Vertical Turbine Research Articles

Preventing scour of monopile foundations using a vertical rotation device

Scour around monopile foundations is a major cause of offshore wind turbine failures, necessitating effective scour prevention measures to ensure the reliability of monopiles. This study investigates a new scour prevention strategy utilizing a vertical turbine rotor. This measure can not only effectively reduce scour around monopile foundations in complex flow field environments but also generate clean electricity, adding value. The effectiveness of the device in mitigating scour is evaluated through experiments. Subsequently, the impact of the flow field around the pile foundation and the seabed shear stress are examined using numerical simulations. The influence of the device’s installation position on seabed shear stress is also discussed. The results indicate that the vertical rotating device significantly reduce scour around the pile foundation, thereby enhancing the reliability of monopile foundations.

Numerical investigation of the impact of the diameter and rotational motion of a multi-blade rotor on the hydrokinetic combined turbine performance

The vertical axis combined hydrokinetic turbine (VACHT) presents promising applications in marine environments due to its high self-starting performance and efficiency. However, traditional VACHTs suffer from significant performance losses in the outer rotor when the diameter ratio is large and the startup dead zone issue of the inner Savonius rotor. To address these challenges, this study proposes a VACHT composed of an H-type rotor and a multi-blade (M-type) rotor, categorized into two structures based on counter-rotating and co-rotating operations. Numerical simulations reveal that the diameter ratio (f) has a greater impact on VACHT performance than the tip speed ratio. Counter-rotating allows the VACHTs to accommodate larger diameter ratios (f > 0.6) than co-rotation. The diameter ratio primarily influences the interference between the inner and outer rotors. The M-type rotor enhances the self-starting performance of both VACHTs, providing enhancements exceeding 200 %. Moreover, cluster arrangements of VACHTs benefit from increased power output due to enhanced blockage effects, with co-rotating VACHTs exhibiting higher gains (13.65 %) compared to counter-rotating VACHTs (9.84 %). The lengths of both VACHTs’ wake are similar to H-type turbines, indicating that the compactness of the VACHT cluster remains unaffected.

Semi-Empirical Model Based on the Influence of Turbulence Intensity on the Wake of Vertical Axis Turbines

In the context of energy shortages and the development of new energy sources, tidal current energy has emerged as a promising alternative. It is typically harnessed by deploying arrays of multiple water turbines offshore. Vertical axis water turbines (VAWTs), as key units in these arrays, have wake effects that influence array spacing and energy efficiency. However, existing studies on wake velocity distribution models for VAWTs are limited in number, accuracy, and consideration of influencing factors. A precise theoretical model (Lam’s formula) for wake lateral velocity can better predict wake decay, aiding in the optimization of tidal current energy array designs. Turbulence in the ocean, serving as a medium for energy exchange between high-energy and low-energy water flows, significantly impacts the wake recovery of water turbines. To simplify the problem, this study uses software ANSYS Fluent 2020 R2 for two-dimensional simulations of VAWT wake decay under different turbulence intensities, confirming the critical role of turbulence intensity in wake velocity decay. Based on the obtained data, a new mathematical approach was employed to incorporate turbulence intensity into Lam’s wake formula for VAWTs, improving its predictive accuracy with a minimum error of 1%, and refining some parameter calculations. The results show that this model effectively reflects the impact of turbulence on VAWT wake recovery and can be used to predict wake decay under various turbulence conditions, providing a theoretical basis for VAWT design, optimization, and array layout.

Design and Analysis of a Vertical Axis Ocean Current Turbine Tunnel Using SolidWorks Computational Fluid Dynamics

The development of renewable energy in the marine power generation sector presents a promising approach to producing electrical energy in a sustainable and environmentally friendly manner. Indonesia, with its vast oceanic territory, holds significant potential for harnessing marine energy. However, the relatively slow speed of ocean currents in the region, typically ranging from 0.1 m/s to 1.5 m/s, poses a challenge to the efficiency of marine power generation. To overcome this limitation, this research focuses on the design and analysis of a vertical-axis ocean current turbine tunnel aimed at increasing the speed of ocean currents, thereby enhancing the overall efficiency of energy production. The study combines a thorough literature review with experimental research methods, utilizing SolidWorks Computational Fluid Dynamics (CFD) software to simulate the tunnel's impact on ocean current velocity. The simulations reveal that the tunnel construction significantly boosts current speeds, increasing them from 1.0 m/s to 1.7 m/s, and from 1.5 m/s to 2.6 m/s. This increase in velocity directly translates to higher kinetic energy available for conversion into electrical power by the turbine. Moreover, the study shows that the tunnel construction contributes to a more uniform flow of ocean currents, as evidenced by the Reynolds numbers obtained—100.250 at a current speed of 1.0 m/s and 150.375 at 1.5 m/s. These values, being below 2000, indicate laminar flow conditions within the tunnel, which are beneficial for optimizing turbine performance by reducing turbulence and ensuring a stable energy output. The findings underscore the effectiveness of the tunnel design in improving the efficiency of vertical-axis ocean current turbines, making it a viable solution for enhancing renewable energy production in regions with low ocean current speeds.

Aerodynamic efficiency assessment of a cross-axis wind turbine integrated with an offshore deflector

The present work examines the performance of an offshore cross-axis wind turbine (CAWT) with a flow deflector by integrating numerical and analytical methods. The deflector's geometry redirects flow in all directions, causing it to exit vertically and collide with the wind turbine's horizontal blades. In contrast, the blades of a vertical axis wind turbine (VAWT) harness the power of horizontal wind flow. The total power absorbed by the horizontal and vertical turbine blades represents the power of CAWT. In this study, the speed of the outflow from the deflector was initially determined through numerical simulation. The numerical simulation output was then utilized as an input for analytical Double Multiple Stream Tube (DMST) and Blade Element Momentum (BEM) methods to evaluate the vertical and horizontal turbine blades, respectively. This approach reduces the overall simulation time and establishes an offline coupling between analytical and numerical approaches. The findings of this research have unveiled a promising future for offshore wind energy generation. Through the implementation of a modeled deflector on a Cross-Axis Wind Turbine (CAWT), the power output reached a remarkable 19 KW with a power coefficient of 0.35 at an 8.4 m/s wind speed. The results indicate that the CAWT with the deflector produced a power output 35 % higher and was 45 % more efficient than a single Vertical-Axis Wind Turbine (VAWT). These outcomes illustrate the potential for greater energy production and efficiency in offshore wind farms.

Development of Savonius Rotor Based on Bezier Curve for Vertical Axis Marine Current Turbine at Sunda Strait, Hindia Ocean

Due to its strategic location and ocean currents, the Sunda Strait has the potential to produce energy that might be used as a source of electricity. As a result, this strait area urgently needs a suitable turbine design. This strait's most significant sea current speed is 1 (one) m/s. The Savonius rotor is one of the rotor kinds of turbines that can operate in the slow sea current—modifying the rotor from semi-circular to use the Bezier curve for the shape to optimize the performance. This paper will discuss the design of the Savonius rotor using the Bezier curve, that have improved performance. The rotor with double stacking will also enhance the performance of the rotor. This design is a novelty for vertical marine current turbine applications in ocean renewable energy.

The Effect of Deflector Angle on the Performance of Turbine Combination Darrieus-Savonius

The Savonius and Darrieus are vertical-axis wind turbines. This turbine has resistance on one side of the blade that makes it difficult for the shaft to rotate resulting in reduced efficiency. However, the vertical shaft turbine type provides the advantage of being able to accept wind speeds from any direction without an additional tail. Savonius and Darrieus turbines show different characteristics in terms of their performances. Savonius turbine has a high power coefficient (CP) in the range of low tip speed ratio (TSR), when its TSR increases the CP will fall. In contrast to Darrieus, high CP is achieved if the TSR is also high but the CP achievement will fall at a low TSR. If it is compared to Savonius, Darrieus has higher power efficiency although it is difficult to self-start. In contrast to Savonius, Darrieus has a better self-starting ability but a lower efficiency. This study aims to improve the performance of vertical shaft wind turbines by creating a new design combination of Darrieus and Savonius turbines with deflectors to produce CP achievement on a wide TSR. The combination of the Darrieus-Savonius turbine is to improve efficiency to make self-start easier. The research method uses numerical simulation by employing CFD Ansys software. On the airfoil with a deflector angle of 70 deg, it shows that there is an increase in speed in several parts of the Darrieus blade airfoil. The increase in speed causes the decrease of static pressure in the area. The pressure difference between the sides of the airfoil surface causes a force. The direction of the force causes the turbine shaft to rotate. The deflector acts as a directional headwind, increasing the local flow velocity to counter the resistance on one side of the rotor blades The average torque produced at an angle of 70 deg is 0.5 Nm. Whereas, at an angle of 90 deg, the average torque generated is lower by around 0.15 Nm.

Exploring the impact of flexible membranes on the performance of H- and S-type hydrokinetic turbines: An experimental investigation

Vertical axis hydrokinetic turbines (VAHTs) have the potential to harness deep-sea current energy without the need for a yaw mechanism. However, H-VAHTs have weak self-starting capabilities, and S-VAHTs also face startup dead point issues. To address the self-starting challenges of VAHTs, this study proposes attaching flexible membranes to the blades of VAHTs. The impact of flexible membranes on the performance of both types of VAHTs is evaluated through Particle Image Velocimetry (PIV) water flume experiments. The results demonstrate that attaching flexible membranes to the blade surfaces resolves the self-starting dead point issue for both turbines, with a greater improvement in self-starting performance for H-VAHTs than for S-VAHTs. The study found that for both turbines, attaching flexible membranes with a large opening on the blade’s outer side offers the best self-starting performance and power output. However, the flexible membranes reduced the CP of H-VAHTs, while slightly enhancing the performance of S-VAHTs. PIV tests showed that the flexible membranes form a cup-shaped structure when facing the flow. The pressure difference between the inside and outside of the membranes generates additional static torque, improving the self-starting performance of both turbines. Furthermore, even with one or two membrane blades missing, the self-starting capability of H-VAHTs was still enhanced; flexible membranes with a certain installation angle can also be attached to the endplates of S-VAHTs to address startup dead issues. In summary, attaching flexible membranes to VAHTs improves their self-starting performance and ensures power output, thereby facilitating the application of such turbines in deep-sea areas with low flow velocities.

Mathematical modeling and performance evaluation of Ducted Horizontal-axis Helical Wind Turbines: Insights into aerodynamics and efficiency.

With the escalating demand for energy, there is a growing focus on decentralized, small-scale energy infrastructure. The success of new turbines in this context is notable. However, many of these turbines do not follow many of the basic ideas established to evaluate their performance, leaving no precise technique or mathematical model. This research developed a Ducted Horizontal-axis Helical Wind Turbine (DHAHWT). The DHAHWT is a duct-mounted helical savonius turbine with a venturi and diffuser to improve flow. Unlike a vertical axis helical savonius turbine, DHAHWT revolves roughly parallel to the wind, making it a horizontal turbine. This complicates mathematical and theoretical analysis. This study created a DHAHWT mathematical model. COMSOL simulations utilizing Menter's Shear Stress Transport model (SST) across an incoming velocity range of 1m/s to 4m/s were used to evaluate the turbine's interaction with the wind. MATLAB was used to train an artificial neural network (ANN) utilizing COMSOL data to obtain greater velocity data. The Mean Average Percentage Error (MAPE) and Root Mean Square Error (RMSE) of ANN data were found to be 3%, indicating high accuracy. Further, using advanced statistical methods the Pearson's correlation coefficient was calculated resulting in a better understanding of the relationship of between incoming velocity and velocity at different sections of the wind turbine. This study will shed light on the aerodynamics and working of DHAHWT.

Systematic Review of Computational Fluid Dynamics Modelling and Simulation Techniques Employed in Vertical Axis Hydrokinetic Turbines

At present, Computational Fluid Dynamics (CFD) is being utilized to explore tidal and hydrokinetic turbine systems, advancing comprehension of turbulent flow phenomena and raising the accuracy of performance predictions for these fluid-driven turbines. Consequently, this utilization of CFD contributes to the optimization of efficiency in these devices. Turbines are subject to variations from the best design point due to the influence of fluctuating flow rates, despite the findings of recent research that have identified the ideal design points. In contrast to conventional literature reviews, systematic analysis offers numerous advantages. The methodological strategy applied in this study entailed cross-referencing the findings obtained from Web of Science (WOS) and Scopus databases to establish the comprehensiveness as well as reliability of researcher data. Improving the review process, elevating the prominence of the field of study, and establishing critical priorities to mitigate research bias are all potential strategies for enhancing the quality of these evaluations. This research divides its findings into three core themes: (1) Performance assessment for practical implications, (2) Numerical analysis for theoretical insights, and (3) Design parameter optimization for engineering relevance. These themes collectively provide a well-rounded examination of the research outcomes across practical, theoretical, and engineering dimensions. Finally, the research findings have the potential to act as a significant point of reference for informing the best design considerations pertaining to vertical axis turbines.

Investigation of hydraulic characteristics of Pelton turbine with casing structure using a moving particle simulation method

Abstract This paper reports the initial results of three dimensional simulation of the jet/bucket interactions in the vertical Pelton turbine with different casing structures. The casing is an important part of the Pelton turbine, and a reasonable casing structure can reduce the interaction between the jet and bucket, so as to improve the hydraulic efficiency of the turbine. Previous research has little numerical simulation analysis on the casing. In this paper, a Moving Particle Simulation(MPS) method without grid generation is adopted to compare and analyze the hydraulic characteristics of the runner under the regular hexagonal and circular casing structures. The simulation results show that the hydraulic efficiency of the runner under the hexagonal casing structure is better, and the runner time average torque is improved by 3.09%, which compared with the circular casing. The distribution of free surface flows in the hexagonal casing is analysis, and the obvious interference phenomenon between jets can be observed, which has an important guiding role in the design of the casing structure of Pelton turbine in the future.

Design and experimental analysis of a new vertical ultra-low-head hydro turbine with the variation of outlet flow level on the head drop section of an open canal

Hydropower generation from ultra-low-head water resources is the salient category. The power can be tapped through different non-conventional turbines and is developing these days with different features. This research aims to develop a technology that applies to ultra-low-head resources from conceptualization to laboratory testing. Among several ultra-low-head water resources, it is concentrated on the power generation from the head drop section of the open canal flow through a new hydro turbine. A vertical shaft turbine with an axial flow type of runner having fixed, flat, and constant blade thickness including fixed guide vanes has been designed conventionally for 0.5 m of head and 0.088 m3/s of discharge. Several experiments have been conducted with fixing the level of flow outlet control from 0.0 m to 0.5 m creating the runner from free to submerged conditions is the novelty of this research. The results obtained for all the independent and dependent variables are presented and discussed for a constant flow of 0.088 m3/s and constant speed of 115 rpm conditions. The uncertainty on measurement was found ±1.85 % and the overall maximum efficiency obtained was 53.8 % for flow 10 % above the design flow. The research has concluded the use of outlet flow control is necessary to achieve the maximum efficiency of the turbine at a specific height and the overall efficiency can be advanced further through the optimization of blade profile.

Effect of number of blades on performance and wake recovery for a vertical axis helical hydrokinetic turbine

Hydrokinetic turbine provides a viable option for tapping energy from free-flowing water, making it an attractive contributor to the renewable power landscape. This study investigates the effects of blade number and solidity on the performance and wake recovery of a small-scale vertical axis helical hydrokinetic turbine under different tip speed ratios and inflow velocities. Computational fluid dynamics simulations are employed, followed by experimental validation, to analyze power, self-start, torque pulsations, velocity deficit and flow field characteristics. The highest power coefficient is found to be 0.24 for a 4-bladed rotor with 0.3 solidity at a tip speed ratio of 1.0 and inflow velocity of 1.0 m/s. The performance of the studied rotors decreases as inflow velocity increases due to high turbulence experienced, resulting in flow separation. The self-start characteristics are shown to improve with solidity, while torque pulsations are greatly diminished with the increase in number of blades. The wake analysis results show that the velocity deficit and turbulence intensity increase significantly as the number of blades increases. Moreover, the time-averaged streamwise velocity values are observed to reach almost 95 % at a downstream distance of 19–25 times the rotor diameter for investigated rotors.

Experimental Study on the Effect of Foil Guide Vane on the Performance of a Straight-Blade Vertical Axis Ocean Current Turbine

Indonesia is a country that has enormous energy potential for ocean currents, but the speed of ocean currents is relatively low. The straight-blade vertical axis ocean current turbines can be used to generate electricity. However, one of the disadvantages is lower performance compared to horizontal axis turbines. This study aims to improve the performance of straight-blade vertical axis ocean current turbines using a foil guide vane (FGV). Experimental studies have been conducted in a water tunnel at the Energy Systems Engineering Laboratory, Institut Teknologi Sumatera (ITERA), South Lampung, Indonesia. The investigation is carried out in two stages: the straight-blade without FGV as the original object; the straight-blade with FGV as a variation to improve the turbine performance. The investigation results show that the FGV can enhance the performance of straight-blade vertical axis ocean current turbines such as self-starting, torque coefficient (C_t), and power coefficient (C_p). The FGV has increased self-starting capability at a minimum current speed of 0.078 m/s by 15.3 rpm. The increase in maximum torque coefficient (C_t max) and power coefficient (C_p max) due to the FGV is 32% and 20%, respectively, with a C_t max of 0.829 and 〖a C〗_p max of 0.519. In addition, an investigation was also carried out on flow visualization. It showed that FGV could absorb a lot of injection ink, which means that the turbine with FGV absorbs more kinetic energy than without FGV.

Numerical Analysis of Three Vertical Axis Turbine Designs for Improved Water Energy Efficiency

A hydrokinetic turbine with a vertical axis is specifically designed to harvest the kinetic energy from moving water. In this study, three vertical axis water turbines, namely Gorlov, Darrieus, and Savonius turbines, were compared for their efficiency via numerical modeling for steady-state conditions via the ANSYS 2022 R2 Fluent model. The Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) was implemented with an SST k-ω turbulence model. The dynamic mesh technique, which allows modeling according to changes in angular velocity at each time step, was used to simulate flow around the turbines for six different velocities (from 0.5 to 3 m/s). The efficiency of the turbines was compared and the results were analyzed. The pressure, velocity, and turbulence kinetic energy distributions around the rotor were measured at different rotational angles and results indicated a wider operating range for the Darrieus and Gorlov turbines compared to the Savonius turbine. The highest power coefficient of 0.293 was achieved in the model featuring a Darrieus turbine, corresponding to a TSR value of 1.34, compared to 0.208 for the Gorlov and 0.257 for the Savonius turbine, at TSR values of 1.3 and 1.06, respectively. Numerical modeling results pointed to a significantly higher self-starting capacity for the Savonius turbine compared to the others.

Numerical modeling and CFD simulation of diffuser augmented dual vertical axis hydrokinetic Banki-Michell turbine

Hydrokinetic Banki turbines present an affordable, technically feasible, environmentally friendly technology. Their construction without requiring more expensive structures like diversion weirs, canals, forebay, and penstock, makes their initial investment much lower than commonly used horizontal Banki turbine of the same capacity. The possibility to install in the existing canals for Ultra Low Head applications is the additional motivating factor for this research. The system studied includes two Banki runners without internal shafts mounted vertically side by side surrounded by nozzle and diffuser structures. In the first scenario, Nozzle and then the Nozzle-diffuser augmented structures were separately studied to enhance the output of the runner for ultra-low head application, and the effects of each on the speed, pressure, and power output were analyzed. For the case of commonly used Banki, without nozzle and diffuser augmentation the speed for Ultra Low Head was minimum and determined to be 344 rpm, which is far below the recommended value of 800 rpm for safe operation at a flow rate of 1 m^3/s. In view of this, in the present study the enhanced speed on account of improvement was found to be 850 rpm and 1025 rpm for the design without and with diffuser assemblies respectively. Besides, the performance is seen to be improved by 7.6% with the diffuser as compared with the one without diffuser assembly. Detailed simulation results are presented and discussed: 3D ANSYS-FLUENT optimization result provided optimum number of blades for each runner to be 19 and with the optimum throat width in both cases as 202 mm. On account of the lack of any results reported so far for this innovative geometry, validation of the simulated results was carried out with reported results for the dual horizontal axis Banki turbines with good agreement.

Performance Assessment of an Aeolian Roof for the Exploitation of Wind Power in Urban Areas

In this work, an innovative system for depletion of wind power in urban areas is presented. The energy conversion system is installed in the place of the roof of the civil building, carrying out the same covering functions, but at the same time it conveys the air flow towards a vertical axis centripetal turbine. The studied system makes it possible to avoid some typical drawbacks of the eolic generation, such as the encumbrance of the blades, noise, cut-in and cut-off velocities of the wind, presence of turbulence. Due to these problems, the wind energy usually is not considered as a suitable energy source for the urban areas. In this work, a study has been performed in order to assess the potentialities of the proposed system for fulfilment of energy demands in urban areas. By means of a finite element analysis, the sensitivity with respect to the design parameters will be evaluated

Application of Smoothed Particle Hydrodynamics Method for the Analysis of the Flow Past Vertical Vortex Turbine of a Micro Hydropower

The Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) has been applied to simulate the flow through a Gravitational Vertical Turbine (GVT) configuration and the motion of the turbine of a small hydropower system. The turbine blades are assumed to be rigid bodies moving with one-degree of freedom, which is the rotation about its shaft due the hydrodynamic forces of the flow. The intake flow is an open channel flow which falls into a cylindrical basin which houses the turbine and impinges on the turbine blades. The method of simulation is the Weakly Compressible Smoothed Hydrodynamics (WCSPH) with the turbulence models in the equations of motion and the boundary conditions. The results are compared with a laboratory experiments conducted for the same dimension and the configuration. The flow features agree well and the motion of the turbine with a representative mass and a load agrees reasonably with the laboratory experiments

Design and Prototype of a Micro Hydrokinetic Vertical Turbine

In Latin America only few countries are 100% connected to national electric networks. In Colombia, 52% of the national territory is known as Non Interconnected Zones with a population of 2 million people. To cover these zones basic electricity needs, the use of natural, local and renewable resources such as the hydraulic is proposed, due to the high energetic potential. For this purpose, there are several types of hydraulic turbines, most of them used for large scale power generation (UPME, 2010). This paper aims to design of hydraulic turbomachines for micro-generation to satisfy the electricity demand on isolated villages is deeply research. To accomplish this, a three straight blades Vertical Axis Micro Turbine H-Darrieus type is designed and modelled using CAD computational tools. Hydraulic characterization is run on a CFD ANSYS module and fluid-structure interaction is analyzed. Prototyping is made using 3D-printing process in a digital fabrication lab.

Numerical analysis of inflow turbulence intensity impact on the stress and fatigue life of vertical axis hydrokinetic turbine

The present study aims to analyze the effect of upstream turbulence intensity on the hydrodynamic and structural performance of the straight-blade vertical axis turbine. To achieve this, a one-way fluid structure interaction analysis is conducted within the ANSYS workbench environment. Initially, computational fluid dynamics (CFD) simulation is performed at different values of upstream velocity values. Additionally, the impact of upstream turbulence intensity is also analyzed. The CFD simulation results were validated against published experimental work. Once CFD simulation is performed then computed fluid loads are transferred to the ANSYS mechanical structural module. Finite element modeling is performed to compute the stresses and the fatigue life. The study reveals that increasing the upstream turbulence intensity from 5% to 20% leads to 8.6% improvement in the turbine's power performance. However, turbulence intensity also results in 35.6% increase in Von-Mises stresses produced within the designed turbine. However, even with this increase, the Von-Mises stresses remain below a critical threshold, measuring at 173.34 MPa when the upstream water velocity is 1.4 m/s, and the inflow turbulence intensity is at 20%. This stress level is well within the material's yield strength, ensuring the turbine's structural integrity. Moreover, the simulation results emphasize that turbulence intensity has a significant impact on the turbine's fatigue life. Further, it is predicted that an increase in turbulence intensity from 5% to 20% leads to a significant 40% reduction in the turbine's fatigue life. The stress analysis results reveal that struts, strut–blade joints, and strut–shaft joints are the key stress concentration areas. The results suggested that an increase in upstream turbulence intensity has favorable impact on turbine performance, however, for highly turbulent flows turbine should have higher strength and key areas should be focused on designing turbine for such flow conditions.