Summary

The calm water towing tank at the Institute of Marine Engineering of the National Research Council (CNR-INM, Rome, Italy), is among a few hydrodynamic testing facilities in Europe and globally where a full-scale device with the characteristics of the CRIMSON turbine can be operated under fully controlled and repeatable conditions. The tank is 460 m long, 13.5 m wide, and 6.5 m deep and is equipped with a towing carriage powered by 4x92 kW electric motors. The carriage speed can reach 15 m/s and is controlled with 0.1% precision. In the towing tank environment, the operating conditions of an instream hydrokinetic device are reproduced by towing the device at imposed speed against water at rest in the tank. 

Turbine model

The helicoidal crossflow turbine tested in this project is the same turbine mounted on ORPC's power systems, such as the RivGen® power system. The turbine is mainly composed of three carbon fiber foils, three glass fiber struts, and a steel shaft. The assembly is 5 m long, 1.8 m in diameter.

Structural Health Monitoring

The structural response of the instrumented foil was characterized by fiber optic with FBG sensors embedded to measure strain at given locations along the foil span. These optical fibers were spliced to a Fiber Optic Rotary Joint (FORJ) which was connected to an interrogator. Once the interrogator interpreted the signal, data was transferred to a panel PC installed on the electrical cabinet.

The foil was equipped with 34 FBG sensors distributed on five custom-made fiber optics. These sensors were placed to capture the maximum strain around each joint and to characterize the strain distribution along the span of the foil. Due to noise on channel 5, two fibers have been swapped during the test period; for consistency of the data, only channels 1, 3, and 4 are shared in the database. Channels and sensors details are defined in Table 1.

Channel FBG Location of the fiber Z coordinate (mm) 1 Sensor 1 Joint locations 800 1 Sensor 2 Joint locations 1000 1 Sensor 3 Joint locations 2400 1 Sensor 4 Joint locations 2600 1 Sensor 5 Joint locations 4000 1 Sensor 6 Joint locations 4200 3 Sensor 1 Cantilever end - Port 4200 3 Sensor 2 Cantilever end - Port 4300 3 Sensor 3 Cantilever end - Port 4400 3 Sensor 4 Cantilever end - Port 4500 3 Sensor 5 Cantilever end - Port 4600 3 Sensor 6 Cantilever end - Port 4700 3 Sensor 7 Cantilever end - Port 4800 4 Sensor 1 Cantilever end – Starboard 800 4 Sensor 2 Cantilever end – Starboard 700 4 Sensor 3 Cantilever end – Starboard 600 4 Sensor 4 Cantilever end – Starboard 500 4 Sensor 5 Cantilever end – Starboard 400 4 Sensor 6 Cantilever end – Starboard 300 4 Sensor 7 Cantilever end – Starboard 200
Table 1

The interrogator used for this test allows recording at a very high frequency (up to 19.67kHz) but only records one channel at a time. Sensing parameters have been established based on the range of the turbine rotation speed and the data storage capacity. Most of the runs have been recorded with the sensing parameters shown in Table 2; some runs have been recorded at 10kHz but with sampling one channel at a time, allowing to have high-resolution data.

Sensing parameters	Value
Sampling frequency (kHz)	10
Sampling time per channel (µs)	2500
Channel switching time (kHz)	1
Number of channels recorded	Varying from 4 to 6
Table 2

 

Test Matrix

The data shared covers a large part of the run schedule performed during the testing period. Other tests, such as reverse runs and end ties, have been performed but are not included in this database.

Test Files

The files shared in this database are separated into three different folders.

• CROP – Covers a single rotation at 2 m/s for several TSR (1.6, 2, 2.4, 2.8, 3.2 and 3.6).
• HR – High-resolution runs for a specific flow condition, 2 m/s at a TSR of 2.4. Files are available for 3 different channels (C1, C3, and C4); these files come from separate runs.
• MAX – Summary table of the maximum and minimum strain recorded during each run shown on the test matrix. It includes flow conditions from 1m/s to 2.25 m/s with a TSR varying from 1.6 to 3.8.

Test files format

The files in the data base are named following the format:

A_125_TSR200_MAX_C1

A: Operating condition, 125: 1.25 Carriage speed (m/s), TSR200: Tip Speed Ratio, MAX: Data Type, C1: Channel recorded