# Application of Large Eddy Simulation to Predict Underwater Noise of Marine Propulsors. Part 2: Noise Generation

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## Abstract

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## 1. Introduction

#### 1.1. State of the Art

#### 1.2. Contributions of Current Work

## 2. Materials and Methods

#### 2.1. Methodology

#### 2.1.1. Hydrodynamics

#### 2.1.2. Acoustic Post-Processing

#### 2.2. Numerical Setup

#### 2.2.1. Free-Running Propellers

#### 2.2.2. Ship–Propeller Configurations

## 3. Results

#### 3.1. Radiated Noise Analysis

#### 3.1.1. Newcastle Propeller Test Case

#### 3.1.2. P1595

#### 3.2. Behind Ship Investigations

#### 3.2.1. ProNoVi Target Case

#### 3.2.2. SCHOTTEL Reference Case 1

#### 3.2.3. SCHOTTEL Reference Case 2

## 4. Discussion

#### 4.1. Noise Generation Mechanisms

- Resolved turbulence,
- Phase transition model, and
- Vorticity-based refinements,

- Reduction of pressure wave propagation by the vapor phase, which dampens the noise, as has been reported in some experiments with steady cavitation;
- Overall, only moderate variation of cavitation volume as a result of the steady tip vortex cavity, which adds purely sinusoidal disturbance to the flow, but no broadband noise.

#### 4.2. Practical Application in the Near Field

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 2.**Newcastle. Distance refinement in tip vortex region based on $Q$-criterion $Q=5\cdot {10}^{5}{s}^{-2}$ for condition C2.

**Figure 3.**Behind ship mesh: (

**a**) ProNoVi Target Case; (

**b**) SCHOTTEL Reference Case 1; (

**c**) SCHOTTEL Reference Case 2.

**Figure 4.**Newcastle. Acoustic investigation: (

**a**) numerical setup with pressure observers H1-H3; (

**b**) comparison of the SL for different solvers with the averaged measurement, condition C1, observer H2.

**Figure 5.**Newcastle. SL for the three pressure observers with measurement for the conditions: (

**a**) C1; (

**b**) C2; (

**c**) C3; (

**d**) C6.

**Figure 6.**P1595. Acoustic investigation: (

**a**) numerical setup with pressure observer; (

**b**) cavitation isosurface.

**Figure 7.**P1595. Sound pressure level spectral evaluation at observer: comparison of KFWH approach under cavitating and non-cavitating conditions with experimental measurements from SINTEF Ocean.

**Figure 8.**ProNoVi target case. Comparison of RANS and ILES Q-criterion $Q=5\cdot {10}^{4}{s}^{-2}$ at model scale on the same mesh: (

**a**) RANS; (

**b**) ILES.

**Figure 9.**ProNoVi target case. Difference between RANS and ILES wake field in the Cartesian components x, y and z, velocities averaged over time, propeller plane indicated by radii sections: (

**a**) velocity difference; (

**b**) velocity standard deviation difference.

**Figure 10.**ProNoVi target case. Locations of the acoustic observers on the hull with respect to the propeller and the headbox of the unit in full scale.

**Figure 11.**ProNoVi target case. Comparison of ILES time signal excerpts: (

**a**) propeller only; (

**b**) propeller and hull.

**Figure 12.**ProNoVi Target Case. Pressure amplitudes at multiples of the blade passing frequency (BPF) in comparison to the experiment with the model propeller only and the model propeller and ship hull in the propulsion condition with the results scaled to full scale.

**Figure 13.**SCHOTTEL reference case 1. Comparison of RANS and ILES Q-criterion $Q=5\cdot {10}^{2}{s}^{-2}$ at model scale on the same mesh: (

**a**) RANS; (

**b**) ILES.

**Figure 14.**SCHOTTEL reference case 1. Differences between the RANS and ILES wake fields in terms of Cartesian components x, y and z, velocities are averaged over one rotation, the propeller plane is indicated by radii sections: (

**a**) velocity difference; (

**b**) velocity standard deviation difference.

**Figure 15.**SCHOTTEL reference case 1. The cavitation region (white) and pressure coefficient with one propeller blade located at 12 o’clock position.

**Figure 16.**SCHOTTEL reference case 1. Locations of the acoustic observers on the hull with respect to the propeller and the rudder of the unit at full scale; observers are symmetrical to the centerline.

**Figure 17.**SCHOTTEL reference case 1. Pressure amplitudes obtained with the direct pressure and KFWH method at blade passing frequencies (BPF) in comparison to the experiment at full scale in propulsion condition with cavitation.

**Figure 18.**SCHOTTEL reference case 2. Comparison of RANS and ILES Q-criterion $Q=1\cdot {10}^{4}{s}^{-2}$ at model scale on the same mesh: (

**a**) RANS; (

**b**) ILES.

**Figure 19.**SCHOTTEL reference case 2. Locations of acoustic observers on the hull with respect to the origin located at the vertical shaftline with propellers and the headbox of the unit at model scale; observers are symmetrical to the centerline.

**Figure 20.**SCHOTTEL reference case 2. Pressure amplitudes at multiples of the blade passing frequency (BPF) in comparison to the experiment and a revised propeller design with model propeller and ship hull and the results scaled to full scale.

Parameter | ${\mathit{n}}_{0}$ | ${\mathit{d}}_{\mathit{N}\mathit{u}\mathit{c}}$ |
---|---|---|

Unit | $1/{m}^{3}$ | $m$ |

Value | $1\cdot {10}^{12}$ | $1\cdot {10}^{-4}$ |

Condition | C1 | C2 | C3 | C6 |
---|---|---|---|---|

$J\left[-\right]$ | $0.4$ | $0.4$ | $0.4$ | $0.5$ |

${\sigma}_{n}\left[-\right]$ | $2.22$ | $1.3$ | $0.72$ | $1.13$ |

$n$ [Hz] | 35 | 35 | 35 | 35 |

Parameter | Symbol | Unit | Value |
---|---|---|---|

Diameter | $\mathrm{D}$ | $\left[\mathrm{mm}\right]$ | $204$ |

Design pitch ratio | ${\mathrm{P}}_{0.7\mathrm{R}}/\mathrm{D}$ | $\left[-\right]$ | $1.188$ |

Chord length at $r/R=0.7$ | ${\mathrm{C}}_{0.7\mathrm{R}}$ | $\left[\mathrm{mm}\right]$ | $79.132$ |

Max. thickness at $r/R=0.7$ | ${\mathrm{t}}_{0.7\mathrm{R}}$ | $\left[\mathrm{mm}\right]$ | $3.617$ |

Area ratio | ${\mathrm{A}}_{\mathrm{E}}/{\mathrm{A}}_{0}$ | $\left[-\right]$ | $0.626$ |

Hub ratio | ${\mathrm{d}}_{\mathrm{h}}/\mathrm{D}$ | $\left[-\right]$ | $0.196$ |

Skew-angle | $\mathsf{\Theta}$ | $\left[\xb0\right]$ | $42$ |

Number of blades | $\mathrm{Z}$ | $\left[-\right]$ | $4$ |

Sense of rotation | - | $\left[-\right]$ | $\mathrm{Right}$ |

Type of propeller | - | $\left[-\right]$ | $\mathrm{FP}\left(\mathrm{Fixed}\mathrm{Propeller}\right)$ |

$\mathbf{Cell}\mathbf{Count}[{10}^{6}\mathbf{Cells}]$ | ||
---|---|---|

Newcastle | P1595 | |

Initial mesh | $13.0$ | $13.1$ |

Refinement step | C1: $32.3$ C2: $24.9$ C3: $27.5$ C6: $40.1$ | - |

Type | ${\mathit{K}}_{\mathit{T}}$ | $10{\mathit{K}}_{\mathit{Q}}$ | $\mathbf{\Delta}{\mathit{K}}_{\mathit{T}}$ | $\mathbf{\Delta}10{\mathit{K}}_{\mathit{Q}}$ | $\Delta {\eta}_{0}$ |
---|---|---|---|---|---|

Experiment (Cav Off) | 0.305 | 0.536 | - | - | - |

Experiment (Cav On) | 0.302 | - | - | - | - |

$\mathrm{RANS}\mathrm{k}-\mathsf{\omega}-\mathrm{SST}\mathrm{no}\mathrm{cavitation}$ | $0.308$ | $0.532$ | $0.9\%$ | $1.8\%$ | $1.8\%$ |

$\mathrm{RANS}\mathrm{k}-\mathsf{\omega}-\mathrm{SST}\mathrm{cavitation}$ | $0.297$ | $0.537$ | $-1.7\%$ | $-$ | $-$ |

$\mathrm{LES}\mathrm{Smagorinsky}\mathrm{no}\mathrm{cavitation}$ | $0.309$ | $0.541$ | $1.3\%$ | $0.4\%$ | $0.4\%$ |

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**MDPI and ACS Style**

Kimmerl, J.; Mertes, P.; Abdel-Maksoud, M.
Application of Large Eddy Simulation to Predict Underwater Noise of Marine Propulsors. Part 2: Noise Generation. *J. Mar. Sci. Eng.* **2021**, *9*, 778.
https://doi.org/10.3390/jmse9070778

**AMA Style**

Kimmerl J, Mertes P, Abdel-Maksoud M.
Application of Large Eddy Simulation to Predict Underwater Noise of Marine Propulsors. Part 2: Noise Generation. *Journal of Marine Science and Engineering*. 2021; 9(7):778.
https://doi.org/10.3390/jmse9070778

**Chicago/Turabian Style**

Kimmerl, Julian, Paul Mertes, and Moustafa Abdel-Maksoud.
2021. "Application of Large Eddy Simulation to Predict Underwater Noise of Marine Propulsors. Part 2: Noise Generation" *Journal of Marine Science and Engineering* 9, no. 7: 778.
https://doi.org/10.3390/jmse9070778