scholarly journals The Efficiency of a Fence of Tidal Turbines in the Alderney Race: Comparison between Analytical and Numerical Models

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 892
Author(s):  
Jérôme Thiébot ◽  
Nasteho Djama Dirieh ◽  
Sylvain Guillou ◽  
Nicolas Guillou
Keyword(s):  
Numerical Models ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Analytical Models ◽  
Yield Potential ◽  
Hydrodynamic Characteristics ◽  
Energy Yield ◽  
Three Dimensional Model ◽  
Lower Efficiency ◽  
Array Efficiency

Assessing the efficiency of a tidal turbine array is necessary for adequate device positioning and the reliable evaluation of annual energy production. Array efficiency depends on hydrodynamic characteristics, operating conditions, and blockage effects, and is commonly evaluated by relying on analytical models or more complex numerical simulations. By applying the conservations of mass, momentum, and energy in an idealized flow field, analytical models derive formulations of turbines’ thrust and power as a function of the induction factor (change in the current velocity induced by turbines). This simplified approach also gives a preliminary characterization of the influence of blockage on array efficiency. Numerical models with turbines represented as actuator disks also enable the assessment of the efficiency of a tidal array. We compare here these two approaches, considering the numerical model as a reference as it includes more physics than the analytical models. The actuator disk approach is applied to the three-dimensional model Telemac3D in realistic flow conditions and for different operating scenarios. Reference results are compared to those obtained from three analytical models that permit the investigation of the flow within tidal farm integrating or excluding processes such as the deformation of the free surface or the effects of global blockage. The comparison is applied to the deployment of a fence of turbines in the Alderney Race (macro-tidal conditions of the English Channel, northwest European shelf). Efficiency estimates are found to vary significantly from one model to another. The main result is that analytical models predict lower efficiency as they fail to approach realistically the flow structure in the vicinity of turbines, especially because they neglect the three-dimensional effects and turbulent mixing. This finding implies that the tidal energy yield potential could be larger than previously estimated (with analytical models).

UV disinfection of water: the need for UV reactor validation

2003 ◽  
Vol 3 (4) ◽  
pp. 293-300 ◽  
Author(s):  
Y.A. Lawryshyn ◽  
B. Cairns
Keyword(s):  
Legionella Pneumophila ◽  
Uv Light ◽  
Numerical Models ◽  
Operating Conditions ◽  
Analytical Models ◽  
Human Consumption ◽  
Average Dose ◽  
Reactor Performance ◽  
Uv Reactor ◽  
Bioassay Data

Disinfection by ultraviolet light (UV) has received wide endorsement as an important contribution to the multiple barrier approach for protection of public health. UV can be used both to disinfect wastewater discharged to the environment, and to disinfect that water when it is picked up again for human consumption. UV readily blocks infectivity by such chlorine-resistant pathogens as Cryptosporidium parvum, Giardia lamblia and Legionella pneumophila. Multiple disinfectant use is now being discussed to broaden the spectrum of pathogens that can be inactivated by using disinfectants in their most strategically advantageous dose and function. Optimizing multiple barrier strategies requires attention to validation of the concepts and technologies involved. UV technology validation ensures that the equipment can deliver the target UV design dose, and that the monitoring/control technology modulates the dose appropriately with changes in water quality or operating conditions. The bioassay approach for UV reactor validation is recommended over analytical and numerical models. Analytical models, which provide an average dose estimate, have been shown to be inadequate. Numerical models, which utilize Computational Fluid Dynamics (CFD) and UV light intensity models to predict reactor performance, can be accurate when used by skilled professionals but require significant validation and/or calibration against bioassay data.

Strength Analysis and Optimization Methods for Four Cylinder Engine Crankshaft Based on CATIA and ANSYS

2014 ◽  
Vol 592-594 ◽  
pp. 1789-1793
Author(s):  
Amarjeet Singh ◽  
Vinod Kumar Mittal ◽  
Surjit Angra
Keyword(s):  
Static Analysis ◽  
Material Selection ◽  
Three Dimensional ◽  
Optimization Methods ◽  
Operating Conditions ◽  
Strength Analysis ◽  
Three Dimensional Model ◽  
Ic Engine ◽  
Stress Zone ◽  
Engine Crankshaft

Crankshaft is one of the most important components of an IC engine. Crankshaft should be checked carefully to ensure that its design is fully optimized. The main objective of this paper is to perform the static analysis on four cylinder engine crankshaft to find out its static strength and the maximum stress zone and analyzing the different methods for the optimization of crankshaft in terms of weight, stress and cost reduction. A three dimensional model of four cylinder engine crankshaft is prepared corresponding to actual conditions in Catia V5 software, static analysis is performed using Ansys under extreme operating conditions and the improvement methods for the optimum design are analyzed in terms of geometric improvement, appropriate material selection and methods used for manufacturing of crankshaft.

Numerical modelling of a microreactor for thermocatalytic decomposition of toxic compounds

2011 ◽  
Vol 32 (3) ◽  
pp. 215-227 ◽  
Author(s):  
Paweł Jóźwik ◽  
Michał Karcz ◽  
Janusz Badur
Keyword(s):  
Numerical Modelling ◽  
Knudsen Diffusion ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Three Dimensional Model ◽  
Toxic Compounds ◽  
Slip Boundary ◽  
Standard Models ◽  
Thermocatalytic Decomposition

Numerical modelling of a microreactor for thermocatalytic decomposition of toxic compounds In this paper a three-dimensional model for determination of a microreactor's length is presented and discussed. The reaction of thermocatalytic decomposition has been implemented on the base of experimental data. Simplified Reynolds-Maxwell formula for the slip velocity boundary condition has been analysed and validated. The influence of the Knudsen diffusion on the microreactor's performance has also been verified. It was revealed that with a given operating conditions and a given geometry of the microreactor, there is no need for application of slip boundary conditions and the Knudsen diffusion in further analysis. It has also been shown that the microreactor's length could be practically estimated using standard models.

Numerical Simulation of a Mini-Channel Three-Way Catalytic Converter

2010 ◽  
Author(s):  
M. H. Akbari ◽  
R. Roohi ◽  
S. A. Asaee
Keyword(s):  
Conversion Efficiency ◽  
Single Channel ◽  
Heterogeneous Reaction ◽  
Catalytic Converter ◽  
Three Dimensional ◽  
Space Velocity ◽  
Kinetic Mechanism ◽  
Operating Conditions ◽  
Three Dimensional Model ◽  
Different Temperatures

A three-dimensional model is developed to simulate the behavior of a single-channel three-way catalytic converter. The flow regime is assumed to be steady and laminar, and the channel walls are considered as isothermal. A multi-step, global heterogeneous reaction mechanism with 16 reactions and 11 species is used in this investigation to enhance the accuracy of the results. The chemical reactions are assumed to occur only on the reactor walls. The developed model is validated against available experimental data for stoichiometric operating conditions. The effect of the feed temperature on the conversion efficiency of the main pollutant components is studied. The light-off temperature for the stoichiometric A/F is found to be about 530 K for CO, NO and UHC, and 425 K for H2 conversion. The model is also applied to predict the effect of reactor length and inlet mixture space velocity on the conversion efficiency at two different temperatures. By using the same kinetics a well-stirred, unsteady model is also developed to identify the sensitivity of the multi-step kinetic mechanism to the mixture composition. The effect of mole fraction variation of each species on the conversion of other mixture components is investigated.

scholarly journals Universal compact lower limb turning module intended for use in orthotic robots

2018 ◽  
Vol 157 ◽  
pp. 03011
Author(s):  
Mateusz Janowski ◽  
Danuta Jasińska-Choromańska ◽  
Dymitr Osiński ◽  
Marcin Zaczyk
Keyword(s):  
Lower Limb ◽  
State Of The Art ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Three Dimensional Model ◽  
Additional Degree ◽  
Rotation System ◽  
University Of Technology ◽  
Impaired Person ◽  
Turning System

In this paper, a model of an orthotic robot’s lower limb rotation system is presented. The system is intended for use in typical contemporary orthotic robots such as the ‘Veni-Prometheus’ System for Verticalization and Aiding Motion designed at the Faculty of Mechatronics, Warsaw University of Technology. In the paper, the state of the art is briefly stated, with the relatively low number of orthotic robots allowing realization of pivoting turns highlighted. The intended two-stage pivoting turning movement is analyzed in detail and the operating conditions as well as limitations of the turning module are indicated. The conception of a turning module introduces additional degree of freedom to the existing orthotic robot designs by realizing the rotation about the lengthwise axis in the thigh link. A three-dimensional model and its analysis are shown. The proposed design ensures the necessary movement of the lower limb and the torso of an impaired person during the execution of pivoting turn while remaining compact in order to ease the introduction of the turning system to different orthotic robot designs.

EFFECTS OF OPERATING CONDITIONS ON THE DEPOSITION OF GaAs IN A VERTICAL CVD REACTOR

2008 ◽  
Vol 15 (01n02) ◽  
pp. 111-116 ◽  
Author(s):  
JAE-SANG BAEK ◽  
JIN-HYO BOO ◽  
YOUN-JEA KIM
Keyword(s):  
Fluid Transport ◽  
Numerical Study ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Rotation Velocity ◽  
Operating Conditions ◽  
Deposition Condition ◽  
Three Dimensional Model ◽  
Trimethyl Gallium ◽  
Vertical Cvd Reactor

A numerical study is needed to gain insight into the growth mechanism and improve the reactor design or optimize the deposition condition in chemical vapor deposition (CVD). In this study, we have performed a numerical analysis of the deposition of gallium arsenide ( GaAs ) from trimethyl gallium (TMG) and arsine in a vertical CVD reactor. The effects of operating parameters, such as the rotation velocity of susceptor, inlet velocity, and inlet TMG fraction, are investigated and presented. The three-dimensional model which is used in this investigation includes complete coupling between the thermal-fluid transport and species transport with chemical reaction.

scholarly journals Mechanical Characterization of Timber-to-Timber Composite (TTC) Joints with Self-Tapping Screws in a Standard Push-Out Setup

2020 ◽  
Vol 10 (18) ◽  
pp. 6534
Author(s):  
Chiara Bedon ◽  
Martina Sciomenta ◽  
Massimo Fragiacomo
Keyword(s):  
Mechanical Characterization ◽  
Numerical Models ◽  
Three Dimensional ◽  
Analytical Models ◽  
Small Scale ◽  
Load Bearing ◽  
Timber Constructions ◽  
Technical Interest ◽  
Push Out

Self-tapping screws (STSs) can be efficiently used in various fastening solutions for timber constructions and are notoriously able to offer high stiffness and load-carrying capacity, compared to other timber-to-timber composite (TTC) joint typologies. The geometrical and mechanical characterization of TTC joints, however, is often hard and uncertain, due to a combination of various influencing parameters and mechanical aspects. Among others, the effects of friction phenomena between the system components and their reciprocal interaction under the imposed design loads can remarkably influence the final estimates on structural capacity, in the same way of possible variations in the boundary conditions. The use of Finite Element (FE) numerical models is well-known to represent a robust tool and a valid alternative to costly and time consuming experiments and allows one to further explore the selected load-bearing components at a more refined level. Based on previous research efforts, this paper presents an extended FE investigation based on full three-dimensional (3D) brick models and surface-based cohesive zone modelling (CZM) techniques. The attention is focused on the mechanical characterization of small-scale TTC specimens with inclined STSs having variable configurations, under a standard push-out (PO) setup. Based on experimental data and analytical models of literature, an extended parametric investigation is presented and correlation formulae are proposed for the analysis of maximum resistance and stiffness variations. The attention is then focused on the load-bearing role of the steel screws, as an active component of TTC joints, based on the analysis of sustained resultant force contributions. The sensitivity of PO numerical estimates to few key input parameters of technical interest, including boundaries, friction and basic damage parameters, is thus discussed in the paper.

Influence of Lined Pipe Fabrication on Liner Wrinkling

2019 ◽  
Author(s):  
Ilias Gavriilidis ◽  
Spyros A. Karamanos
Keyword(s):  
Plastic Material ◽  
Numerical Models ◽  
Three Dimensional ◽  
Local Buckling ◽  
Short Wave ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Imperfection Sensitivity ◽  
Elastic Plastic ◽  
Outer Pipe

Abstract An economical method to protect offshore pipelines against corrosive ingredients of hydrocarbons is a double-walled (also called “lined” or “bi-metallic”) pipe, in which a thick-walled low-alloy carbon steel (“outer pipe”) is lined internally with a thin layer (“liner pipe”) from a corrosion resistant alloy material. During the deep-water installation, a lined pipe is subjected to severe plastic loading, which may result in detachment of the liner pipe from the outer pipe forming short-wave wrinkles, followed by local buckling. In the current study, alternative lined pipe manufacturing processes are investigated, including elastic, plastic hydraulic and thermo-hydraulic expansion of the outer pipe, for different initial gaps between the two pipes. The problem is solved numerically, accounting for geometric non-linearities, local buckling phenomena and elastic-plastic material behaviour for both the liner and outer pipe. Two types of numerical models are developed, a quasi-two-dimensional model, examining the mechanical bonding between the pipes, and a three-dimensional model, repeating the manufacturing process and investigating its effect on the mechanical behaviour of a lined pipe subjected to monotonic bending. In addition, the influence of initial geometric imperfections on liner pipe buckling is investigated, showing the imperfection sensitivity of the lined pipe bending behaviour, for each fabrication process.

scholarly journals Study of Flow Induced Noise in Vertical Inline Pump Using Lighthill Analogy

2018 ◽  
Vol 172 ◽  
pp. 01010
Author(s):  
Stephen Christopher ◽  
Shouqi Yuan ◽  
Ji Pei ◽  
G Xing Cheng ◽  
Wang Yiyun
Keyword(s):  
Power Level ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Return Flow ◽  
Sound Power ◽  
Inlet Pipe ◽  
Three Dimensional Model ◽  
Source Power ◽  
Flow Passage ◽  
Flow Induced Noise

The pump user demands for specification along with noise and vibration magnitude for extreme operating conditions apart from best efficiency flow. In order to predict the noise level in pumps, the entire unit of pump has to be considered for acoustic evaluation. Hence, the full three dimensional model of vertical inline pump which consists of inlet pipe, impeller, and volute casing is considered for detailing the flow induced noise using Lighthill analogy. The performance characteristics of pump are well matched between experimental and computational results and the overall sound power level at best efficiency flow using computation was compared with empirical relations and found to be agreed well. The streamline patterns along the inlet pipe shows the effects of recirculation and return flow at partload condition and confirm that the utilization of flow passage is not well streamlined even for nominal flow rate. Further, the detailed study of inlet pipe cross sections reveals the nature of different noise sources such as dipole and quadrupole sound levels along with Proudman source power level. The intensity of turbulence and vortices in flow passage is predicted well using quadrupole source and Proudman sound power levels.

Flexible Pipe Modeling Using Finite Macro-Elements

2014 ◽  
Author(s):  
Rodrigo Provasi ◽  
Clóvis de Arruda Martins
Keyword(s):  
Numerical Models ◽  
Local Level ◽  
Three Dimensional ◽  
Analytical Models ◽  
Great Effort ◽  
Algebraic Equations ◽  
Flexible Pipe ◽  
Commercial Software ◽  
Macro Elements ◽  
Pipe Model

Modeling flexible pipes in the local level is not a trivial task and many authors have employed a great amount of time in such task. The non-triviality arises from the various layers and their interaction, which are pretty tough to correctly model. The possible approaches to solve the problem are divided in to major categories: analytical models and numerical models. The analytical ones rely on a great number of hypotheses and, after a great effort, result in a system of algebraic equations. The numerical ones can be further differentiated in the ones developed using commercial software and the other ones using proprietary models. The authors choose the second way to approach the problem and presented in previous works a group of elements called macro-elements, including a cylindrical element for orthotropic layers, a three dimensional curved beam for helical elements, a rigid connection and a contact element, both dealing with different node displacement natures. These elements take into account the physical and geometrical characteristics of the components. In this paper a pipe model, with a flexible internal core, two tensile armors and an external sheath, will be simulated and its the results will be checked against commercial software and commented.

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