Tow-tank testing of a 1/20th scale horizontal axis tidal turbine with uncertainty analysis

Abstract

Tidal turbine developers and researchers use small scale testing (i.e. tow tank and flume testing) as a cost effective and low risk way to conduct proof-of-concept studies and evaluate early stage device performance. This paper presents experimental performance data for a three-bladed 1/20 th scale NREL S814 tidal turbine rotor, produced at the 4.6 x 2.5 m and 76 m long Kelvin Hydrodynamics Laboratory tow tank at Strathclyde University. The rotor performance was characterised from very low tip speed ratios to runaway for four carriage speeds. A maximum C P of 0.285 and a maximum C T of 0.452 were recorded at tip speed ratios of 3.53 and 4.45 for a carriage speed of 1m/s. The uncertainty in the instrument calibration and experimental measurements was quantified, allowing accurate representation of the experiments in numerical models. The methodology behind the uncertainty calculations is described in this paper. The uncertainty in the experimental measurements was found to be less than 5% for over 87% of the tests. Reynolds number scaling effects were found to be influential on the rotor performance in the range of velocities tested.

Numerical Validation of Floating Offshore Wind Turbine Scaled Rotors for Surge Motion

“…Its essential to consider the large difference between the extremes for structural stress and related fatigue issues during full scale design of wind turbines rotor and its pitching control for floating applications. The possible source of errors: (1) Experiments-It is estimated to be around 2-4% error from various sources of uncertainties from measurement system, random error and systematic error as the model is very similar to [23] and yet to be quantified in detail (2) CFD-numerical discretization, error due to mesh deformation techniques and time step selection for high frequency and larger amplitude motions (3) LR-AeroDyn and LR-uBEM-Load computations are completely based on the design data of scaled 2D airfoil airfoil lift and drag data, not with scaled 2D airfoil experimental data and 3D correction errors. A detailed investigation is needed to quantify the uncertainties of these methods.…”

Effects of turbulence on tidal turbines: Implications to performance, blade loads, and condition monitoring

“…The calibration resulted in linear correlations with coefficients of determination of 0.9998 or better, as shown in Figure 22(a) for the edgewise blade root bending moment. Table 5 shows the results from an uncertainty analysis performed using the method described in [22], and discussed in [15], [23]. It can be seen that in all cases the total uncertainty is low, and is less than 1.5% of the mean.…”

Design of a Horizontal Axis Tidal Turbine for Less Energetic Current Velocity Profiles

“…Two aerofoil-specific blade geometries are analysed in this study: a NACA 638xx blade (TSR C P max ≈ 5.75) [30] and an NREL S814 blade (TSR C P max ≈ 4) designed for low-Reynolds-number flow [31]. Comparison of the performance of the blades with the subsequent parametric modifications gives an outlook on the challenges and benefits of using a high-TSR blade in a less energetic environment, as opposed to using a usual low-TSR blade.…”

“…Each blade geometry from [30,31] was altered using two parameters: (a) chord distribution and (b) twist distribution. The published chord and twist values for the root and tip sections of [30,31] were used as references for the application of scaling coefficients given by the conic equation:…”