Offshore wind turbines(OWTs) suffer wind, wave and earthquake loads. The investigation of OWTs' dynamic response under environmental loads is essential for structural safety assessment. The soil-structure interact...
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Offshore wind turbines(OWTs) suffer wind, wave and earthquake loads. The investigation of OWTs' dynamic response under environmental loads is essential for structural safety assessment. The soil-structure interaction(SSI)significantly affects the responses of OWT under environmental loads. However, there is few systematic research about the difference in the dynamic response of different SSI models under environmental loads. In order to solve the problem, the OWT is modeled by shell element, and several SSI models are built. The wind, wave and earthquake loads are taken into account. Moreover, the dynamic response, fatigue and buckling analysis are performed by ANSYS. The results indicate that SSI cannot be ignored in the dynamic response of the OWT under wind and wave loads. The SSI can decrease the displacement response of the OWT by 19% under wind and wave loads and reduce the fatigue damage of the pile. Multi-layer SSI can strongly influence the OWT's dynamic response under wind and wave loads or earthquake-only load. The vertical earthquake load increases the dynamic response in three ***, in order to simulate real environment, multi-layer SSI, soil damping and vertical SSI must be considered to evaluate the displacement response of the OWT under wind, wave and earthquake loads. The earthquake and gravity loads can cause more obvious response of the OWT than that of only wind and wave loads. The top and bottom of the tower are prone to occur buckling.
Given the proper band gap, low cost and good stability, hematite (α-Fe2O3) has been considered as a promising candidate for photoelectrochemical (PEC) water splitting, however suffers from the sluggish surface wa...
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Given the proper band gap, low cost and good stability, hematite (α-Fe2O3) has been considered as a promising candidate for photoelectrochemical (PEC) water splitting, however suffers from the sluggish surface water oxidation reaction kinetics. In this study, a simple dip-coating process was used to modify the surface of α-Fe2O3 nanorod arrays with cobalt oxide (COOx) and carbon (C) for the improved PEC performance, with a photocurrent density at 1.6V (vs. reversible hydrogen electrode, RHE) increased from 0.10 mA/cm2 for the pristine α-Fe2O3 to 0.37 mA/cm2 for the CoOx/C modified α-Fe2O3 nanorods. As revealed by electrochemical analysis, thanks to the synergistic effect of CoOx and C, the PEC enhancement could be attributed to the enhanced charge transfer ability, decreased surface charge recombination, and accelerated water oxidation reaction kinetics. This study serves as a good example for improving PEC water splitting performance via a simple method.
Accurate measurement of gas-liquid phase fraction is essential for the proper modelling of the pressure drop, heat transfer coefficient, mass transfer rate and interfacial area in two-phase flows. In this paper, takin...
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Accurate measurement of gas-liquid phase fraction is essential for the proper modelling of the pressure drop, heat transfer coefficient, mass transfer rate and interfacial area in two-phase flows. In this paper, taking the issue of optical distortion into account, an analytical model was proposed to estimate and correct the liquid holdup in gas-liquid annular flow through a circular pipe using high-speed camera method. The error in the liquid holdup measurement generated from different refractive indices among transparent circular pipe, liquid film and air core was firstly theoretically analyzed based on the geometric optics. Experimental tests were then carried out to identify the difference as well as to validate the proposed model. Results indicated that the prediction of the liquid holdup has a good performance with the experimental data(i.e., mean relative error is 4.1%) and the measured liquid holdup is larger than the real one. It was found that the measured liquid holdup is larger than the real one. Generally, when the real liquid holdup gets smaller, the discrepancy between the measured liquid holdup by image and the real liquid holdup becomes more significant. Thus, after measuring the liquid holdup from the images, the value of the measured liquid holdup must be corrected by the present model in order to obtain the real liquid holdup.
Cold plate is an important component for a liquid battery thermal management *** order to study the transient thermal performance of the cold plate under conditions with sharply increasing heat loads,the numerical mod...
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Cold plate is an important component for a liquid battery thermal management *** order to study the transient thermal performance of the cold plate under conditions with sharply increasing heat loads,the numerical model of a battery cold plate is *** validation experiment shows that the error between the simulation and experiment is around 2.5%to 5%.Effects of the coolant flow rate,the increase in heat flux,and the channel number are analyzed to study the transient thermal performance of the cold *** show that the average temperature of the cold plate at 540 s is lowered from 28.3℃ to 26.9℃ when the coolant flow rate is raised from 0.065 kg/s to 0.165 kg/*** temperature deviation is decreased when the coolant flow rate is increased from 0.065 kg/s to 0.115 kg/s;however,it is slightly increased if the coolant flow rate is further *** average temperature and temperature deviation are raised if the final heat flux is increased from11000 W/m^(2) to 16500 W/m^(2),which are 2 and 3 times of the initial,*** addition,increasing the channel number has slightly positive effect on the average temperature of the cold plate,while the temperature deviation is increased when the channel number is increased from 3 to 11 due to the non-uniform velocity distribution between each *** results of this study will be helpful during the design of cold plate for battery thermal management,especially for transient conditions with sudden rising heat loads like thermal runaway.
Particle streak velocimetry (PSV) has become one of the important branches of flow filed measurements. It extracts velocity information from particle trajectories captured by single frame long exposure images. Since t...
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Particle streak velocimetry (PSV) has become one of the important branches of flow filed measurements. It extracts velocity information from particle trajectories captured by single frame long exposure images. Since the defocus of moving particle is inevitable during a long exposure time and under a large magnification, a novel three-dimensional (3D) velocity measurement method named defocusing particle streak velocimetry (DPSV) is proposed in this paper. On the one hand, an extension from two-dimensional (2D) to 3D velocity measurement with a monocular system is carried out. The depth information of the particle, which reflects the position in the third dimension, is indicated by the defocusing degree (characteristic parameter σ) of the particle images. The variation of σ along the trajectory is recognized by surface fitting of the gray value distribution of particle images, assuming that σ varies linearly along the trajectory. On the other hand, based on the linear fitting for the straight trajectory, an arc fitting model is developed for curved trajectories which are commonly captured in turbulent flow. The relationship between σ and the particle depth position z is experimentally calibrated using a LED light and a diaphragm. Finally, the DPSV method is verified in a submerged jet flow field as well as in a microchannel flow field to obtain the 3D velocity field with single monocular system.
Within the pressure range of 9-28 MPa,mass 200-500 kW/m2,experiments were performed to investigate the heat transfer to water in the inclined upward internally ribbed tube with an inclined angle of 19.5 degrees,a maxi...
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Within the pressure range of 9-28 MPa,mass 200-500 kW/m2,experiments were performed to investigate the heat transfer to water in the inclined upward internally ribbed tube with an inclined angle of 19.5 degrees,a maximum outer diameter of 38.1 mm,and a thickness of 7.5 *** on the experiments,it was found that heat transfer enhancement of the internally ribbed tube could postpone departure from nucleate boiling at the sub-critical ***,the heat transfer enhancement decreased near the critical *** supercritical pressure,the temperature difference between the wall and the fluid increased near the pseudo-critical temperature,but the increase of wall temperature was less than that of departure from nucleate boiling at sub-critical *** pressure is closer to the critical pressure,the temperature difference between the wall and the fluid increased greatly near the pseudo-critical *** transfer to supercritical water in the inclined upward internally ribbed tube was enhanced or deteriorated near the pseudo-critical temperature with the variety of ratio between the mass velocity and the heat *** the rotational flow of the internal groove reduced the effect of natural convection,the internal wall temperature of internally ribbed tube uniformly distributed along the *** maximum internal wall temperature difference of the tube along the circumference was only 10 degrees when the fluid enthalpy exceeded 2 000 J/*** the effect of acute variety of the fluid property on heat transfer,the correlation of heat transfer coefficient on the top of the internally ribbed tube was orovided.
The stability of platform structure is the paramount guarantee of the safe operation of the offshore floating wind turbine. The NREL 5MW floating wind turbine is established based on the OC3-Hywind Spar Buoy platform ...
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The stability of platform structure is the paramount guarantee of the safe operation of the offshore floating wind turbine. The NREL 5MW floating wind turbine is established based on the OC3-Hywind Spar Buoy platform with the supplement of helical strakes for the purpose to analyze the impact of helical strakes on the dynamic response of the floating wind turbine Spar platform. The dynamic response of floating wind turbine Spar platform under wind, wave and current loading from the impact of number, height and pitch ratio of the helical strakes is analysed by the radiation and diffraction theory, the finite element method and orthogonal design method. The result reveals that the helical strakes can effectively inhibit the dynamic response of the platform but enlarge the wave exciting force; the best parameter combination is two pieces of helical strakes with the height of 15%D (D is the diameter of the platform) and the pitch ratio of 5; the height of the helical strake and its pitch ratio have significant influence on pitch response.
Offshore wind farm construction is nowadays state of the art in the wind power generation ***,deep water areas with huge amount of wind energy require innovative floating platforms to arrange and install wind turbines...
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Offshore wind farm construction is nowadays state of the art in the wind power generation ***,deep water areas with huge amount of wind energy require innovative floating platforms to arrange and install wind turbines in order to harness wind energy and generate *** conventional floating offshore wind turbine system is typically in the state of force imbalance due to the unique sway characteristics caused by the unfixed foundation and the high center of gravity of the ***,a floating wind farm for 3×3 barge array platforms with shared mooring system is presented here to increase stability for floating *** NREL 5 MW wind turbine and ITI Energy barge reference model is taken as a basis for this ***,the unsteady aerodynamic load solution model of the floating wind turbine is established considering the tip loss,hub loss and dynamic stall correction based on the blade element momentum(BEM)*** second development of AQWA is realized by FORTRAN programming language,and aerodynamic-hydrodynamic-Mooring coupled dynamics model is established to realize the algorithm solution of the ***,the 6 degrees of freedom(DOF)dynamic response of single barge platform and barge array under extreme sea condition considering the coupling effect of wind and wave were observed and investigated in *** research results validate the feasibility of establishing barge array floating wind farm,and provide theoretical basis for further research on new floating wind farm.
Wavelike slug-flow is a representative flow type in horizontal pneumatic *** theory was introduced to establish a 3D kinetic numerical model for wavelike slug gas-solid flow in this *** motion of particulate slugs in ...
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Wavelike slug-flow is a representative flow type in horizontal pneumatic *** theory was introduced to establish a 3D kinetic numerical model for wavelike slug gas-solid flow in this *** motion of particulate slugs in horizontal pipes was numerically *** formation and motion process of slugs and settled layer were *** characteristics of the flow,such as pressure drop,air velocity distribution,slug length and settled layer thickness,and the detailed changing characteristics of slug length and settled layer thickness with air velocity were *** results indicate that kinetic theory can represent the physical characteristics of the non-suspension dense phase flow of wavelike slug pneumatic *** experiment in this paper introduced a new idea for the numerical calculation of slug-flow pneumatic conveying.
China advanced large-scale Pressurized Water Reactor (PWR) implements series of passive safety systems to provide core cooling and decay heat removal in case of some unexpected accidents. The development of reactor be...
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