# Effect of a Support Tower on the Performance and Wake of a Tidal Current Turbine

^{1}

^{2}

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## Abstract

**:**

_{P}). Coefficient of performance for a 3.5 m tower diameter is 0.472 which is followed by 3, 2.5 and 2 m with coefficients of performance of 0.476, 0.478 and 0.476 respectively. Similarly, the coefficient of thrust (C

_{T}) on the rotor for 3.5 m tower diameter is 0.902, for 3 m diameter 0.906 and for 2.5 and 2 m diameters are 0.908 and 0.906 respectively.

## 1. Introduction

## 2. Numerical Method

## 3. Performance Parameter

## 4. Mesh Set Up

^{6}elements.

## 5. Computational Domain with Boundary Condition

^{3}). The diameter of the cylindrical IRD is 24 m where as its thickness is 5.4 m.

## 6. Results and Discussion

_{P}for tower diameter of 2 and 2.5 m while Figure 5b for 3 and 3.5 m. The coefficient of performance in all diameter cases increases as the blades move from vertical to horizontal positions and decrease as the blades tend towards vertical positions. This phenomenon is called the tower shadow effect, which is also experienced by other researchers in [1,6,7]. The tower diameter has little effect on the overall performance of tidal current turbine. However, the effect exists. With the increase of diameter from 2 to 3.5 m, the increment of 0.5 m the coefficient of performance has been increased. The maximum C

_{P}of 0.522 is observed at 2.5 m. This may be due to the combined effect of blockage at this point. The performance of the turbine with the decreasing tower diameter is increasing because the tower shadow effect of the tower is decreasing which affects the performance. Apart from this, the quality of the power extraction is highly affected, as the diameter of the tower increase the fluctuation of the power extraction increase. These fluctuations in the power extraction may have an effect on the fatigue life of the turbine and tower [6,33,34].

_{P}are high for the greater diameter. The fluctuation from the mean C

_{P}for a tower diameter of 3.5 m is 17.1%, followed by 16.1% for a 3 m diameter tower, and 15.6% and 15.7% for a 2.5 and 2 m diameter, respectively. The difference in C

_{P}fluctuation between turbines with towers of 2 and 2.5 m diameter is 0.1%, which is negligible because it is CFD study and CFD results account for small error. Similarly, the difference in fluctuation between 2.5 m diameter tower and 3 m diameter tower is 0.5 and the differences between 3 m diameter and 3.5 m diameter is 1 when the diameter of the tower is increased from 2 to 3.5 m and the fluctuation in the power extraction increases from 15.7% to 17%. This discussion supports the argument that the fluctuation in the power extraction increases by increasing the tower diameter of the turbine.

## 7. Conclusions

_{P}increases as the blades moves away from the tower for all diameters cases. The largest difference between coefficients of performance is for the 3.5 m diameter and 2.5 m diameter, which is 0.006. This difference is 1.25% of 0.478 (0.478 is the coefficient of performance of 3.5 m diameter tower). Similarly, the fluctuation from the mean value of the coefficient of performance for the 3.5 m diameter is 17.1%, followed by the 3 m, 2.5 m and 2 m diameter towers with respective percent fluctuation from mean value (16.1%, 15.6% and 15.7%). The change between fluctuations for a different tower diameter is nearly one.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

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**Figure 7.**Velocity contour of the water throughout the domain at the center line of the turbine (

**a**) TCT with tower 2, 2.5 m diameter (

**b**) TCT with tower 3 and 3.5 m diameter.

Tower Diameter(m) | Mean C_{P} | Fluctuations (%) |
---|---|---|

3.5 | 0.472 | 17.1% |

3 | 0.476 | 16.1% |

2.5 | 0.478 | 15.6% |

2 | 0.476 | 15.7% |

Tower Diameter (m) | Mean C_{T} | Fluctuations (%) |
---|---|---|

3.5 | 0.902 | 8.22% |

3 | 0.906 | 7.82% |

2.5 | 0.908 | 7.58% |

2 | 0.906 | 7.62% |

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**MDPI and ACS Style**

Rehman, Z.U.; Badshah, S.; Rafique, A.F.; Badshah, M.; Jan, S.; Amjad, M.
Effect of a Support Tower on the Performance and Wake of a Tidal Current Turbine. *Energies* **2021**, *14*, 1059.
https://doi.org/10.3390/en14041059

**AMA Style**

Rehman ZU, Badshah S, Rafique AF, Badshah M, Jan S, Amjad M.
Effect of a Support Tower on the Performance and Wake of a Tidal Current Turbine. *Energies*. 2021; 14(4):1059.
https://doi.org/10.3390/en14041059

**Chicago/Turabian Style**

Rehman, Zia Ur, Saeed Badshah, Amer Farhan Rafique, Mujahid Badshah, Sakhi Jan, and Muhammad Amjad.
2021. "Effect of a Support Tower on the Performance and Wake of a Tidal Current Turbine" *Energies* 14, no. 4: 1059.
https://doi.org/10.3390/en14041059