BEM–FEM coupling for the analysis of flexible propellers in non-uniform flows and validation with full-scale measurements

BEM–FEM coupling for the analysis of flexible propellers in non-uniform flows and validation with full-scale measurements

Maljaars, P.J. (TU Delft Ship Hydromechanics and Structures)
Grasso, N. (Maritime Research Institute Netherlands (MARIN))
den Besten, J.H. (TU Delft Ship Hydromechanics and Structures)
Kaminski, M.L. (TU Delft Ship Hydromechanics and Structures)

2020

The first part of the paper presents a partitioned fluid–structure interaction (FSI) coupling for the non-uniform flow hydro-elastic analysis of highly flexible propellers in cavitating and non-cavitating conditions. The chosen fluid model is a potential flow solved with a boundary element method (BEM). The structural sub-problem has been modelled with a finite element method (FEM). In the present method, the fully partitioned framework allows one to use another flow or structural solver. An important feature of the present method is the time periodic way of solving the FSI problem. In a time periodic coupling, the coupling iterations are not performed per time step but on a periodic level, which is necessary for the present BEM–FEM coupling, but can also offer an improved convergence rate compared to a time step coupled method. Thus, it allows to solve the structural problem in the frequency domain, meaning that any transients, which slow down the convergence process, are not computed. As proposed in the method, the structural equations of motion can be solved in modal space, which allows for a model reduction by involving only a limited number of mode shapes. The second part of the paper includes a validation study on full-scale. For the full-scale validation study a purposely designed composite propeller with a diameter of 1 m has been manufactured. Also an underwater measurement set-up including a stereo camera system, remote control of the optics and illumination system has been developed. The propeller design and the underwater measurement set-up are described in the paper. During sea trials blade deflections have been measured in three different positions. A comparison between measured and calculated torque shows that the measured torque is much larger than computed. This is attributed to the differences between effective and nominal wakefields, where the latter one has been used for the calculations. To correct for the differences between measured and computed torque the calculated pressures have been amplified accordingly. In that way the deformations which have been computed with the BEM–FEM coupling for non-uniform flows became very similar to the measured results.

Flexible marine propellers
Fluid–structure interaction
Full-scale validation
Numerical modelling

http://resolver.tudelft.nl/uuid:e889a161-9fd2-469f-bd40-b8187991ecaf

https://doi.org/10.1016/j.jfluidstructs.2020.102946

2022-04-22

0889-9746

Journal of Fluids and Structures, 95

Accepted Author Manuscript

Institutional Repository

journal article

© 2020 P.J. Maljaars, N. Grasso, J.H. den Besten, M.L. Kaminski