F. Taruffi
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2 records found
1
The influence of flow field non-uniformity on the natural frequencies of hydrofoils
A numerical study using the staggered two-way coupled fluid structure interaction approach to investigate the influence of flow field non-uniformity on the natural frequencies of hydrofoils
To prevent vibration problems of a hydrofoil, it is important to be able to accurately predict its natural frequencies and the potential influence of increasing flow field non-uniformity on these natural frequencies. This master thesis presents research into the influence of this flow field non-uniformity on the natural frequencies, conducted using a case study of a Hull Vane. In this case study, the natural frequencies of a specific Hull Vane design were determined under three different levels of flow field non-uniformity and under a range of ship speeds. To determine the natural frequencies, a staggered two-way coupled fluid-structure interaction approach was used. With this approach, a transient response of the Hull Vane was simulated, after which the natural frequencies were determined from the simulated vibration signals. The case study revealed that the natural frequencies of the Hull Vane can change under increasing (non-)uniform flow speed. The magnitude of this change depends heavily on the case examined, the mode shape associated with the natural frequency, and the structural properties of this mode shape. The results of the study show that in a uniform flow field, changes in both fluid added stiffness and fluid added damping can cause a change in the natural frequencies under increasing ship speed. The study further showed that under a non-uniform flow field, an additional change in fluid added mass may occur, resulting in a change in the natural frequencies.
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To prevent vibration problems of a hydrofoil, it is important to be able to accurately predict its natural frequencies and the potential influence of increasing flow field non-uniformity on these natural frequencies. This master thesis presents research into the influence of this flow field non-uniformity on the natural frequencies, conducted using a case study of a Hull Vane. In this case study, the natural frequencies of a specific Hull Vane design were determined under three different levels of flow field non-uniformity and under a range of ship speeds. To determine the natural frequencies, a staggered two-way coupled fluid-structure interaction approach was used. With this approach, a transient response of the Hull Vane was simulated, after which the natural frequencies were determined from the simulated vibration signals. The case study revealed that the natural frequencies of the Hull Vane can change under increasing (non-)uniform flow speed. The magnitude of this change depends heavily on the case examined, the mode shape associated with the natural frequency, and the structural properties of this mode shape. The results of the study show that in a uniform flow field, changes in both fluid added stiffness and fluid added damping can cause a change in the natural frequencies under increasing ship speed. The study further showed that under a non-uniform flow field, an additional change in fluid added mass may occur, resulting in a change in the natural frequencies.
Aerodynamic characterization of rotor sails
An experimental study on the effects of end plate size
This study aims to characterize the aerodynamics of rotor sails with the focus on the effects of end plate configuration. This is achieved through an experimental campaign on the wake development behind a scaled rotor sail (1:100) with varying end plate sizes in the SLT wind tunnel at TU Delft. Measurements were conducted for Re=15000, spin ratio up to 3, using a rotor of aspect ratio AR=5.2 and end plate diameters of De/D=1.0, 1.6 and 3.0. To omit heavy vibrations, a modal analysis was performed to determine the eigen frequency of the model.
Wake measurements were obtained using both a pressure rake and a 7-hole probe, making this the first experimental study to report results on all three velocity components in the wake of a scaled rotor sail. Three main wake characteristics were analyzed: 1) flow direction of the wake, 2) vortical topology of the wake flow and 3) shedding of the flow.
Results demonstrate that the end plate configuration has a large influence on the development and structure of tip vortices near the rotor’s free ends. A key limitation of this research was the increase in wake blockage for higher spin ratios affecting the pressure measurements. These findings provide new insights into the role of end plate geometry in rotor sail performance and wake dynamics. ...
Wake measurements were obtained using both a pressure rake and a 7-hole probe, making this the first experimental study to report results on all three velocity components in the wake of a scaled rotor sail. Three main wake characteristics were analyzed: 1) flow direction of the wake, 2) vortical topology of the wake flow and 3) shedding of the flow.
Results demonstrate that the end plate configuration has a large influence on the development and structure of tip vortices near the rotor’s free ends. A key limitation of this research was the increase in wake blockage for higher spin ratios affecting the pressure measurements. These findings provide new insights into the role of end plate geometry in rotor sail performance and wake dynamics. ...
This study aims to characterize the aerodynamics of rotor sails with the focus on the effects of end plate configuration. This is achieved through an experimental campaign on the wake development behind a scaled rotor sail (1:100) with varying end plate sizes in the SLT wind tunnel at TU Delft. Measurements were conducted for Re=15000, spin ratio up to 3, using a rotor of aspect ratio AR=5.2 and end plate diameters of De/D=1.0, 1.6 and 3.0. To omit heavy vibrations, a modal analysis was performed to determine the eigen frequency of the model.
Wake measurements were obtained using both a pressure rake and a 7-hole probe, making this the first experimental study to report results on all three velocity components in the wake of a scaled rotor sail. Three main wake characteristics were analyzed: 1) flow direction of the wake, 2) vortical topology of the wake flow and 3) shedding of the flow.
Results demonstrate that the end plate configuration has a large influence on the development and structure of tip vortices near the rotor’s free ends. A key limitation of this research was the increase in wake blockage for higher spin ratios affecting the pressure measurements. These findings provide new insights into the role of end plate geometry in rotor sail performance and wake dynamics.
Wake measurements were obtained using both a pressure rake and a 7-hole probe, making this the first experimental study to report results on all three velocity components in the wake of a scaled rotor sail. Three main wake characteristics were analyzed: 1) flow direction of the wake, 2) vortical topology of the wake flow and 3) shedding of the flow.
Results demonstrate that the end plate configuration has a large influence on the development and structure of tip vortices near the rotor’s free ends. A key limitation of this research was the increase in wake blockage for higher spin ratios affecting the pressure measurements. These findings provide new insights into the role of end plate geometry in rotor sail performance and wake dynamics.