scholarly journals Performance of a Direct-Driven Wave Energy Point Absorber with High Inertia Rotatory Power Take-off

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2332 ◽  
Author(s):  
Simon Thomas ◽  
Marianna Giassi ◽  
Malin Göteman ◽  
Martyn Hann ◽  
Edward Ransley ◽  
...  
Keyword(s):  
Natural Frequencies ◽  
Cost Effective ◽  
Rotatory Power ◽  
Scale Model ◽  
Absorption Characteristic ◽  
Wave Tank ◽  
Point Absorber ◽  
Physical Scale ◽  
Current Break ◽  
Linear Damping

An alternating rotatory generator using an eddy current break is developed as a physical scale model of a direct-driven floating point absorber power take-off (PTO) for wave tank tests. It is shown that this design is a simple and cost-effective way to get an accurate linear damping PTO. The device shows some beneficial characteristics, making it an interesting option for full scale devices: For similar weights the inertia can be significantly higher than for linear generators, allowing it to operate with natural frequencies close to typical wave frequencies. The influence of the higher inertia on the power absorption is tested using both a numerical simulation and physical wave tank tests. With the increased inertia the PTO is able to absorb more than double the energy of a comparable direct-driven linear generator in some sea states. Moreover, the alternating rotatory generator allows the absorption characteristic to be tuned by changing the inertia and the generator damping.

scholarly journals Multiphasic Study of Fluid-Dynamics and the Thermal Behavior of a Steel Ladle during Bottom Gas Injection Using the Eulerian Model

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1082
Author(s):  
Antonio Urióstegui-Hernández ◽  
Pedro Garnica-González ◽  
José Ángel Ramos-Banderas ◽  
Constantin Alberto Hernández-Bocanegra ◽  
Gildardo Solorio-Díaz
Keyword(s):  
Heat Exchange ◽  
Thermal Behavior ◽  
Gas Flow ◽  
Fluid Dynamic ◽  
Steel Slag ◽  
Scale Model ◽  
Discrete Ordinates ◽  
Transfer Model ◽  
Steel Ladle ◽  
Physical Scale

In this work, the fluid dynamic and thermal behavior of steel was analyzed during argon gas stirring in a 140-t refining ladle. The Eulerian multiphase mathematical model was used in conjunction with the discrete ordinates (DO) thermal radiation model in a steel-slag-argon system. The model was validated by particle image velocimetry (PIV) and the analysis of the opening of the oil layer in a physical scale model. The effect of Al2O3 and Mg-C as a refractory in the walls was studied, and the Ranz-Marshall and Tomiyama models were compared to determine the heat exchange coefficient. The results indicated that there were no significant differences between these heat exchange models; likewise, the radiation heat transfer model adequately simulated the thermal behavior according to plant measurements, finding a thermal homogenization time of the steel of 2.5 min for a gas flow of 0.45 Nm3·min−1. Finally, both types of refractory kept the temperature of the steel within the ranges recommended in the plant; however, the use of Al2O3 had better heat retention, which would favor refining operations.

scholarly journals Roughness Lengths for Momentum and Heat Derived from Outdoor Urban Scale Models

2007 ◽  
Vol 46 (7) ◽  
pp. 1067-1079 ◽  
Author(s):  
M. Kanda ◽  
M. Kanega ◽  
T. Kawai ◽  
R. Moriwaki ◽  
H. Sugawara
Keyword(s):  
Wind Direction ◽  
Roughness Length ◽  
Scale Dependence ◽  
Scale Model ◽  
Small Scale ◽  
Physical Scale ◽  
Scale Models ◽  
Roughness Lengths ◽  
Urban Sites ◽  
Obstacle Height

Abstract Urban climate experimental results from the Comprehensive Outdoor Scale Model (COSMO) were used to estimate roughness lengths for momentum and heat. Two different physical scale models were used to investigate the scale dependence of the roughness lengths; the large scale model included an aligned array of 1.5-m concrete cubes, and the small scale model had a geometrically similar array of 0.15-m concrete cubes. Only turbulent data from the unstable boundary layers were considered. The roughness length for momentum relative to the obstacle height was dependent on wind direction, but the scale dependence was not evident. Estimated values agreed well with a conventional morphometric relationship. The logarithm of the roughness length for heat relative to the obstacle height depended on the scale but was insensitive to wind direction. COSMO data were used successfully to regress a theoretical relationship between κB−1, the logarithmic ratio of roughness length for momentum to heat, and Re*, the roughness Reynolds number. Values of κB−1 associated with Re* for three different urban sites from previous field experiments were intercompared. A surprising finding was that, even though surface geometry differed from site to site, the regressed function agreed with data from the three urban sites as well as with the COSMO data. Field data showed that κB−1 values decreased as the areal fraction of vegetation increased. The observed dependency of the bulk transfer coefficient on atmospheric stability in the COSMO data could be reproduced using the regressed function of Re* and κB−1, together with a Monin–Obukhov similarity framework.

AN EXPERIMENTAL STUDY ON THE RELATIVE MOTIONS BETWEEN A FLOATING HARBOUR TRANSHIPPER AND A FEEDER VESSEL IN REGULAR WAVES

2021 ◽  
Vol 154 (A2) ◽  
Author(s):  
G J Macfarlane ◽  
T Lilienthal ◽  
R J Ballantyne ◽  
S Ballantyne
Keyword(s):  
Open Water ◽  
Scale Model ◽  
Regular Waves ◽  
Inclement Weather ◽  
Port Operations ◽  
Physical Scale ◽  
Feeder Vessel ◽  
Primary Advantage ◽  
Exposed Location ◽  
Relative Motions

The Floating Harbour Transhipper (FHT) is a pioneering logistics solution that was designed to meet the growing demands for coastal transhipment in the mining sector as well as commercial port operations. The primary advantage of the FHT system is that it can reduce transhipment delays caused by inclement weather, by reducing relative motions between the FHT and feeder vessel. The feeder is sheltered when inside the FHT well dock when compared to the more exposed location when a feeder is in a traditional side-by-side mooring arrangement. This paper discusses previously published studies into the relative motions of vessels engaged in side-by-side mooring arrangements and also presents details and results from a series of physical scale model experiments. In these experiments, both side-by-side and aft well dock mooring arrangements are investigated. The results provide strong evidence that the FHT well dock concept can significantly reduce the heave, pitch and roll motions of feeder vessels when transhipping in open seas – this being the cornerstone of any successful open water transhipment operation.

Effective Shear Area in One Dimensional Ship Hull Finite Element Models to Predict Natural Frequencies of Vibration

2013 ◽  
Author(s):  
Osvaldo Pinheiro de Souza e Silva ◽  
Severino Fonseca da Silva Neto ◽  
Ilson Paranhos Pasqualino ◽  
Antonio Carlos Ramos Troyman
Keyword(s):  
Finite Element ◽  
Natural Frequencies ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Numerical Results ◽  
Computational Method ◽  
Scale Model ◽  
Dimensional Model ◽  
One Dimensional ◽  
Shear Area

This work discusses procedures used to determine effective shear area of ship sections. Five types of ships have been studied. Initially, the vertical natural frequencies of an acrylic scale model 3m in length in a laboratory at university are obtained from experimental tests and from a three dimensional numerical model, and are compared to those calculated from a one dimensional model which the effective shear area was calculated by a practical computational method based on thin-walled section Shear Flow Theory. The second studied ship was a ship employed in midshipmen training. Two models were made to complement some studies and vibration measurements made for those ships in the end of 1980 decade when some vibration problems in them were solved as a result of that effort. Comparisons were made between natural frequencies obtained experimentally, numerically from a three dimensional finite element model and from a one dimensional model in which effective shear area is considered. The third and fourth were, respectively, a tanker ship and an AHTS (Anchor Handling Tug Supply) boat, both with comparison between three and one dimensional models results out of water. Experimental tests had been performed in these two ships and their results were used in other comparison made after the inclusion of another important effect that acts simultaneously: the added mass. Finally, natural frequencies experimental and numerical results of a barge are presented. The natural frequencies numerical results of vertical hull vibration obtained from these approximations of effective shear areas for the five ships are finally discussed.

scholarly journals THE USE OF ARRAY PROCESSORS FOR NUMERICAL MODELLING OF TIDAL ESTUARY DYNAMICS

1980 ◽  
Vol 1 (17) ◽  
pp. 142
Author(s):  
D. Prandle ◽  
E.R. Funke ◽  
N.L. Crookshank ◽  
R. Renner
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Hybrid Model ◽  
Numerical Models ◽  
Computer Time ◽  
Scale Model ◽  
Hybrid Modelling ◽  
Tidal Propagation ◽  
Physical Scale ◽  
Array Processors

The use of array processors for the numerical modelling of estuarine systems is discussed here in the context of "hybrid modelling", however, it is shown that array processors may be used to advantage in independent numerical simulations. Hybrid modelling of tidal estuaries was first introduced by fiolz (1977) and later by Funke and Crookshank (1978). In a hybrid model, tidal propagation in an estuary is simulated by dynamically linking an hydraulic (or physical) scale model of part of the estuary to a numerical model of the remaining part in a manner such that a free interchange of flow occurs at the interface(s). Typically, the elevation of the water surface at the boundary of the scale model is measured and transmitted to the numerical model. In return, the flow computed at the boundary of the numerical model is fed directly into the scale model. This approach enables the extent of the scale model to be limited to the area of immediate interest (or to that area where flow conditions are such that they can be most accurately simulated by a scale model). In addition, since the region simulated by the numerical model can be extended almost indefinitely, the problems of spurious reflections from downstream boundaries can be eliminated. In normal use, numerical models are evaluated on the basis of computing requirements, cost and accuracy. The computer time required to simulate one tide cycle is, in itself, seldom of interest except in so far as it affects the above criteria. However in hybrid modelling this parameter is often paramount since concurrent operation of the numerical and scale models requires that the former must keep pace with the latter. The earlier hybrid model of the St. Lawrence (Funke and Crookshank, 1978) involved a one-dimensional numerical model of the upstream regions of the river. However, future applications are likely to involve extensive two-dimensional numerical simulation.

scholarly journals Similarity Analysis between Scale Model and Prototype of Large Vibrating Screen

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Zerong Zhang ◽  
Yongyan Wang ◽  
Zhimin Fan
Keyword(s):  
Frequency Response ◽  
Natural Frequencies ◽  
Similarity Theory ◽  
Similarity Criteria ◽  
Scale Model ◽  
Mode Shapes ◽  
Dynamic Stresses ◽  
Operating Condition ◽  
Vibrating Screen ◽  
Scale Down

In order to predict the physical characteristics of the large vibrating screen from its scale-down model, the similarity ratios of the frequency response functions, mode shapes, and dynamic stresses between the prototype and the scale model screen are built according to the similarity theory. The natural frequencies and modal shapes are extracted from the frequency response function by means of modal tests, in which the relative error of the natural frequencies is less than 9% and the modal shapes are consistent between the prototype and the model. The operating condition parameters including dynamic stress, displacement, velocity, and acceleration were also measured and conform to the similarity criteria. The results show that the inherent and operating condition parameters of the large vibrating screen can be obtained from the scale-down model conveniently, which provides an effective method for structural optimization and substructure coupling analysis of the large vibrating screen.

scholarly journals Numerical and Experimental Investigation on a Moonpool-Buoy Wave Energy Converter

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2364 ◽  
Author(s):  
Hengxu Liu ◽  
Feng Yan ◽  
Fengmei Jing ◽  
Jingtao Ao ◽  
Zhaoliang Han ◽  
...  
Keyword(s):  
Numerical Model ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Scale Model ◽  
Energy Converter ◽  
Point Absorber ◽  
Motion Responses ◽  
Computational Fluid Dynamics Cfd ◽  
The Time Domain ◽  
Good Agreement

This paper introduces a new point-absorber wave energy converter (WEC) with a moonpool buoy—the moonpool platform wave energy converter (MPWEC). The MPWEC structure includes a cylinder buoy and a moonpool buoy and a Power Take-off (PTO) system, where the relative movement between the cylindrical buoy and the moonpool buoy is exploited by the PTO system to generate energy. A 1:10 scale model was physically tested to validate the numerical model and further prove the feasibility of the proposed system. The motion responses of and the power absorbed by the MPWEC studied in the wave tank experiments were also numerically analyzed, with a potential approach in the frequency domain, and a computational fluid dynamics (CFD) code in the time domain. The good agreement between the experimental and the numerical results showed that the present numerical model is accurate enough, and therefore considering only the heave degree of freedom is acceptable to estimate the motion responses and power absorption. The study shows that the MPWEC optimum power extractions is realized over a range of wave frequencies between 1.7 and 2.5 rad/s.

scholarly journals Modeling Storm Surge Attenuation by an Integrated Nature-Based and Engineered Flood Defense System in the Scheldt Estuary (Belgium)

2020 ◽  
Vol 8 (1) ◽  
pp. 27
Author(s):  
Sven Smolders ◽  
Maria João Teles ◽  
Agnès Leroy ◽  
Tatiana Maximova ◽  
Patrick Meire ◽  
...  
Keyword(s):  
Storm Surge ◽  
Flood Control ◽  
Storm Surges ◽  
Scheldt Estuary ◽  
Scale Model ◽  
Defense System ◽  
Height Reduction ◽  
Flood Defense ◽  
Physical Scale ◽  
Surge Height

There is increasing interest in the use of nature-based approaches for mitigation of storm surges along coasts, deltas, and estuaries. However, very few studies have quantified the effectiveness of storm surge height reduction by a real-existing, estuarine-scale, nature-based, and engineered flood defense system, under specific storm surge conditions. Here, we present data and modelling results from a specific storm surge in the Scheldt estuary (Belgium), where a hybrid flood defense system is implemented, consisting of flood control areas, of which some are restored into tidal marsh ecosystems, by use of culvert constructions that allow daily reduced tidal in- and outflow. We present a hindcast simulation of the storm surge of 6 December 2013, using a TELEMAC-3D model of the Scheldt estuary, and model scenarios showing that the hybrid flood defense system resulted in a storm surge height reduction of up to half a meter in the estuary. An important aspect of the work was the implementation of model formulations for calculating flow through culverts of restored marshes. The latter was validated comparing simulated and measured discharges through a physical scale model of a culvert, and through a real-scale culvert of an existing restored marsh during the storm surge.

scholarly journals Computational Analyses of the Effects of Wind Tunnel Ground Simulation and Blockage Ratio on the Aerodynamic Prediction of Flow over a Passenger Vehicle

Vehicles ◽  
2020 ◽  
Vol 2 (2) ◽  
pp. 318-341
Author(s):  
Chen Fu ◽  
Mesbah Uddin ◽  
Chunhui Zhang
Keyword(s):  
Wind Tunnel ◽  
Boundary Conditions ◽  
Physical Simulation ◽  
Cost Effective ◽  
Aerodynamic Characteristics ◽  
Operating Conditions ◽  
Scale Model ◽  
Blockage Ratio ◽  
Road Tunnel ◽  
Test Conditions

With the fast-paced growth of computational horsepower and its affordability, computational fluid dynamics (CFD) has been rapidly evolving as a popular and effective tool for aerodynamic design and analysis in the automotive industry. In the real world, a road vehicle is subject to varying wind and operating conditions that affect its aerodynamic characteristics, and are difficult to reproduce in a traditional wind tunnel. CFD has the potential of becoming a cost-effective way of achieving this, through the application of different boundary conditions. Additionally, one can view wind tunnel testing, be it a fixed-floor or rolling road tunnel, as a physical simulation of actual on-road driving. The use of on-road track testing, and static-floor, and rolling-road wind tunnel measurements are common practices in industry. Subsequently, we investigated the influences of these test conditions and the related boundary conditions on the predictions of the aerodynamic characteristics of the flow field around a vehicle using CFD. A detailed full-scale model of Hyundai Veloster with two vehicle configurations, one with the original and the other with an improved spoiler, were tested using a commercial CFD code STAR-CCM+ from Siemens. Both vehicle configurations were simulated using four different test conditions, providing overall eight different sets of simulation settings. The CFD methodology was validated with experimental data from the Hyundai Aero-acoustic Wind Tunnel (HAWT), by accurately reproducing the test section with static floor boundary conditions. In order to investigate the effect of the blockage ratio on the aerodynamic predictions, the vehicle models were then tested with moving ground plus rotating wheel boundary conditions, using a total of four virtual wind tunnel configurations, with tunnel solid blockage ratios ranging from 1.25%, which corresponds to the actual HAWT, to 0.04%, which presents an open air driving condition.

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