scholarly journals Conceptual Design and Hydrodynamic Performance of a Modular Hybrid Floating Foundation

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7605
Author(s):  
Xiaobin Qu ◽  
Yingxue Yao ◽  
Jianjun Du
Keyword(s):  
Hydrodynamic Performance ◽  
Irregular Waves ◽  
Critical Parameters ◽  
Windward Side ◽  
Test Model ◽  
Solar Panels ◽  
Horizontal Axis Wind Turbine ◽  
Pitch Motion ◽  
Floating Foundation ◽  
The Impact

The comprehensive utilization of offshore renewable energies is an effective way to solve the intermittency and variability of power supply. This paper aims to present a hybrid floating system (HFS) based on a modular buoyancy-distributed floating foundation (BDFF) that can be equipped with a horizontal-axis wind turbine, solar panels, and wave energy converters (WEC). A simplified test model with a Froude scale ratio of 1/10 is employed to perform the experiments in a deep-water basin to validate the numerical results computed from the code program ANSYS AQWA based on the potential flow theory. The Response Amplitude Operators (RAOs) under regular waves are compared to evaluate the hydrodynamic performance. There is a good agreement in the surge, pitch, and heave RAOs for experiments and the numerical simulation, with a maximum of 6.45 degrees per meter for the pitch motion. Furthermore, the mooring tensions in the time domain are analyzed under different wave conditions.The tension RAOs from simulations are slightly higher than those from measurements with a maximum value at the period of 3.416 s. The mooring line on the windward side has a more considerable mooring tension that is far less than the allowable tensile strength, especially under the wave height of 2 m and the wave period of 2.873 s. The influence of loaded weight representing solar panels is weak, and the impact of winds is acceptable, as the platform deviates 1.3 degrees from the equilibrium state under the test wind speed. Eventually, the effect of irregular waves on the HFS is presented with the critical parameters of mooring tension and pitch motion. The results show that the HFS has a good motion performance.

Frequency and Time-Domain Models for a Two-Body Wave Power Device That Extracts Energy From Sea Waves by Relative Pitch Motion

2008 ◽  
Author(s):  
Paulo Justino ◽  
Jose´ C. Amador ◽  
Tiago Morais ◽  
Marc Hadden ◽  
Nuno Ferreira
Keyword(s):  
Time Domain ◽  
Body Wave ◽  
Domain Analysis ◽  
Hydrodynamic Performance ◽  
Irregular Waves ◽  
Power Device ◽  
Wave Power ◽  
Sea Waves ◽  
Pitch Motion ◽  
Relative Pitch

In this paper analytical and numerical tools are used to describe the behaviour of a new wave power device. This device extracts energy from sea waves by relative pitch motion between their two independent parts. Frequency-domain analysis is carried out assuming that its hydrodynamic performance and its power take-off equipment behaviour may be considered linear. For regular waves optimal mechanical damping coefficients are computed assuming restrictions to hold for relative pitch motion between the two device parts. Useful power, capture length as well as rotations and displacements are computed. Time-domain analysis is necessary if one needs to compute the device’s performance under more realistic operational conditions. In order to get device’s variables trajectories for irregular sea conditions, a time-domain approach is adopted since the hydraulic power take-off equipment exhibits a non-linear behaviour. Results are obtained for irregular waves, i.e. for different sea states, and thus trajectories for several device variables are presented. Power available to the hydraulic machine is computed and presented.

Hydrodynamic Performance Analysis and Optimization of Cylindrical Wave Energy Converters

2018 ◽  
Vol 52 (4) ◽  
pp. 106-119
Author(s):  
Zhiyang Zhang ◽  
Ningyu Li ◽  
Liang Zhang ◽  
Weixing Liu ◽  
Qingwei Ma
Keyword(s):  
Wave Energy ◽  
Weight Distribution ◽  
Cylindrical Wave ◽  
Safety Performance ◽  
Hydrodynamic Performance ◽  
Irregular Waves ◽  
Unit Mass ◽  
Pitch Motion ◽  
Wave Energy Converters ◽  
Energy Converters

AbstractTo examine the hydrodynamic performance of cylindrical wave energy converters (WECs), the expressions of velocity potentials and excitation forces were formulated by using the characteristic function expansion method, based on linear regular wave theory. The hydrodynamic coefficients in the frequency domain were obtained for different geometries in a certain water depth by using the boundary matching method. The concept of total energy per unit mass of irregular waves was introduced to optimize and maximize the ability of wave energy conversion. The effects of weight distribution on coupled surge-pitch motion were also considered in order to optimize the safety performance of the device. The results show that there will be sharp resonance at a certain frequency and the draft-to-radius ratios of WECs have a great effect on the hydrodynamic performance when its mass is fixed. The unit mass of energy in heave is highly dependent on the ratio and mass of the WEC. The weight distribution has no effect on the hydrodynamic performance of the device but has a great effect on the pitch motion, and the center of gravity has a decisive effect on the safety performance of the WEC.

Low Temperature Pre-Epi Treatment: Critical Parameters to Control Interface Contamination

2009 ◽  
Vol 145-146 ◽  
pp. 177-180 ◽  
Author(s):  
Roger Loo ◽  
Andriy Hikavyy ◽  
Frederik E. Leys ◽  
Masayuki Wada ◽  
Kenichi Sano ◽  
...  
Keyword(s):  
Low Temperature ◽  
Sige Layer ◽  
Ex Situ ◽  
Critical Parameters ◽  
Process Equipment ◽  
Successful Implementation ◽  
Lifetime Measurements ◽  
Deposition Processes ◽  
Cleaning Methods ◽  
The Impact

Several device concepts have been further evaluated after the successful implementation of epitaxial Si, SiGe and/or Si:C layers. Most of the next device generations will put limitations on the thermal budget of the deposition processes without making concessions on the epitaxial layer quality. In this work we address the impact of ex-situ wet chemical cleans and in-situ pre-epi bake steps, which are required to obtain oxide free Si surfaces for epitaxial growth. The combination of defect measurements, Secondary Ion Mass Spectroscopy, photoluminescence, lifetime measurements, and electrical diode characterization gives a very complete overview of the performance of low-temperature pre-epi cleaning methods. Contamination at the epi/substrate interface cannot be avoided if the pre-epi bake temperature is too low. This interface contamination is traceable by the photoluminescence and lifetime measurements. It may affect device characteristics by enhanced leakage currents and eventually by yield issues due to SiGe layer relaxation or other defect generation. A comparison of state of the art 200 mm and 300 mm process equipment indicates that for the same thermal budgets the lowest contamination levels are obtained for the 300 mm equipments.

scholarly journals Phononic Band Gap and Free Vibration Analysis of Fluid-Conveying Pipes with Periodically Varying Cross-Section

2021 ◽  
Vol 11 (21) ◽  
pp. 10485
Author(s):  
Hao Yu ◽  
Feng Liang ◽  
Yu Qian ◽  
Jun-Jie Gong ◽  
Yao Chen ◽  
...  
Keyword(s):  
Free Vibration ◽  
Band Gap ◽  
Cross Section ◽  
Natural Frequencies ◽  
Free Vibration Analysis ◽  
Critical Parameters ◽  
Mode Shapes ◽  
Beam Model ◽  
The Impact ◽  
Fluid Conveying Pipes

Phononic crystals (PCs) are a novel class of artificial periodic structure, and their band gap (BG) attributes provide a new technical approach for vibration reduction in piping systems. In this paper, the vibration suppression performance and natural properties of fluid-conveying pipes with periodically varying cross-section are investigated. The flexural wave equation of substructure pipes is established based on the classical beam model and traveling wave property. The spectral element method (SEM) is developed for semi-analytical solutions, the accuracy of which is confirmed by comparison with the available literature and the widely used transfer matrix method (TMM). The BG distribution and frequency response of the periodic pipe are attained, and the natural frequencies and mode shapes are also obtained. The effects of some critical parameters are discussed. It is revealed that the BG of the present pipe system is fundamentally induced by the geometrical difference of the substructure cross-section, and it is also related to the substructure length and fluid–structure interaction (FSI). The number of cells does not contribute to the BG region, while it has significant effects on the amplitude attenuation, higher order natural frequencies and mode shapes. The impact of FSI is more evident for the pipes with smaller numbers of cells. Moreover, compared with the conventional TMM, the present SEM is demonstrated more effective for comprehensive analysis of BG characteristics and free vibration of PC dynamical structures.

scholarly journals Dust-related impacts of mining operations on rangeland vegetation and soil: a case study in Yazd province, Iran

2021 ◽  
Author(s):  
Shahab IbrahimPour ◽  
Alireza KhavaninZadeh ◽  
Ruhollah Taghizadeh mehrjardi ◽  
Hans De Boeck ◽  
Alvina Gul
Keyword(s):  
Seed Germination ◽  
Vegetation Cover ◽  
Microbial Respiration ◽  
Germination Rate ◽  
Windward Side ◽  
Leeward Side ◽  
Mining Operations ◽  
Soil Microbial ◽  
Soil Microbial Respiration ◽  
The Impact

Abstract Destructive mining operations are affecting large areas of natural ecosystems, especially in arid lands. The present study aims at investigating the impact of iron mine exploitation on vegetation and soil in Nodoushan (Yazd province, central Iran). Based on the dominant wind, topography, slope, vegetation and soil of the area, soil and vegetation parameters close to ​the mine were recorded and analyzed according to the distance from the mine. In order to obtain the vegetation cover, a transect and plot on the windward and leeward side of the mine, with 100 m intervals and three replicates at each sampling location was used, yielding 96 soil samples. The amount of dust on the vegetation, the seed weight and seed germination rate of Artemisia sp. as the dominant species within the area, and the soil microbial respiration were measured. The relationship between vegetation cover and distance from the mine was not linear, which was due to an interplay between pollution from the mine and local grazing, while other factors did increase or decrease linearly. The results showed that, as the distance from the mine increased, the weight of 1000 seeds of Artemisia sp. was significantly increased from 271 to 494 mg and seed germination rate and soil microbial respiration were significantly increased from 11.7 to 48.4 % and from 4.5 to 5.9 mg CO2 g− 1 soil day− 1 respectively, while the amount of dust significantly decreased from 43.5 to 6 mg (g plant)−1 between the distance of 100 to 600 m from the mine in the leeward direction. A similar trend was observed in the windward side, though negative effects were lower compared to the same distance along the leeward sample locations. The direct and indirect effects on plant growth and health from mining impacts generally decreased linearly with increasing distance from the mine, up to at least 600 m. Our study serves as a showcase for the potential of bio-indicators as a cost-effective method for assessing impacts of mining activities on the surrounding environment.

Parameter assessment for virtual Stackelberg game in aerodynamic shape optimization

2018 ◽  
Vol 32 (12n13) ◽  
pp. 1840044
Author(s):  
Jing Wang ◽  
Fangfang Xie ◽  
Yao Zheng ◽  
Jifa Zhang
Keyword(s):  
Shape Optimization ◽  
Stackelberg Game ◽  
Critical Parameters ◽  
Aerodynamic Shape Optimization ◽  
Aerodynamic Optimization ◽  
Aerodynamic Shape ◽  
Design Variables ◽  
Design Cycle ◽  
Parametric Studies ◽  
The Impact

In this paper, parametric studies of virtual Stackelberg game (VSG) are conducted to assess the impact of critical parameters on aerodynamic shape optimization, including design cycle, split of design variables and role assignment. Typical numerical cases, including the inverse design and drag reduction design of airfoil, have been carried out. The numerical results confirm the effectiveness and efficiency of VSG. Furthermore, the most significant parameters are identified, e.g. the increase of design cycle can improve the optimization results but it will also add computational burden. These studies will maximize the productivity of the effort in aerodynamic optimization for more complicated engineering problems, such as the multi-element airfoil and wing-body configurations.

Adiabatic Effectiveness and Flow Field Measurements in a Realistic Effusion Cooled Lean Burn Combustor

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Antonio Andreini ◽  
Riccardo Becchi ◽  
Bruno Facchini ◽  
Lorenzo Mazzei ◽  
Alessio Picchi ◽  
...  
Keyword(s):  
Flow Field ◽  
Field Measurements ◽  
Injection System ◽  
Wall Region ◽  
Test Model ◽  
Nox Emissions ◽  
Lean Burn ◽  
Experimental Apparatus ◽  
Adiabatic Effectiveness ◽  
The Impact

Over the last ten years, there have been significant technological advances toward the reduction of NOx emissions from civil aircraft engines, strongly aimed at meeting stricter and stricter legislation requirements. Nowadays, the most prominent way to meet the target of reducing NOx emissions in modern combustors is represented by lean burn swirl stabilized technology. The high amount of air admitted through a lean burn injection system is characterized by very complex flow structures such as recirculations, vortex breakdown, and precessing vortex core (PVC) that may deeply interact in the near wall region of the combustor liner. This interaction makes challenging the estimation of film cooling distribution, commonly generated by slot and effusion systems. The main purpose of the present work is the characterization of the flow field and the adiabatic effectiveness due to the interaction of swirling flow, generated by real geometry injectors, and a liner cooling scheme made up of a slot injection and an effusion array. The experimental apparatus has been developed within EU project LEMCOTEC (low emissions core-engine technologies) and consists of a nonreactive three-sectors planar rig; the test model is characterized by a complete cooling system and three swirlers, replicating the geometry of a GE Avio PERM (partially evaporated and rapid mixing) injector technology. Flow field measurements have been performed by means of a standard 2D PIV (particle image velocimetry) technique, while adiabatic effectiveness maps have been obtained using PSP (pressure sensitive paint) technique. PIV results show the effect of coolant injection in the corner vortex region, while the PSP measurements highlight the impact of swirled flow on the liner film protection separating the contribution of slot and effusion flows. Furthermore, an additional analysis, exploiting experimental results in terms of heat transfer coefficient, has been performed to estimate the net heat flux reduction (NHFR) on the cooled test plate.

Full-Scale Reynolds Number VIV Testing of Tri-Helically Grooved Drill Riser Buoyancy Module

2018 ◽  
Author(s):  
Collin Gaskill ◽  
Jie Wu ◽  
Decao Yin
Keyword(s):  
Reynolds Number ◽  
Large Scale ◽  
Hydrodynamic Force ◽  
Oscillation Amplitude ◽  
Cross Flow ◽  
Hydrodynamic Performance ◽  
Test Model ◽  
Force Coefficient ◽  
Test Cylinder ◽  
Test Models

A newly developed Tri-Helically Grooved drilling riser buoyancy module design was tested in the towing tank of SINTEF Ocean in June 2017. This new design aims to reduce riser drag loading and suppress vortex-induced vibrations (VIV). Objectives of the test program were two-fold: to assess the hydrodynamic performance of the design allowing for validation of previous computational fluid dynamics (CFD) studies through empirical measurements, and, to develop a hydrodynamic force coefficient database to be used in numerical simulations to evaluate drilling riser deformation due to drag loading and fatigue lives when subjected to VIV. This paper provides the parameters of the testing program and a discussion of the results from the various testing configurations assessed. Tests were performed using large scale, rigid cylinder test models at Reynolds numbers in the super-critical flow regime, defined as starting at a Reynolds number of Re = 3.5 × 105 – 5.0 × 105 (depending on various literatures) and continuing until Re = 3 × 106. Towing tests, with fixed and freely oscillating test models, were completed with both a bare test cylinder and a test cylinder with the Tri-Helical Groove design. Additional forced motion tests were performed on the helically grooved model to calculate lift and added mass coefficients at various amplitudes and frequencies of oscillation for the generation of a hydrodynamic force coefficient database for VIV prediction software. Significant differences were observed in the hydrodynamic performance of the bare and helically grooved test models considering both in-line (IL) drag and cross-flow (CF) cylinder excitation and oscillation amplitude. For the helically grooved model, measured static drag shows a strong independence from Reynolds number and elimination of the drag crisis region with an average drag coefficient of 0.63. Effective elimination of VIV and subsequent drag amplification was observed at relatively higher reduced velocities, where the bare test model shows a significant dynamic response. A small level of expected response for the helically grooved model was seen across the lower range of reduced velocities. However, disruption of vortex correlation still occurs in this range and non-sinusoidal and highly amplitude-modulated responses were observed.

Farmland transfer and agricultural economic growth nexus in China: agricultural TFP intermediary effect perspective

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yuan-pei Kuang ◽  
Jia-li Yang ◽  
Meseret-Chanie Abate
Keyword(s):  
Economic Growth ◽  
Agricultural Economic ◽  
Test Model ◽  
Promoting Effect ◽  
Content Type ◽  
Effect Model ◽  
Intermediary Role ◽  
Multidimensional Effects ◽  
The Impact

PurposeThe multidimensional effects of farmland transfer in China have been profoundly unstudied. The purpose of this paper is to provide insights on the effects of the intermediary role of agricultural total factor productivity (TFP) of farmland transfer on agricultural economic growth in China.Design/methodology/approachBased on the agricultural data of 30 provinces in China over the period 2005–2018, this paper uses the intermediary effect model to test the relationship between farmland transfer, agricultural TFP and agricultural economic growth. This paper employed an intermediary effect test model to investigate the intermediary role of agricultural TFP in the influence of farmland transfer on agricultural economic growth.FindingsThe findings indicated that farmland transfer has a significant effect on promoting agricultural economic growth. There is a significant “inverted U-shaped” relationship between farmland transfer and agricultural TFP. The sample value of 84.3% of farmland transfers in China is still within the TFP promoting effect range. In addition, farmland transfer has an indirect impact on agricultural economic growth through the channel of agricultural TFP. Agricultural TFP plays a significant intermediary role, but the effect is relatively lowOriginality/valueThis paper is the first to provide fundamental evidence on the impact of farmland transfers on agricultural economic growth in China, driven by agricultural TFP as an intermediary factor. Agricultural TFP can reduce the involution effect of farmland transfer and promote an indirect effect on agricultural economic growth.

The Impact of IFRS Adoption on the Quality of Accounting Information: Systematic Literature Review

2021 ◽  
pp. 5-15
Author(s):  
Achmad Farid Dedyansyah ◽  
◽  
Sri Pujiningsih ◽  
Satia Nur Maharani ◽  
◽  
...  
Keyword(s):  
Literature Review ◽  
Systematic Literature Review ◽  
Value Relevance ◽  
Accounting Information ◽  
Test Model ◽  
European Continent ◽  
Theoretical Approaches ◽  
Quality Of Accounting Information ◽  
The Impact

The quality of accounting information cannot be separated from the adopted accounting standards. More than 87% of countries worldwide have implemented IFRS standards as financial guidelines in their countries. The goal of IFRS is to make companies more transparent and flexible in producing accounting information based on which users can predict future investment values. The purpose of this article is a systematic literature review on the quality of accounting information associated with adopting IFRS. The sample of this study - 125 articles reviewed in four main classifications: research subject areas, measurement of accounting information quality, theoretical approaches, and research methods. Previous research was obtained from online databases such as Science Direct, Emerald Group, Sage Journal, and Taylor & Francis. The PICO framework in this study was applied to minimize bias from previous studies. The analysis results show that average the most articles on the quality of accounting information were found in journals categorized in the accounting field. Most studies have been found on the European continent regarding the quality of accounting information – 52 (37.7%). Determining the quality of accounting information requires several tests. As a result, 49 (38.8%) and 47 (37.1%) articles emphasize the accrual test model and value relevance model in assessing the quality of accounting information. The results show that 56 articles (44.8%) use the regression analysis method to test value relevance, accrual, and timely loss reporting models.

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