Study of horizontal axis tidal turbine performance and investigation on the optimum fixed pitch angle using CFD

2019 ◽  
Vol 30 (1) ◽  
pp. 206-227 ◽  
Author(s):  
Hoseyn A. Amiri ◽  
Rouzbeh Shafaghat ◽  
Rezvan Alamian ◽  
Seyed Mohamad Taheri ◽  
Mostafa Safdari Shadloo
Keyword(s):  
Pitch Angle ◽  
Flow Characteristics ◽  
Horizontal Axis ◽  
Speed Ratio ◽  
Wall Region ◽  
Computational Domain ◽  
Thrust Coefficient ◽  
Content Type ◽  
Tidal Turbine ◽  
Fixed Pitch

Purpose The purpose of this paper is to design, investigate and optimize a horizontal axis tidal turbine (HATT) using computer-aided numerical simulation and computational fluid dynamics (CFD). This is the first step of research and development (R&D) for implementation in the Persian Gulf condition. To do so, suitable locations are reviewed. Then, the optimization is focused on determining the optimum fixed pitch angle (β) of a three-bladed HATT based on the widespread multiple reference frame (MRF) technique to calculate power and thrust coefficients at different operational rotating speeds. Design/methodology/approach To simplify the problem and reducing the computational costs due to cyclic symmetry only one blade, accordingly one-third of the whole computational domain is considered in the modeling. Due to flow’s nature involving rotating, separation and recirculation, a realizable κ-ε turbulence model with standard wall function is selected to capture flow characteristics influenced by the rotor and near the wall region. Simulations are conducted for two free-stream velocities, then compared with their dependencies through the dimensionless tip speed ratio (TSR) parameter. Findings The validation process of the simulations is carried out by the use of AeroDyn BEM code, which has been evaluated by comparing with two experimental data. As results, the highest coefficient of power is achieved at ß = 19.3° at TSR = 4 with the value around 0.41 and 0.816 for thrust coefficient. Furthermore, to comprehend the rotor’s performance and simulation method, flow characteristics due to the rise in angular velocity is discussed in detail. Moreover, the major phenomenon, cavitation occurrence, is also checked at the critical situation where it is found to be safe. Originality/value By comparing and evaluating the results to other HATTs, it implies that the proposed rotor of this study is feasible and proved by CFD evaluation at this step. However, the current rotor is awaiting a justification through experimental assessment.

Study of gaseous velocity slip in nano-channel using molecular dynamics simulation

2014 ◽  
Vol 24 (6) ◽  
pp. 1338-1347 ◽  
Author(s):  
Fubing Bao ◽  
Zhihong Mao ◽  
Limin Qiu
Keyword(s):  
Molecular Dynamics ◽  
Gas Flow ◽  
Interaction Strength ◽  
Flow Characteristics ◽  
Velocity Slip ◽  
Dynamics Simulation ◽  
Wall Region ◽  
Content Type ◽  
Slip Phenomenon ◽  
Near Wall

Purpose – The purpose of this paper is to investigate the gas flow characteristics in near wall region and the velocity slip phenomenon on the wall in nano-channels based on the molecular dynamics simulation. Design/methodology/approach – An external gravity force was employed to drive the flow. The density and velocity profiles across the channel, and the velocity slip on the wall were studied, considering different gas temperatures and gas-solid interaction strengths. Findings – The simulation results demonstrate that a single layer of gas molecules is adsorbed on wall surface. The density of adsorption layer increases with the decrease of gas temperature and with increase of interaction strength. The near wall region extents several molecular diameters away from the wall. The density profile is flatter at higher temperature and the velocity profile has the traditional parabolic shape. The velocity slip on the wall increases with the increase of temperature and with decrease of interaction strength linearly. The average velocity decreases with the increase of gas-solid interaction strength. Originality/value – This research presents gas flow characteristics in near wall region and the velocity slip phenomenon on the wall in nano-channels. Some interesting results in nano-scale channels are obtained.

scholarly journals Performance and wake characteristics of a tidal turbine under yaw

2018 ◽  
Vol 1 (1 (Aug)) ◽  
pp. 41-50 ◽  
Author(s):  
P. Modali ◽  
N. S. Kolekar ◽  
A. Banerjee
Keyword(s):  
Center Of Mass ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Thrust Coefficient ◽  
Tip Vortices ◽  
Downstream Distance ◽  
Tidal Turbine ◽  
Yaw Angle

In tidal streams and rivers, the flow of water can be at yaw to the turbine rotor plane causing performance degradation and a skewed downstream wake. The current study aims to quantify the performance variation and associated wake behavior caused by a tidal turbine operating in a yawed inflow environment. A three-dimensional computational fluid dynamics study was carried out using multiple reference frame approach using κ-ω SST turbulence model with curvature correction. The computations were validated by comparison with experimental results on a 1:20 scale prototype for a 0° yaw case performed in a laboratory flume. The simulations were performed using a three-bladed, constant chord, untwisted tidal turbine operating at uniform inflow. Yaw effects were observed for angles ranging from 5° to 15°. An increase in yaw over this range caused a power coefficient deficit of 26% and a thrust coefficient deficit of about 8% at a tip speed ratio of 5 that corresponds to the maximum power coefficient for the tested turbine. In addition, wake propagation was studied up to a downstream distance of ten rotor radius, and skewness in the wake, proportional to yaw angle was observed. At higher yaw angles, the flow around the turbine rotor was found to cushion the tip vortices, accelerating the interaction between the tip vortices and the skewed wake, thereby facilitating a faster wake recovery. The center of the wake was tracked using a center of mass technique. The center of wake analysis was used to better quantify the deviation of the wake with increasing yaw angle. It was observed that with an increase in yaw angle, the recovery distance moved closer to the rotor plane. The wake was noticed to meander around the turbine centerline with increasing downstream distance and slightly deviate towards the free surface above the turbine centerline, magnitude of which varied depending on yaw.

Aerodynamic Design and Wind Tunnel Tests of Small-scale Horizontal-axis Wind Turbines for Low Tip Speed Ratio Applications

2022 ◽  
pp. 1-34
Author(s):  
Ojing Siram ◽  
Neha Kesharwani ◽  
Niranjan Sahoo ◽  
Ujjwal K. Saha
Keyword(s):  
Wind Tunnel ◽  
Wind Turbines ◽  
Pitch Angle ◽  
Horizontal Axis ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Small Scale ◽  
Wind Tunnel Tests ◽  
Tip Speed Ratio ◽  
Horizontal Axis Wind Turbines

Abstract In recent times, the application of small-scale horizontal axis wind turbines (SHAWTs) has drawn interest in certain areas where the energy demand is minimal. These turbines, operating mostly at low Reynolds number (Re) and low tip speed ratio (λ) applications, can be used as stand-alone systems. The present study aims at the design, development, and testing of a series of SHAWT models. On the basis of aerodynamic characteristics, four SHAWT models viz., M1, M2, M3, and M4 composed of E216, SG6043, NACA63415, and NACA0012 airfoils, respectively have been developed. Initially, the rotors are designed through blade element momentum theory (BEMT), and their power coefficient have been evaluated. Thence, the developed rotors are tested in a low-speed wind tunnel to find their rotational frequency, power and power coefficient at design and off-design conditions. From BEMT analysis, M1 shows a maximum power coefficient (Cpmax) of 0.37 at λ = 2.5. The subsequent wind tunnel tests on M1, M2, M3, and M4 at 9 m/s show the Cpmax values to be 0.34, 0.30, 0.28, and 0.156, respectively. Thus, from the experiments, the M1 rotor is found to be favourable than the other three rotors, and its Cpmax value is found to be about 92% of BEMT prediction. Further, the effect of pitch angle (θp) on Cp of the model rotors is also examined, where M1 is found to produce a satisfactory performance within ±5° from the design pitch angle (θp, design).

scholarly journals Structural design and analysis of composite blade for horizontal-axis tidal turbine

2018 ◽  
Vol 25 (6) ◽  
pp. 1075-1083
Author(s):  
Quang Duy Nguyen ◽  
Hoon Cheol Park ◽  
Taesam Kang ◽  
Jin Hwan Ko
Keyword(s):  
Structural Design ◽  
Thickness Distribution ◽  
Beam Theory ◽  
High Strength ◽  
Horizontal Axis ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Composite Blade ◽  
Tidal Turbine ◽  
Twisted Beam

AbstractIn this work, we report on the structural design of a 5-m-long composite blade intended for use in a horizontal-axis tidal turbine. The blade geometry is constructed through an optimization process to obtain the maximum power coefficient at the desired tip speed ratio of 4.5 by applying the blade element-momentum theory (BEMT). The blade is primarily designed using a NACA 63-424 hydrofoil. The blade structure is designed by using the BEMT to compute the loading conditions at various inflow velocities. Two parallel spars were chosen to produce the blade structure grid, and the preliminary lay-up structure of the composite blade was determined according to the thickness distribution identified using the twisted beam theory under the assumption that the two spars plus the upper and lower skins mostly contribute to the flap-wise bending stiffness while withstanding an external load. Then, high-strength unidirectional and double-bias fiber glass/epoxy materials were chosen to fabricate the blade. The final blade structure was then analyzed in ANSYS Workbench using the finite element method. The results show that the blade structure can withstand the applied load with failure indices <0.4.

scholarly journals Design and Pitch Angle Optimisation of Horizontal Axis Hydrokinetic Turbine with Constant Tip Speed Ratio

2017 ◽  
Vol 95 ◽  
pp. 06004 ◽  
Author(s):  
Suyash Nigam ◽  
Shubham Bansal ◽  
Tanmay Nema ◽  
Vansh Sharma ◽  
Raj Kumar Singh
Keyword(s):  
Pitch Angle ◽  
Horizontal Axis ◽  
Speed Ratio ◽  
Tip Speed Ratio ◽  
Hydrokinetic Turbine

scholarly journals Designing an efficient tidal turbine blade through bio-mimicry: a systematic review

2018 ◽  
Vol 16 (1) ◽  
pp. 101-124 ◽  
Author(s):  
Siddharth Kulkarni ◽  
Craig Chapman ◽  
Hanifa Shah ◽  
Erika Anneli Parn ◽  
David John Edwards
Keyword(s):  
Turbine Blade ◽  
Renewable Energy Sources ◽  
Clean Energy ◽  
Horizontal Axis ◽  
Maximum Efficiency ◽  
Energy Sources ◽  
Caudal Fin ◽  
Content Type ◽  
Tidal Turbine ◽  
Ocean Environment

Purpose This paper aims to conduct a comprehensive literature review in the tidal energy physics, the ocean environment, hydrodynamics of horizontal axis tidal turbines and bio-mimicry. Design/methodology/approach The paper provides an insight of the tidal turbine blade design and need for renewable energy sources to generate electricity through clean energy sources and less CO2 emission. The ocean environment, along with hydrodynamic design principles of a horizontal axis tidal turbine blade, is described, including theoretical maximum efficiency, blade element momentum theory and non-dimensional forces acting on tidal turbine blades. Findings This review gives an overview of fish locomotion identifying the attributes of the swimming like lift-based thrust propulsion, the locomotion driving factors: dorsal fins, caudal fins in propulsion, which enable the fish to be efficient even at low tidal velocities. Originality/value Finally, after understanding the phenomenon of caudal fin propulsion and its relationship with tidal turbine blade hydrodynamics, this review focuses on the implications of bio-mimicking a curved caudal fin to design an efficient horizontal axis tidal turbine.

scholarly journals A computational design method for bio-mimicked horizontal axis tidal turbines

2018 ◽  
Vol 36 (2) ◽  
pp. 188-209
Author(s):  
Siddharth Suhas Kulkarni ◽  
Craig Chapman ◽  
Hanifa Shah ◽  
David John Edwards
Keyword(s):  
Turbine Blade ◽  
Turbulence Model ◽  
Design Method ◽  
Lift Coefficient ◽  
Computational Design ◽  
Horizontal Axis ◽  
Power Coefficient ◽  
Content Type ◽  
Tidal Turbines ◽  
Tidal Turbine

Purpose The purpose of this paper is to conduct a comparative analysis between a straight blade (SB) and a curved caudal-fin tidal turbine blade (CB) and to examine the aspects relating to geometry, turbulence modelling, non-dimensional forces lift and power coefficients. Design/methodology/approach The comparison utilises results obtained from a default horizontal axis tidal turbine with turbine models available from the literature. A computational design method was then developed and implemented for “horizontal axis tidal turbine blade”. Computational fluid dynamics (CFD) results for the blade design are presented in terms of lift coefficient distribution at mid-height blades, power coefficients and blade surface pressure distributions. Moving the CB back towards the SB ensures that the total blade height stays constant for all geometries. A 3D mesh independency study of a “straight blade horizontal axis tidal turbine blade” modelled using CFD was carried out. The grid convergence study was produced by employing two turbulence models, the standard k-ε model and shear stress transport (SST) in ANSYS CFX. Three parameters were investigated: mesh resolution, turbulence model, and power coefficient in the initial CFD, analysis. Findings It was found that the mesh resolution and the turbulence model affect the power coefficient results. The power coefficients obtained from the standard k-ε model are 15 to 20 per cent lower than the accuracy of the SST model. Further analysis was performed on both the designed blades using ANSYS CFX and SST turbulence model. The variation in pressure distributions yields to the varying lift coefficient distribution across blade spans. The lift coefficient reached its peak between 0.75 and 0.8 of the blade span where the total lift accelerates with increasing pressure before drastically dropping down at 0.9 onwards due to the escalating rotational velocity of the blades. Originality/value The work presents a computational design methodological approach that is entirely original. While this numerical method has proven to be accurate and robust for many traditional tidal turbines, it has now been verified further for CB tidal turbines.

scholarly journals The effects of surge motion on floating horizontal axis tidal turbines

2020 ◽  
Vol 3 (2) ◽  
pp. 45-54
Author(s):  
Mohamad Osman ◽  
Richard H. J. Willden ◽  
Christopher R. Vogel
Keyword(s):  
Reference Frame ◽  
Rotational Frequency ◽  
Horizontal Axis ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Navier Stokes Equation ◽  
Tidal Turbine ◽  
Sst Turbulence Model ◽  
Wave Induced

Wave induced motions due to actual sea state conditions will impact the performance of floating horizontal axis tidal turbine systems. This paper presents the results from numerical simulations of a 3-bladed horizontal axis tidal turbine oscillating in surge motion in a moving reference frame. The optimum tip-speed ratio, λ = 4.4 and k-ω SST turbulence model were used in the present study. The Navier-Stokes equation was modified by adding an inertial term to the equation and the Dirichlet boundary condition was also modified in order to simulate in the moving reference frame. The surge oscillations were parameterised in terms of the ratio of surge amplitude to rotor radius, A*, and the ratio of oscillation frequency to the rotational frequency of the rotor, ω*. A series of tests were conducted to study the effect of each parameter on the hydrodynamic performance of the tidal turbine. The results show that stall can occur on the blade when the velocity relative to the rotor is sufficiently high. In certain cases, negative thrust and power coefficients were observed when the velocity relative to the rotor is low. The fluctuation in blade loading increases together with the amplitude and frequency of oscillation, which will contribute to the fatigue of the rotor.

scholarly journals The effect of using winglets to enhance the performance of swept blades of a horizontal axis wind turbine

2019 ◽  
Vol 11 (9) ◽  
pp. 168781401987831 ◽  
Author(s):  
Mohamed G Khalafallah ◽  
Abdelnaby M Ahmed ◽  
Mohamed K Emam
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Turbine ◽  
Twist Angle ◽  
Three Dimensional ◽  
Horizontal Axis ◽  
Cfd Modeling ◽  
Speed Ratio ◽  
Computational Domain ◽  
Horizontal Axis Wind Turbine

One of the recent methods to improve the performance of horizontal axis wind turbine is to attach a winglet at the tip of the blade of these turbines. Winglets reduce the effect of vortex flow at the blade tip and thus improve the performance of the blade. This article presents a parametric study using the computational fluid dynamics (CFD) modeling to investigate the capability of a winglet to increase the turbine power of swept blades as well as straight blades of a horizontal axis wind turbine. The effects of winglet direction, cant angle, and twist angle are studied for two winglet orientations: upstream and downstream directions. The numerical simulation was performed using ANSYS Fluent computational fluid dynamics code. A three-dimensional computational domain, cylindrical rotationally periodic, was used in the computations. The k-ω shear-stress transport turbulence model was adopted to demonstrate turbulence in the flow. Results show that horizontal axis wind turbine with winglet and sweep could enhance more power compared to their equivalent straight or swept blade. The best improvement in the coefficient of power is 4.39% at design tip speed ratio. This is achieved for downstream swept blades with winglets pointing in the upstream direction and having cant and twist angles of 40° and 10°, respectively.

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