Hydroelastic simulation of the acoustic behaviour of ship-propeller configurations with and without cavitation
Engineering Design, Machine Elements, Product Development
Mechanics
Final Report Abstract
The aim of the present project was the development of a numerical method to evaluate and, in a further step, to optimize flexible ship propellers with regard to the noise level under non-cavitating and cavitating conditions. In the first period of the project a partitioned approach for the fluid-structure interaction was developed using the boundary element method panMARE to solve the hydrodynamic part of the problem. Here, the flexibility of the propeller blade is considered including the deformation velocity in the Neumann boundary condition to compute the source strengths of the panels. The solution of the boundary value problem leads to the fluid velocities and to the hydrodynamic pressure and the respective traction which are returned to the structural solver. Beside of this, a partially nonlinear cavitation model was included in the partitioned approach. In this context, a dynamic and kinematic boundary condition, in which also the fluid-structure interaction (FSI) related motions are taken into account, are solved in an iterative process. For the evaluation of the acoustic signature a model based on the Ffowcs Williams-Hawkings equation (FWHE) has been implemented into the hydrodynamic solver panMARE. In the model the overall acoustic pressure is superposed by a thickness term, in which also the cavitation effects are included, and a loading term. Both terms are functions of data to be collected solely on the body surface, which is highly favorable for boundary element methods. The model also considers surface reflections at either ground or water surface. Furthermore, it allows to perform the acoustic evaluation as post-processing step of the FSI simulation without specification of the observer location in advance. The established FSI approach and the acoustic model have been verified by simulating the flow on the SVA-P1356 propeller. The hydrodynamic performance of the propeller was computed in homogeneous and inhomogeneous inflow conditions under consideration of blade flexibility and cavitation. The results showed physically consistent behaviour regarding the influence of the blade deformation on propeller performance, its tendency to cavitate and its acoustic signature. A successful validation of the full FSI-approach based on thrust and torque coefficients and local strains has been conducted on the example of a multilayered submersible mixer. Furthermore, the open water characteristic of a ship propeller has been validated comparing the results of a rigid and a flexible blade for two different rotational speeds. The simulations showed that the thrust and the torque of a flexible propeller compared to a rigid one are increased for lower advance ratios and decrease towards higher advance ratios. The comparison of the results with experiments indicated that the partitioned approach matches well regarding the change of the thrust and torque due to the deformation. For the KCS propeller a multistage optimization process has been successfully implemented. In the first step, the shape of the rigid propeller under realistic inflow conditions has been optimized in a two stage optimization based on hydrodynamic simulations to reduce the cavitation volume and its variation, keep efficiency high and meet the thrust goal. Based on the resulting propeller, another optimization searching for the optimal pitch deformation of the propeller blades rotating in the ship wake to further reduce the cavitation and the thrust variation has been carried out. Apart from this, the optimized rigid propeller has been used as a basis for the optimization of the flexible anisotropic propeller. A model for the structural side of the propeller based on layered carbon fiber reinforced polymer has been developed. In this model the fiber orientation and the stiffness of the structure was optimized in combination with the pitch angle. A particular difficulty at this point was the appearance of singular panels in the hydrodynamic solver which are caused by the distortion of panels due to large structural deformations. This problem does not arise when the fully coupled FSI approach is applied for optimisation. The duration of the fully coupled FSI optimisation was reduced using advanced convergence acceleration methods. The propeller optimization under consideration of the deformation of the blade has been successfully conducted. The optimized flexible propeller using the fully coupled FSI simulation shows a significant reduction in thrust fluctuation and an increase of efficiency of up to 2% compared to the rigid propeller. The results obtained using FSI simulations and the non-linear cavitation model confirm that the cavitation of the optimized flexible propeller was significantly reduced with respect to the reference propeller. Furthermore, the evaluation of the acoustic characteristic indicated that the noise level of the optimized flexible propeller is reduced as compared to the reference propeller.
Publications
- ”Partitionierte Simulation der Fluid-Struktur-Interaktion von elastischen Schiffspropellern”. In: Jahrbuch der Schiffbautechnischen Gesellschaft 111 (2017), pp. 58–65
T. Lampe, L. Radtke, A. Düster, and M. Abdel-Maksoud
- ”A partitioned solution approach for the simulation of the dynamic behaviour of flexible marine propellers”. In: Ship Technology Research 67.1 (2018), pp. 37-50
L. Radtke, T. Lampe, M. Abdel-Maksoud, and A. Düster
(See online at https://doi.org/10.1080/09377255.2018.1542782) - ”Partitioned simulation of the fluid-structure interaction of flexible marine propellers in unsteady flow conditions”. In: Proceeding in Applied Mathematics and Mechanics 18.1, e201800471, 2018
T. Lampe, L. Radtke, M. Abdel-Maksoud, and A. Düster
(See online at https://doi.org/10.1002/pamm.201800471) - ”Evaluation of performance and acoustic signature of flexible marine propellers under consideration of fluid-structure interaction by means of partitioned simulation”. In: Proceedings of the 6th International Symposium on Marine Propulsors, 2019
T. Lampe, L. Radtke, U. Göttsche, A. Düster, and M. Abdel-Maksoud
- ”A partitioned solution approach for the simulation of dynamic behaviour and acoustic signature of flexible cavitating marine propellers”. In: Ocean Engineering 197 (2020), p. 106854
T. Lampe, L. Radtke, M. Abdel-Maksoud, and A. Düster
(See online at https://doi.org/10.1016/j.oceaneng.2019.106854) - ”Partitioned simulation of the acoustic behavior of flexible marine propellers using finite and boundary elements.” In: Proceeding in Applied Mathematics and Mechanics 20.1, e202000315, 2020
L. Radtke, T. Lampe, M. Abdel-Maksoud, and A. Düster
(See online at https://doi.org/10.1002/pamm.202000315) - ”Optimally Blended Spectral Elements in Structural Dynamics: Selective Integration and Mesh Distortion”, In: International Journal of Computational Methods 18.10 (2021), 2150042
L. Radtke, D. Müller, A. Düster
(See online at https://doi.org/10.1142/S0219876221500420) - ”A two-stage optimization approach for propellers with unconventional blade shape in a wake field using BEM”, In: Proceedings of the Seventh International Symposium on Marine Propulsors, 2022
J. C. Neitzel-Petersen, D. Ferreira González, Roland Gosda, M. Abdel-Maksoud
- ”Advanced Methods for Partitioned Fluid-Structure Interaction Simulations applied to Ship Propellers”, In: Proceedings of the ASME 2022 41st International Conference on Ocean, Offshore and Arctic Engineering, Volume 7: CFD and FSI, 2022
J. Lund, D. Ferreira González, L. Radtke, M. Abdel-Maksoud, A. Düster
(See online at https://doi.org/10.1115/OMAE2022-80507) - ”Validation of a Partitioned Fluid-Structure Interaction Simulation for Turbo Machine Rotors”, In: Ships and Offshore Structures, (2022)
J. Lund, D. Ferreira González, J. C. Neitzel-Petersen, L. Radtke, M. Abdel-Maksoud, A. Düster
(See online at https://doi.org/10.1080/17445302.2022.2069389)
