## 2 Methodology
### Experimental Details  
The towing tank is a specialized laboratory facility utilized for conducting hydrodynamic tests on various models, including ships, offshore structures, and hydrokinetic turbines. The towing tank at the University of New Orleans is a rectangular basin with specific dimensions: 30.8 m long, 4.6 m wide, and 2.4 m deep. The tank is equipped with a carriage system that runs along rails installed along the length of the tank. This carriage system is driven by a cable and a 10 HP AC motor, capable of a maximum speed of 3.66 m per second. The speed of the carriage can be digitally controlled utilizing an electric-powered horizontal planar motion system (PMM). The main purpose of the carriage system is to support and tow the hydrokinetic turbine model during the testing process. The model is mounted on a structure that can be adjusted in terms of depth, angle, and orientation comparatively with the water stream. This customizability allows for the study of the turbine's performance under different working conditions. This model is associated with a carriage system utilizing cables and pulleys, enabling it to be towed at various speeds and angles to simulate different water stream conditions. To maintain consistent testing conditions, the towing tank is equipped with filtration and  
Figure 2: (**a**) SolidWorks sketch of the insert base, (**b**) SolidWorks sketch of the insert cap, (**c**) SolidWorks sketch of the nacelle, (**d**) and nacelle coated with epoxy. Parts (**a**,**b**) represent separate components of the insert. These components slide into the nacelle. The nacelle itself is a distinct entity from the insert components. treatment systems. Consequently, water circulates within the tank, and any pollutants are eliminated. Moreover, the water temperature and salt concentration are observed and controlled to maintain exact and reliable testing conditions. The hydrokinetic turbine model features an electric motor which can be run as a generator, and various sensors. They are all housed inside the insert. Specifically, a PMDC motor of the type DCX 35 L (Maxon Precision Motors, Inc., Taunton, MA, USA), with a power rating of 80 to 120 Watts, was used as the motor/generator. To control its operation, the PMDC motor was associated with a driver, which allowed exact control of the motor's speed. To adjust the motor speed, a variable DC voltage source was connected to the driver. By varying the input voltage to the motor, its rotational speed could be adjusted as desired for testing purposes. The PMDC motor utilized in the hydrokinetic turbine model has a speed rating of 8130 RPM (Revolutions per Minute). However, to suit the scaled-down size of the turbine model, a planetary gear-head of the sort GPX 37 (Maxon Precision Motors, Inc., Taunton, MA, USA), with a reduction ratio of 16:1 was utilized to reduce the speed output of the motor. The decision to employ a gear-head with a reduction ratio was necessary and essential due to the fact that the hydrokinetic turbine model is restricted to a more limited rotational speed. In the experimental setup for the hydrokinetic turbine model, different sensors and equipment were installed to measure and control various aspects of the system. The detailed specifications can be found in the product datasheets. * TRS605 Rotational Force Sensor (FUTEK Advanced Sensor Technology, Inc., Irvine, CA, USA): This non-contact shaft-to-shaft rotary torque sensor, equipped with an encoder, was placed between the motor and propeller shafts. The reason was to precisely evaluate the driving torque applied to the system and to quantify the rotational speed of the turbine. The accuracy of the TRS605 Rotational Force Sensor was within \(\pm\)0.1%. * ESCON 50/5 servo controller (Maxon Precision Motors, Inc., Taunton, MA, USA): This motor driver, known as an ESCON 50/5 servo controller, was used to maintain a setpoint motor rotational speed and adjust it to maintain a desired speed during testing. The accuracy of the ESCON 50/5 servo controller was within \(\pm\)0.05%.