GJ
G. Jacobi
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3 records found
1
Hydrokinetic turbines are increasingly seen as a promising way to generate renewable energy from tidal and river currents, offering high energy density without the ecological costs of dams or large-scale hydropower. Placing turbines close to the free surface allows them to access higher flow velocities and thus greater power potential, but it also makes them more vulnerable to wave-current interactions. Horizontal-Axis Hydrokinetic Turbines (HAHTs) have shown strong potential at full scale, but their development and testing at laboratory scale are still constrained by scaling effects, limited structural data, and an incomplete understanding of unsteady wave-induced loads. Moreover, only a handful of studies document the detailed design process of model-scale turbines, and even fewer investigate the structural performance of 3D-printed blades. To help close these gaps, this thesis presents the design, construction, and experimental testing of a 0.74 m diameter model-scale HAHT developed at the TU Delft.
The design process combined actuator disc theory and Blade Element Momentum Theory (BEMT) to define the blade geometry and expected operational loads. A modular hub concept with adjustable pitch and interchangeable blades was developed, allowing rapid prototyping and cost-efficient manufacturing. The blades were produced using 3D printing, and static tests confirmed that they withstood thrust forces up to 441 N without failure. The nacelle was conceptually designed but not constructed; instead, the existing gondola system was employed for testing.
Experiments in the towing tank under steady and wave conditions showed good agreement with BEMT predictions once Reynolds numbers exceeded 1.1 * 105. The turbine achieved a maximum power coefficient of approximately 0.44, comparable to other model-scale studies. Under wave forcing, mean power remained stable, but unsteady loads dominated, with torque oscillations over 100% of the mean. Tip deflections of up to 33 mm were observed during operation, far exceeding static predictions, which underscores the role of deformation in dynamic response.
Overall, the study shows that it is possible to build a reliable and affordable model turbine using 3D printing and modular design, and to validate it experimentally. The results not only demonstrate the feasibility of this approach, but also underline how strongly turbine performance is shaped by Reynolds number effects, wave-current interaction, and fluid-structure dynamics. This makes the turbine a practical platform for future research and development in hydrokinetic energy.
...
Hydrokinetic turbines are increasingly seen as a promising way to generate renewable energy from tidal and river currents, offering high energy density without the ecological costs of dams or large-scale hydropower. Placing turbines close to the free surface allows them to access higher flow velocities and thus greater power potential, but it also makes them more vulnerable to wave-current interactions. Horizontal-Axis Hydrokinetic Turbines (HAHTs) have shown strong potential at full scale, but their development and testing at laboratory scale are still constrained by scaling effects, limited structural data, and an incomplete understanding of unsteady wave-induced loads. Moreover, only a handful of studies document the detailed design process of model-scale turbines, and even fewer investigate the structural performance of 3D-printed blades. To help close these gaps, this thesis presents the design, construction, and experimental testing of a 0.74 m diameter model-scale HAHT developed at the TU Delft.
The design process combined actuator disc theory and Blade Element Momentum Theory (BEMT) to define the blade geometry and expected operational loads. A modular hub concept with adjustable pitch and interchangeable blades was developed, allowing rapid prototyping and cost-efficient manufacturing. The blades were produced using 3D printing, and static tests confirmed that they withstood thrust forces up to 441 N without failure. The nacelle was conceptually designed but not constructed; instead, the existing gondola system was employed for testing.
Experiments in the towing tank under steady and wave conditions showed good agreement with BEMT predictions once Reynolds numbers exceeded 1.1 * 105. The turbine achieved a maximum power coefficient of approximately 0.44, comparable to other model-scale studies. Under wave forcing, mean power remained stable, but unsteady loads dominated, with torque oscillations over 100% of the mean. Tip deflections of up to 33 mm were observed during operation, far exceeding static predictions, which underscores the role of deformation in dynamic response.
Overall, the study shows that it is possible to build a reliable and affordable model turbine using 3D printing and modular design, and to validate it experimentally. The results not only demonstrate the feasibility of this approach, but also underline how strongly turbine performance is shaped by Reynolds number effects, wave-current interaction, and fluid-structure dynamics. This makes the turbine a practical platform for future research and development in hydrokinetic energy.
Master thesis
(2025)
-
B. van Broekhoven, D. Fiscaletti, G. Jacobi, T.J.C. van Terwisga, B. Vera Garcia
Wind assisted ship propulsion is one of the realistic options that are considered as alternative ways to propel a ship, with the goal of reducing a ship's emissions. With WASP, the propeller is still needed, but will be less loaded as wind energy takes over part of the required thrust force. Ships that sail are always under a small drift angle. This does not only affect the forces on the ship, but also the performance of the propeller. Previous research studies are mainly focussing on manoeuvring applications. However, an important difference is that the speed of the ship is close to zero here, whilst the drift angles are very high. The goal of this thesis is to experimentally capture the influence of small drift angles on propeller performance. Also, the influence of the advance ratio is studied, as this will vary, as it is dependent on the wind speed.
For the experiment, a gondola is used. The gondola was connected to the HexaPod to alter the position of the gondola and the propeller. The propeller was positioned downstream of the gondola, in pulling condition. The results of the experiments showed that the gondola upstream of the propeller affects the thrust and torque of the propeller for small drift angles. Therefore, measurements were also performed at pitch angles to avoid this influence.
The results show an increase in both thrust and torque for increasing pitch angle. Due to the high uncertainty, the increase is not significant for the smallest angle considered. For experiments performed at higher Reynolds numbers, these experimental uncertainties decreased, and they showed the same trend. Moreover, it was found that the advance ratio also influences the change in thrust and torque. This shows that a lightly-loaded propeller is more prone to fluctuations in the inflow than a highly-loaded propeller.
Lastly, a numerical analysis was performed to also capture the blade loads and the wake of the propeller. Here, an increase in torque was observed for increasing pitch angle. However, this was not the case for thrust. The results showed that thrust and torque on a single blade start to oscillate, also for small angles. The in-plane loads were observed, as a result of imbalance of side and vertical force. The wake also showed the inclination angle and the imbalance of the thrust generation during a propeller revolution. ...
For the experiment, a gondola is used. The gondola was connected to the HexaPod to alter the position of the gondola and the propeller. The propeller was positioned downstream of the gondola, in pulling condition. The results of the experiments showed that the gondola upstream of the propeller affects the thrust and torque of the propeller for small drift angles. Therefore, measurements were also performed at pitch angles to avoid this influence.
The results show an increase in both thrust and torque for increasing pitch angle. Due to the high uncertainty, the increase is not significant for the smallest angle considered. For experiments performed at higher Reynolds numbers, these experimental uncertainties decreased, and they showed the same trend. Moreover, it was found that the advance ratio also influences the change in thrust and torque. This shows that a lightly-loaded propeller is more prone to fluctuations in the inflow than a highly-loaded propeller.
Lastly, a numerical analysis was performed to also capture the blade loads and the wake of the propeller. Here, an increase in torque was observed for increasing pitch angle. However, this was not the case for thrust. The results showed that thrust and torque on a single blade start to oscillate, also for small angles. The in-plane loads were observed, as a result of imbalance of side and vertical force. The wake also showed the inclination angle and the imbalance of the thrust generation during a propeller revolution. ...
Wind assisted ship propulsion is one of the realistic options that are considered as alternative ways to propel a ship, with the goal of reducing a ship's emissions. With WASP, the propeller is still needed, but will be less loaded as wind energy takes over part of the required thrust force. Ships that sail are always under a small drift angle. This does not only affect the forces on the ship, but also the performance of the propeller. Previous research studies are mainly focussing on manoeuvring applications. However, an important difference is that the speed of the ship is close to zero here, whilst the drift angles are very high. The goal of this thesis is to experimentally capture the influence of small drift angles on propeller performance. Also, the influence of the advance ratio is studied, as this will vary, as it is dependent on the wind speed.
For the experiment, a gondola is used. The gondola was connected to the HexaPod to alter the position of the gondola and the propeller. The propeller was positioned downstream of the gondola, in pulling condition. The results of the experiments showed that the gondola upstream of the propeller affects the thrust and torque of the propeller for small drift angles. Therefore, measurements were also performed at pitch angles to avoid this influence.
The results show an increase in both thrust and torque for increasing pitch angle. Due to the high uncertainty, the increase is not significant for the smallest angle considered. For experiments performed at higher Reynolds numbers, these experimental uncertainties decreased, and they showed the same trend. Moreover, it was found that the advance ratio also influences the change in thrust and torque. This shows that a lightly-loaded propeller is more prone to fluctuations in the inflow than a highly-loaded propeller.
Lastly, a numerical analysis was performed to also capture the blade loads and the wake of the propeller. Here, an increase in torque was observed for increasing pitch angle. However, this was not the case for thrust. The results showed that thrust and torque on a single blade start to oscillate, also for small angles. The in-plane loads were observed, as a result of imbalance of side and vertical force. The wake also showed the inclination angle and the imbalance of the thrust generation during a propeller revolution.
For the experiment, a gondola is used. The gondola was connected to the HexaPod to alter the position of the gondola and the propeller. The propeller was positioned downstream of the gondola, in pulling condition. The results of the experiments showed that the gondola upstream of the propeller affects the thrust and torque of the propeller for small drift angles. Therefore, measurements were also performed at pitch angles to avoid this influence.
The results show an increase in both thrust and torque for increasing pitch angle. Due to the high uncertainty, the increase is not significant for the smallest angle considered. For experiments performed at higher Reynolds numbers, these experimental uncertainties decreased, and they showed the same trend. Moreover, it was found that the advance ratio also influences the change in thrust and torque. This shows that a lightly-loaded propeller is more prone to fluctuations in the inflow than a highly-loaded propeller.
Lastly, a numerical analysis was performed to also capture the blade loads and the wake of the propeller. Here, an increase in torque was observed for increasing pitch angle. However, this was not the case for thrust. The results showed that thrust and torque on a single blade start to oscillate, also for small angles. The in-plane loads were observed, as a result of imbalance of side and vertical force. The wake also showed the inclination angle and the imbalance of the thrust generation during a propeller revolution.
Master thesis
(2025)
-
C. Navas Rodríguez, D. Fiscaletti, G. Jacobi, Manuel Aguiar Ferreira, Luigi Minerva, I. Akkerman
This dissertation investigates the mechanisms of ventilation inception on surface-piercing hydrofoils under quasi-static variations of the angle of attack (AoA). Two hydrofoil geometries, a Semi- Ogive profile with a blunt trailing edge and a streamlined NACA 0010-34, were tested in a towing tank across a range of Froude numbers (Fnh) and aspect ratios (AR). The study introduces a novel experimental methodology, quasi-static testing, which eliminates inertial effects associated with acceleration by maintaining constant Fnh while varying AoA. This approach contrasts with traditional ”static tests” found in the literature. A new flow regime map in the α−Fnh parametric space was developed, tracing distinct ventilation inception boundaries for the two hydrofoils and offering a more detailed representation of transitions between flow regimes. The findings challenge the validity of previous methodologies, which assumed that ventilation inception boundaries were dominated by stall angles and fixed AoA, overlooking the dynamics of ventilation inception. At low Fnh, leading-edge (LE) ventilation appears as the dominant mechanism, slightly enhancing lift by stabilizing flow on the suction surface. As Fnh increases, transitions to Rayleigh-Taylor (RT) instabilities become evident, particularly at moderate Reynolds numbers. At high Fnh (≥ 2.5), RT instabilities prevail, with trailing-edge (TE) effects becoming significant for the Semi-Ogive hydrofoil. In contrast, the streamlined NACA 0010-34 primarily exhibits RT-driven mechanisms. The results demonstrate that this new methodology yields precise and repeatable inception boundaries, representing a significant improvement over historical techniques. Notably, contrary to prior assumptions, the AoA at which ventilation inception occurs exceeds 15◦ and is no longer constant across various Fnh. Additionally, trailing-edge geometry was found to influence ventilation inception, particularly at higher AR, as evidenced by the diverging trends observed between the two hydrofoil profiles. Furthermore, the experimental results align well with semi-empirical models for lift and drag coefficients at Fnh ≥ 1.0, reinforcing the robustness of the findings. These contributions provide more in-depth insights into ventilation inception dynamics and offer valuable guidance for the design of hydrofoils in marine applications.
...
This dissertation investigates the mechanisms of ventilation inception on surface-piercing hydrofoils under quasi-static variations of the angle of attack (AoA). Two hydrofoil geometries, a Semi- Ogive profile with a blunt trailing edge and a streamlined NACA 0010-34, were tested in a towing tank across a range of Froude numbers (Fnh) and aspect ratios (AR). The study introduces a novel experimental methodology, quasi-static testing, which eliminates inertial effects associated with acceleration by maintaining constant Fnh while varying AoA. This approach contrasts with traditional ”static tests” found in the literature. A new flow regime map in the α−Fnh parametric space was developed, tracing distinct ventilation inception boundaries for the two hydrofoils and offering a more detailed representation of transitions between flow regimes. The findings challenge the validity of previous methodologies, which assumed that ventilation inception boundaries were dominated by stall angles and fixed AoA, overlooking the dynamics of ventilation inception. At low Fnh, leading-edge (LE) ventilation appears as the dominant mechanism, slightly enhancing lift by stabilizing flow on the suction surface. As Fnh increases, transitions to Rayleigh-Taylor (RT) instabilities become evident, particularly at moderate Reynolds numbers. At high Fnh (≥ 2.5), RT instabilities prevail, with trailing-edge (TE) effects becoming significant for the Semi-Ogive hydrofoil. In contrast, the streamlined NACA 0010-34 primarily exhibits RT-driven mechanisms. The results demonstrate that this new methodology yields precise and repeatable inception boundaries, representing a significant improvement over historical techniques. Notably, contrary to prior assumptions, the AoA at which ventilation inception occurs exceeds 15◦ and is no longer constant across various Fnh. Additionally, trailing-edge geometry was found to influence ventilation inception, particularly at higher AR, as evidenced by the diverging trends observed between the two hydrofoil profiles. Furthermore, the experimental results align well with semi-empirical models for lift and drag coefficients at Fnh ≥ 1.0, reinforcing the robustness of the findings. These contributions provide more in-depth insights into ventilation inception dynamics and offer valuable guidance for the design of hydrofoils in marine applications.