2024 - 2025
alessandro Giusti
alessio Torrielli
Andi Xhelaj
Andrea Orlando
Olivier Flamand
2024 - 2025
Experimental investigation of the VORtex shedding of offshore wind turbine towers during SEA transit
ERIES-VORSEA
Dataset Description
This research addresses an important challenge in the wind energy industry, related to the offshore installation of wind turbines. Specifically, it focuses on the sea transport of wind turbine towers, without rotor-nacelle assembly, mounted vertically on the grillage of the installation vessel (or feeder barge), either as isolated units or in group arrangements. While wind-induced vibrations of towers with a fixed base have been widely investigated in literature, the scenario of sea transport, in which towers experience vessel-induced motion from waves and navigation, remains relatively unexplored. This research is the first step to fill this gap with an experimental investigation of the pressure distribution and vortex shedding on finite-length circular cylinders, spanning from subcritical to transcritical Reynolds number regimes, under both fixed and rolling support conditions, simulating the vessel-like movements. The outcomes are expected to serve as an important benchmark for aerodynamic coefficients and pressure distributions. Furthermore, these tests provide initial insights into how a base rolling motion influences vortex shedding, and whether the typically used models and aerodynamic parameters for the evaluation of the structural response are still valid. Finally, the extensive measurements collected in these experiments yield a comprehensive “data library” which can be used for advanced analyses (e.g., reduced order models, missing data reconstruction, CFD validations) and to guide the development or refinement of theoretical, numerical, or empirical models related to fluid-structure interaction of finite-length circular cylinders.
Specimens
1. Phase 1 : Tests on one cylinder at transcritical Reynolds numbers with fixed and rolling base
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This phase was focused on the investigation of the pressure distribution around the cylinder all along the height, for different Reynolds numbers, rolling frequencies and angles of attack (with some redundancy to double check the symmetry of the test model). All the eight rings were active; however, because of the limited pressure range of the scanners, the flow velocity could not go beyond 40 m/s, corresponding to a Reynolds number of about 9.5×E5, i.e., at the beginning of the supercritical regime. Only one cylinder (see pictures) was tested in this phase, and it was mounted on the tilting apparatus. The accelerations at the top of the cylinder were measured as well.
1. Investigation of the effect of the angle of attack in case of fixed base and for several flow velocities
The experiment aims to investigate vortex shedding by pressure measurements around the cylinder, in case of fixed base. The variables are the flow velocity, limited to maximum 40 m/s because of capabilities of the pressure scanners, and the angle of attack, which can provide indications on the symmetry of the cylinder.
Number of cylinders: 1.
Rolling frequency: fixed base.
Angle of attack: 0.0 deg, 7.2 deg, 43.2 deg, 86.4 deg.
Flow velocity: 22-38 m/s (1 m/s step). Note: for 0.0 deg angle of attack the maximum velocity is 40 m/s.
Pressures: measured on Rings 1 to 8 (25 pressure taps each).
Accelerations: measured at the top of the cylinder.
Instrumentation
7 pressure scanners from Pressure System Incorporated, model 32RG-010300000, with a pressure range of +/-2500 Pa and a sampling rate of 200 Hz. Output checked with a pressure calibrator; sensitivity of each channel used in the recording software to provide outputs in Pa.
A 3D accelerometer from PCB Piezotronics, model 356A03, with the sensitivity of each channel directly used by the recording system to provide measurements in m/s². Output checked with a calibrator from B&K providing a 10 m/s² acceleration at 159 Hz. Sampling rate of 300 Hz.
2. Investigation of the effect of the base movement for several flow velocities
The experiment aims to investigate vortex shedding by pressure measurements around the cylinder in case of rolling base. The variable is the flow velocity, limited to maximum 38 m/s because of capabilities of the pressure scanners. This experiment can provide first indications on the role of the base movement in the development of vortex shedding.
Number of cylinders: 1.
Rolling frequency: 1.74 Hz.
Angle of attack: 0.0 deg.
Flow velocity: 22-38 m/s (1 m/s step).
Pressures: measured on Rings 1 to 8 (25 pressure taps each).
Accelerations: measured at the top of the cylinder.
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Instrumentation
Same as experiment 1.
3. Investigation of the effect of the angle of attack and rolling frequency for one flow velocity
The experiment aims to investigate vortex shedding by pressure measurements around the cylinder in case of rolling base. The variables are the rolling frequency and the angle of attack. The flow velocity is set to 38 m/s. This experiment can provide indications on the role of rolling frequency and angle of attack in the development of vortex shedding.
Number of cylinders: 1.
Rolling frequency: 0.7-1.5 Hz (0.1 Hz step). Note: for -90.0 deg angle of attack the maximum frequency is 1.2 Hz.
Angle of attack: 0.0 deg, -10.0 deg, -43.2 deg, -90.0 deg.
Flow velocity: 38 m/s.
Pressures: measured on Rings 1 to 8 (25 pressure taps each).
Accelerations: measured at the top of the cylinder.
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Instrumentation
Same as experiment 1
2. Phase 2 : Tests on one cylinder from subcritical to supercritical Reynolds numbers with fixed base
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This phase was focused on the investigation of the pressure distribution on two selected rings for a broader Reynolds number range, to explore whether all the regimes, especially the supercritical, could be achieved. Scanners with a higher-pressure range were used, and the cylinder (see pictures) was directly connected to the floor of the wind tunnel without tilting apparatus. Accelerations were not measured in this phase.
1. Investigation from subcritical to supercritical Reynolds numbers of one cylinder with fixed base
The experiment aims to investigate the pressures at two significant heights (rings) exploring Reynolds number regimes from subcritical to supercritical. The variable is the flow velocity.
Number of cylinders: 1.
Rolling frequency: fixed base. Note: the cylinder was directly connected to the wind tunnel floor without the tilting apparatus.
Angle of attack: 0.0 deg.
Flow velocity: 5-70 m/s (about 5 m/s step).
Pressures: measured on Rings 6 and 7 (25 pressure taps each).
Accelerations: not measured.
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Instrumentation
(2 scanners used) Pressure System Incorporated, model ESP-32HD, with a pressure range of +/-7000 Pa and a sampling rate of 200 Hz. Output checked with a pressure calibrator; sensitivity of each channel used in the recording software to provide outputs in Pa.
3. Phase 3 : Tests on cylinders (single and tandem) from subcritical to supercritical Reynolds numbers with fixed and rolling base
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This phase was focused on the investigation of the pressure distribution around the cylinder from subcritical to supercritical Reynolds number regime, including the effect of the rolling motion. The measurements where restricted to three significant rings of pressure taps, selected based on the preliminary results of Phase 2. To measure those three rings with the available high range pressure scanners, four pressure taps per ring were not connected to the scanners. The criteria for the selection of the pressure taps to be suppressed were the preservation of the PSD of the lift force and the preservation of the mean pressure distribution, based on the measurements of Phase 2. The setups with only one cylinder and a tandem (see pictures), consisting of a dummy cylinder windward and the instrumented cylinder leeward, were tested in this phase, both mounted on the tilting apparatus. In the case of tandem, also an additional angle of attack close to zero degrees was tested, being a configuration that most likely produces higher vortex shedding loads. The accelerations at the top of the cylinder and the rolling base were measured.
1. Investigation from subcritical to supercritical Reynolds numbers of one cylinder with fixed and rolling base
The experiment aims to extend Phase 2 and investigate the pressures at three significant heights (rings) exploring Reynolds number regimes from subcritical to supercritical. The variables are the rolling frequency and the flow velocity. This experiment can provide indications on the role of rolling frequency in the development of vortex shedding for a wide range of Reynolds numbers.
Number of cylinders: 1.
Rolling frequency: fixed base, 1.04 Hz, 1.40 Hz.
Angle of attack: 0.0 deg.
Flow velocity: 10-70 m/s (2 m/s step). Note: for 1.40 Hz rolling frequency the minimum velocity is 40 m/s.
Pressures: measured on Rings 2, 4 and 6 (21 pressure taps each).
Accelerations: measured at the top of the cylinder and rolling base.
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Instrumentation
Pressure scanners (2 scanners used) : Pressure System Incorporated, model ESP-32HD, with a pressure range of +/-7000 Pa and a sampling rate of 200 Hz. Output checked with a pressure calibrator; sensitivity of each channel used in the recording software to provide outputs in Pa.
Accelerometer : PCB Piezotronics, model 356A03, with the sensitivity of each channel directly used by the recording system to provide measurements in m/s². Output checked with a calibrator from B&K providing a 10 m/s² acceleration at 159 Hz. Sampling rate of 200 Hz.
2. Investigation from subcritical to supercritical Reynolds numbers of two cylinders in tandem with fixed base
The experiment aims to investigate the pressures at three significant heights (rings) of two cylinders in tandem, exploring Reynolds number regimes from subcritical to supercritical. The variables are the angle of attack and the flow velocity, whereas the base is fixed.
Number of cylinders: 2.
Rolling frequency: fixed base.
Angle of attack: 0.0 deg, 7.2 deg.
Flow velocity: 40-70 m/s (2 m/s step) for 0.0 deg angle of attack; 40-68 m/s (4 m/s step) for 7.2 deg angle of attack.
Pressures: measured on Rings 2, 4 and 6 (21 pressure taps each).
Accelerations: measured at the top of the cylinder and rolling base.
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Instrumentation
Pressure scanners (2 scanners used) : Pressure System Incorporated, model ESP-32HD, with a pressure range of +/-7000 Pa and a sampling rate of 200 Hz. Output checked with a pressure calibrator; sensitivity of each channel used in the recording software to provide outputs in Pa.
Accelerometer : PCB Piezotronics, model 356A03, with the sensitivity of each channel directly used by the recording system to provide measurements in m/s². Output checked with a calibrator from B&K providing a 10 m/s² acceleration at 159 Hz. Sampling rate of 200 Hz.
3. Investigation from subcritical to supercritical Reynolds numbers in case of two cylinders in tandem with rolling base
The experiment aims to investigate the pressures at three significant heights (rings) in case of two cylinders in tandem, exploring Reynolds number regimes from subcritical to supercritical. The variables are the angle of attack and the flow velocity, whereas the base rolls at only one frequency.
Number of cylinders: 2.
Rolling frequency: 0.80 Hz.
Angle of attack: 0.0 deg, 7.2 deg.
Flow velocity: 40-68 m/s (4 m/s step).
Pressures: measured on Rings 2, 4 and 6 (21 pressure taps each).
Accelerations: measured at the top of the cylinder and rolling base.
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Instrumentation
Pressure scanners (2 scanners used) : Pressure System Incorporated, model ESP-32HD, with a pressure range of +/-7000 Pa and a sampling rate of 200 Hz. Output checked with a pressure calibrator; sensitivity of each channel used in the recording software to provide outputs in Pa.
Accelerometer : PCB Piezotronics, model 356A03, with the sensitivity of each channel directly used by the recording system to provide measurements in m/s². Output checked with a calibrator from B&K providing a 10 m/s² acceleration at 159 Hz. Sampling rate of 200 Hz.
4. Phase 4 : Aeroelastic tests on one cylinder
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This phase is an exploratory test focused on the reproduction of vortex-induced vibration (VIV) on the setup with one cylinder to investigate the development of the lock-in range at relatively high Reynolds numbers. The aeroelastic model used in this part is an aluminum cylinder without pressure taps. The stiffness is concentrated at the base connection (pivot model), which was properly machined to achieve the wanted first natural frequency. The cylinder was tested both mounted on the tilting apparatus and with the base directly connected to the floor. Only the latter was successful, and some VIV events were identified. The accelerations at the top of the cylinder were measured.
1. Investigation of modal properties in conditions of resonance with vortex shedding in case of fixed base.
The experiment aims to identify the modal parameters (especially the modal damping) from structural response measurements obtained during VIV events. The variables are the flow velocity, varying around the critical wind speed, and the base connection (2 pivot models were tested), which affects the natural frequency of the cylinder and, in turn, the critical wind speed. The cylinder was tested with the base directly connected to the floor of the wind tunnel. This experiment can provide indications about the effect of vortex shedding resonance on the modal damping of finite-length circular cylinders.
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Instrumentation
Number of cylinders: 1.
Rolling frequency: fixed base.
Angle of attack: 0.0 deg.
Natural frequency: 8.89 Hz and 6.48 Hz.
Flow velocity: 12-20 m/s (0.2 m/s increments) and 9-19 m/s (0.2 m/s increments).
Pressures: no pressure measurements.
Accelerations: 1 triaxial accelerometer at top of the cylinder.
Project Metadata
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Creative Commons Attribution 4.0 International.
CC BY 4.0
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