A.S. Mukadam
info
Please Note
<p>This page displays the records of the person named above and is not linked to a unique person identifier. This record may need to be merged to a profile.</p>
1 records found
1
Towed Transportation of Floating Monopiles
A Linearised Dynamic Stability Analysis
The growth in offshore wind energy has resulted in an increase of the size of the wind turbines and consequently, the monopiles supporting them. Due to limited space on decks of the installation vessels, an alternative method of transportation of the monopiles to the installation site is desirable. One possible approach is towing the monopiles directly on the sea by using plugs to seal both the ends. The towed monopile may experience lateral instability during transport. This thesis presents a theoretical linearised rigid body model to investigate the stability of the system.
The analytical equation of motion for a towed flexible cylinder in still water is derived using linear assumptions, which is then further simplified using rigid body assumption. Using the frequency domain analysis, the analytical equations are solved for complex frequency roots to draw conclusions regarding the stability of the system. Additionally, stochastic lateral distributed drag is also incorporated in the model. However, the analytical model does not include the effect of added mass and damping due to the fluid. The necessary numerical hydrodynamic added mass, damping and forces are obtained through ANSYS Aqwa, using linear potential theory with one way fluid structure interaction.
The hydrodynamic numerical results are however, only for real and positive frequencies and are not solvable analytically. The D-decomposition method is employed in order to circumvent this limitation of the numerical model with added mass and damping, that maps the critical axis of frequency roots on a complex plane of a chosen parameter. This allows the formation of the zones of stability through which critical values can be obtained for a parameter.
A parametric analysis, excluding the geometric parameters of the monopile, shows that the axial drag resistance terms do not affect the stability of the system, while the stochastic drag is an unreliable means of stabilising the system due to wave angle dependence. On the other hand, the added mass and damping tend to destabilise the system as tow velocity increases and their effect is significant. Furthermore, the mathematical boundary damper shows that the stabilising appendage at the tail, in the form of a skeg, can stabilise the system. Though, a detailed study on the stabilising appendage needs to be performed.
In conclusion, this study provides a basis for a linearised dynamic stability analysis of a floating monopile under tow with added mass and damping effects, upon which further studies, experimental as well as theoretical, can be performed for validation and improvements. ...
The analytical equation of motion for a towed flexible cylinder in still water is derived using linear assumptions, which is then further simplified using rigid body assumption. Using the frequency domain analysis, the analytical equations are solved for complex frequency roots to draw conclusions regarding the stability of the system. Additionally, stochastic lateral distributed drag is also incorporated in the model. However, the analytical model does not include the effect of added mass and damping due to the fluid. The necessary numerical hydrodynamic added mass, damping and forces are obtained through ANSYS Aqwa, using linear potential theory with one way fluid structure interaction.
The hydrodynamic numerical results are however, only for real and positive frequencies and are not solvable analytically. The D-decomposition method is employed in order to circumvent this limitation of the numerical model with added mass and damping, that maps the critical axis of frequency roots on a complex plane of a chosen parameter. This allows the formation of the zones of stability through which critical values can be obtained for a parameter.
A parametric analysis, excluding the geometric parameters of the monopile, shows that the axial drag resistance terms do not affect the stability of the system, while the stochastic drag is an unreliable means of stabilising the system due to wave angle dependence. On the other hand, the added mass and damping tend to destabilise the system as tow velocity increases and their effect is significant. Furthermore, the mathematical boundary damper shows that the stabilising appendage at the tail, in the form of a skeg, can stabilise the system. Though, a detailed study on the stabilising appendage needs to be performed.
In conclusion, this study provides a basis for a linearised dynamic stability analysis of a floating monopile under tow with added mass and damping effects, upon which further studies, experimental as well as theoretical, can be performed for validation and improvements. ...
The growth in offshore wind energy has resulted in an increase of the size of the wind turbines and consequently, the monopiles supporting them. Due to limited space on decks of the installation vessels, an alternative method of transportation of the monopiles to the installation site is desirable. One possible approach is towing the monopiles directly on the sea by using plugs to seal both the ends. The towed monopile may experience lateral instability during transport. This thesis presents a theoretical linearised rigid body model to investigate the stability of the system.
The analytical equation of motion for a towed flexible cylinder in still water is derived using linear assumptions, which is then further simplified using rigid body assumption. Using the frequency domain analysis, the analytical equations are solved for complex frequency roots to draw conclusions regarding the stability of the system. Additionally, stochastic lateral distributed drag is also incorporated in the model. However, the analytical model does not include the effect of added mass and damping due to the fluid. The necessary numerical hydrodynamic added mass, damping and forces are obtained through ANSYS Aqwa, using linear potential theory with one way fluid structure interaction.
The hydrodynamic numerical results are however, only for real and positive frequencies and are not solvable analytically. The D-decomposition method is employed in order to circumvent this limitation of the numerical model with added mass and damping, that maps the critical axis of frequency roots on a complex plane of a chosen parameter. This allows the formation of the zones of stability through which critical values can be obtained for a parameter.
A parametric analysis, excluding the geometric parameters of the monopile, shows that the axial drag resistance terms do not affect the stability of the system, while the stochastic drag is an unreliable means of stabilising the system due to wave angle dependence. On the other hand, the added mass and damping tend to destabilise the system as tow velocity increases and their effect is significant. Furthermore, the mathematical boundary damper shows that the stabilising appendage at the tail, in the form of a skeg, can stabilise the system. Though, a detailed study on the stabilising appendage needs to be performed.
In conclusion, this study provides a basis for a linearised dynamic stability analysis of a floating monopile under tow with added mass and damping effects, upon which further studies, experimental as well as theoretical, can be performed for validation and improvements.
The analytical equation of motion for a towed flexible cylinder in still water is derived using linear assumptions, which is then further simplified using rigid body assumption. Using the frequency domain analysis, the analytical equations are solved for complex frequency roots to draw conclusions regarding the stability of the system. Additionally, stochastic lateral distributed drag is also incorporated in the model. However, the analytical model does not include the effect of added mass and damping due to the fluid. The necessary numerical hydrodynamic added mass, damping and forces are obtained through ANSYS Aqwa, using linear potential theory with one way fluid structure interaction.
The hydrodynamic numerical results are however, only for real and positive frequencies and are not solvable analytically. The D-decomposition method is employed in order to circumvent this limitation of the numerical model with added mass and damping, that maps the critical axis of frequency roots on a complex plane of a chosen parameter. This allows the formation of the zones of stability through which critical values can be obtained for a parameter.
A parametric analysis, excluding the geometric parameters of the monopile, shows that the axial drag resistance terms do not affect the stability of the system, while the stochastic drag is an unreliable means of stabilising the system due to wave angle dependence. On the other hand, the added mass and damping tend to destabilise the system as tow velocity increases and their effect is significant. Furthermore, the mathematical boundary damper shows that the stabilising appendage at the tail, in the form of a skeg, can stabilise the system. Though, a detailed study on the stabilising appendage needs to be performed.
In conclusion, this study provides a basis for a linearised dynamic stability analysis of a floating monopile under tow with added mass and damping effects, upon which further studies, experimental as well as theoretical, can be performed for validation and improvements.