Boundary Element Modelling Aspects for the Hydro-Elastic Analysis of Flexible Marine Propellers
Boundary element methods (BEM) have been used for propeller hydrodynamic calculations since the 1990s. More recently, these methods are being used in combination with finite element methods (FEM) in order to calculate flexible propeller fluid–structure interaction (FSI) response. The main...
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| Format: | Article |
| Language: | English |
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MDPI AG
2018-06-01
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| Series: | Journal of Marine Science and Engineering |
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| Online Access: | http://www.mdpi.com/2077-1312/6/2/67 |
| _version_ | 1831557904438657024 |
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| author | Pieter Maljaars Mirek Kaminski Henk den Besten |
| author_facet | Pieter Maljaars Mirek Kaminski Henk den Besten |
| author_sort | Pieter Maljaars |
| collection | DOAJ |
| description | Boundary element methods (BEM) have been used for propeller hydrodynamic calculations since the 1990s. More recently, these methods are being used in combination with finite element methods (FEM) in order to calculate flexible propeller fluid–structure interaction (FSI) response. The main advantage of using BEM for flexible propeller FSI calculations is the relatively low computational demand in comparison with higher fidelity methods. However, the BEM modelling of flexible propellers is not straightforward and requires several important modelling decisions. The consequences of such modelling choices depend significantly on propeller structural behaviour and flow condition. The two dimensionless quantities that characterise structural behaviour and flow condition are the structural frequency ratio (the ratio between the lowest excitation frequency and the fundamental wet blade natural frequency) and the reduced frequency. For both, general expressions have been derived for (flexible) marine propellers. This work shows that these expressions can be effectively used to estimate the dry and wet fundamental blade frequencies and the structural frequency ratio. This last parameter and the reduced frequency of vibrating blade flows is independent of the geometrical blade scale as shown in this work. Regarding the BEM-FEM coupled analyses, it is shown that a quasi-static FEM modelling does not suffice, particularly due to the fluid-added mass and hydrodynamic damping contributions that are not negligible. It is demonstrated that approximating the hydro-elastic blade response by using closed form expressions for the fluid added mass and hydrodynamic damping terms provides reasonable results, since the structural response of flexible propellers is stiffness dominated, meaning that the importance of modelling errors in fluid added mass and hydrodynamic damping is small. Finally, it is shown that the significance of recalculating the hydrodynamic influence coefficients is relatively small. This fact might be utilized, possibly in combination with the use of the closed form expressions for fluid added mass and hydrodynamic damping contributions, to significantly reduce the computation time of flexible propeller FSI calculations. |
| first_indexed | 2024-12-17T05:01:12Z |
| format | Article |
| id | doaj.art-a2ddd7c47c27470e8055a92a497ad3d0 |
| institution | Directory Open Access Journal |
| issn | 2077-1312 |
| language | English |
| last_indexed | 2024-12-17T05:01:12Z |
| publishDate | 2018-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Journal of Marine Science and Engineering |
| spelling | doaj.art-a2ddd7c47c27470e8055a92a497ad3d02022-12-21T22:02:34ZengMDPI AGJournal of Marine Science and Engineering2077-13122018-06-01626710.3390/jmse6020067jmse6020067Boundary Element Modelling Aspects for the Hydro-Elastic Analysis of Flexible Marine PropellersPieter Maljaars0Mirek Kaminski1Henk den Besten2Maritime & Transport Technology Department, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The NetherlandsMaritime & Transport Technology Department, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The NetherlandsMaritime & Transport Technology Department, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The NetherlandsBoundary element methods (BEM) have been used for propeller hydrodynamic calculations since the 1990s. More recently, these methods are being used in combination with finite element methods (FEM) in order to calculate flexible propeller fluid–structure interaction (FSI) response. The main advantage of using BEM for flexible propeller FSI calculations is the relatively low computational demand in comparison with higher fidelity methods. However, the BEM modelling of flexible propellers is not straightforward and requires several important modelling decisions. The consequences of such modelling choices depend significantly on propeller structural behaviour and flow condition. The two dimensionless quantities that characterise structural behaviour and flow condition are the structural frequency ratio (the ratio between the lowest excitation frequency and the fundamental wet blade natural frequency) and the reduced frequency. For both, general expressions have been derived for (flexible) marine propellers. This work shows that these expressions can be effectively used to estimate the dry and wet fundamental blade frequencies and the structural frequency ratio. This last parameter and the reduced frequency of vibrating blade flows is independent of the geometrical blade scale as shown in this work. Regarding the BEM-FEM coupled analyses, it is shown that a quasi-static FEM modelling does not suffice, particularly due to the fluid-added mass and hydrodynamic damping contributions that are not negligible. It is demonstrated that approximating the hydro-elastic blade response by using closed form expressions for the fluid added mass and hydrodynamic damping terms provides reasonable results, since the structural response of flexible propellers is stiffness dominated, meaning that the importance of modelling errors in fluid added mass and hydrodynamic damping is small. Finally, it is shown that the significance of recalculating the hydrodynamic influence coefficients is relatively small. This fact might be utilized, possibly in combination with the use of the closed form expressions for fluid added mass and hydrodynamic damping contributions, to significantly reduce the computation time of flexible propeller FSI calculations.http://www.mdpi.com/2077-1312/6/2/67flexible (composite) propellersBEM modellingfluid–structure interaction |
| spellingShingle | Pieter Maljaars Mirek Kaminski Henk den Besten Boundary Element Modelling Aspects for the Hydro-Elastic Analysis of Flexible Marine Propellers Journal of Marine Science and Engineering flexible (composite) propellers BEM modelling fluid–structure interaction |
| title | Boundary Element Modelling Aspects for the Hydro-Elastic Analysis of Flexible Marine Propellers |
| title_full | Boundary Element Modelling Aspects for the Hydro-Elastic Analysis of Flexible Marine Propellers |
| title_fullStr | Boundary Element Modelling Aspects for the Hydro-Elastic Analysis of Flexible Marine Propellers |
| title_full_unstemmed | Boundary Element Modelling Aspects for the Hydro-Elastic Analysis of Flexible Marine Propellers |
| title_short | Boundary Element Modelling Aspects for the Hydro-Elastic Analysis of Flexible Marine Propellers |
| title_sort | boundary element modelling aspects for the hydro elastic analysis of flexible marine propellers |
| topic | flexible (composite) propellers BEM modelling fluid–structure interaction |
| url | http://www.mdpi.com/2077-1312/6/2/67 |
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