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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]

Multiphase reactors' performance depends on the mesoscale structures formed due to multiphase hydrodynamics. Examples of mesoscale structures include gas bubbles in a fluidized bed and particle clusters in a riser. Experimental investigation of these mesoscale structures is challenging and expensive. To this end, computational fluid dynamics (CFD) simulations are extensively employed; however, post‐processing CFD data to capture mesoscale structures is challenging. This article develops a density‐based spatial clustering of applications with noise (DBSCAN)‐based methodology to capture and characterize mesoscale structures from multiphase CFD simulation data. DBSCAN is an unsupervised machine‐learning algorithm, which requires the value of two hyperparameters. A simple technique to calculate these hyperparameters is provided and the performance of DBSCAN is assessed on CFD‐DEM simulations of bubbling fluidized beds and particle clustering. We demonstrate the computational complexity of DBSCAN to be 풪(nlogn), lower than the existing techniques, by testing its scalability on highly resolved grids (up to 100 million grid points). [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.

The riser system acts as the vital link between the subsea blow-out preventer and the drilling platform. Affected by factors like top tension and marine environmental forces, the riser undergoes deformation and wear, carrying the risk of environmental pollution and financial losses upon failure. Hence, this study examines the riser's dynamic response to marine environmental loading. Initially, the motion differential equation for the riser system under the influence of nonlinear oceanic load is deduced using the principle of minimum potential energy and the variational method for extremum seeking. Subsequently, a nonlinear wave-current load model based on the Morrison equation is established, and the resulting equation is discretized into a finite element model using third-order Hermite interpolation function and the Galerkin weighted residual method. Finally, the dynamic response of the riser is scrutinized employing the Newmark numerical integration method. The study also investigates the impact of both oceanic environmental parameters and drilling parameters on the riser's dynamic behavior. Comparative analysis of the numerical results reveals that the maximum displacement of the riser occurs at the middle section, whereas the maximum deflection angle is observed at the end of the riser. The periodicity of the deflection angle response is influenced by the position of the riser, showing a trend of decreasing and then increasing from the middle section towards the ends. Notably, the top tension and the velocity of the surface tidal current significantly affect the dynamic behavior of the riser. The findings of this study provide a theoretical foundation for the assessment of riser reliability and the determination of operational parameters. [ABSTRACT FROM AUTHOR]

Gulf of Eilat is rich with energy resources, however any industrial natural resource development requires additional safety, as local eco‐system has to be preserved. In contrast to bivariate reliability approaches, known to their accurate predictions of extreme response and load levels for two‐dimensional dynamic systems, this study suggests and validates novel structural reliability method, which is being appropriate method for high‐dimensional dynamic systems. Conventional reliability methods do not have an advantage of dealing easily with high‐dimensional nonlinear dynamic systems, especially with non‐linear cross‐correlations between different system components. Advocated approach does not have limitations on the system's number of degrees of freedom, and it can accurately assess dynamic system's failure risks. Main purpose of this study was to benchmark state‐of‐the‐art reliability methodology, while utilizing available dataset efficiently. Note that advocated approach is not limited to offshore engineering example, studied here, and it has wide range of potential engineering and design applications. [ABSTRACT FROM AUTHOR]

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.

As marine renewable energy technologies developing, there is a growing need for energy transportation systems. During offshore operations, deep sea risers can be subjected to excessive environmental loadings, causing operational risks. In this study, hydrodynamic loads, caused by in situ sea currents, acting on a riser under real-world sea conditions were modelled and examined, with experimental data being used as a calibration tool. Major safety problems for various offshore energy systems being an accurate assessment of excessive riser external loads, under influence of local sea currents, and hence resulting vortex induced vibrations (VIV). The method outlined in this study may be applied to complex sustainable energy systems, that are exposed to environmental loads, throughout the whole period of their intended service life. Approach advocated in this study offers practical way to estimate failure risks for nonlinear multidimensional dynamic offshore riser systems in an easy yet accurate manner. With regard to defense technology, risers and umbilicals play an important role for modern submarine operations. Key points: ▪ Novel dynamic system lifespan assessment technique has been developed for offshore energy deep sea riser systems. ▪ Relevant lab validation tests were conducted. ▪ Based on experimental lab data, accurate multi-dimensional reliability evaluation has been carried out. [ABSTRACT FROM AUTHOR]

Industry processes require large amounts of energy inputs and often generate high temperatures exit gases that can potentially serve as secondary sources of energy. Waste heat recovery offers an opportunity for energy conservation that deserves more attention in the current global effort. Recovery of such waste heat can result in substantial reductions in net energy demand. Based on these objectives, this report describes the result of an experimental study that used solid particles in a vertical riser to recover gas energy from hot air through co‐current contact with solid particles. To study the hydrodynamic aspects of the riser section, this study utilized a fabricated experimental apparatus similar to the vertical duct used in the cement industry. The purpose of this study is to collect hydrodynamic data because there is limited information available about these aspects in the literature. A metallic fluid particle heat exchanger has been investigated through experiments. Various sizes of quarry dust and iron ore particles are studied in the present study. An empirical correlation is used to fit the mixing length (LA) determined at different parametric levels (gas velocity, particle size, solid feed rate, and solid density). Experimental correspondence for mixing length or LA is given as LAdt=5.1875dpdt0.1837wswg−0.1374ugμgdt2gρg0.3015ρpρg0.3961. The constructed experimental setup demonstrates a suspension preheater (SP) used in modern cement plants, but the correlation can be extended to a variety of other industries where waste heat recovery is feasible. [ABSTRACT FROM AUTHOR]

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]

In this paper, an experimental platform for dynamic control of offshore drilling riser suspensions in offshore drilling is developed. A six-degree-of-freedom platform is used to simulate the motion of offshore floating drilling platform. A scale model of riser is designed based on the centralized mass method and dynamic similarity principle. The suspension system of the experimental platform can realize 3 kinds of actions: up stroke control, down stroke control and non-control locking. The measurement and control system is developed by using monitor and control generated system (MCGS) configuration software, Siemens S7-1200 programmable logic controller (PLC) and proportion integral derivative (PID) control algorithm. By using this experimental platform, students can increase their perceptual knowledge of the dynamic control of riser suspension in offshore drilling. Through practical hands-on training, they can deepen their understanding of the theory, technology and device of riser suspension dynamic control, improve the teaching effect and cultivate students' innovative consciousness. [ABSTRACT FROM AUTHOR]

The paper reports the analysis of an accident that occurred in a petroleum refinery. During the start‐up maneuver of the topping column, the anchoring of the riser pipe to metal guide support on the topping column suddenly failed. This caused a rip in the riser pipe, and gasoline squirted out, followed by the ignition of a jet fire. The investigations showed an unusual differential thermal expansion between the topping column and riser. The riser guide to the column was wrongly installed, preventing adequate relative displacements when thermal expansion occurred. Metallographic and fractographic analyses did not discover any inadequacy in the steel of the failed parts. But the lack of penetration of the welding seam resulted in a weak bond between the support and the riser. The high stress induced by the badly installed guide and the weakness of the welding was the cause of the failure and the jet fire. The paper also analyses the application of existing codes to the riser support installation and shows that the code recommendations do not satisfactorily cover the case of topping column risers. The issue is raised to alert operators in the plant, stimulate the improvement of the codes and standards, and avoid future accidents. [ABSTRACT FROM AUTHOR]

The marine riser is an important equipment for offshore oil and gas drilling and production. The vortex-induced vibration generated by the current flowing around the riser will reduce the stability and service life of the riser. Bionic non-smooth drag reduction technology is considered to be the most promising drag reduction method at present due to its low energy consumption and significant drag reduction effect. In this paper, the non-smooth groove structure is placed on the surface of the riser, and the turbulent flow of the smooth riser and the non-smooth riser is numerically simulated using the SST k-ω model. The drag reduction effect of the non-smooth groove structure on the flow resistance and lift is analyzed. The simulation results show that the non-smooth riser has good drag reduction performance under different inflow velocities. The drag reduction rate of resistance is 16.94% when the current velocity is 2 m/s, and 37.78% when the current velocity is 5 m/s. The inhibition effect of the grooved non-smooth structure on the vortex shedding on the leeward side of the riser and the vortex pad effect of the vortex in the groove can reduce the lift and resistance of the flow around the riser, thus effectively improving the stress condition of the riser and improving the stability of the riser under water. [ABSTRACT FROM AUTHOR]

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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]

The finite element method was used to analyse the interface stress of composite piles under vertical, horizontal and temperature loads. The results show that under vertical load, the cementing cement of composite piles has stress concentration at the position where section varied, and when the settlement of the pile top exceeds 150 mm, the cement has the risk of crushing. Under horizontal load, a tensile crack area appears on the tensile side of the cement, and the length of the tensile fracture area increases with the increase of the displacement of the pile top. Under temperature load, the maximum interface shear stress increases with the increase of temperature. Under the action of vertical, horizontal and temperature loads, the shear stress between each material of the pile is less than the bonding strength of the material, and the bonding surface will not slide relative to each other. [ABSTRACT FROM AUTHOR]

Publications on form in popular music have largely assumed the formal sections germane to pop-rock to be the formal designs of "popular music." But the most popular music of our time--music charting on the Billboard Top-40--has absorbed the influence of electronic dance music (EDM) in a way that has fundamentally changed its formal structure. This results in "Top-40 EDM," a genre defined by collaborations between seasoned EDM producers and A-list pop singers. This article begins by defining EDM's three core formal functions (verse, riser, and drop), and compares them to more familiar functions heard in pop-rock music (verse, prechorus, chorus, and postchorus). Part two draws on de Clercq's (2017) concept of blended formal functions to define Top-40 EDM's most recognizable section, the "riserchorus." Part three examines the larger structure of these tracks, including their "compound AAA" forms, in which each of the song's rotations feature the same formal functions, though presented differently. Finally, the article demonstrates how Top-40 EDM producers regularly combine samples at the end of their tracks, resulting in cumulative hyper-blended sections like "riserchorus-bridge" and "riserchorusdrop." [ABSTRACT FROM AUTHOR]

In this study, the dynamics of the tendon/top tension riser (TTR) system of a tension-leg platform (TLP) are investigated through an experiment and by using absolute nodal coordinate formulation (ANCF). First, the model test of the TLP system is conducted in the water tank of Harbin Engineering University to examine the motion response of the TLP and the dynamic response characteristics of the tendon and TTR. The test scale ratio is set to 1: 66.3. Then, on the basis of the ANCF, the stiffness, external load, and mass matrices of the element are deduced to establish the motion equation of the tendon/riser. Finally, the static and dynamic characteristics of the tendon/TTR system of TLP are analyzed systematically by using the ANCF method. The results are compared with commercial software and test results. The motion response of tendon/TTR is affected by the TLP movement and environmental load simultaneously. The analysis proves the effectiveness and accuracy of the ANCF method despite the low number of riser units, suggesting the superiority of the ANCF method for calculating the dynamics of tendon/riser in the field of ocean engineering. [ABSTRACT FROM AUTHOR]

The present work aims to develop an integrated heat transfer and hydrodynamic model for the study of boiler dynamics in fluctuating load conditions. A transient heat transfer model has been developed to estimate water side heat transfer and it is directly integrated with the hydrodynamic model. Two independent natural circulation circuits for furnace water wall and convection tube bank have been considered due to differences in heat transfer, dryness fraction, and void fraction. The transient heat transfer model calculates the heat transfer and water wall temperature of the various sections to calculate total gas side heat transfer, gas temperature profile, and waterside heat transfer in the furnace water wall and convection tube bank. Mass momentum and energy conservation equations are generated for both natural circulation circuits using the estimated value of waterside heat transfer of the transient heat transfer model. These equations are integrated with mass and energy conservation equations for the drum below water level and drum above water level to generate a system of equations to estimate drum pressure and water level fluctuation. This model has been extended for boiler feedback control systems, including the load management and the water level control system. [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]

A dry sorbent post-combustion CO 2 capture process using a circulating fluidized bed (CFB) was developed to a 10 MWe scale. Particle attrition is a major challenge for many CFBs owing to the loss of particles and increased operating costs. Furthermore, predicting and alleviating the rate of particle attrition in an entire CFB is difficult owing to limited information on attrition in the riser and cyclone. This study experimentally investigated particle attrition in risers and cyclones and the effect of system scale-up using CO 2 adsorbent particles used in a 10 MWe scale CFB. Experiments were conducted in two types of CFBs to measure the attrition rate in the riser and cyclone for 22 and 12 h for each experimental condition. To verify the scaled-up effect, internals were added to the riser to measure the effect of the surface-area-to-volume ratio. Correlations for the attrition rate of CO 2 adsorbent particles in riser and cyclone were proposed, and a model for the scale-up effect was suggested. In the 10 MWe scale system, particle attrition mainly occurred in the cyclone (58.0 %) and riser (37.3 %) according to the calculation, and the calculated overall attrition rate reasonably matched the operational data. Figure: (a) Calculated attrition rate of CO 2 adsorbent particles in the circulating fluidized bed of 10 MWe scale CO 2 capturing process, and (b) effect of cyclone inlet gas velocity on the particle attrition rate in cyclone. [Display omitted] • Particle attrition mainly occur in the cyclone and riser of a CFB. • Attrition rate in cyclone was proportional to the square of the gas velocity. • The top size of fines formed by attrition in riser increased with gas velocity. • Attrition rate in the riser increases by increasing surface area. • Correlation for particle attrition rate in the riser and cyclone are proposed. [ABSTRACT FROM AUTHOR]

The study of gas-liquid interface evolution and pressure fluctuation mechanism in the pipeline-riser system is the key to ensuring the safety of oil and gas transportation. This paper investigates the influence of the riser on the gas-liquid interface in the system with a 1657 m pipeline and risers of 16 m, 22 m, and 29 m. In severe slugging, the differential pressure in the horizontal pipeline exhibits a low-frequency large-amplitude fluctuation consistent with those in the riser. During the gas blowdown of the riser, the pressure fluctuation breaks the force equilibrium of the gas-liquid interface and induces numerous liquid slugs in the horizontal pipeline. A strong correlation is found between the differential pressure in the riser and the slug velocity in the horizontal pipeline by the Spearman Rank coefficient. The correlations between the slug velocity and the gas volume fraction and the void fraction under different riser heights are established, and the errors are 15% and 10%, respectively. The linear relationship between the Strouhal number of liquid slugs and the Lockhart-Martinelli parameter is constructed during the gas blowdown. • Gas-liquid two-phase flow in a riser system with a kilometer pipeline is researched. • The influence mechanism of the riser on the flow in the horizontal pipeline is revealed. • There is a strong correlation of flow parameters in a long pipeline and those in a riser. • Correlations of velocity and frequency of liquid slug during gas blowdown are studied. [ABSTRACT FROM AUTHOR]

This paper deals with the dynamic modelling and pure delayed H∞ control for a deepwater drilling riser system in the presence of the friction force of seawater and drilling discharge mud. First, by simplifying a drilling riser system as a spring-mass-damping unit with three degrees of freedom, an increment equation of the riser system subject to friction force of seawater and drilling discharge mud is established. Then, by artificially introducing a time-varying delay with given lower and upper bounds into the control channel, a pure delayed H∞ control scheme is presented to restrain the recoil responses of the riser system. Based on the Lyapunov–Krasovskii functional approach, several new sufficient conditions are derived to design the pure delayed H∞ controller. Finally, comparative simulation results are given to show the effectiveness and merits of the proposed control scheme. It is demonstrated that to mitigate recoil response of the deepwater riser in the event of emergency disconnection, the proposed pure delayed H∞ controllers are more economic than the delay-free H∞ controller. [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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(12)-(15)) embed the catalyst holdup variable HT ht given by Eq. (11). Alternatively, the ratio HT ht , known as the slip factor, measures the relative dominance of the gas velocity over the solid velocity. The profile equation is given by: HT ht Graph (7) The different holdups viz. HT ht and HT ht are obtained from Eqs. [Extracted from the article]

• 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]

To guarantee the safety and reliability of drilling riser after emergency disconnection, it is significant to investigate and refrain recoil response of the riser. This paper deals with the problem of Takagi–Sugeno (T-S) fuzzy recoil dynamic modeling and optimal recoil control of nonlinear deepwater drilling riser systems subject to friction resistance of fluid discharge and platform heave motion. First, a nonlinear recoil control model of coupled riser-tensioner is proposed by taking the nonlinear top tension of tensioner into account. Then, a T-S fuzzy dynamic model of the riser-tensioner system is established to approximate the original nonlinear one by using fuzzy modeling scheme. Third, an augmented T-S fuzzy model of riser system is proposed, where the linear exosystem model of friction resistance and platform heave motion is utilized. Fourth, a finite-time fuzzy optimal recoil controller is designed to suppress the recoil response of the riser, the existence and design algorithm of the fuzzy optimal recoil controller are derived. Simulation results demonstrate that the nonlinear recoil model is more accurate than the existing linear one to describe the recoil characteristics of the riser, and the fuzzy optimal recoil controllers are effective to reduce recoil responses and guarantee the safety of the riser significantly. • A nonlinear recoil dynamic model of coupled riser-tensioner is proposed by considering the nonlinear tension. • An augmented T-S fuzzy dynamical model of riser system is developed, where an exosystem of friction resistance is utilized. • Finite-time fuzzy optimal recoil controllers are designed to suppress the recoil response of the riser. • The fuzzy optimal recoil controllers are effective to reduce recoil responses and guarantee the safety of the riser. [ABSTRACT FROM AUTHOR]

This study addresses discrete dynamic modelling and the optimal recoil control problem of deepwater drilling riser systems subject to the friction resistance of fluid discharge and platform heave motion. First, a discrete-time exosystem model for friction resistance of drilling fluid discharge is developed; then, a discrete-time dynamic model of platform heave motion is established. Third, a finite-time discrete optimal recoil controller with feedforward compensation mechanisms was designed. The optimal recoil controller gains can be obtained by iteratively solving discrete equations. The simulation results show that under the discrete feedforward and feedback optimal recoil controller and pure feedback optimal recoil controller, the recoil movements of the riser system are significantly restrained. Moreover, the former is more effective than the latter at resisting the riser recoil response. • A discrete-time exosystem model of the friction resistance induced by drilling fluid discharge on the riser is proposed. • A discrete-time dynamic model of irregular heave motion of drilling platform is established. • A discrete-time recoil control model of the drilling riser system subject to viscous resistance of fluid discharge and platform heave motion is developed. • A finite-timediscrete optimal recoil control scheme with feedforward mechanism is designed to suppress the recoil response of the riser. [ABSTRACT FROM AUTHOR]

Bending strain data from 3 well-instrumented VIV model test programs on simply supported bare pipes under uniform flow are processed using rainflow counting to get fatigue damage rates directly. These are presented in terms a dimensionless fatigue-equivalent bending strain amplitude, ϵ e , which for the structurally undamped simply supported span under constant axial force N undergoing small rotations depends on 5 dimensionless parameters, and only weakly on the fatigue resistance curve used. Existing and new approximations are discussed as assessed whereby the number of dimensionless parameters that affect ϵ e may be reduced from 5 to 1. Thus a scaling approach is developed, whereby any VIV test can be scaled to represent any prototype at a current velocity determined by the scaling procedure. The procedure uses scaling only for the dynamic part of the response, and structural analysis for the static part. It works for single as well as multi-mode response. It is illustrated for a 150m-long prototype span subject to high currents. The test and/or scaling results are also compared to predictions by existing methods, including DNVGL-RP-F105 ("F105") and Vivana. The example also illustrates how the proposed method can be used for partially strake-covered ("straked") pipes, provided the strake coverage is similar for model and prototype. The scatter in the data gives an indication of the uncertainties involved in estimating VIV fatigue damage rates from limited experimental data where high-mode and multi-mode response is possible. • VIV fatigue assessment for pipelines and risers by direct scaling of model tests. • Normalized test parameters from 3 well-instrumented test programs. • L/D similarity not required with principle of local action. • Test data are compared to predictions from DNVGL-RP-F105 and Vivana. [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]