# Experimental and Numerical Investigation of Wake Interactions of Marine Hydrokinetic Turbines

^{1}

^{2}

^{3}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Experimental Setup

#### 2.2. DES-BEM Model

## 3. Results and Discussion

#### 3.1. Flow Field Downstream of the Turbines

#### 3.2. Turbine Performance

#### 3.3. Turbine–Bathymetry Interactions

## 4. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## Abbreviations

MHK | marine hydrokinetic |

BEM | blade element momentum |

ADM | actuator disk model |

ALM | actuator lines model |

DES | detached-eddy simulation |

HATT | horizontal-axis tidal turbines |

URANS | unsteady Reynolds-averaged Navier–Stokes |

DAQ | data acquisition |

TSR | tip-speed ratio |

ST | single turbine |

TT | two turbines |

## References

- Vazquez, A.; Iglesias, G. Device interactions in reducing the cost of tidal stream energy. Energy Convers. Manag.
**2015**, 97, 428–438. [Google Scholar] [CrossRef] - Zhou, Z.; Benbouzid, M.; Charpentier, J.F.; Scuiller, F.; Tang, T. Developments in large marine current turbine technologies—A review. Renew. Sustain. Energy Rev.
**2017**, 71, 852–858. [Google Scholar] [CrossRef] - Paboeuf, S.; Yen Kai Sun, P.; Macadré, L.M.; Malgorn, G.; Yen, P.; Sun, K.; Quimper, S.; Laura, F.; Macadré, M.; Malgorn, G. Power Performance Assessment of the Tidal Turbine Sabella D10 Following IEC62600-200; Volume 6: Ocean Space Utilization; Ocean Renewable Energy; ASME: New York, NY, USA, 2016; Volume 6, p. V006T09A007. [Google Scholar] [CrossRef]
- Nash, S.; Phoenix, A. A review of the current understanding of the hydro-environmental impacts of energy removal by tidal turbines. Renew. Sustain. Energy Rev.
**2017**, 80, 648–662. [Google Scholar] [CrossRef] - Magagna, D.; Uihlein, A. Ocean energy development in Europe: Current status and future perspectives. Int. J. Mar. Energy
**2015**, 11, 84–104. [Google Scholar] [CrossRef] - Yuce, M.I.; Muratoglu, A. Hydrokinetic energy conversion systems: A technology status review. Renew. Sustain. Energy Rev.
**2015**, 43, 72–82. [Google Scholar] [CrossRef] - Yang, X.; Khosronejad, A.; Sotiropoulos, F. Large-eddy simulation of a hydrokinetic turbine mounted on an erodible bed. Renew. Energy
**2017**, 113, 1419–1433. [Google Scholar] [CrossRef] - Martin-Short, R.; Hill, J.; Kramer, S.; Avdis, A.; Allison, P.; Piggott, M. Tidal resource extraction in the Pentland Firth, UK: Potential impacts on flow regime and sediment transport in the Inner Sound of Stroma. Renew. Energy
**2015**, 76, 596–607. [Google Scholar] [CrossRef] [Green Version] - Chamorro, L.P.; Hill, C.; Morton, S.; Ellis, C.; Arndt, R.E.; Sotiropoulos, F. On the interaction between a turbulent open channel flow and an axial-flow turbine. J. Fluid Mech.
**2013**, 716, 658–670. [Google Scholar] [CrossRef] - Chamorro, L.; Hill, C.; Neary, V.; Gunawan, B.; Arndt, R.; Sotiropoulos, F. Effects of energetic coherent motions on the power and wake of an axial-flow turbine. Phys. Fluids
**2015**, 27, 055104. [Google Scholar] [CrossRef] - Kang, S.; Yang, X.; Sotiropoulos, F. On the onset of wake meandering for an axial flow turbine in a turbulent open channel flow. J. Fluid Mech.
**2014**, 744, 376–403. [Google Scholar] [CrossRef] - Howard, K.B.; Singh, A.; Sotiropoulos, F.; Guala, M. On the statistics of wind turbine wake meandering: An experimental investigation. Phys. Fluids
**2015**, 27, 075103. [Google Scholar] [CrossRef] - Maganga, F.; Germain, G.; King, J.; Pinon, G.; Rivoalen, E. Experimental characterisation of flow effects on marine current turbine behaviour and on its wake properties. IET Renew. Power Gener.
**2010**, 4, 498. [Google Scholar] [CrossRef] - Mycek, P.; Gaurier, B.; Germain, G.; Pinon, G.; Rivoalen, E. Numerical and experimental study of the interaction between two marine current turbines. Int. J. Mar. Energy
**2013**, 1, 70–83. [Google Scholar] [CrossRef] [Green Version] - Mycek, P.; Gaurier, B.B.B.; Germain, G.G.G.; Pinon, G.G.G.; Rivoalen, E. Experimental study of the turbulence intensity effects on marine current turbines behaviour. Part II: Two interacting turbines. Renew. Energy
**2014**, 66, 729–746. [Google Scholar] [CrossRef] - Hill, C.; Musa, M.; Chamorro, L.P.; Ellis, C.; Guala, M. Local Scour around a Model Hydrokinetic Turbine in an Erodible Channel. J. Hydraul. Eng.
**2014**, 140, 04014037. [Google Scholar] [CrossRef] - Hill, C.; Musa, M.; Guala, M. Interaction between instream axial flow hydrokinetic turbines and uni-directional flow bedforms. Renew. Energy
**2016**, 86, 409–421. [Google Scholar] [CrossRef] - Musa, M.; Heisel, M.; Guala, M. Predictive model for local scour downstream of hydrokinetic turbines in erodible channels. Phys. Rev. Fluids
**2018**, 3, 1–20. [Google Scholar] [CrossRef] - Musa, M.; Hill, C.; Sotiropoulos, F.; Guala, M. Performance and resilience of hydrokinetic turbine arrays under large migrating fluvial bedforms. Nat. Energy
**2018**. [Google Scholar] [CrossRef] - Tedds, S.C.; Owen, I.; Poole, R.J. Near-wake characteristics of a model horizontal axis tidal stream turbine. Renew. Energy
**2014**, 63, 222–235. [Google Scholar] [CrossRef] [Green Version] - Bowman, J.; Bhushan, S.; Thompson, D.S.; O’Doherty, D.; O’Doherty, T.; Mason-Jones, A. A Physics-Based Actuator Disk Model for Hydrokinetic Turbines. In 2018 Fluid Dynamics Conference; AIAA: Reston, VA, USA, 2018; pp. 1–20. [Google Scholar] [CrossRef]
- Batten, W.M.J.; Harrison, M.E.; Bahaj, A.S. Accuracy of the actuator disc-RANS approach for predicting the performance and wake of tidal turbines. Philos. Trans. R. Soc. A
**2013**, 371, 20120293. [Google Scholar] [CrossRef] [Green Version] - Shives, M.; Crawford, C. Adapted two-equation turbulence closures for actuator disk RANS simulations of wind & tidal turbine wakes. Renew. Energy
**2016**, 92, 273–292. [Google Scholar] [CrossRef] - Koh, W.X.; Ng, E.Y. A CFD study on the performance of a tidal turbine under various flow and blockage conditions. Renew. Energy
**2017**, 107, 124–137. [Google Scholar] [CrossRef] - Malki, R.; Masters, I.; Williams, A.J.; Nick Croft, T. Planning tidal stream turbine array layouts using a coupled blade element momentum—Computational fluid dynamics model. Renew. Energy
**2014**, 63, 46–54. [Google Scholar] [CrossRef] - Abutunis, A.; Hussein, R.; Chandrashekhara, K. A Neural Network Approach to Enhance Blade Element Momentum Theory Performance for Horizontal Axis Hydrokinetic Turbine Application. Renew. Energy
**2018**. [Google Scholar] [CrossRef] - Rahimian, M.; Walker, J.; Penesis, I. Performance of a horizontal axis marine current turbine: A comprehensive evaluation using experimental, numerical, and theoretical approaches. Energy
**2018**, 148, 965–976. [Google Scholar] [CrossRef] - Ahmadi, M.H. Influence of upstream turbulence on the wake characteristics of a tidal stream turbine. Renew. Energy
**2018**, 132, 989–997. [Google Scholar] [CrossRef] [Green Version] - Apsley, D.D.; Stallard, T.; Stansby, P.K. Actuator-line CFD modelling of tidal-stream turbines in arrays. J. Ocean. Eng. Mar. Energy
**2018**. [Google Scholar] [CrossRef] - Gajardo, D.; Escauriaza, C.; Ingram, D.M. Capturing the development and interactions of wakes in tidal turbine arrays using a coupled BEM-DES model. Ocean Eng.
**2019**, 181, 71–88. [Google Scholar] [CrossRef] [Green Version] - Spalart, P.R. Detached-Eddy Simulation. Annu. Rev. Fluid Mech.
**2009**, 41, 181–202. [Google Scholar] [CrossRef] - Stallard, T.; Collings, R.; Feng, T.; Whelan, J. Interactions between tidal turbine wakes: Experimental study of a group of three-bladed rotors. Philos. Trans. R. Soc. A
**2013**, 371, 20120159. [Google Scholar] [CrossRef] - Zhou, Z.; Scuiller, F.; Charpentier, J.F.; Benbouzid, M.; Tang, T. An up-to-date review of large marine tidal current turbine technologies. In Proceedings of the 2014 International Power Electronics and Application Conference and Exposition, Shanghai, China, 5–8 November 2014; IEEE PEAC: Piscataway, NJ, USA, 2014; pp. 480–484. [Google Scholar] [CrossRef]
- Van Rijn, L.C. Sediment Transport, Part II: Suspended Load Transport. J. Hydraul. Eng.
**1984**, 110, 1613–1641. [Google Scholar] [CrossRef] - Nishino, T.; Willden, R.H.J. The efficiency of an array of tidal turbines partially blocking a wide channel. J. Fluid Mech.
**2012**, 708, 596–606. [Google Scholar] [CrossRef] - Parsheh, M.; Sotiropoulos, F.; Porté-Agel, F. Estimation of Power Spectra of Acoustic-Doppler Velocimetry Data Contaminated with Intermittent Spikes. J. Hydraul. Eng.
**2010**, 136, 368–378. [Google Scholar] [CrossRef] - Musa, M.; Hill, C.; Guala, M. Interaction between hydrokinetic turbine wakes and sediment dynamics: array performance and geomorphic effects under different siting strategies and sediment transport conditions. Renew. Energy
**2019**, 138, 738–753. [Google Scholar] [CrossRef] - Smirnov, A.; Shi, S.; Celik, I. Random flow generation technique for large eddy simulations and particle-dynamics modeling. J. Fluids Eng.
**2001**, 123, 359–371. [Google Scholar] [CrossRef] - Creech, A.; Früh, W.G.; Maguire, A.E. Simulations of an Offshore Wind Farm Using Large-Eddy Simulation and a Torque-Controlled Actuator Disc Model. Surv. Geophys.
**2015**, 36, 427–481. [Google Scholar] [CrossRef] [Green Version] - Gebreslassie, M.G.; Sanchez, S.O.; Tabor, G.R.; Belmont, M.R.; Bruce, T.; Payne, G.S.; Moon, I. Experimental and CFD analysis of the wake characteristics of tidal turbines. Int. J. Mar. Energy
**2016**, 16, 209–219. [Google Scholar] [CrossRef] [Green Version] - Olczak, A.; Stallard, T.; Feng, T.; Stansby, P.K. Comparison of a RANS blade element model for tidal turbine arrays with laboratory scale measurements of wake velocity and rotor thrust. J. Fluid Struct.
**2016**, 64, 87–106. [Google Scholar] [CrossRef] - Bai, G.; Li, W.; Chang, H.; Li, G. The effect of tidal current directions on the optimal design and hydrodynamic performance of a three-turbine system. Renew. Energy
**2016**, 94, 48–54. [Google Scholar] [CrossRef] - Hunt, J.C.R. Studying turbulence using direct numerical simulation: 1987 Center for Turbulence Research NASA Ames/Stanford Summer Programme. J. Fluid Mech.
**1988**, 190, 375–392. [Google Scholar] [CrossRef] - Blackmore, T.; Myers, L.E.; Bahaj, A.S. Effects of turbulence on tidal turbines: Implications to performance, blade loads, and condition monitoring. Int. J. Mar. Energy
**2016**, 14, 1–26. [Google Scholar] [CrossRef] [Green Version] - Blackmore, T.; Batten, W.M.; Bahaj, A.S. Influence of turbulence on the wake of a marine current turbine simulator. Proc. R. Soc. A
**2014**, 470. [Google Scholar] [CrossRef] [PubMed]

Sample Availability: All data is available from the authors. |

**Figure 1.**Flume setup for the TT case. Both turbines are aligned and centered. The side-looking Nortek ADV velocimeter is mounted on the DAQ Carriage.

**Figure 2.**(

**a**) Points measured for both cases. Black: hub height (${h}_{h}$) for the deficit at the centerline, green: long exposure for the energy spectrum, red: transverse profiles, blue: vertical profiles. The disk on this image represents primary turbine. (

**b**) Schematic view of the cylindrical volume V that represents turbines. Forces calculated from BEM theory are only applied over nodes inside this volume. (

**c**) Schematic view of the turbine rotor and differential radius $dr$ used on BEM.

**Figure 3.**Longitudinal mean velocity $\langle U\rangle $ deficit for both study cases normalized by upstream velocity. The ST deficit (

**top**) fits better to experiments than the TT case (

**bottom**). At $10D$ downstream, the wake recovered 80% of the mean streamwise velocity.

**Figure 4.**Transverse velocity profiles for the first three diameters of distance downstream of the primary turbine for the (

**top**) ST and (

**bottom**) TT cases. The DES-BEM model shows agreement with the experimental profiles, but the model is not capable of representing the asymmetry observed in the measurements.

**Figure 5.**Vertical longitudinal velocity profiles for the ST (

**top**) and TT (

**bottom**) cases. In this case, the model cannot reproduce the asymmetry of the experiments either.

**Figure 6.**Instantaneous q-iso surfaces from two different perspectives. Both cases show the annular vortex produced by the averaged blade tips and the high pressure point at the nacelle area. Wake vortical structures are shorter for the TT case due to the larger turbulent intensity that faces the primary turbine in that case. The dashed line indicates the position of the downstream turbine.

**Figure 7.**Voltage spectra for both study cases. The first peaks indicate the primary turbine rotational frequency for each case. At lower frequencies, surrounding flow effects are perceived.

**Figure 8.**Velocity spectrum upstream and downstream of the primary turbine for the ST (

**top**) and TT (

**bottom**) cases. Surrounding flow effects are perceived in the same frequency range of the voltage spectrum.

**Figure 9.**(

**a**) Experimental elevation after experiments and (

**b**) average shear stress calculated from the DES-BEM model. The DES-BEM model results show a similar low-shear zone after the turbines, which is coincident with experimental measurements.

Parameter | Definition | ST | TT | Unit |
---|---|---|---|---|

D | Diameter | 0.092 | 0.092 | m |

${D}_{h}$ | Hub diameter | 0.02 | 0.02 | m |

${h}_{h}$ | Hub height | 0.010 | 0.010 | m |

${N}_{b}$ | Number of blades | 6 | 6 | - |

$Re$ | Reynolds number | 1.26 × ${10}^{3}$ | 1.26 × ${10}^{3}$ | - |

$Fr$ | Froude number | 0.24 | 0.24 | - |

${U}_{\infty}$ | Upstream velocity | 0.42 | 0.42 | m·s${}^{-1}$ |

$\Omega $ | Rotor rotational velocity | 16.6 | 12.4 | rad·s${}^{-1}$ |

$TSR$ | Tip-speed ratio | 3.65 | 2.01 | - |

Parameter | Value |
---|---|

${N}_{x}\times {N}_{y}\times {N}_{z}$ | $282\times 325\times 101$ |

Total number of nodes | 9,256,650 |

Number of nodes inside turbine volume | 164,125 |

Inlet boundary condition | Random flow |

Outlet boundary condition | Zero gradient |

Wall boundary condition | Wall function |

Bottom boundary condition | Non-slip condition |

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Gotelli, C.; Musa, M.; Guala, M.; Escauriaza, C.
Experimental and Numerical Investigation of Wake Interactions of Marine Hydrokinetic Turbines. *Energies* **2019**, *12*, 3188.
https://doi.org/10.3390/en12163188

**AMA Style**

Gotelli C, Musa M, Guala M, Escauriaza C.
Experimental and Numerical Investigation of Wake Interactions of Marine Hydrokinetic Turbines. *Energies*. 2019; 12(16):3188.
https://doi.org/10.3390/en12163188

**Chicago/Turabian Style**

Gotelli, Clemente, Mirko Musa, Michele Guala, and Cristián Escauriaza.
2019. "Experimental and Numerical Investigation of Wake Interactions of Marine Hydrokinetic Turbines" *Energies* 12, no. 16: 3188.
https://doi.org/10.3390/en12163188