarded tires have become an ongoing environmental problem worldwide. In Korea, approximately 20 million tires are discarded annually as shown in Fig. 1. More than 500 million tires are discarded in the United States every year. Some of these tires are left stockpiled in landfills or are illegally dumped, providing breeding grounds for harmful insects and rodents (Rubber Manufacturers Association, 2006). Discarded tires can be classified into several groups, based on shape and size: whole tire, slit tire, shredded or chipped tire, ground rubber, or crumb rubber.
Numerical Simulation of Tsunami Generation By the Potential Flank Collapse of the Cumbre Vieja Volcano
Abadie, Stéphane (Laboratoire SIAME, Université de Pau et des Pays de l'Adour, Department of Ocean Engineering, University of Rhode Island) | Harris, Jeffrey (Department of Ocean Engineering, University of Rhode Island) | Grilli, Stéphan (Department of Ocean Engineering, University of Rhode Island)
ABSTRACT: We perform numerical simulations of wave generation by the potential flank collapse of the Cumbre Vieja Volcano (CVV; La Palma, Canary Islands, Spain). Subaerial slide scenarios are first defined based on recent slope stability studies of CVV; the identified scenarios have smaller volumes than those proposed by Ward and Day (2001), in the pioneering work that triggered the interest of the research community for CVV. Simulations of tsunami sources are performed using the previously validated (Abadie et al., 2010) 3D incompressible multifluid Navier-Stokes model THETIS. Both 2D and 3D simulations (the latter using a cylindrical mesh) are performed, which investigate near field wave generation. Results show that a slide of 60–70 km3 would have very significant consequences, at least for la Palma and other surrounding islands. Far field waves (tsunamis) are simulated in the 2D horizontal, fully nonlinear and dispersive, Boussinesq model FUNWAVE, which is initialized with the 3D Navier-Stokes solution. Results of preliminary tests are shown in the paper and more results will be presented at the conference. INTRODUCTION Since the pioneering, but controversial, work of Ward and Day (2001), the potential flank collapse of the Cumbre Vieja Volcano (CVV) on La Palma island (Canary Islands, Spain; Fig. 1) has been the object of numerous studies of the related tsunami hazard. Their simulations resulted in extremely large local waves, which reached still up to a 20 meters elevation, in the far field off of the US East coast (particularly in Florida). This catastrophic landslide scenario was severely criticized (e.g., Mader, 2001; or Pararas-Carayannis, 2002) as well as the wave modeling approach used in the work. Masson et al. (2002, 2006) later found evidences of past large paleo-submarine landslides of O(100 km3) volume, around the canary islands, at least demonstrating that such events were not purely speculative.
- North America > United States (1.00)
- Europe > Spain > Canary Islands (0.74)
- South America > Atlantic Basin (0.99)
- North America > Atlantic Basin (0.99)
- Europe > Atlantic Basin (0.99)
- Africa > Atlantic Basin (0.99)
- Reservoir Description and Dynamics > Reservoir Characterization (1.00)
- Data Science & Engineering Analytics > Information Management and Systems (1.00)