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Collaborating Authors
The Twenty-fifth International Ocean and Polar Engineering Conference
Abstract Steel Catenary Riser (SCR) is widely used in oil and gas development. And the operability envelopes of SCR during its installation are to determine the environment conditions of J Lay installation and find the boundaries between Abandon and Recovery. The code API RP 2RD and the max tension capability of the SEMI lay barge are selected to be the constraint of operability envelopes. FEM models are established by ORCAFLEX, during the installation, strength analysis and max effective tension of SCR with different angle between wave and current, wave-period under different wave direction, wave-current are presented to carry out the operability envelopes, and their graphs are drawn after calculation. The environment condition is in South China Sea with water depth 3000m, the max tension capability of the SEMI is 900t, and the riser size is 0.4572m outer diameter and 0.0254m thickness. The results show that the operability envelopes turn small when 1) wave and current in same direction, and 2) wave direction in 180° with its period near natural period of SEMI. Furthermore, J lay system is more sensitive to the wave conditions. Except the wave and current, performances of SEMI and SCR have obvious impact on J lay operability envelopes. In the design of J lay system and SCR installation, environment, SEMI and SCR should be considered overall. Proper SEMI type and riser type should be chosen, and the J lay operation should be executed in mild sea conditions.
Influence of Joint Flexibility on Local Dynamics of a Jacket Support Structure
Popko, Wojciech (Fraunhofer Institute for Wind Energy and Energy System Technology IWES Northwest) | Georgiadou, Sofia (Norwegian University of Science and Technology) | Loukogeorgaki, Eva (Fraunhofer Institute for Wind Energy and Energy System Technology IWES Northwest) | Vorpahl, Fabian (Aristotle University of Thessaloniki)
Abstract The effect of different modeling techniques of the local joint flexibility on the local dynamics of a jacket support structure for an offshore wind turbine is investigated. Two numerical models of a jacket supporting a generic turbine are analyzed in the aero-hydro-servo-elastic tool ADCoSOffshore. The first model is setup with Euler-Bernoulli beam elements, while the second one utilizes superelements for the joints' representation and Euler-Bernoulli beams for the remaining parts of the structure. Time domain simulations are run for deterministic and stochastic load cases and local jacket dynamics are investigated. The local response of the braces is compared with the global response at the jacket legs in terms of power spectral densities. Damage equivalent loads are calculated at several positions along the jacket to capture the impact of local and global dynamics on those loads. It is observed that the superelement model leads in general to higher fatigue loads than the beam model. A methodology to remove the global motion component from the displacement time history of the brace central joint is discussed. Larger displacements of the brace central joints are observed for the superelement model than for the beam model. It is recommended to use superelement modeling technique for more a accurate representation of joints in the jacket support structures.
- Europe (1.00)
- North America > United States (0.68)
Abstract Steel catenary riser (SCR) has been widely used in deepwater oil and gas field development. A simple catenary shape is the most popular form of the SCR hanging off from a floating production system (FPS); and a lazy wave configuration is often considered when the riser experiences high fatigue effects associated with severe environmental conditions in the field. The design of deepwater risers depends on a large number of parameters, which may constantly change during execution of a project. It is always a great challenge for the riser design methodology to quickly and effectively accommodate these changes. Quick and correct responses to a design change are particularly critical for an on-going project, where concurrent engineering is of foremost concern. This paper presents a numerical method for simulating the deepwater SCR in-field profiles in simple catenary and/or lazy wave configurations. By using closed-form analytical formulations of various catenary shapes, the SCR can be described as a function of top tension and displacements at the hang-off point due to the floating production platform motions. The method is suitable for determining the relationships among riser properties, riser instant profiles, and the platform motions. The simulation quickly and correctly provides the hang-off loads at top, riser span variation and touch-down point (TDP) walking and curvature change, associated with the platform motions in the field. The results quantify the complex interplay among these key design variables, identify the controlling design variables, and allow the designer to improve and optimize riser system design.
- North America > United States (0.48)
- Asia (0.29)
These wave components must represent the total energy of the spectral model, This work describes a simplified analysis procedure, intended for and also the wave elevations and velocities observed in the actual preliminary design stages of risers connected to floating production irregular seastate. For this purpose, it is common to use at least 200 systems (FPS). The procedure may be seen as an extension of the regular wave components, or even more. Moreover, long simulation "equivalent regular wave" approach proposed in some design codes, times (typically 3 hours, or 10800s) are required to achieve statistical where the amplitude of a single regular wave (equivalent to a given stability of the random response to the irregular seastate, including for irregular seastate) is determined taking the motion RAO for a given instance the extreme values of platform motions, and riser top tensions. D.O.F. of the platform assumed to be the most critical for the riser response (usually the heave motions). Here, we consider an extension All those aforementioned factors may lead to excessive computational of this procedure where an ensemble of six regular waves is generated, times, and motivate the studies presented in this work, related to a one for each rigid-body D.O.F.. This wave ensemble could then be simplified representation of irregular seastates, adequate for employed for the dynamic analyses, allowing shorter simulation times preliminary design stages. For instance, in the context of the design (since the loading is deterministic), and leading to reasonable results methodology proposed by Girón et al. (2014), where thousands of with substantial reduction in CPU times. Case studies are presented to environmental loading cases should be employed in expedite analyses assess the proposed procedure, comparing its results with those intended to select critical cases, which should be subsequently verified provided by the full spectral irregular seastate approach.
Abstract Effects of phase transition of LNG during sloshing are investigated by numerically simulating LNG and its vapor as the approaching liquid inside tank. Boiling mechanism of liquid cargo in saturated state based on the basic theory of heat transfer is clarified with consideration of the LNG thermodynamic properties. And the effect of phase transition of cargo liquid during the sloshing is simulated using CFD code-Fluent. The parameter sensitivity analysis on LNG tank sloshing impact load is conducted based on the developed numerical method above. Liquid sloshing phenomenon inside tank is analyzed under the theoretical study and numerical method. The time histories of the liquid free surface shape and the dynamic sloshing impact inside the tank are obtained, which are well agreed with related data. The sloshing impact assessment method is developed through the parameter sensitivity analysis based on the numerical method.
- Energy > Oil & Gas > Midstream (1.00)
- Transportation > Freight & Logistics Services > Shipping > Tanker (0.52)
Research on Proper Fins Designed for An Axial Flow Fan to Produce Homogeneous Wind for Model Test of Floating Wind Turbines
Yu, Long (Shanghai Jiao Tong University) | Huang, Chao (Shanghai Jiao Tong University) | Zhao, Yongsheng (Shanghai Jiao Tong University) | He, Yanping (Shanghai Jiao Tong University)
Abstract This paper describes the effort for design proper fins behind the blades for producing possible anti-twist flow. According to the Computational Fluid Dynamics(CFD) methods, the whole geometry model of a specified axial fan has been built. The authors adopt the techniques for previously analyzing the ducted propeller and energy saving devices for designing a set of proper fins behind the fan blades. The numerical investigation has been carried out for full scale fins. The effect of fins is promising and the method of installing these fins can be an appropriate solution for axial fans producing homogeneous flow.
Abstract The objective of this paper is to present a methodology of unsteady CFD simulation of a floating offshore wind turbine (FOWT) experiencing platform motions. Based on the RANS equations and the SST α-ω turbulence model, aerodynamic simulations for a NREL 5MW turbine combined with OC3-Hywind spar buoy have been studied. The simulation results of a fixed wind turbine to verify the numerical model show relatively good agreement with NREL published data. Furthermore, based on the validation of three-dimensional CFD model the effect of typical periodic surge, pitch and yaw motions of the platform are investigated. With different periods and magnitudes of the platform motions, the aerodynamic performance of the wind turbine is demonstrated to vary dramatically. The power output performance of the turbine and the fatigue strength of structures could be significantly improved by reasonable controlling of the platform motions.
Abstract Typically, the fracture toughness of welded joints are evaluated using Charpy-V tests. This method has been sufficient for traditional steels, which obey Charpy-T0 correlation. In recent years ultra-high-strength steel (UHSS) has come to market in which the Charpy correlation is not reliable. To validate the weld toughness of two different types of UHSS, fracture tests were performed according to ASTM procedures on different portions of weld and heat affected zones (HAZ) as well as the base material. The results show that when using the proper heat input during welding the fracture toughness is appropriate in the weld area. Naturally these results are valid only for the tested steel grades and cannot be used with other UHSS products.
Abstract In this paper, the sediment-laden flow around a circular cylinder is numerically simulated in order to obtain better understanding of hydrodynamics associated. A range of cases with different Reynolds numbers (Re) are studies. The effects of the concentration of the sediment on the drag coefficient are investigated. Results show that due to the fact that the laden sand particle colliding the cylinder, it amplifies the drag coefficients, which increase as the increase of the sediment concentration, within the range of the application of the study. It is also observed that as the flow becomes more turbulent (higher Re), the effects of the laden particle on the drag coefficients become more significant.
- Asia > China (0.17)
- North America > United States (0.16)
- Research Report > New Finding (0.51)
- Research Report > Experimental Study (0.51)
Abstract This paper aims at the problem of the precise sinking for the overweight and huge immerse tunnel elements in construction of the undersea tunnels. To avoid application of the measuring tower in traditional construction and reduce the rounds of the diving by divers, a method based on underwater acoustic positioning technique is proposed in this paper that can reduce the cost and risk of construction effectively. Meanwhile, increasing the positioning precision, the key techniques of the underwater acoustic positioning technique are also involved. Finally, the paper gives an entire method for sinking the immerse tunnel elements based on underwater acoustic positioning technique and the simulation results show that the algorithm has a good precision in positioning the tunnel elements.
- Africa > Middle East > Morocco > Figuig Province > Tarfaya Basin > Tendrara License > Tendrara Field > Saharan Hercynian Formation > Tendrara-2 Well (0.89)
- Africa > Middle East > Morocco > Figuig Province > Tarfaya Basin > Tendrara License > Tendrara Field > Saharan Hercynian Formation > Tendrara-1 Well (0.89)
- Africa > Middle East > Morocco > Figuig Province > Tarfaya Basin > Tendrara License > Tendrara Field > Algerian Triassic Province Formation > Tendrara-2 Well (0.89)
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