# Evaluation of Model Predictions of the Unsteady Tidal Stream Resource and Turbine Fatigue Loads Relative to Multi-Point Flow Measurements at Raz Blanchard

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## Abstract

**:**

## 1. Introduction

## 2. Site Focus

#### 2.1. Modelling the Resource

**Figure 2.**All model and measurement locations across the site at Raz Blanchard. Contours of bathymetry shown by the blue variegation, light to dark corresponding to shallow to deep. Deployment location areas show sites for the development of tidal arrays by developers; Normandie Hydrolienne and Hydroquest [27], domain size shown in figure is 1.9 km by 2 km, grid spacing of 400 m in the horizontal and 500 m in the vertical directions.

## 3. Model Set-Up

#### 3.1. Turbine Fatigue Load Prediction

#### 3.2. Turbine Load Prediction in Unsteady Onset Flow

#### 3.3. Onset Flow Field

#### 3.4. Onset Flow Characteristics

## 4. Onset Flow Conditions

#### 4.1. Occurrence of Conditions

#### 4.2. Shear Profiles

#### 4.3. Waves

#### 4.4. Turbulence

#### 4.5. Spatial Variation of Turbulence

## 5. Loading on a Device

#### 5.1. Influence of Site Location

#### 5.2. Influence of Modelled Conditions

#### 5.3. Influence of High-Fidelity Turbulent Conditions

#### 5.4. Through-Life Loading across Sites

## 6. Discussion

## 7. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**Area map of Raz Blanchard, showing the Channel Island of Alderney on the left and the French coast on the right. Markers have been included to show previous ADCP deployments, with OpenHydro datasets used in [23,24], and the locations of the THYMOTE and HYD2M project deployments given in [14,24], respectively; the dashed box outlines the area of focus in this study, and the domain of this study is shown in detail in Figure 2.

**Figure 3.**Process used to combine the occurrence and analysis of onset flow conditions with the predicted loading, in order to determine the through-life loading on a turbine component.

**Figure 4.**Percentage of occurrence of the disk-averaged flow speeds for the ebb and flood tides for the two vertical turbine positions, using the measurement data from each ADCP (MU, NH1, NH2) and the corresponding model data from Telemac RANS.

**Figure 5.**Variation of shear profile, ±1 standard deviation, for the range of binned disk-averaged velocities, for the near-bed and near-surface turbine location, at the MU ADCP location.

**Figure 6.**Normalised across-rotor variations of velocity are compared for each disk-averaged velocity value for (

**a**–

**c**), the near-surface turbine and (

**d**–

**f**) for the near-bed turbine, the measurement range is shown by the blue band and the Telemac RANS variation is shown by the red band. For both cases, the range is calculated using 2 standard deviations of the profile values.

**Figure 7.**Comparison of shear profiles at a single ${U}_{DA}$ of 2.2–2.4 m/s, over the rotor plane for (

**a**–

**c**) the near-surface turbine and (

**d**–

**f**) the near-bed turbine, within a range of two standard deviations, for each ADCP location, as can be seen in Figure 2. Measured mean shown by a dashed black line, and measurement range shown by the grey band, Telemac RANS variation shown by the red band.

**Figure 8.**Comparison of $\mathsf{\Delta}U$ which defines the shear across the rotor for a ${U}_{DA}$ of 2.2–2.4 m/s, predicted from the three resource models, for the ebb and flood tides and the two vertical turbine positions, where (∘) is the near surface in the Ebb tide, (□) is the near surface in the flood tide, (∆) is the near bed in the Ebb tide, and (+) is the near bed in the flood tide. (

**a**) Measurements versus Telemac RANS (3 locations); (

**b**) Telemac LES versus Telemac RANS (8 locations); and (

**c**) LBM-LES versus Telemac RANS (9 locations), at the specific extraction locations from Figure 2.

**Figure 9.**Joint probability of the occurrence of the significant wave height (${H}_{S}$) with the disk averaged velocity (${U}_{DA}$) for the measurement data at one ADCP location, MU see Figure 2, and the peak wave time period (${T}_{P}$) with the disk-averaged velocity, with the mean of each condition at the near-surface ${U}_{DA}$ values for the measurement period, as shown in red (solid line) and the mean over an annual interval for the modelled case in red (dashed line).

**Figure 10.**Mean and variation to within one standard deviation of the intensity with disk-averaged velocity for the ebb and flood tides for each ADCP location, given in Figure 2, near the surface (

**a**–

**c**) and near the bed (

**d**–

**f**).

**Figure 11.**Comparison of the mean disk-averaged turbulence intensity for a ${U}_{DA}$ of 2.2–2.4 m/s, predicted from the three resource models, for the ebb and flood tides and the two vertical turbine positions, where (∘) is the near surface in the Ebb tide, (□) is the near surface in the flood tide, (∆) is the near bed in the Ebb tide, and (+) is the near bed in the flood tide. (

**a**) Measurements versus Telemac RANS (3 locations); (

**b**) Telemac LES versus Telemac RANS (8 locations); and (

**c**) LBM-LES versus Telemac RANS (9 locations), at the specific extraction locations from Figure 2.

**Figure 12.**Spatial variation of mean turbulence intensity at the single ${U}_{DA}$ value (2.2–2.4 m/s), scale shown in (

**d**,

**h**) and is consistent across the figure, for (

**a**–

**d**) Telemac RANS and (

**e**–

**h**) Telemac LES, in the flood and ebb tides and for the two vertical turbine positions for the eight locations given in Figure 2 for the Telemac LES.

**Figure 13.**Spatial variation of mean turbulence intensity at the single ${U}_{DA}$ value (2.2–2.4 m/s), scale shown in (

**d**,

**h**) and is consistent across the figure, for (

**a**–

**d**) Telemac RANS and (

**e**–

**h**) LBM-LES, in the flood and ebb tides and for the two vertical turbine positions for the nine locations given in Figure 2 for the LBM-LES.

**Figure 14.**Normalised damage equivalent loads (${\widehat{L}}_{10}$) from the root bending moment for (

**a**) a near-bed turbine and (

**b**) a near-surface turbine using varying turbulence (triangles) and a mean turbulence intensity (circles), for the MU ADCP (black), NH1 (blue) and NH2 (red).

**Figure 15.**Normalised damage equivalent loads for (

**a**) a near-bed turbine and (

**b**) a near-surface turbine, using varying turbulence (triangles) and a mean turbulence intensity (circles), determined from modelled data using the Telemac RANS modelling at the ADCP locations, MU location (black), NH1 location (blue) and NH2 location (red), with previous measurement results in greyscale.

**Figure 16.**Normalised damage equivalent loads for the two vertical turbine positions using varying turbulence (triangles) and a mean turbulence intensity (circles) determined using the modelled shear data using the Telemac RANS modelling at the ADCP locations and combined with the measured turbulence from the ADCPs modelling at the ADCP locations, which is shown by MU location (black), NH1 location (blue) and NH2 location (red), with previous measurement results in greyscale.

**Figure 17.**Variation in the normalised damage equivalent loads from the root bending moments when the disk-averaged velocity is 2.2–2.4 m/s, scale shown in (

**d**,

**h**) and is consistent across the figure, for the eight different site locations, and for the ebb and flood tides at the two turbine positions, using the input flow conditions from the Telemac RANS model (

**a**–

**d**) and the Telemac LES model (

**e**–

**h**), for the eight locations given in Figure 2 for the Telemac LES.

**Figure 18.**The spatial variation in damage equivalent loads, calculated for the single disk-averaged velocity case (2.2–2.4 m/s), scale shown in (

**d**,

**h**) and is consistent across the figure, for the nine different site locations, for the ebb and flood tides at the two turbine positions, for (

**a**–

**d**) the Telemac RANS model and (

**e**–

**h**) the LBM-LES model, for the nine locations given in Figure 2 for the LBM-LES.

**Figure 19.**Spatial variation in normalised damage equivalent loads from the root bending moment, as determined for (

**a**,

**b**) from the Telemac RANS model and (

**c**,

**d**) from the Telemac LES model, scale shown in (

**d**) and is consistent across the figure, for the two turbine positions and the flood and ebb tides, across all operating flow speeds for a 5-year period, for the eight locations given in Figure 2 for the Telemac LES.

**Table 1.**Name, position, and period of deployment for each ADCP deployed in Raz Blanchard as part of the TIGER project.

Device Name | Latitude | Longitude | From | Days |
---|---|---|---|---|

NH1 (Teledyne RDI Workhorse Sentinel 600) | 49.72259 | −1.9974 | 15/01/2022 | 63 |

NH2 (Teledyne RDI Workhorse Sentinel 600) | 49.72225 | −1.9946 | 14/01/2022 | 61 |

MU (Nortek Signature 500) | 49.72238 | −1.9954 | 15/01/2022 | 78 |

**Table 2.**Resource models used within this study, details of the types of resource modelled, and references with additional detail, a more detailed overview is given in [21].

Model Type | Turbulence Closure | Accounts for Waves | Concurrent with ADCPs | References |
---|---|---|---|---|

Telemac RANS | RANS k-$\u03f5$ | No | Yes | [33,34] |

Telemac LES | LES | No | No | [16,24] |

LBM-LES | LES | No | No | [13,17,35] |

Delft3D | No | Yes | Yes | [20,36] |

**Table 3.**Differences in the predicted damage equivalent loads for the 5-year lifespan between the measurement data and various model conditions, at one measurement location (NH1).

Type of Model | Near Surface | Near Bed |
---|---|---|

Telemac RANS (shear and TI) | −30.8% | −32.1% |

Telemac RANS (shear) with measured TI | −2.7% | −2.9% |

Telemac LES (shear and TI) | −8.1% | −16.1% |

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## Share and Cite

**MDPI and ACS Style**

Mullings, H.; Draycott, S.; Thiébot, J.; Guillou, S.; Mercier, P.; Hardwick, J.; Mackay, E.; Thies, P.; Stallard, T.
Evaluation of Model Predictions of the Unsteady Tidal Stream Resource and Turbine Fatigue Loads Relative to Multi-Point Flow Measurements at Raz Blanchard. *Energies* **2023**, *16*, 7057.
https://doi.org/10.3390/en16207057

**AMA Style**

Mullings H, Draycott S, Thiébot J, Guillou S, Mercier P, Hardwick J, Mackay E, Thies P, Stallard T.
Evaluation of Model Predictions of the Unsteady Tidal Stream Resource and Turbine Fatigue Loads Relative to Multi-Point Flow Measurements at Raz Blanchard. *Energies*. 2023; 16(20):7057.
https://doi.org/10.3390/en16207057

**Chicago/Turabian Style**

Mullings, Hannah, Samuel Draycott, Jérôme Thiébot, Sylvain Guillou, Philippe Mercier, Jon Hardwick, Ed Mackay, Philipp Thies, and Tim Stallard.
2023. "Evaluation of Model Predictions of the Unsteady Tidal Stream Resource and Turbine Fatigue Loads Relative to Multi-Point Flow Measurements at Raz Blanchard" *Energies* 16, no. 20: 7057.
https://doi.org/10.3390/en16207057