Hydrokinetic Applications Research Articles

Optimization of a Gorlov Helical Turbine for Hydrokinetic Application Using the Response Surface Methodology and Experimental Tests

The work presents an analysis of the Gorlov helical turbine (GHT) design using both computational fluid dynamics (CFD) simulations and response surface methodology (RSM). The RSM method was applied to investigate the impact of three geometric factors on the turbine’s power coefficient (CP): the number of blades (N), helix angle (γ), and aspect ratio (AR). Central composite design (CCD) was used for the design of experiments (DOE). For the CFD simulations, a three-dimensional computational domain was established in the Ansys Fluent software, version 2021R1 utilizing the k-ω SST turbulence model and the sliding mesh method to perform unsteady flow simulations. The objective function was to achieve the maximum CP, which was obtained using a high-correlation quadratic mathematical model. Under the optimum conditions, where N, γ, and AR were 5, 78°, and 0.6, respectively, a CP value of 0.3072 was achieved. The optimal turbine geometry was validated through experimental testing, and the CP curve versus tip speed ratio (TSR) was determined and compared with the numerical results, which showed a strong correlation between the two sets of data.

Selection criteria for rotor number and rotational direction in arrays of closely spaced Darrieus turbines

Abstract The efficiency gains observed in a pair of closely spaced Darrieus turbines suggest the deployment of multiple turbines as an appealing solution for wind and, particularly, hydrokinetic applications, where the inflow direction is constant. The present study develops some design guidelines for closely spaced hydrokinetic Darrieus turbines by analyzing the trends of both power augmentation and wake development within arrays of multiple rotors, including not only an even number of rotors, which is the usual case in literature, but also an odd one. The analysis is carried out by means of two-dimensional Computational Fluid Dynamics simulations and includes not only the assessment of instantaneous blade forces but also locally sampled flow fields past each blade that allowed the reconstruction of dynamic polar data, contributing to a more comprehensive understanding of the physical mechanisms at play in such compact setups. The study demonstrates a consistent power augmentation mechanism across different layouts, even in the case of an odd number of rotors. This enhancement originates from flow blockage in the mutual interaction areas, favorably altering the inflow angle and subsequently increasing the angle of attack and lift generation. While this mechanism aligns with previous observations on arrays of counter-rotating pairs, its application to multiple turbines introduces complexities due to potential asymmetries in inflow, leading to an uneven power enhancement across turbines within the array. The identified efficiency improvement pattern suggests that maximizing leeward mutual interactions within an array of multiple Darrieus turbines would enhance the overall efficiency of the setup.

Performance Improvement of a Straight-Bladed Darrieus Hydrokinetic Turbine through Enhanced Winglet Designs

The global climate and energy crisis have underscored the importance of sustainability in energy systems and their efficiency. In the case of vertical axis turbines (VATs) for hydrokinetic applications, the increment in efficiency is a topic of interest. Using winglets as passive flow control devices has the potential to improve the power coefficient of straight-bladed (SB) Darrieus turbines highly due to their impact in the dynamics of the flow close to the tip blade and the general impact in the hydrodynamic performance of each blade. The aim of the present work is to study the influence of the geometric parameters of a symmetric winglet in the performance of an SB-VAT for hydrokinetic applications via numerical simulations based on Computational Fluid Dynamics (CFD). Several simulations were performed in Star CCM+ v2206 varying the cant and sweep angles of the designed winglet. Numerical results show that a cant angle of 45° in combination with a sweep angle of 60° achieved the highest power coefficient with an increment around 20% with respect to the model without winglets. Furthermore, the vortical flow structures that form around straight and winglet blades are examined. This involves assessing the distribution of pressure and skin friction coefficients at different blade azimuthal positions during a turbine revolution. In general, the predicted increment in performance is related to the influence of the winglets in the strength of the tip vortices and in the delay in the flow separation.

Two-stage Taguchi-based optimization on dynamically-vented blade flaps to enhance the rotor performance of a Savonius turbine

Among the vertical-axis turbine groups for small-scale wind and hydrokinetic applications, the Savonius type is considered practical due to its simple construction, easy maintenance, and good self-starting characteristics. Unfortunately, it has a poor efficiency due to the exertion of negative torques during its returning sweeps. Recently, the technique of controlled dynamic venting has been shown to reduce this negative torque on a two-bladed Savonius rotor while preserving its omnidirectional capability. That investigation was extended in this numerical study by refining the controllable flaps of the same rotor to improve its performance using a two-stage optimization procedure. In the first stage, the design parameters of the controllable flaps were optimized using the Taguchi and Analysis of Variance (ANOVA) methods. In this analysis, the flap length was found to be the most significant parameter affecting the rotor performance with a contribution ratio of 79.8%, in contrast to a ratio of only 6.7% by the least effective parameter: the flap opening angle. The first optimization stage produced an improvement of 16.7% on the average power coefficient (CP) of the vented rotor, compared to the unvented one, at the optimal tip-speed ratio (TSR) of 1.0. In the second stage, the flap length was refined further to a shorter flap of 22.5% of the blade length, resulting in an improvement of 21% on the same metric at the same TSR. Crucially, these controllable flaps only used an energy cost of 6.1% of the total energy produced by the rotor, a significant improvement from the 12.2% energy cost obtained in the previous study.

Performance simulation of water turbines by using 6-DoF UDF and sliding mesh methods

In this work, a comparison between the six degrees of freedom (6-DoF) method and the sliding mesh approach in computational fluid dynamics simulations of an Archimedes screw turbine for hydrokinetic applications was performed using ANSYs Fluent software. The numerical curves obtained by representing the power coefficient () values versus the tip speed ratio ( or ) were compared based on the experimental data available in the literature. Therefore, by considering the values as the comparison benchmark parameter between the numerical and experimental data, the error obtained when using the 6-DoF method and the sliding mesh approach was 13% and 40%, respectively. Both methods allowed the simulation of the rotor rotation, although the 6-DoF method was more accurate in the prediction of the turbine performance, higher computational resources were consumed in comparison with the sliding mesh method, which allows to obtain a computational solution in affordable times.

An insight on the physical mechanisms responsible of power augmentation in a pair of counter-rotating Darrieus turbines

In recent years, Darrieus turbines have received increasing attention by both the industrial and the academic sector due to their advantages for both wind and hydrokinetic applications. Experimental and numerical investigations showed that the interaction between closely spaced Darrieus rotors can lead to a significant increase in their efficiency. To date, however, the physics underlying this phenomenon has been only argued or qualitatively discussed, since no robust method to determine the actual angle of attack was available.This study provides a novel insight into the physical mechanisms that lead to performance enhancement in twin Darrieus rotors. A pair of counter-rotating, two-blade Darrieus hydrokinetic turbines are investigated while spinning in both the revolution senses, namely, inward and outward, by means of unsteady Computational Fluid Dynamics. After a preliminary analysis on the effect of rotor spacing, an improved flow sampling method is used to analyze the instantaneous flow kinematics past the blades in combination with computed blade loads, thus allowing the calculation of lift and drag forces. Results show that the optimum center-to-center distance for the turbines under consideration is 2D. Also, it is shown that the optimum operating point of the twin rotors tends to shift toward higher Tip-Speed Ratios (TSRs). Compared to the stand-alone turbine, the efficiency improves by 16.1% and 8.7% for the inward and outward twin rotors setups, respectively. A detailed study of the local flow field shows a complete suppression of the streamtube expansion within the area of mutual interactions between the adjacent rotors. This allows more momentum flux to enter the rotor area compared to that of the isolated rotor. More interestingly, it is observed that the change in the inflow velocity direction leads to an increase in the angle of attack for both the inward and outward setups, causing an increase in the generated lift, which is found as the main reason for the efficiency improvement.

Performance of an Archimedes screw turbine with spiral configuration for hydrokinetic applications

The performance of an Archimedes spiral turbine (AST) for hydrokinetic applications was examined using a three-dimensional unsteady numerical model utilizing the six degrees of freedom (6-DOF) solver that is available in ANSYs Fluent software. From the computational fluid dynamics (CFD) simulations, the power coefficient (Cp) curve was estimated. This curve was compared with the curve of an Archimedes screw hydrokinetic turbine (ASHT) reported in the literature. The ASHT was found to be more efficient than the AST for electricity generation. The highest value of Cp for the AST was 0.337, which is a relatively high value in comparison with that of other types of hydrokinetic turbines. The results calculated from the CFD for the AST were compared with an experimental study reported for wind applications.

Experimental Investigation of the Power Storage System for Savonius Turbines in Wind and Water

The Savonius turbine is practical in generating off-grid electrical power for hydrokinetic applications due to its simple design, particularly for small rivers in rural areas. However, despite many studies on methods to improve turbine performance, the electrical aspect of the turbine system is rarely discussed. Therefore, the present study aims to evaluate the performance of a simple and affordable power storage system using a conventional 2-bladed Savonius turbine. The experiment was conducted in a wind tunnel and a water channel with flow speeds of 6 m/s and 0.33 m/s, respectively, corresponding to a Reynolds number of 62700. A power coefficient of 0.09 was discovered for the wind experiment and 0.11 for the water. The total amount of energy extracted from the water was 60% less than from the wind due to the lower available power. It was observed that the tip speed ratio decreases over the charging period due to the constant current and voltage of the Lithium-Ion batteries. This will allow for a fluctuation in the amount of required current and consequently affect the torque needed to spin the generator. The findings confirmed the functionality of the electrical storage system and contributed to the low manufacturing and maintenance cost of the hydrokinetic turbines.

Experimental Study of a Hybrid Turbine for Hydrokinetic Applications on Small Rivers in Malaysia

Energy consumption has become a primary commodity due to technological revolutions in developing countries, such as the expansion of the hydrokinetic turbine as a renewable energy source to mitigate environmental issues. However, conventional vertical axis turbines in hydrokinetic applications particularly for small rivers with low speeds, have limited capabilities such as great power but poor self-start or vice versa. Therefore, the current study aims to address this issue by investigating a hybrid turbine through quantitative and qualitative wind tunnel experiments to improve the performance and self-start capability by integrating Savonius and Darrieus turbines. The findings discovered that the maximum torque coefficient of the hybrid turbine is 37% higher than that of a single conventional Savonius turbine. The integration of the hybrid turbine has resulted in a higher torque coefficient which has enhanced the self-start performance. The hybrid turbine achieved a maximum power output improvement of 30% at a low Reynolds number of 89500, typically representing the small river flow conditions. The presence of a substantial wake captured by the smoke generator at the rear part of the hybrid turbine signifies large drag resulting in power loss and a subsequent decrement in power output. The hybrid turbine has demonstrated its potential to be implemented in hydrokinetic applications in developing countries such as Malaysia for sustainable energy generation.

Experimental Investigation of the Savonius Turbine for Low-Speed Hydrokinetic Applications in Small Rivers

The current study aims to investigate the power performance of 2-bladed and 3-bladed Savonius turbine rotors in a water channel to simulate a low river flow speed. The results were compared to those obtained in a wind tunnel under the same dynamic flow conditions. The comparison was made to determine the turbine characteristics in terms of their power performance when operating in different fluid mediums. The Reynolds number was set to 90200 in both cases, corresponding to an equivalent water flow speed of 0.59 m/s and a wind speed of 10 m/s, respectively. The low water flow speed tested in the water channel represents a narrower and shallower river, commonly found in rural areas of developing countries. The maximum obtained in the water channel was 0.0070 for the 2-bladed rotor and 0.0053 for the 3-bladed rotor at λ = 0.16, respectively. The difference in maximum obtained in the water channel compared with the wind tunnel was 5.7% for the 2-bladed rotor and 22% for the 3-bladed rotor, respectively. Despite being tested in different fluid mediums, the turbines in this study performed similarly, with the 2-bladed rotor outperforming the 3-bladed rotor. The results show that the turbine’s performance is independent of fluid mediums, as both have demonstrated a similar trend. Therefore, the results for the turbine tested in wind or water medium should be applicable in both conditions and can be used in a practical application.

Experimental investigation on the effects of deflector angles on the power performance of a Savonius turbine for hydrokinetic applications in small rivers

A vertical-axis drag-driven Savonius turbine has various advantages and has demonstrated strong potential in hydrokinetic applications for sustainable rural electrification. However, its applicability is limited by the low coefficient of power inherent in the system. To solve this issue, the present study aims to evaluate the power performance improvement of a conventional Savonius turbine using two deflectors on the advancing and returning blades. Wind tunnel experiments conducted at Reynolds number, Re = 148,000 corresponding to 7.0 m/s (equivalent to 0.4 m/s water flow speed for hydrokinetic applications) revealed that, among the 30 deflector angle configurations tested, the advancing and returning blade deflectors were optimally configured at 30° and 90°, respectively. This combination of deflector angles resulted in the highest maximum coefficient of power at CPmax= 0.21, a 61.53% improvement relative to the case without the deflectors. This optimal configuration deflected the flow to the advancing blade while blocking the flow from impinging on the returning blade, effectively increasing the net positive torque and consequently the power performance. Moreover, it was found that variations in the returning blade deflector angle, δR had more significant effects on the turbine power than variations in the advancing blade deflector angle, δA. Conclusively, careful optimization of the deflector angle configurations was able to increase turbine power performance, suitable for practical implementation in small rivers with low flow rates for optimal power production.

Comparative study of the cavitation resistance of the traditional and high-lift hydrofoils for hydrokinetic application

The cavitation phenomena should be considered during the design of hydrokinetic turbines due to cavitation could cause surface erosion, mechanical vibrations, undesirable noise and efficiency reduction in the energy transformation. Therefore, the aim of this work is to conduct a numerical comparison of the cavitation resistance of 3 hydrofoils (NACA0015, Eppler420 and S822) with the purpose of selecting the best foil for the blade cross-section design. For each hydrofoil, the traditional and the high-lift configurations were evaluated. The hydrodynamic factors, including the lift and the drag (CL and CD, respectively) coefficients were determined by using JavaFoil software for several angles of attack (α). Additionally, for the computational fluid dynamics (CFD) study in ANSYs Fluent software, the SST and the Schnerr and Sauer turbulence and cavitation models were respectively utilized to validate the values of CL and CD, and to calculate the pressure coefficient (CP). The values of CP were compared with the cavitation number (σ) for identifying cavitation on the blade and comparing the cavitation resistance of the hydrofoils studied. The methods used and the numerical results obtained were subsequently analyzed and validated using relevant experimental values available in the literature for the NACA0015 hydrofoil. CFD simulations revealed that the NACA0015 traditional hydrofoil and the high-lift configuration of the Eppler420 hydrofoil have the best resistance to cavitation inception in comparison with the traditional hydrofoils and the high-lift configurations studied, respectively.

Comparison of Sliding and Overset Mesh Techniques in the Simulation of a Vertical Axis Turbine for Hydrokinetic Applications

The application of Computational Fluid Dynamics (CFD) to energy-related problems has increased in the last decades in both renewable and conventional energy conversion processes. In recent years, the application of CFD in the study of hydraulic, marine, tidal, and hydrokinetic turbines has focused on the understanding of the details of the complex turbulent flow and also in improving the prediction of the performance of these devices. There are several complexities involved in the simulation of Vertical Axis Turbine (VAT) for hydrokinetic applications. One of them is the necessity of a dynamic mesh model. Typically, the model used in the simulation of these devices is the sliding mesh technique, but in recent years the fast development of the overset (also known as chimera) mesh technique has caught the attention of the academic community. In the present paper, a comparison between these two techniques is done in order to establish their advantages and disadvantages in the two-dimensional simulation of vertical axis turbines. The comparison was done not only for the prediction of performance parameters of the turbine but also for the capabilities of the models to capture complex flow phenomena in these devices and computational costs.

Comparison of the power performance of a conventional Savonius turbine with various deflector configurations in wind and water

Savonius turbines for wind and hydrokinetic applications both operate on the same principle in terms of power generation. However, the effects of their power performance when augmented with various deflector configurations in wind and water have not been comprehensively investigated, and the comparative analysis in the literature still lacks due to the different fluid mediums. Therefore, the present study aims to evaluate and compare the power performance of a conventional Savonius turbine augmented with various deflector longitudinal positions, heights, and angles using a water channel and a wind tunnel with identical flow dynamics. The same turbine model and deflector configurations were tested at equivalent flow rates with the same Reynolds number of 1.48 × 105, corresponding to a typical flow condition in hydrokinetic applications. The turbine power performance, when operated in the wind tunnel, was found to match relatively well with the corrected results of the turbine power performance operated in the water channel, despite being tested in different fluid mediums. In addition, the trends for maximum coefficients of power for both tests are similar in terms of the variations of the deflector angles and the longitudinal positions, resulting in the same deflector parameters that contributed to the best power performance. The maximum coefficient of power, its corresponding coefficient of torque, and tip speed ratio obtained in the wind tunnel differ from the water channel results by 3.98%, 4.44%, and -1.08%, respectively. As a result, this study validates wind tunnel measurements of the power performance of Savonius turbines for hydrokinetic applications, augmented with flow deflectors. Therefore, results obtained in wind tunnel experiments can be used to evaluate the turbine power performance for hydrokinetic applications provided that the principle of flow similarity between the two mediums, wind and water, is satisfied.

Application of a central composite face-centered design in the optimization of an Archimedean hydrokinetic turbine

Currently, in the literature, there are no general guidelines for the optimal hydraulic design of Archimedean screw turbines (AST) used in hydrokinetic applications. Therefore, this study is aiming at selecting the most significant geometric factors, such as the diameter ratio between the inner (𝐷𝑖 ) and the outer (𝐷𝑜) diameters (i.e., 𝐷𝑖/𝐷𝑜), the axle length (𝐿) and the blade stride (𝑝), influencing the AST performance by using a central composite face-centered (CCF) experimental design combined with the response surface methodology (RSM). The statistical analysis of variance (ANOVA) test identified with a significance level of 0.05 that the most significant variables on the performance of the turbine were 𝑝 and 𝐷𝑖/𝐷𝑜. The AST efficiency was evaluated by means of the power coefficient (𝐶𝑃), which was calculated by means of computational fluid dynamics (CFD) methods coupled with the 6-degrees of freedom (6-DoF) approach. The second-order polynomial model was used to predict the 𝐶𝑃 and the coefficient of determination (𝑅 2 ) was found to be 97.4%.

Experimental investigation on the characterization of self-starting capability of a 3-bladed Savonius hydrokinetic turbine using deflector plates

The use of deflectors as augmentation devices to improve the power performance of a 3-bladed conventional Savonius turbine has been investigated by analyzing the deflectors’ effects on self-starting capability and power performance at various deflector angles. Two deflector plates positioned at the upstream of the turbine were tested inside a closed-circuit wind tunnel at an air flow speed of 7.0 m/s (equivalent to 0.4 m/s water flow speed). The self-starting capability of the turbine was characterized in terms of the coefficient of static torque, CTS at various advancing blade deflector angles and returning blade deflector angles of δA= 15°, 30°, 45°, 60° and 75°and δR= 30°, 60°, 90°, respectively. It was found that the CTS profiles were generally higher than without any deflector. The increment of δR showed that it had a significant effect on the CTS profile due to the reduction of drag force on the returning blade as compared to the variation of δA. The study highlighted that the CTS profiles shifted away from the no-self-start conditions (CTS< 0) with the presence of deflectors. The experimental results also revealed that the coefficient of power, CP significantly improved for the case with the deflectors, particularly at δR=90°. The highest CP of 0.183 was achieved at δA= 75° and δR= 90°, which was also the optimal deflector configuration for the best self-starting characteristics. Thus, deflector augmentation may be a practical solution to improve the power performance and self-starting capability of the Savonius turbine in hydrokinetic applications, particularly at the low speeds of narrow and shallower rivers commonly found in rural areas.

Design optimization of an Archimedes screw turbine for hydrokinetic applications using the response surface methodology

In this study, the performance of an Archimedes screw turbine (AST), in terms of the power coefficient (CP), was evaluated. The design parameters, including the inner and the outer diameter (Di and Do, respectively), the axle length (L), the blade inclination with respect to the longitudinal axis of the screw (α) and the blade stride (p), were selected as the studied factors to be optimized by using the response surface methodology and particularly a central composite design of experiments (CCD) to maximize the CP value. Computational fluid dynamics simulations were conducted to investigate the interaction among the referred parameters on the turbine performance. In the numerical simulation, six degrees of freedom (6-DoF) user defined function (UDF) method was used. Furthermore, the results obtained for the initial and the optimized turbine configurations were compared based on the experimental data available in the literature. The numerical results showed a good agreement with the reported experimental data. The highest CP values obtained under optimal design conditions; i.e., at aDi/Do, L, α and a p equal to 0.1, 360 mm, 73.94∘ and 220 mm, respectively, were 0.5515 (CFD result) and 0.5137 (predicted value derived from the validated reduced second-order regression model).

The effects of a deflector on the self-starting speed and power performance of 2-bladed and 3-bladed Savonius rotors for hydrokinetic application

The present study investigates the effects of a deflector on the self-starting speed and power performance of two-bladed and three-bladed Savonius rotors for hydrokinetic applications under low water flow speed conditions. The rotors were tested inside a closed-circuit wind tunnel both with and without a deflector with air as the flow medium. The air data obtained from the experiment were used to calculate the equivalent water flow speed based on the same Reynolds number. The density and viscosity of both mediums were taken into consideration to ensure that the flows were dynamically similar. It was found that the self-starting speeds of the rotors varied with respect to the initial rotor angle. The 3-bladed rotor had lower self-starting speeds than the 2-bladed rotor due to a smaller blade orientation. With the presence of the deflector positioned upstream of the returning blade, the self-starting speeds of both rotors were reduced for all tested deflector angles. The deflector shielded the returning blade of the rotors from being impinged by an incoming flow, reducing the negative torque that would hinder the rotor's rotational motion. The deflector angle of δ = 90° with respect to the incoming flow direction was found to be the optimal configuration, contributing the largest reduction in the self-starting speeds for all initial rotor angles for both rotors. In terms of rotor power performance, the deflector blocking the incoming freestream flow from impinging on the returning blade was found to significantly improve the coefficient of power of the rotors. The largest improvements of coefficient of power by 84.6% and 227.3% were obtained with the deflector configured δ = 90° for the 2-bladed rotor and the 3-bladed rotor, respectively, and the optimal deflector angle was found to be δ = 90°, regardless of the number of blades. The present study has demonstrated the practicality of using a deflector to improve the self-starting speed capability and power performance of Savonius rotors for hydrokinetic application in rivers with low water flow speeds, particularly the narrow and shallower rivers common in rural areas in developing countries.

Performances of vertical-axis hydrokinetic turbines with chordwise-flexible blades

This paper presents a parametric study of Vertical-Axis Turbines (VAT) equipped with chordwise-flexible blades. The objective of this study is to assess the possibility of increasing the efficiency of VATs by allowing passive foil deformations that take advantage of the periodically changing hydrodynamic conditions inherent to VATs. The study is carried out with numerical simulations based on a partitioned Fluid–Structure Interaction (FSI) code implemented within OpenFOAM. Two-dimensional URANS numerical simulations are carried out at a Reynolds number of 107 based on the turbine diameter, which is representative of hydrokinetic applications. A single-blade rotor equipped with a chordwise-flexible NACA 0015 profile is considered. The flexibility is located in the rear part of the foil, between the attach point and the trailing edge. The tip-speed ratio range extends from 2 to 8 and the solidity is set to 0.286. The characteristics of the blade are specified with a dimensionless flexibility parameter and a so-called pressure-to-inertia ratio. The pressure-to-inertia values investigated are larger than one and are representative of hydrokinetic applications in water. The flexibility is varied from zero (rigid blade) to large values involving large deformations. The FSI effects related to these two parameters are investigated and the mechanisms that allow efficiency improvements are presented. It is shown that flexibility introduces a stall mitigation mechanism that helps in improving the efficiency of low tip-speed ratio configurations. Flexibility also reduces blades’ drag in the downstream portion of the cycle when the turbine operates at high tip-speed ratios. More specifically, relative efficiency improvement of about 12% to 15% are observed with moderate flexibilities at tip-speed ratios of 2 (lower than optimal) and 6 (higher than optimal). However, at the optimal tip-speed ratio, flexibility strictly reduces the efficiency, although this reduction remains small for moderate flexibilities. Overall, results also show that blade flexibility tends to extend the tip-speed ratio range of high-efficiency configurations, which may provide interesting advantages when the turbine operates in changing flow conditions.

Some design guidelines to adapt a Darrieus vertical axis turbine for use in hydrokinetic applications

The use of vertical-axis turbines is raising interest in the field of hydropower production from rivers or water channels, where suitable mass flows are available, without the need of high water jumps or large construction sites. Although many optimization studies on vertical-axis turbines have been carried out for wind applications, lesser examples exist in the technical literature regarding hydrokinetic turbines. In the latter case, the best trade-off between power output and low structural stress is more dependent on the fluid dynamic loadings rather than the inertial loadings, due to the higher fluid density and lower rotation speed. The present work shows the results of an industrial study case application, in which the design of a traditional three-blade Darrieus rotor has been adapted for operating in water flows via hydrokinetic technology. Some specific design rules will be discussed, showing the different concepts adopted for the machine layout in order to achieve the best efficiency and performance. Multiple geometrical parameters of the rotor configuration were involved during the analysis: the number of rotor blades, i.e. two or three blades, the rotor’s shape, i.e. traditional H-shape or unconventional L-shape, and the use of power augmentation systems. The analysis of the numerical results was focused on the following output targets: maximum power coefficient, optimal tip speed ratio (TSR), rotor thrust, blade normal force and the upstream and downstream flow field influence. The outcome of the study shows how the best configuration differs from the common solutions for wind application. Moreover, a high power enhancement can be achieved while guaranteeing a good compromise in terms of structural loads.