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Green hydrogen presents a sustainable and environmentally friendly solution for clean energy production and transportation. This study aims to identify the optimal profile of green hydrogen transportation risers originating from a floating offshore wind turbine (FOWT) integrated with a hydrogen production facility. Employing the Cummins equation, a fully coupled dynamic analysis for FOWT with a flexible riser was conducted, with the tower, mooring lines, and risers described using a lumped mass line model. Initially, motion response amplitude operators (RAOs) were compared with openly published results to validate the numerical model for the FOWT. Subsequently, a parametric study was conducted on the length of the buoyancy module section and the upper bare section of the riser by comparing the riser’s tension and bending moment. The results indicated that as the length of the buoyancy module increases, the maximum tension of the riser decreases, while it increases with the lengthening of the bare section. Furthermore, shorter buoyancy modules are expected to experience less fatigue damage, with the length of the bare section having a relatively minor impact on this phenomenon. Consequently, to ensure safety under extreme environmental conditions, both the upper bare section and the buoyancy module section should be relatively short.

In order to investigate the effects of the top-end dynamic boundary of risers caused by floater motions on their vortex-induced vibration (VIV) characteristics, a combined model comprising a buoyancy can with a relatively simple structural form and a riser is taken as the research object in the present study. The aspect ratios of the buoyancy can and the riser model are 5.37 and 250, respectively. A set of experimental devices is designed to support the VIV test of the riser with a dynamic boundary stimulating the vortex-induced motion (VIM) of the buoyancy can under different uniform flow and regular wave conditions. Several data processing methods are applied in the model test, i.e., mode superposition, Euler angle conversion, band pass filter, fast Fourier transform, and wavelet transform. Based on the testing results, the effect of low-frequency VIM on the high-frequency VIV of the riser is discussed in relation to a single current, a single wave, and a combined wave and current. It is found that the coupling effect of VIM on the riser VIV presents certain orthogonal features at low current velocities. The effect of the cross-flow VIM component on VIV is far more prominent than that of its counterpart, the in-line VIM, with increasing flow velocity. The VIM in the combined wave–current condition significantly enhances the modulation of vibration amplitude and frequency, resulting in larger fluctuation peaks of vibration response and further increasing the risk of VIV fatigue. [ABSTRACT FROM AUTHOR]

O slug flow em risers de extração de petróleo em águas profundas é um fenômeno amplamente conhecido por seu potencial destrutivo nos casos em que esse efeito se torna extremo, fazendo com que a pressão se acumule e, consequentemente, origine o fluxo de pressão oscilante. Esse tipo de escoamento ocorre devido à característica multifásica na extração do óleo, formada geralmente pelas fases óleo e ar (gás). Ao longo de toda a história da extração de petróleo, o controle e reconhecimento desse padrão de fluxo gera desafios à engenharia de poços, e ainda hoje o método de mitigação e controle utilizado é subjetivo e dependente da experiência do operador de sonda. A proposta deste artigo é apresentar uma ferramenta de diagnóstico utilizando inteligência artificial a partir das informações de variação de pressão (velocidades de escoamento) coletadas pelos sensores do BOP (Blow Out Preventer) para o reconhecimento do fluxo de golfadas (slugging). Para analisar o slugging em toda a sua faixa e variação de velocidades, aplica-se uma análise numérica fluidodinâmica computacional (CFD) utilizando o software ANSYS Fluent. Os mapas identificadores dos tipos de escoamento devidos à velocidade de escoamento das fases, amplamente aceitos na literatura pertinente, foram utilizados para validar os resultados encontrados na análise CFD, comprovando que o modelo implementado neste estudo está em consonância com o fenômeno real. Os resultados obtidos foram usados para gerar um banco de dados que possibilitou o desenvolvimento de uma rede neural para diagnóstico de slugging. Algumas maneiras de controlar ou mitigar o slugging pesado também são discutidas.

Fluid catalytic cracking could convert crude palm oil into valuable green fuels to substitute fossil fuels. This study aimed to predict the phenomenon and green fuels yield in the industrial fluid catalytic cracking riser using computational fluid dynamics. A three-dimensional transient simulation using the Eulerian-Lagrangian with the multiphase particle-in-cell is to investigate reactive gas-particle hydrodynamics and the four-lump kinetic network model with the rare earth-Y catalyst for crude palm oil cracking behaviors. The study results show that the fluid and catalyst velocity profile increase in the middle of the riser reactor because the cracking reaction process that produces OLP and Gas products has a lighter molecular weight. The endothermic reaction causes the temperature profile to decrease because the heat of the reaction comes from the catalyst. This analysis shows that the simulation accurately predicts green fuel products from crude palm oil. As a result, the crude palm oil conversion, organic liquid product yield, and Gas yield correspond to 70 wt%, 28.8 wt%, and 27.5 wt%, respectively. Compared to the experimental study, the computational prediction of yield products showed good agreement and determined the optimal riser dimension. The methodology and results are guidelines for optimizing the FCC riser process using CPO.

Fluid catalytic cracking could convert crude palm oil into valuable green fuels to substitute fossil fuels. This study aimed to predict the phenomenon and green fuels yield in the industrial fluid catalytic cracking riser using computational fluid dynamics. A three-dimensional transient simulation using the Eulerian-Lagrangian with the multiphase particle-in-cell is to investigate reactive gas-particle hydrodynamics and the four-lump kinetic network model with the rare earth-Y catalyst for crude palm oil cracking behaviors. The study results show that the fluid and catalyst velocity profile increase in the middle of the riser reactor because the cracking reaction process that produces OLP and Gas products has a lighter molecular weight. The endothermic reaction causes the temperature profile to decrease because the heat of the reaction comes from the catalyst. This analysis shows that the simulation accurately predicts green fuel products from crude palm oil. As a result, the crude palm oil conversion, organic liquid product yield, and Gas yield correspond to 70 wt%, 28.8 wt%, and 27.5 wt%, respectively. Compared to the experimental study, the computational prediction of yield products showed good agreement and determined the optimal riser dimension. The methodology and results are guidelines for optimizing the FCC riser process using CPO. [ABSTRACT FROM AUTHOR]

In order to investigate the effects of the top-end dynamic boundary of risers caused by floater motions on their vortex-induced vibration (VIV) characteristics, a combined model comprising a buoyancy can with a relatively simple structural form and a riser is taken as the research object in the present study. The aspect ratios of the buoyancy can and the riser model are 5.37 and 250, respectively. A set of experimental devices is designed to support the VIV test of the riser with a dynamic boundary stimulating the vortex-induced motion (VIM) of the buoyancy can under different uniform flow and regular wave conditions. Several data processing methods are applied in the model test, i.e., mode superposition, Euler angle conversion, band pass filter, fast Fourier transform, and wavelet transform. Based on the testing results, the effect of low-frequency VIM on the high-frequency VIV of the riser is discussed in relation to a single current, a single wave, and a combined wave and current. It is found that the coupling effect of VIM on the riser VIV presents certain orthogonal features at low current velocities. The effect of the cross-flow VIM component on VIV is far more prominent than that of its counterpart, the in-line VIM, with increasing flow velocity. The VIM in the combined wave–current condition significantly enhances the modulation of vibration amplitude and frequency, resulting in larger fluctuation peaks of vibration response and further increasing the risk of VIV fatigue.

This work presents a steady-state one-dimensional model of the FCC riser considering the vaporisation of the gas oil feed and subsequent cracking reactions. The evaporation of droplets is studied using three models: the classical homogeneous model and the heterogeneous vaporisation models from the literature. Droplets are modelled using the Lagrangian framework model for particles moving through a fluid. This was coupled with the gas–solid flow field describing the catalyst particulate transport in the riser. Cracking reaction kinetics are modelled using a four-lumped model. The model was then validated against published plant data. The model performed well in terms of gas oil conversion, gasoline yield, pressure drop, and phase temperature profiles. Therefore, it is suitable for use in the design and optimisation of new and existing FCC unit risers, particularly in cost–benefit analysis considering the current push away from petroleum energy sources. It was found that vaporisation models are largely insignificant in terms of gas oil conversion profiles and gasoline yield for usual operation conditions of FCC risers, which is a finding that had yet to be proven in the literature. Vaporisation models are shown to only affect conversion and yield when the initial droplet exceeds 2000   μ m . [ABSTRACT FROM AUTHOR]

The flow field induced by internal solitary waves (ISWs) is peculiar wherein water motion occurs in the whole water depth, and the strong shear near the pycnocline can be generated due to the opposite flow direction between the upper and lower layers, which is a potential threat to marine risers. In this paper, the flow field of ISWs is obtained with the Korteweg-de Vries (KdV) equation for a two-layer fluid system. Then, a linear analysis is performed for the dynamic response of a riser with its two ends simply supported under the action of ISWs. The explicit expressions of the deflection and the moment of the riser are deduced based on the modal superposition method. The applicable conditions of the theoretical expressions are discussed. Through comparisons with the finite element simulations for nonlinear dynamic responses, it is proved that the theoretical expressions can roughly reveal the nonlinear dynamic response of risers under ISWs when the approximation for the linear analysis is relaxed to some extent. [ABSTRACT FROM AUTHOR]

To produce low olefin gasoline with high octane number by Fischer-Tropsch (F-T) wax fluid catalytic cracking (FCC) process, operating conditions optimization were carried out in the pilot-scale riser and turbulent fluidized bed (TFB) FCC unit. The experimental results in the riser indicated that under the condition of low reaction temperature and regenerated catalyst temperature, large catalyst-to-oil weight ratio (C/O) and long reaction time, the gasoline olefin content could be reduced to 20.28 wt%, but there is large octane number loss owing to a great loss in high octane number olefin. Therefore, a novel FCC process using the TFB reactor was proposed to strengthen the aromatization reaction. The reaction performance of TFB reactor were investigated. The result demonstrated that the TFB reactor has more significant effect in reducing olefins and improving aromatics. At the expense of certain gasoline yield, the gasoline olefin content reduced to 23.70 wt%, aromatics content could increase to 26.79 wt% and the RON was up to 91.0. The comparison of reactor structure and fluidization demonstrated that the TFB reactor has higher catalyst bed density. The reaction heat and coke combustion heat was calculated indicating the feasibility of its industrial application of the TFB process. [ABSTRACT FROM AUTHOR]

Maintaining structural safety for the public is one of the most utmost importance to avoid catastrophic events involving human casualty. For this reason, vast amount of research is being conducted around the globe to create an efficient system to detect structure damage. In this study, a local damage detection method known as the electromechanical impedance method is improved with the new concept introduced in this study. The idea allows one to detect debonding of composite structures at a reduced cost. Since the electromechanical impedance requires one to permanently attach the piezoelectric (PZT) transducer onto the target structure, a moving device was made which creates temporarily contact with the target structure to investigate the possibility of replacing hundreds of PZT transducers into a single device. The experiment involves using two different glass fiber epoxy composite plates with different thicknesses to evaluate the performance of the roller PZT device. The findings from the experiments show possibility of detecting debonding of composite plate using the proposed idea. [ABSTRACT FROM AUTHOR]

This paper deals with the recoil suppression problem of a deepwater drilling riser system via active H ∞ control using both current and delayed states. First, based on the three degrees of freedom spring–mass–damping model of the riser system, an incremental dynamic equation of the system subject to the platform heave motion and the friction force induced by drilling discharge mud and seawater is established. Then, to reject recoil movements of the riser, a delayed state feedback H ∞ controller with delayed states as well as current states is designed. The existence conditions and the design method of the delayed H ∞ recoil controllers are presented. Third, the effects of the introduced time-delays on the recoil control of the riser are analyzed, and the design of optimal artificial time-delays is formulated as the minimum value problem of a series of quintic algebraic polynomials, which are related to the weights of average response amplitudes, steady-state errors, and the control force. Lastly, simulation results are provided to demonstrate the effectiveness of delay-free and delayed H ∞ recoil control schemes for the riser. It is shown that (i) under the delayed H ∞ controllers, the recoil responses of the riser can be controlled significantly; (ii) the decay rate of the recoil response under the delay-free H ∞ controller is slightly faster than the one under the delayed H ∞ controllers. However, the former requires more control cost than the latter; (iii) compared with the delayed H ∞ controller with the existing linear quadratic optimal controller, the control cost by the former is larger than that by the latter. However, the steady-state errors of the riser under the latter are slightly smaller than that under the former; (iv) the introduced time-delays with proper size play positive role of suppressing recoil response of the system, and the corresponding delayed H ∞ controller series provide more options for recoil control of the riser. • An incremental dynamic equation of the deepwater drilling riser recoil system is proposed. • Delayed state feedback H ∞ recoil controllers are designed for the riser system. • An algorithm to design optimal time-delays is developed for the riser control system. • The time-delays with proper size play positive role of reducing riser recoil response. [ABSTRACT FROM AUTHOR]

Renewable energy resources are promising in power generation due to their sustainability aspect and environment friendliness as they are means of pollution free power production. Wind energy.y is utilized for power production with the help of wind turbines. The offshore and onshore windfarms consisting of horizontal axis wind turbines are major contributors in the wind energy. However, this type of turbine is not domestically viable mainly due to limitations of directionality and noise. Vertical axis wind turbines do not have these constraints and may blend in the urban environments. In built environments, the wind flow is quite complex due to large scale effects and turbulence. In this paper, the academic building of a university is studied as a possible platform for harnessing the wind energy resources. This case study is performed on academic blocks of University of Gujrat. These building environments were modeled and analyzed with computational fluid dynamic software to model the wind behavior on the building roof top. These results show that there is potential in setting up micro windfarms for the academic environments. The simulation for single building showed a potential for 61.8kW whereas this potential decreased substantially when terrain effects are considered using the circular arrangement for the simulation. [ABSTRACT FROM AUTHOR]

Abstract In this study, we will discuss the process of casting used aluminum metal. Used aluminum is one of the industrial wastes that can be converted into products using the casting method. This study aims to obtain a good casting material with good hardness values ​​and minimal defects. The research will focus on the results of castings by analyzing the visuals and hardness values ​​of the specimens. The research design is a pre-experimental type of One-Shot Case Study by conducting treatments whose results will be directly observed and analyzed descriptively. The treatment given is to increase the number of risers in recycled aluminum castings. Variations in the number of risers are 1 riser, 2 riser, and 3 riser. Each variation has 3 specimens, so there are 9 specimens in the study. The data from the test results contained a fairly large porosity value for each riser variation. The hardness value that has been tested using the Rockwell hardness tester obtained the highest hardness value occurs in the 2 riser variation, namely 27.69 HRA and the lowest hardness value occurs in the 3 riser variation, namely 21.56 HRA. Thus, for casting used aluminum with a casting pattern as in this study, it is best to use 2 risers.

To reduce the vibration damage to the riser, hydrodynamic parameters of a smooth riser and a riser with triple symmetrically distributed helical strakes are evaluated in an experiment. The wave and current in natural environment are conceptualized to the experimental condition of the oscillatory flow and the uniform flow. Experiment cases are divided into the static flow and the uniform flow, while the risers oscillate along the in-line, the transverse, and the diagonal direction. The added mass coefficient Cm and the drag coefficient Cd are calculated from experimental data by using the Morison equation. The results of the riser with strakes indicate that Cm is independent of the Keulegan-Carpenter (KC) number and the oscillating direction. Cd is found to be in inverse proportion to the ratio of 1/3 power of the KC number and the maximum flow speed to oscillatory velocity. This finding is consistent with the format of Morison parameters of a flat plate in oscillatory flow, which endows the classical theory with novel validation and implication in the design of a riser. Under the same condition, the Cd of the helical strake riser is promoted over 273% than the bare riser, which indicates that the helical strakes efficiently reduce the influence of oscillation under complex conditions. The results provide a new solution for vibration reduction of offshore structures, which is of high value in ocean engineering.

In the extraction and production of oil and gas in sea environments, multiple components and systems are used, among them, flexible dynamic pipes, responsible for the transport of fluids. Because they are exposed to mechanical stress and corrosive conditions, it is important to assess the fatigue performance of the flexible pipe's components when there are signs of corrosion on their surfaces. Especially, the steel wires that bear the mechanical load during a riser's operation, are often vulnerable components to failure derived from the combination of corrosion and oscillating loads. The present work has the objective to assess the effects of corrosion pits, characterized by their dimensions, quantities and location, in the fatigue life of flexible pipes' tension wires. To make possible the correlation of the pits' parameters with their fatigue performance, the electrical discharge machining process was used, allowing a greater control of pits' development when compared to natural corrosion. The Taguchi method was employed to reduce the total amount of parameter combinations to be tested and to ascertain the effects of each parameter in the fatigue performance. Some pits obtained by electrical discharge machining didn't have the determined dimensions, especially the narrower and deeper pits. Fatigue tests were conducted in tensile armor wire specimens to assess the number of cycles to failure at pre-defined load levels. The fatigue testing results of electrical discharge machining corroded specimens suggest a more significant effect of the pits' diameter in reducing the fatigue performance, when compared to the controlled parameters of depth, quantity, location and aspect ratio. The maximum cycles reduction was around 73%, for wider pits, located in the planar face of the specimen, and the minimum reduction, around 40%, for narrower pits, located at the edge of the specimen.

This work presents a steady-state one-dimensional model of the FCC riser considering the vaporisation of the gas oil feed and subsequent cracking reactions. The evaporation of droplets is studied using three models: the classical homogeneous model and the heterogeneous vaporisation models from the literature. Droplets are modelled using the Lagrangian framework model for particles moving through a fluid. This was coupled with the gas–solid flow field describing the catalyst particulate transport in the riser. Cracking reaction kinetics are modelled using a four-lumped model. The model was then validated against published plant data. The model performed well in terms of gas oil conversion, gasoline yield, pressure drop, and phase temperature profiles. Therefore, it is suitable for use in the design and optimisation of new and existing FCC unit risers, particularly in cost–benefit analysis considering the current push away from petroleum energy sources. It was found that vaporisation models are largely insignificant in terms of gas oil conversion profiles and gasoline yield for usual operation conditions of FCC risers, which is a finding that had yet to be proven in the literature. Vaporisation models are shown to only affect conversion and yield when the initial droplet exceeds 2000 μm.

The increasing energy demand has led to more explorations in the oil and gas industry. To achieve this, marine risers and pipelines are used to convey fluid and other resources to meet the increasing demand. In recent years, hybrid flexible composite risers have become more adaptable. Flexible risers have already proven to be a popular riser solution for various floating production systems in shallow to deepwater in many parts of the world due to their good dynamic behaviour and dependability. The hybrid flexible composite riser is made up of numerous layers of plastics, flexible pipes, composites, and steel. Some innovative monitoring methods, such as Fiber Optics Bragg Gratings (FBG), are based on a clamped composite structure with embedded optical fibre. This study presents characteristics of the monitoring techniques of composite flexible riser technology. The advantages of the monitoring techniques include aiding composite riser measurements, recording data from riser deformation, improving integrity assurance, and dependability of design from stable readings. It also proposes some design approaches as guidelines that are advised, with some policy implications. [ABSTRACT FROM AUTHOR]

One of the most serious incidents that can occur in offshore drilling and exploration is damage to the well structure and subsea components which can result in uncontrolled hydrocarbon release to the environment and present a safety hazard to rig personnel. Over decades, there have been substantial developments to the mathematical models and algorithms used to analyze the stresses on the related structure and to define the operational and integrity windows in which operations can proceed safely and where the mechanical integrity of the well is preserved. The purpose of this work is to present a time-domain solution to the system of equations that model the dynamic behavior of the riser and casing strings, when connected for well drilling/completion during the event of drift-off of the rig. The model combines a solution using finite differences for the riser dynamics and a recursive method to analyze the behavior of the casing in the soil. It allows for the coupling between the equations related to the riser and casing and for the coupling with the equations that describe the dynamics of the rig when station keeping capabilities are lost. The use of the forward–backward finite-differences coupled with the recursive method does not require linearization of the forces acting on the structure making it an ideal methodology for riser analysis while improving convergence. The findings of this study can help improve understanding of the impact of the watch circle limits to riser/well integrity, whether these limits are set based on a quasi-static drive-off/drift-off or fully dynamic. The gain in accuracy in using the fully coupled equations of drift-off dynamics, where there is interaction between the rig and the top of the riser during drive-off/drift-off, is evaluated, and the effects of varying the riser top tension and the compressive loads on the casing string are also analyzed. In particular, it is shown that the results of the fully coupled system of equations representing the dynamics of the riser and casing during drift-off/drive-off are less conservative than the quasi-static approach. Another important finding is that the gain in accuracy in coupling the top of the riser and the rig during drift-off/drive-off is not substantial, which indicates that solving separately the rig dynamics equations and the riser-casing equations is an approach that provides reasonable results with less computational effort. The model can also be used to evaluate wellhead and casing fatigue during the life of the intervention. Finally, the model limitations are discussed. [ABSTRACT FROM AUTHOR]

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• Distributed ECVT was proposed to enlarge the imaging spatial scale. • A 64-electrode ECVT sensor with a HDR of 12 was built to investigate the axial flow. • Axial dynamic flow of slugging flow in a CFB riser was investigated experimentally. • Axial dispersion of solid fraction, slug velocity, and slug length are extracted. Understanding particle flow characteristics within circulating fluidized bed (CFB) reactors is crucial for enhancing reaction efficiency. To study the flow characteristics of Geldart D particles with a mean diameter of 3.0 mm and a bulk density of 1640 kg/m3 in a CFB riser with a height of 1090 mm, a 64-electrode electrical capacitance volume tomography (ECVT) sensor with a height-to-diameter ratio (HDR) of 12 is arranged on the CFB riser with an inner diameter of 59 mm. A distributed ECVT architecture under the control of a timing controller is formed to synchronously acquire capacitance data of two 32-electrode ECVT data acquisition systems. So, the three-dimensional axial flow imaging of a CFB riser with a branch pipe is realized with a 14-plane ECVT sensor. The flow rules of slugging flow in the CFB riser under gas velocities of 3.5 m/s, 2.86 m/s, and 2.5 m/s are analyzed from the continuous ECVT images, especially the process of rupture, decomposition, and collapse of particle slugs. The flow parameter characteristics, such as the solid fraction in the riser, the slug rising tail velocity, the slug length, and the spectral characteristics, are investigated. The experimental results demonstrate that the proposed distributed ECVT can effectively realize the collaborative operation of multiple ECVT data acquisition systems and then splice sub-ECT images to achieve complex space imaging. [ABSTRACT FROM AUTHOR]

Vortex induced vibrations is a withstanding ubiquitous problem in the marine industry. Although seemingly simple, cylindrical structures in cross-flows originate extremely complex and, at times, chaotic hydrodynamics which are not fully understood nowadays. One of the biggest industries driving economic development that has had to deal which this problem is Offshore Oil & Gas. Key to a safe oil extraction, marine risers have to operate and withstand the erratic process that arises from the fluid–structure interaction of marine risers with vortex induced hydrodynamic forces. In the following paper we put forward a methodology to assimilate large amounts of data into empirical models. In doing so, we hope to bring attention to the potential that sensors and data collected by them can have in improving predictions of VIV phenomena. Although we leverage a semi-empirical VIV prediction tool (VIVA), the optimization methods used to extract robust hydrodynamic databases for a Steel Catenary Riser (SCR) are not limited to this method. The performance of the extracted databases are systematically cross-validated. To the authors' best knowledge, an extensive cross-validation of this methodology has not been performed in previous studies. [ABSTRACT FROM AUTHOR]

The differential quadrature method (DQM) is a numerical technique widely applied in structure mechanics problems. In this work, a top-tensioned riser conveying fluid is considered. The governing equation of this riser under parametric excitations is deduced. Through Galerkin's method, the partial differential governing equation with respect to time t and vertical coordinate z is reduced into a 1D differential equation with respect only to time. Moreover, the DQM is applied to discretize the governing equation to give solution schemes for the risers' parametric vibration problem. Furthermore, the instability region of Mathieu equation is studied by both the DQM and the Floquet theory to verify the effectiveness of the DQM, and the solutions of both methods show good consistency. After that, the influences of some factors such as damping coefficient, internal flow velocity, and wet-weight coefficient on the parametric instability of a top-tensioned riser are discussed through investigating the instability regions solved by the DQM solution scheme. Hence, conclusions are obtained that the increase of damping coefficient will save the riser from parametric resonance while increasing internal flow velocity, or the wet-weight coefficient will deteriorate the parametric instability of the riser. Finally, the time-domain responses of several specific cases in both stable region and unstable region are presented. [ABSTRACT FROM AUTHOR]

Ductile cast iron has typical characteristics of mushy solidification and ductile expansion. The feeding effect of ductile cast iron was studied by means of numerical simulation and pouring tests. The prototypes used for experiments were designed into three types: riser without neck; riser with narrow neck; and riser-less. The corresponding molds were made of coated sand. The pouring temperature was set to 1350 °C, 1300 °C, and 1250 °C, separately. Results showed that the feeding effect could be controlled by the riser structure and the pouring temperature comprehensively. If the pouring temperature was higher than a certain value, the casting should be fed by a riser, and the riser structure would play an important role. However, it was very hard to design a riser exactly, and the unsuitable riser would cause macro porosity or surface sink. When the pouring temperature decreased to a certain value, there was no macro porosity or surface sink. It could provide a potential method to simplify the feeding process and improve the casting quality. [ABSTRACT FROM AUTHOR]

The feasibility of gas kick early detection outside the riser was analyzed based on gas-liquid multiphase flow theory. Then an experimental platform for gas kick early detection based on Doppler ultrasonic wave was established and the propagation experiments in two-phase flow of gas-water (sucrose solutions) were conducted. The time and frequency domains of the Doppler ultrasonic wave signals during the experiments were analyzed. The results show that: (1) No matter the pump was on or off, the detected average Doppler ultrasonic signal voltage increased first and then decreased with the increase of the gas void fraction, and had a quadratic function relation with gas void fraction, so the average voltage change of the monitored signals can be used to deduce the approximate gas void fraction. The Doppler ultrasonic wave signal voltage was significantly reduced in magnitude and variation in the solution with higher viscosity, and the viscosity has stronger impact on the magnitude of signal than density. (2) When the pump was stopped, the Doppler shift increased with the increase of gas void fraction, and the two showed a nearly linear relation, so the detected amount of Doppler shift can reflect the variation of gas void fraction quantitatively. When the pump was on, the sound energy produced by frequency converter had a more significant impact on amplitude spectrum than gas void fraction, so it is impossible to determine whether gas kick occurs by frequency domain signal analysis. (3) This method is a non-contact measurement, with no contact with the drilling fluid and no disruption to the drilling operation. It can quantitatively characterize the gas void fraction according to the change of Doppler ultrasonic signal, enabling earlier detection of gas kick.

Pressure testing should be conducted on auxiliary lines during riser reentry to ensure the seal security of connection positions. The proper setting of the number and positions of pressure testing is essential because it can significantly reduce the high costs of offshore drilling. However, the analysis and optimization models for pressure testing during riser reentry were not resolved satisfactorily in engineering practice. This study proposes an efficient optimization procedure for pressure testing during riser reentry. A time-efficiency evaluation model and a risk assessment model are established based on the pressure testing process and entropy theory. The modified artificial bee colony (ABC) algorithm is used to optimize the pressure testing process by incorporating the above proposed models. The optimization procedure is illustrated by a case study. The optimal results from the proposed procedure are compared with those from the recommended practices. The resulting variabilities due to seal reliability, water depth, and pressure testing time are also discussed. The study shows that the optimization procedure can improve the operation efficiency of the riser reentry process by 20% and 38% compared to two recommended practices. The proposed procedure is verified to be an efficient alternative for decision making in pressure testing to improve the economic efficiency and ensure safety during riser reentry.

Riser recoil control is a complicated nonlinear control problem. An intelligent control methodology is proposed to control the complicated riser recoil response based on fuzzy control theory. A dynamic nonlinear model of drilling riser/tensioner coupling system is established for riser recoil analysis. The riser system is divided into several elements and the coupling effect between the riser and discharged mud is considered in the dynamic model. A fuzzy controller for the opening of the recoil control valve is designed for the riser recoil control. A comprehensive analysis method is proposed for riser recoil control simulation. Simulation results show that the designed fuzzy controller can effectively control the riser recoil response. The adaptability of the designed controller is also proved by the simulation results. The application of the designed controller can reduce the risk of accidents during riser recoil process.

А riser, which is an offshore water separation column is the main difference between offshore drilling and onshore drilling. The idea of the research is to calculate the stressed-deformed state of a riser made of various materials to identify technological advantages during drilling on the shelf and at sea in the Arctic. The article is the result of research conducted in the Mathematica application program to determine the operating stresses that depend on the drilling process conditions and the external environment. Modern drilling technologies are designed to increase the capacity of the equipment or to use alternative materials. Given the pace of development of the fields of the Northern Shelf of Russia, there is a need to explore the use of alternative materials for such marine equipment as risers.

Casting industries play a crucial role in various industrial sectors like Defence, Automotive sectors, Construction, Agriculture, Aerospace, Oil & Gas (energy sector), Mining, Railroad, Water infrastructure, Transportation, and Health & Medical care. The review article integrates various algorithms, methods, and processes to design an industrially accepted, scientifically sound, reliable feeding system. This systematic review brings out the use of different software used in industry to create and analyze the overall casting process like PRO-cast, MAGMASOFT, ANSYS, CAD software, etc. It also highlights various gating systems for many vital metals and alloys like AZ91, Al-12Si, steel, etc. Moreover, it gives an insight into the casting technology for manufacturing profound components of industrial locomotives and machines like turbine housing, large full-spade carrier housing with axisymmetric large offshore structures with the optimization of the gating system. It concludes that designing a sound feeding system is possible by adequate mathematical tools and numerical simulations.

A model test was carried out to reveal the vortex-induced vibration characteristics of a deep-sea riser under bidirectional shear flow. Bandpass filtering and modal analysis were used to process the test strain data, and the amplitude and frequency response characteristics of the vortex-induced vibration of the riser in the bidirectional shear flow field were obtained. The results of the test data analysis show that the dominant frequency of the vortex-induced vibration of the riser model under bidirectional shear flow is locked in the natural frequency of the riser and does not increase with the increase in flow velocity, that the average resistance coefficient of the riser model has little change under different flow velocities because of the distribution characteristics of the “bidirectional shear” flow field, that there is an extreme value of the shear force in the middle of the riser model, and that the Strouhal number in the transverse direction of the vortex-induced vibration under bidirectional shear flow is less than the recommended value of the current vortex-induced vibration prediction software. The obtained results provide basic data for the prediction of vortex-induced vibration and research into the fatigue analysis method of a riser under an internal wave flow field.

The increasing energy demand has led to more explorations in the oil and gas industry. To achieve this, marine risers and pipelines are used to convey fluid and other resources to meet the increasing demand. In recent years, hybrid flexible composite risers have become more adaptable. Flexible risers have already proven to be a popular riser solution for various floating production systems in shallow to deepwater in many parts of the world due to their good dynamic behaviour and dependability. The hybrid flexible composite riser is made up of numerous layers of plastics, flexible pipes, composites, and steel. Some innovative monitoring methods, such as Fiber Optics Bragg Gratings (FBG), are based on a clamped composite structure with embedded optical fibre. This study presents characteristics of the monitoring techniques of composite flexible riser technology. The advantages of the monitoring techniques include aiding composite riser measurements, recording data from riser deformation, improving integrity assurance, and dependability of design from stable readings. It also proposes some design approaches as guidelines that are advised, with some policy implications.

Fluid Catalytic cracking (FCC) process are frequently used for the upgrading of heavy crude oil into more valuable products. Traditionally, the FCC process occurs in a riser reactor, where both vaporised hydrocarbon feed-stock and solid catalyst flow in the direction against gravity. This kind of reactor presents heterogeneous flow distributions that affect the axial and radial flow structures, as well as the product quality. To understand the effect of operational variables over riser flow distribution, a numerical study of the two-phase cold-flow in the pre-acceleration zone of a riser reactor fed with catalyst particles used in this kind of reactors is presented in this work considering a two-dimensional model. The Computational Fluids Dynamics (CFD) software ANSYS® Fluent® is used to study two-dimensional gas (air) and solid (catalyst particle) flow in a riser section of a cold-flow Circulation Fluidized Bed (CFB) system under different flow inlet conditions (i.e., either for the gas and solid flux), as well the particle diameter size. An Eulerian-Eulerian approach, including the turbulence (κ−ε model) and the Kinetic Theory of Granular Flow (KTGF) models, are solved for the gas phase and the solid particles treated as a dispersed phase. The implemented computational model is validated by comparing numerical results for solid velocity and volume fraction distribution to values reported by peers. As expected, a higher concentration towards the axis of the reactor is obtained for the solid volume fraction values. The RNI index estimated for gas velocities of 3 m/s and 4 m/s are significantly lower than the others, indicating that as the inlet gas velocity is reduced, a more homogeneous profile is obtained. Finally, the numerical results obtained shown closer to the experimental data used for the validation as the steady-state is attained.

A multibody system including a drilling riser system, tensioners and a floating platform is key equipment for offshore oil and gas drilling. Most of the previous studies only focus on the drilling riser system rather than the multibody system. Mechanical characteristics of the deepwater drilling riser system cannot be analyzed accurately in a simplified model. Therefore, a three-dimensional multibody analysis program is developed. The static and dynamic characteristics of the deepwater drilling riser system under different platform motions are analyzed based on the developed program. The results show that the static displacement of the riser system with tensioners is smaller than that without tensioners, which means the tensioners can suppress the deformation of the riser system. Under surge and sway motions of the platform, the dynamic displacement of the riser system with tensioners is also smaller than that without tensioners due to the tensioner suppression effect. Besides, the heave motion induces a uniform axial vibration of the riser system, while roll and pitch motions excite the riser system to vibrate laterally. Compared with the stress amplitude due to surge and sway motions, the stress amplitude of the riser system due to heave, roll and pitch motions is relatively small but cannot be neglected. [ABSTRACT FROM AUTHOR]

The differential quadrature method (DQM) is a numerical technique widely applied in structure mechanics problems. In this work, a top-tensioned riser conveying fluid is considered. The governing equation of this riser under parametric excitations is deduced. Through Galerkin’s method, the partial differential governing equation with respect to time t and vertical coordinate z is reduced into a 1D differential equation with respect only to time. Moreover, the DQM is applied to discretize the governing equation to give solution schemes for the risers’ parametric vibration problem. Furthermore, the instability region of Mathieu equation is studied by both the DQM and the Floquet theory to verify the effectiveness of the DQM, and the solutions of both methods show good consistency. After that, the influences of some factors such as damping coefficient, internal flow velocity, and wet-weight coefficient on the parametric instability of a top-tensioned riser are discussed through investigating the instability regions solved by the DQM solution scheme. Hence, conclusions are obtained that the increase of damping coefficient will save the riser from parametric resonance while increasing internal flow velocity, or the wet-weight coefficient will deteriorate the parametric instability of the riser. Finally, the time-domain responses of several specific cases in both stable region and unstable region are presented.

Heavy petroleum industries, including the fluid catalytic cracking (FCC) unit, are useful for producing fuels but they are among some of the biggest contributors to global greenhouse gas (GHG) emissions. The recent global push for mitigation efforts against climate change has resulted in increased legislation that affects the operations and future of these industries. In terms of the FCC unit, on the riser side, more legislation is pushing towards them switching from petroleum-driven energy sources to more renewable sources such as solar and wind, which threatens the profitability of the unit. On the regenerator side, there is more legislation aimed at reducing emissions of GHGs from such units. As a result, it is more important than ever to develop models that are accurate and reliable, that will help optimise the unit for maximisation of profits under new regulations and changing trends, and that predict emissions of various GHGs to keep up with new reporting guidelines. This article, split over two parts, reviews traditional modelling methodologies used in modelling and simulation of the FCC unit. In Part I, hydrodynamics and kinetics of the riser are discussed in terms of experimental data and modelling approaches. A brief review of the FCC feed is undertaken in terms of characterisations and cracking reaction chemistry, and how these factors have affected modelling approaches. A brief overview of how vaporisation and catalyst deactivation are addressed in the FCC modelling literature is also undertaken. Modelling of constitutive parts that are important to the FCC riser unit such as gas-solid cyclones, disengaging and stripping vessels, is also considered. This review then identifies areas where current models for the riser can be improved for the future. In Part II, a similar review is presented for the FCC regenerator system.

Water recycle system is formed by shell and tube waste heat boiler body,drum,down comer and riser. The riser connects boiler body and drum. When the production of steam is less account in the system,the riser supports the whole mass of boiler drum and bears internal pressure,boiler drum’s operating mass,seismic load and wind load. In this paper,FEA of riser was completed by ANSYS,and the local stresses on the shell were studied with the change of different thicknesses of riser. Thus,the thickness of riser was confirmed to achieve material rationality and economical efficiency.

The effect of a hollow riser on the upper heat dissipation of 76 tons and 8 corners ingots is studied by numerical simulation in this paper. Through the simulation of the heat transfer of the traditional riser, the 1 gap riser and the 2 gaps riser ingot, this paper draws a conclusion that the solidification time of the riser part of the riser is the longest in the 2 gaps scheme, and the solidification time of the central molten steel is 31417s, which is far higher than the other two schemes. The heat flux in the riser of the 2 gaps scheme is obviously larger than the other two schemes, which slows down the advance of the solidification front. The 2 gaps scheme is stronger than the other two schemes for reducing the cooling speed of the riser line center and the shoulder joint. It is particularly significant to reduce the cooling rate of the shoulder joints, which is more conducive to expanding the angle of the solidification front and fully filling.

This paper presents numerical simulations of vortex-induced vibrations of a vertical riser which is sinusoidally excited at its top end in both one and two directions in still water. A computational fluid dynamics method based on the strip theory is used. The riser's responses to both top-end and two-end excitations are carefully examined. In low reduced velocity cases, the in-line vibrations consist of three components, the low-frequency oscillation, the first-natural-frequency vibration during the riser reversal, and the second-natural-frequency vibration due to vortex shedding. The sheared oscillatory flow along the span causes low-frequency oscillations in higher modes in the in-line direction, thus forming ‘X’ shaped, ‘II’ shaped, and ‘O’ shaped trajectories at various positions along the span when the riser is excited at its top end in one direction. In the presence of excitations in the other direction, more complex trajectories appear.

• Experimental data of supercritical water circulating fluidized bed(SCWCFB) was gotten. • Pressure characteristics and axial void fractions of SCWCFB were analyzed. • The transition velocity of SCWCFB was obtained and a correlation was proposed. There are few experimental reports about supercritical water circulating fluidized beds (SCWCFBs) as far as we know. Experiments were conducted to investigate flow dynamics in the riser of a SCWCFB. The average, standard deviation, and power spectral density of pressure signals were analysed. The main frequencies of pressure drops were mainly below 1 Hz. The axial void fractions were obtained, and they were low at the bottom and high at the top of the riser in the SCWCFB. Several types of axial void fraction distributions of conventional gas-solid circulating fluidized beds were also observed in this SCWCFB. The transition velocity between fast fluidization and pneumatic conveying (U pt), was obtained according to the axial void fractions. U pt increased with increasing return flow velocities, and decreased with increasing pressures. An empirical correlation of U pt for SCWCFBs was proposed, Re pt = 0.182 × Ar 0.6161 × (U ret / U mf)−0.00916+78.8, and its error range was in ±20%. [Display omitted] [ABSTRACT FROM AUTHOR]

In modern times, there are increasing requirements for products quality in every part of manufacturing industry and in foundry industry it is not different. That is why a lot of foundries are researching, how to effectively produce castings with high quality. This article is dealing with search of the influence of using different types of risers or chills on shrinkage cavity production in ductile iron castings. Differently shaped risers were designed using the Wlodawer’s modulus method and test castings were poured with and without combination of chills. Efficiency of used risers and chills was established by the area of created shrinkage cavity using the ultrasound nondestructive method. There are introduced the production process of test castings and results of ultrasound nondestructive reflective method. The object of this work is to determine an optimal type of riser or chill for given test casting in order to not use overrated risers and thus increase the cost effectiveness of the ductile iron castings production.

This presentation describes a model used to study gas diffusion through layers of flexible pipes by time. The temperature gradient pipe is considered as temperature dependent permeability rates. This model is coupled with a calculation that indicate changes in pressure and volume of vapors resulting in the annular space. Associated mathematical models and methods for solving the results obtained are presented in Math Soft with a user-friendly interface that helps in data entry and processing results. In this presentation will show the possibilities of this software.

This work presents the simulation of a steam generator or water-tube boiler through the implementation in MATLAB® for a proposed mathematical model. Mass and energy balances for the three main components of the boiler—the drum, the riser and down-comer tubes—are presented. Three alternative solutions to the ordinary differential equation (ODE) were studied, based on Runge–Kutta 4th order method, Heun’s method, and MATLAB function Ode45. The best results were obtained using MATLAB® function Ode45 based on the Runge–Kutta 4th Order Method. The error was less than 5% for the simulation of the steam pressure in the drum, the total volume of water in the boiler, and the mixture quality in relation to what was reported.

In this paper a brief review on hydrodynamic characteristic of coal gasification is presented. Firstly an introduction of hydrodynamics then parameters related to hydrodynamics is discussed. In the last several decades Coal gasification is an important method to use of coal resources. The hydrodynamic characteristics have an important role to design of Circulating fluidized bed gasifiers. Circulating fluidized bed (CFB) gasifiers widely use due to their high reaction rates and high thermal efficiency. The present study includes some hydrodynamics properties of coal gasification such as effect of pressure and temperature, solid hold up, solid circulation rate, gas-solid contact, particle residency time, coal feeding rate and coal feeding position. During the brief review on hydrodynamics characteristics of coal each section of CFBs such as riser, cyclone, stand-pipe and loop seal have been considered. [ABSTRACT FROM AUTHOR]

Highlights • The numerical analysis method of ultrasonic detection of gas kick in deepwater riser was established. • The optimal emission frequency and the optimal location of the receiving probes was determined. • The response law of coda wave velocity to the gas fraction was obtained by using the coda wave interference method. • The eccentricity of drill pipe and the non-uniform distribution of bubbles in the actual drilling process were discussed. Abstract Ultrasonic monitoring of gas kick in risers is an effective method for early gas kick detection in deepwater drilling operations. At present, the research on the ultrasonic propagation in gas-liquid two-phase flow within the risers and the response rules of ultrasonic signals under actual working conditions is not deep enough. In this paper, the numerical simulation method that can accurately control parameters such as the distribution and size of bubbles was introduced, and its effectiveness and accuracy were verified by experimental means. Through the analysis of the effective sensitivity fields under different gas-fraction conditions, the key monitoring parameters (emission frequency and receiving probe position) were optimized first. On this basis, the characteristic parameters of ultrasonic signals were optimized and their applicable conditions were also analyzed: The response law of coda wave velocity to the gas fraction was gained by using the coda wave interference method and it is suitable for the condition of small gas fraction (less than 0.42%); The response rule of main frequency on gas fraction was obtained through frequency domain analysis; The arrival time of head wave was relatively sensitive to the gas fraction of 2–8%. Finally, the conditions of the eccentricity of drill pipe and the non-uniform distribution of bubbles were discussed. The influence of drill pipe eccentricity on ultrasonic propagation under different frequencies was noted, and the monitoring solution under the condition of non-uniform distribution of bubbles was proposed based on the effective sensitivity of different receiving positions. This study not only optimized the key parameters of ultrasonic monitoring method, but also explored its applicable conditions and the influence rules of actual working conditions on the ultrasonic propagation. [ABSTRACT FROM AUTHOR]

Highlights • Kinetics of steam methane reforming and carbonation were incorporated in CFD model. • 2k factorial design was used to analyze parameters. • Hydrogen purity could reach equilibrium as well as that conducted in bubbling bed. • Gas velocity, riser diameter and solid flux had major effects on system designing. Abstract Computational fluid dynamics was applied for sorption enhanced steam methane reforming (SESMR) operating in a circulating fluidized bed (CFB) riser. The solid mixtures consisted of Ni-based catalyst and CaO sorbent. The aim of study was to design a proper pilot-scale CFB riser which produced hydrogen (H 2) with both high purity and high flux. The design parameters and the reaction parameters were examined with 2k full factorial design. The significances of each parameter were analyzed by analysis of variance. Using the optimum result, the highest H 2 purity reached 98.58% in dry basis accompanied with the highest H 2 flux of 0.301 kg/m2 s. The hydrodynamics of this optimum case showed that SESMR was nearly completed since 5.0 m height because axial and radial distributions of solid were well developed without excessive segregation between catalyst and sorbent. Thus, the H 2 purity and the H 2 flux approached fully developed within the riser height. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The aerodynamic theory is introduced into two-phase flow analysis for riser/downer. • The core-annulus in riser is quantified by a new transverse force. • The particle concentration gradient force is introduced and analyzed. • The new transverse force is analyzed in different scales. Abstract The radial particle concentration distribution in riser is comparatively low in the central area and increases sharply near the wall. It is the so-called typical core-annulus structure. The occurrence of the core-annulus was usually contributed to the velocity gradient in the boundary layer or the drag force. In this paper, an aerodynamic theory is used in the two-phase flow analysis. A transverse force on the particles, the Kutta-Joukowski force, is introduced to explain and quantify the formation of the core-annulus in riser. This force is the function of the particle velocity curl, the slip velocity and the gas density. Based on the experimental results combining with the data proposed in the published literatures, the distribution of the Kutta-Joukowski transverse force in riser is discussed. The results show that this force is the main factor of the core-annulus occurrence. [ABSTRACT FROM AUTHOR]

Highlights • An ANN model for predicting short-term VIV fatigue damage of TTR was developed and trained successfully using generated 21,532 datasets. • The proposed ANN technique was verified by test cases of current. • It can serve as an alternative approach for VIV fatigue damage assessment at early design stage of TTR. Abstract Marine riser is the critical component transporting hydrocarbon and fluid from well to the platform and vice versa. Riser experiences vortex-induced vibration (VIV) caused by current, leading to fatigue damage. Estimation of VIV fatigue damage is essential in designing feasible and operable riser. A simplified approach for predicting fatigue damage is required to reduce the computation time to analyse the fatigue damage. This study aims to propose a simplified approach to predict VIV fatigue damage of top tensioned riser (TTR) using artificial neural network (ANN). A total of 21,532 riser model was generated with different combination of six main input parameters: riser outer diameter, wall thickness, top tension, water depth, surface and bottom current velocity. The modal analysis was performed using OrcaFlex and VIV fatigue damage of the riser was computed using SHEAR7. The six input parameters and corresponding fatigue damage results made up the database for training a 2-layer neural network. Weight and bias values acquired from the training of ANN were used to develop the VIV fatigue damage prediction model of the riser. The hyperparameters of the ANN model were tuned to optimize performance of the model. The results showed the final ANN model predict fatigue damage well with shorter time compared to conventional semi-empirical method. Hence, the proposed approach is suitable to be used for prediction of VIV fatigue damage of TTR at early design stage of TTR. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Risers are an indispensable component of offshore oil and gas exploitation structures, and they are vulnerable to vortex-induced vibration (VIV). Although many studies have been conducted to investigate the VIV characteristics of risers, the effects of combination of multiple parameters and the relative significance of each parameter on the risers' VIV characteristics have rarely been considered. In this paper, 36 experimental cases were investigated to study the risers' VIV characteristics due to the combination of multiple parameters. The natural frequencies, response microstrains and frequencies of VIV for the risers were obtained. Meanwhile, the effect of each parameter and the relative significance of these parameters on the amplitude of VIV in risers were calculated using grey relational analysis (GRA). The results show that all the parameters considered—i.e., material property (modulus and density), end condition, top tension force and flow velocity—affect risers' VIV response, and the grey relational grade of these parameters are: r 02 (velocity) > r 04 (constraints) > r 05 (density) > r 03 (tension) > r 01 (modulus) . [ABSTRACT FROM AUTHOR]