scholarly journals A Hybrid BEM-CFD Virtual Blade Model to Predict Interactions between Tidal Stream Turbines under Wave Conditions

2020 ◽  
Vol 8 (12) ◽  
pp. 969
Author(s):  
Nicolo’ Lombardi ◽  
Stephanie Ordonez-Sanchez ◽  
Stefania Zanforlin ◽  
Cameron Johnstone
Keyword(s):  
Numerical Study ◽  
Experimental Tests ◽  
Full Scale ◽  
Small Scale ◽  
Ansys Fluent ◽  
Narrow Channels ◽  
Tidal Turbine ◽  
Performance Deterioration ◽  
Set Up ◽  
Blade Model

Tidal turbine array optimization is crucial for the further development of the marine sector. It has already been observed that tidal turbines within an array can be heavily affected by excessive aerodynamic interference, thus leading to performance deterioration. Small-scale experimental tests aimed at understanding the physical mechanisms of interaction and identifying optimal distances between machines can be found in the literature. However, often, the relatively narrow channels of laboratories imply high blockage ratios, which could affect the results, making them unreliable if extrapolated to full-scale cases. The main aim of this numerical study was to analyze the effects of the blockage caused by the laboratory channel walls in cases of current and also current surface waves. For this purpose, the performance predictions achieved for two turbines arranged in line for different lateral offsets in case of a typical laboratory scale were compared to the predictions obtained for a full scale, unconfined environment. The methodology consisted in the adoption a hybrid Blade Element Momentum–Computational Fluid Dynamics (BEM-CFD) approach, which was based on the Virtual Blade Model of ANSYS-Fluent. The results indicate that (1) the performance of a downstream turbine can increase up to 5% when this has a lateral separation of 1.5D from an upstream device in a full-scale environment compared to a misleading 15% calculated for the laboratory set-up, and (2) the relative fluctuations of power and thrust generated by waves are not significantly affected by the domain dimensions.

Numerical Study of Methane and Air Combustion Inside Heat-Recirculating Combustors

2013 ◽  
Author(s):  
Yanxia Li ◽  
Zhongliang Liu ◽  
Yan Wang ◽  
Jiaming Liu
Keyword(s):  
Gas Flow ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Central Area ◽  
Small Scale ◽  
Inlet Velocity ◽  
Strong Convection ◽  
Simulation Results ◽  
Lean Fuel ◽  
Set Up

A numerical model on methane/air combustion inside a small Swiss-roll combustor was set up to investigate the flame position of small-scale combustion. The simulation results show that the combustion flame could be maintained in the central area of the combustor only when the speed and equivalence ratio are all within a narrow and specific range. For high inlet velocity, the combustion could be sustained stably even with a very lean fuel and the flame always stayed at the first corner of reactant channel because of the strong convection heat transfer and preheating. For low inlet velocity, small amounts of fuel could combust stably in the central area of the combustor, because heat was appropriately transferred from the gas to the inlet mixture. Whereas, for the low premixed gas flow, only in certain conditions (Φ = 0.8 ～ 1.2 when ν0 = 1.0m/s, Φ = 1.0 when ν0 = 0.5m/s) the small-scale combustion could be maintained.

Arriving at the Optimum Overlap Ratio for an Elliptical-Bladed Savonius Rotor

2017 ◽  
Author(s):  
Nur Alom ◽  
Ujjwal K. Saha
Keyword(s):  
Numerical Study ◽  
Superior Performance ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Small Scale ◽  
Efficient Manner ◽  
Ansys Fluent ◽  
Savonius Rotor ◽  
Velocity Magnitude ◽  
Overlap Ratio

The Savonius rotor appears to be particularly promising for the small-scale applications because of its design simplicity, good starting ability, and insensitivity to wind directions. There has been a growing interest in recent times to harness wind energy in an efficient manner by developing newer blade profiles of Savonius rotor. The overlap ratio (OR), one of the important geometric parameters, plays a crucial role in the turbine performance. In a recent study, an elliptical blade profile with a sectional cut angle (θ) of 47.5° has demonstrated its superior performance when set at an OR = 0.20. However, this value of OR is ideal for a semicircular profile, and therefore, requires further investigation to arrive at the optimum overlap ratio for the elliptical profile. In view of this, the present study attempts to make a systemic numerical study to arrive at the optimum OR of the elliptical profile having sectional cut angle, θ = 47.5°. The 2D unsteady simulation is carried out around the elliptical profile considering various overlap ratios in the range of 0.0 to 0.30. The continuity, unsteady Reynolds Averaged Navier-Stokes (URANS) equations and two equation eddy viscosity SST (Shear Stress transport) k-ω model are solved by using the commercial finite volume method (FVM) based solver ANSYS Fluent. The torque and power coefficients are calculated as a function of tip speed ratio (TSR) and at rotating conditions. The total pressure, velocity magnitude and turbulence intensity contours are obtained and analyzed to arrive at the intended objective. The numerical simulation demonstrates an improved performance of the elliptical profile at an OR = 0.15.

scholarly journals Application of different turbulence models for improving construction of small-scale boiler fired by solid fuel

2017 ◽  
Vol 21 (suppl. 3) ◽  
pp. 809-823
Author(s):  
Nebojsa Manic ◽  
Vladimir Jovanovic ◽  
Dragoslava Stojiljkovic ◽  
Zagorka Brat
Keyword(s):  
Turbulence Model ◽  
Solid Fuel ◽  
Turbulence Modeling ◽  
Turbulence Models ◽  
Experimental Tests ◽  
Computer Hardware ◽  
Small Scale ◽  
Heat Output ◽  
Ansys Fluent ◽  
Model Fluid

Due to the rapid progress in computer hardware and software, CFD became a powerful and effective tool for implementation turbulence modeling in defined combustion mathematical models in the complex boiler geometries. In this paper the commercial CFD package, ANSYS FLUENT was used to model fluid flow through the boiler, in order to define velocity field and predict pressure drop. Mathematical modeling was carried out with application of Standard, RNG, and Realizable k-? turbulence model using the constants presented in literature. Three boilers geometry were examined with application of three different turbulence models with variants, which means consideration of 7 turbulence model arrangements in FLUENT. The obtained model results are presented and compared with data collected from experimental tests. All experimental tests were performed according to procedures defined in the standard SRPS EN 303-5 and obtained results are presented in this paper for all three examined geometries. This approach was used for improving construction of boiler fired by solid fuel with heat output up to 35 kW and for selection of the most convenient construction.

Evaluation of Wearing Pipe for Subsea Mining With Large Particles in Slurry Transportation

2015 ◽  
Author(s):  
Satoru Takano ◽  
Masao Ono ◽  
Sotaro Masanobu
Keyword(s):  
Full Scale ◽  
Small Scale ◽  
Pipe Material ◽  
Test Results ◽  
Material Loss ◽  
Large Particles ◽  
Fundamental Understanding ◽  
Maximum Particle ◽  
Scale Test ◽  
Set Up

For a fundamental understanding of pipe wear under hydraulic transportation of deep-sea mining, a small scale test is conducted because there are many restrictions in conducting a full scale test. The small scale test apparatus are set up using the pipes of about 80mm in diameter and the rocks of which maximum particle diameters are about 20mm are used. In the test, the pipe materials and the pipe inclination are changed to evaluate the differential of the amount of pipe material loss. Furthermore, the amount of the pipe material loss in full scale is estimated based on the small scale test results.

scholarly journals Experimental and numerical study of maximum ceiling temperature in a tunnel

2019 ◽  
Vol 11 (12) ◽  
pp. 168781401989749
Author(s):  
ZP Bai ◽  
YF Li
Keyword(s):  
Heat Release ◽  
Temperature Variation ◽  
Numerical Study ◽  
Experimental Tests ◽  
Maximum Temperature ◽  
Small Scale ◽  
Experimental Conditions ◽  
Longitudinal Ventilation ◽  
Ceiling Temperature ◽  
Ventilation Velocity

Maximum ceiling temperatures in a tunnel with different ventilation velocities with three heat release fires are studied experimentally and theoretically. This article investigates the ventilation velocity effects on maximum ceiling temperature combustible materials around ignition source in tunnel fires. Several fire experimental tests are conducted with longitudinal ventilation velocity changes in a small-scale tunnel (23 m in length, 2 m in width, and 0.98 m in height), where three heat release fires (237, 340, and 567 kW) and their corresponding values in the real tunnel are 20, 30, and 50 MW, respectively. This article modifies the current temperature prediction model taking the ignition materials near the fire source into account in tunnels. Results show that the ceiling maximum temperature increases, corresponding to the burn time when other experimental conditions remain unchanged for a given fire heat level source. The ceiling temperature reduces quickly when the ventilation velocity is increased from 0.5 to 2.0 m/s. Moreover, this article proposes an equation that can be used to estimate the ceiling maximum temperature variation value with three heat release fires in tunnels. Finally, experimental results are also compared with the tunnel ceiling temperature attenuation equations established by Alpert, Heskestad, and Ingason. The equation proposed in this article appears to provide better estimates of ceiling temperature variation than the Kurioka model developed in their scaled experiments. The prediction agrees well with the experimental and measured data by the modified equations of this article.

Simulation of a Full-Scale CO2 Fracture Propagation Test

2018 ◽  
Author(s):  
Gaute Gruben ◽  
Stephane Dumoulin ◽  
Håkon Nordhagen ◽  
Morten Hammer ◽  
Svend T. Munkejord
Keyword(s):  
Fluid Dynamics ◽  
Numerical Model ◽  
Numerical Study ◽  
Crack Opening ◽  
Fracture Propagation ◽  
Full Scale ◽  
Coupling Scheme ◽  
Outer Diameter ◽  
Fe Model ◽  
Set Up

In this study, we present results from a numerical model of a full-scale fracture propagation test where the pipe sections are filled with impure, dense liquid-phase carbon dioxide. All the pipe sections had a 24″ outer diameter and a diameter/thickness ratio of ∼32. A near symmetric telescopic set-up with increasing toughness in the West and East directions was applied. Due to the near symmetric conditions in both set-up and results, only the East direction is modelled in the numerical study. The numerical model is built in the framework of the commercial finite element (FE) software LS-DYNA. The fluid dynamics is solved using an in-house computational fluid dynamics (CFD) solver which is coupled with the FE solver through a user-defined loading subroutine. As part of the coupling scheme, the FE model sends the crack opening profile to the CFD solver which returns the pressure from the fluid. The pipeline is discretized by shell elements, while the backfill is represented by the smoothed-particle hydrodynamics (SPH) method. The steel pipe is described by the J2 constitutive model and an energy-based fracture criterion, while the Mohr-Coulomb material model is applied for the backfill material. The CFD solver applies a one-dimensional homogeneous equilibrium model where the thermodynamic properties of the CO2 are represented by the Peng-Robinson equation-of-state (EOS). The results from the simulations in terms of crack velocity and pressure agree well with the experimental data for the low and medium toughness pipe sections, while a conservative prediction is given for the high-toughness section. Further work for strengthening the reliability of the model to predict the arrest vs. no-arrest boundary of a running ductile fracture is addressed.

Numerical Study on Concentric Braced X Frames under Monotonic and Cyclic Loads

2018 ◽  
Vol 763 ◽  
pp. 633-641 ◽  
Author(s):  
Beatrice Faggiano ◽  
Antonio Formisano ◽  
Generoso Vaiano ◽  
Federico M. Mazzolani
Keyword(s):  
Numerical Study ◽  
Elastic Field ◽  
Seismic Energy ◽  
Experimental Tests ◽  
Cyclic Loads ◽  
Braced Frames ◽  
Structural Behaviour ◽  
Factors Affecting ◽  
Strength And Stiffness ◽  
Set Up

Concentric Braced Frames (CBF) are designed for dissipating the seismic energy mainly through plastic deformations of diagonals in tension, while beams and columns, designed on the basis of the hierarchy resistance criterion, should resist the design loads in elastic field without undergoing buckling and yielding phenomena. For such structural systems there are still some uncertainties on the performances under cyclic loadings, due to the degradation of the strength and stiffness under tension for the occurrence of instability problems in compression. The current paper deepens such key issues, presenting the numerical simulation of some literature experimental tests conducted on CBX frames subjected to monotonic and cyclic loads both in presence and in absence of vertical loads. The refined FE structural models of the study systems are developed through the software ABAQUS v6.13-1. The models set up have provided a very good replication of both monotonic and hysteretic behaviours in terms of strength, stiffness, ductility and energy dissipation. They are powerful analysis instruments to perform parametric studies, aiming at detecting the main factors affecting the cyclic structural behaviour, thus leading towards appropriate design criteria.

scholarly journals Design and testing of a full-scale 2 MW tidal turbine blade

2020 ◽  
Author(s):  
Edward Fagan ◽  
Finlay Wallace ◽  
Yadong Jiang ◽  
Afrooz Kazemi ◽  
Jamie Goggins
Keyword(s):  
Web Design ◽  
Full Scale ◽  
Design Study ◽  
Composite Blade ◽  
Cost Of Energy ◽  
Access Programme ◽  
Tidal Turbine ◽  
Set Up ◽  
The Cost ◽  
The Impact

The Large Structures Research Group of MaREI, Orbital Marine Power Ltd and ÉireComposites Teo. have designed a full-scale blade for a next-generation 2 MW tidal turbine as part of the H2020 FloTEC project. The 8.5 m long blade will be tested under static load conditions through the H2020 MaRINET2 transnational access programme and fatigue conditions through the OCEAN ERA-NET SEABLADE project. This paper provides an overview of the initial design study which analysed the impact of using a single shear web or two shear webs in the design. The result of this design study led to optimisation of the laminates throughout the blade to reduce the cost of manufacture and, hence, the levelized cost of energy of the device. The finite element analyses were performed using the MaREI@NUI Galway composite blade design software BladeComp. From the results of the analyses a single web design was chosen for the blade. The present work also describes the set-up for the structural tests and an overview of the data acquisition and instrumentation requirements for full-scale static and fatigue blade testing.

Coupled Simulations of Natural and Forced Circulation Tests in NACIE Facility Using RELAP5 and ANSYS Fluent Codes

2014 ◽  
Author(s):  
D. Martelli ◽  
N. Forgione ◽  
G. Barone ◽  
A. Del Nevo ◽  
I. Di Piazza ◽  
...  
Keyword(s):  
Natural Circulation ◽  
Experimental Tests ◽  
Research Centre ◽  
Assisted Circulation ◽  
Coupling Scheme ◽  
Ansys Fluent ◽  
Forced Circulation ◽  
Model Set ◽  
Set Up ◽  
2D And 3D

In this work the activity performed at the DICI (Dipartimento di Ingegneria Civile e Industriale) of the Pisa University in collaboration with the ENEA Brasimone Research Centre is presented. In particular the document deals with the application of an in-house developed coupling methodology between a modified version of RELAP5/Mod3.3 and Fluent commercial CFD code, to the NACIE (Natural Circulation Experiment) LBE experimental loop (built and located at the ENEA Brasimone research centre). The first part of the document treats the description of the NACIE loop type facility, while in the second part, the developed coupling tool is presented and the obtained numerical results are compared to stand alone RELAP5 results and to data obtained from the NACIE experimental campaign. The experimental tests are performed varying the argon flow rate and the electric power supplied to the heater and both natural and assisted circulation tests are investigated. The numerical model set-up is based on a two-way explicit coupling scheme and 2D and 3D geometrical domain were investigated. Comparative analyses among numerical and experimental results showed good agreement, giving positive feedback on the feasibility and capability of the developed coupling methodology.

Numerical Study on Moment Resisting Frames under Monotonic and Cyclic Loads

2018 ◽  
Vol 763 ◽  
pp. 625-632 ◽  
Author(s):  
Beatrice Faggiano ◽  
Antonio Formisano ◽  
Generoso Vaiano ◽  
Federico M. Mazzolani
Keyword(s):  
Seismic Behavior ◽  
Numerical Study ◽  
Seismic Energy ◽  
Experimental Tests ◽  
Design Criteria ◽  
Cyclic Loads ◽  
Factors Affecting ◽  
Moment Resisting Frames ◽  
Moment Resisting ◽  
Set Up

Moment Resisting Frames (MRF) should ideally dissipate the seismic energy through the development of plastic hinges in the beams and at the column bases with the purpose to pursue a global failure mechanism. The current seismic design criteria, through hierarchy resistance and ductility requirements, are conceived to achieve this objective. However there are still some inaccuracies in the prediction of the structural performances, mainly under cyclic loadings, as much important as the number of bays and stories augments. The current paper would give a contribution for deepening key issues related to MRF seismic behavior, presenting the numerical simulation of some literature experimental tests conducted on simple portal MRF subjected to monotonic and cyclic loads both in presence and in absence of vertical loads. The refined Finite Element structural models of the study systems are developed through the software ABAQUS (v6.13-1). The models set up provide very good replications of both monotonic and hysteretic behaviors in terms of strength, stiffness, ductility and energy dissipation. They represent powerful analysis instruments to perform parametric studies, aiming at detecting the main factors affecting the seismic behavior of MRFs, thus leading towards appropriate design criteria.

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