CFD Simulations of Under Water Turbine in Gulf Stream Using RANS Method

2010 ◽  
Author(s):  
Chaouki Ghenai ◽  
Ben Oliver
Keyword(s):  
Gulf Stream ◽  
Numerical Study ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Power Coefficient ◽  
Total Power ◽  
Cfd Simulations ◽  
Local Flow ◽  
Water Turbine ◽  
Volume Method

The principal objective of this numerical study is to investigate the hydrodynamic behavior of horizontal axis underwater turbine in the Gulf Stream. The CFD analysis provides detailed information about the local flow and the performance of the underwater turbine under varying flow conditions. Three dimensional simulations were performed using a 5.6 meter diameter turbine with 3 blades. The finite volume method was used to solve the equations of conservation of mass and momentum and turbulence (k-ε equations). The flow field, turbulence, pressure distribution on the turbine blades and turbine power were obtained for a range of water speed (1–6 m/s) and rotation speed of turbine (1–10 rad/s). The z-velocity profiles behind the turbine were used to calculate the induction factor a, the power coefficient Cp and the total power P from the turbine. The results show a turbine power coefficient of 33% to 37.5% with an induction factors between 0.10 and 0.12.

scholarly journals Numerical analysis on the performance of Dual Rotor wind turbine

2020 ◽  
Vol 8 (03) ◽  
pp. 352-368
Author(s):  
Hazem Ali Abdel Karim ◽  
Ahmed Reda El-Baz ◽  
Nabil Abdel Aziz Mahmoud ◽  
Ashraf Mostafa Hamed
Keyword(s):  
Wind Turbine ◽  
Rotational Speed ◽  
Pitch Angle ◽  
Numerical Study ◽  
Three Dimensional ◽  
Scale Model ◽  
Power Coefficient ◽  
Peak Performance ◽  
Small Scale ◽  
Cfd Simulations

This study investigates the aerodynamic performance of wind turbines aiming to maximize the power extracted from the wind. The study is focusing on the effect of introducing a second rotor to the main rotor of the wind turbine in what is called a dual rotor wind turbine (DRWT).  The numerical study took place on the performance of small-scale model of wind turbine of 0.9 m diameter using S826 airfoil. Both the Co-rotating and Counter rotating configurations were investigated at different tip speed ratios (TSR) and compared with the performance of the single rotor wind turbine (SRWT). Many parameters were studied for dual rotor turbines. These include the spacing between the two rotors, the pitch angle of the rear rotor and the rotational speed of ratio rear to front rotor. Three-dimensional simulations performed and employed using CFD simulations with Multi Reference Frame (MRF) technique. The Co Rotating Wind Turbine (CWT) and Counter Rotating Wind Turbine (CRWT) found to have better performance compared to that of the SRWT with an increase ranging from 12 to 14% in peak power coefficient. Moreover, the effect of changing the pitch angle of the rear rotor on the overall performance found to be of a negligible effect between angles 0⁰ until 2⁰ degrees tilting toward the front rotor. On the other hand, the ratio of rotational speed of the rear rotor to the front rotor found to cause a further increase in the peak performance of the CWT and CRWT ranging from 3 to 5%.

scholarly journals Dynamics of Single Droplet Splashing on Liquid Film by Coupling FVM with VOF

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 841
Author(s):  
Yuzhen Jin ◽  
Huang Zhou ◽  
Linhang Zhu ◽  
Zeqing Li
Keyword(s):  
Liquid Film ◽  
Weber Number ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Single Droplet ◽  
Navier Stokes Equations ◽  
Volume Method ◽  
The Relationship

A three-dimensional numerical study of a single droplet splashing vertically on a liquid film is presented. The numerical method is based on the finite volume method (FVM) of Navier–Stokes equations coupled with the volume of fluid (VOF) method, and the adaptive local mesh refinement technology is adopted. It enables the liquid–gas interface to be tracked more accurately, and to be less computationally expensive. The relationship between the diameter of the free rim, the height of the crown with different numbers of collision Weber, and the thickness of the liquid film is explored. The results indicate that the crown height increases as the Weber number increases, and the diameter of the crown rim is inversely proportional to the collision Weber number. It can also be concluded that the dimensionless height of the crown decreases with the increase in the thickness of the dimensionless liquid film, which has little effect on the diameter of the crown rim during its growth.

Performance study of twisted Darrieus hydrokinetic turbine with novel blade design

2021 ◽  
pp. 1-37
Author(s):  
Mabrouk Mosbahi ◽  
Mouna Derbel ◽  
Mariem Lajnef ◽  
Bouzid Mosbahi ◽  
Zied Driss ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Maximum Power ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Small Scale ◽  
Performance Study ◽  
Hydrokinetic Turbine ◽  
Blade Shape ◽  
Water Turbine ◽  
Water Canals

Abstract Twisted Darrieus water turbine is receiving growing attentiveness for small-scale hydropower generation. Accordingly, the need for raised water energy conversion incentivizes researchers to focalise on the blade shape optimization of twisted Darrieus turbine. In view of this, an experimental analysis has been performed to appraise the efficiency of a spiral Darrieus water rotor in the present work. To better the performance parameters of the studied water rotor with twisted blades, three novel blade shapes, namely U-shaped blade, V-shaped blade and W-shaped blade, have been numerically tested using a computational fluid dynamics three-dimensional numerical model. Maximum power coefficient of Darrieus rotor reaches 0.17 at 0.63 tip-speed ratio using twisted blades. Using V-shaped blades, maximum power coefficient has been risen up to 0.185. The current study could be practically applied to provide more effective employment of twisted Darrieus turbines and to improve the generated power from flowing water such as river streams, tidal currents, or other man made water canals.

Effect of Periodic Imposed Heat Flux on Three-Dimensional Natural Convection in a Partially Heated Cubical Enclosure

2016 ◽  
Vol 831 ◽  
pp. 83-91
Author(s):  
Lahoucine Belarche ◽  
Btissam Abourida
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Study ◽  
Control Volume ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Maximum Temperature ◽  
Cubical Enclosure ◽  
Simplec Algorithm ◽  
Volume Method

The three-dimensional numerical study of natural convection in a cubical enclosure, discretely heated, was carried out in this study. Two heating square sections, similar to the integrated electronic components, are placed on the vertical wall of the enclosure. The imposed heating fluxes vary sinusoidally with time, in phase and in opposition of phase. The temperature of the opposite vertical wall is maintained at a cold uniform temperature and the other walls are adiabatic. The governing equations are solved using Control volume method by SIMPLEC algorithm. The sections dimension ε = D / H and the Rayleigh number Ra were fixed respectively at 0,35 and 106. The average heat transfer and the maximum temperature on the active portions will be examined for a given set of the governing parameters, namely the amplitude of the variable temperatures a and their period τp. The obtained results show significant changes in terms of heat transfer, by proper choice of the heating mode and the governing parameters.

Flow Characteristics in a Three-Dimensional Rectangular Channel With a Pair of Ribs Placed Symmetrically at the Channel Walls

2000 ◽  
Author(s):  
M. Singh ◽  
P. K. Panigrahi ◽  
G. Biswas
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Complex Flow ◽  
Energy Equations

Abstract A numerical study of rib augmented cooling of turbine blades is reported in this paper. The time-dependent velocity field around a pair of symmetrically placed ribs on the walls of a three-dimensional rectangular channel was studied by use of a modified version of Marker-And-Cell algorithm to solve the unsteady incompressible Navier-Stokes and energy equations. The flow structures are presented with the help of instantaneous velocity vector and vorticity fields, FFT and time averaged and rms values of components of velocity. The spanwise averaged Nusselt number is found to increase at the locations of reattachment. The numerical results are compared with available numerical and experimental results. The presence of ribs leads to complex flow fields with regions of flow separation before and after the ribs. Each interruption in the flow field due to the surface mounted rib enables the velocity distribution to be more homogeneous and a new boundary layer starts developing downstream of the rib. The heat transfer is primarily enhanced due to the decrease in the thermal resistance owing to the thinner boundary layers on the interrupted surfaces. Another reason for heat transfer enhancement can be attributed to the mixing induced by large-scale structures present downstream of the separation point.

scholarly journals A Comparative Study on the Performance of a Horizontal Axis Ocean Current Turbine Considering Deflector and Operating Depths

2020 ◽  
Vol 12 (8) ◽  
pp. 3333
Author(s):  
Nauman Riyaz Maldar ◽  
Cheng Yee Ng ◽  
Lee Woen Ean ◽  
Elif Oguz ◽  
Ahmad Fitriadhy ◽  
...  
Keyword(s):  
Fluid Pressure ◽  
Three Dimensional ◽  
Horizontal Axis ◽  
Ocean Current ◽  
Power Coefficient ◽  
Cfd Simulations ◽  
Torque Coefficient ◽  
Computational Fluid Dynamics Cfd ◽  
Turbine Design ◽  
Current Turbine

Several different designs and prototypes of ocean current turbines have been tested over recent years. For every design test, emphasis is given to achieving an optimum power output from the flow. In this study, the performance of a Horizontal Axis Ocean Current Turbine (HAOCT) has been investigated using three-dimensional Computational Fluid Dynamics (CFD) simulations for three cases, namely, (1) a turbine without a deflector, (2) a turbine with a deflector, and (3) a turbine with a deflector operating at a higher fluid depth. The turbine design was modeled in DesignModeler software and simulations were carried out in commercial CFD software Flow-3D. The Torque Coefficient (Cm) and Power Coefficient (Cp) for the turbine have been investigated for a certain range of Tip-Speed Ratios (TSRs) in a flow velocity of 0.7 m/s. Furthermore, comparisons have been made to demonstrate the effect of the deflector on the performance of the turbine and the influence of a higher fluid pressure on the same. The results from the simulations indicate that the higher value of Cp was achieved for Case 2 as compared to the other two cases. The findings from the study indicate that the use of the deflector enhances the performance of the turbine. Furthermore, a higher fluid pressure acting on the turbine has a significant effect on its performance.

scholarly journals Investigation of an Innovative Rotor Modification for a Small-Scale Horizontal Axis Wind Turbine

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2649 ◽  
Author(s):  
Artur Bugała ◽  
Olga Roszyk
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Cfd Simulation ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Horizontal Axis ◽  
Power Coefficient ◽  
Small Scale ◽  
Horizontal Axis Wind Turbine ◽  
Airflow Distribution

This paper presents the results of the computational fluid dynamics (CFD) simulation of the airflow for a 300 W horizontal axis wind turbine, using additional structural elements which modify the original shape of the rotor in the form of multi-shaped bowls which change the airflow distribution. A three-dimensional CAD model of the tested wind turbine was presented, with three variants subjected to simulation: a basic wind turbine without the element that modifies the airflow distribution, a turbine with a plano-convex bowl, and a turbine with a centrally convex bowl, with the hyperbolic disappearance of convexity as the radius of the rotor increases. The momentary value of wind speed, recorded at measuring points located in the plane of wind turbine blades, demonstrated an increase when compared to the base model by 35% for the wind turbine with the plano-convex bowl, for the wind speed of 5 m/s, and 31.3% and 49% for the higher approaching wind speed, for the plano-convex bowl and centrally convex bowl, respectively. The centrally convex bowl seems to be more appropriate for higher approaching wind speeds. An increase in wind turbine efficiency, described by the power coefficient, for solutions with aerodynamic bowls was observed.

Numerical Study of the Winter-Kennedy Method—A Sensitivity Analysis

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Binaya Baidar ◽  
Jonathan Nicolle ◽  
Chirag Trivedi ◽  
Michel J. Cervantes
Keyword(s):  
Boundary Conditions ◽  
Secondary Flow ◽  
Numerical Study ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Local Flow ◽  
Spiral Case ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Changes

The Winter-Kennedy (WK) method is commonly used in relative discharge measurement and to quantify efficiency step-up in hydropower refurbishment projects. The method utilizes the differential pressure between two taps located at a radial section of a spiral case, which is related to the discharge with the help of a coefficient and an exponent. Nearly a century old and widely used, the method has shown some discrepancies when the same coefficient is used after a plant upgrade. The reasons are often attributed to local flow changes. To study the change in flow behavior and its impact on the coefficient, a numerical model of a semi-spiral case (SC) has been developed and the numerical results are compared with experimental results. The simulations of the SC have been performed with different inlet boundary conditions. Comparison between an analytical formulation with the computational fluid dynamics (CFD) results shows that the flow inside an SC is highly three-dimensional (3D). The magnitude of the secondary flow is a function of the inlet boundary conditions. The secondary flow affects the vortex flow distribution and hence the coefficients. For the SC considered in this study, the most stable WK configurations are located toward the bottom from θ=30deg to 45deg after the curve of the SC begins, and on the top between two stay vanes.

Dynamics of high-Deborah-number entry flows: a numerical study

2011 ◽  
Vol 677 ◽  
pp. 272-304 ◽  
Author(s):  
A. M. AFONSO ◽  
P. J. OLIVEIRA ◽  
F. T. PINHO ◽  
M. A. ALVES
Keyword(s):  
Finite Volume Method ◽  
Finite Volume ◽  
Newtonian Fluid ◽  
Numerical Study ◽  
Chaotic Regime ◽  
Deborah Number ◽  
Weissenberg Number ◽  
Local Flow ◽  
Abrupt Contraction ◽  
Volume Method

High-elasticity simulations of flows through a two-dimensional (2D) 4 : 1 abrupt contraction and a 4 : 1 three-dimensional square–square abrupt contraction were performed with a finite-volume method implementing the log-conformation formulation, proposed by Fattal & Kupferman (J. Non-Newtonian Fluid Mech., vol. 123, 2004, p. 281) to alleviate the high-Weissenberg-number problem. For the 2D simulations of Boger fluids, modelled by the Oldroyd-B constitutive equation, local flow unsteadiness appears at a relatively low Deborah number (De) of 2.5. Predictions at higher De were possible only with the log-conformation technique and showed that the periodic unsteadiness grows with De leading to an asymmetric flow with alternate back-shedding of vorticity from pulsating upstream recirculating eddies. This is accompanied by a frequency doubling mechanism deteriorating to a chaotic regime at high De. The log-conformation technique provides solutions of accuracy similar to the thoroughly tested standard finite-volume method under steady flow conditions and the onset of a time-dependent solution occurred approximately at the same Deborah number for both formulations. Nevertheless, for Deborah numbers higher than the critical Deborah number, and for which the standard iterative technique diverges, the log-conformation technique continues to provide stable solutions up to quite (impressively) high Deborah numbers, demonstrating its advantages relative to the standard methodology. For the 3D contraction, calculations were restricted to steady flows of Oldroyd-B and Phan-Thien–Tanner (PTT) fluids and very high De were attained (De ≈ 20 for PTT with ϵ = 0.02 and De ≈ 10000 for PTT with ϵ = 0.25), with prediction of strong vortex enhancement. For the Boger fluid calculations, there was inversion of the secondary flow at high De, as observed experimentally by Sousa et al. (J. Non-Newtonian Fluid Mech., vol. 160, 2009, p. 122).

Calculations of three-dimensional viscous flow in a multiblade centrifugal fan by modelling blade forces

2003 ◽  
Vol 217 (3) ◽  
pp. 287-297 ◽  
Author(s):  
S-J Seo ◽  
K-Y Kim ◽  
S-H Kang
Keyword(s):  
Mathematical Model ◽  
Turbulent Flows ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Centrifugal Fan ◽  
Complex Flows ◽  
Flow Through ◽  
Volume Method ◽  
The Mathematical Model

A numerical study is presented for Reynolds-averaged Navier-Stokes analysis of three-dimensional turbulent flows in a multiblade centrifugal fan. Present work aims at development of a relatively simple analysis method for these complex flows. A mathematical model of impeller forces is obtained from the integral analysis of the flow through the impeller. A finite volume method for discretization of governing equations and a standard k-ɛ model as turbulence closure are employed. For the validation of the mathematical model, the computational results for velocity components, static pressure, and flow angles at the exit of the impeller were compared with experimental data. The comparisons show generally good agreement, especially at higher flow coefficients.

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