Session: 06-05-01 Marine Hydrodynamics I

Paper Number: 102792

102792 - Motion Response Study of the Floating Dock During the Spar Installation 

Floating wind turbines are an evolving source of renewable energy. However, the installation of wind turbines at offshore locations is a complex task. The entire process becomes more challenging as it is susceptible to weather conditions.

Many novel concepts have been used to install offshore wind turbines, such as cranes for lifting, floatover technique (3), and catamaran installation vessels (1) . The floating dock concept (2) is the most recent method used for elevating offshore wind turbine technology.

This paper investigates a floating dock that provides shielding to the spar foundation during the 5 MW wind turbine installation at the offshore site. This dock helps avoid the unnecessary disturbances caused in the installation process due to weather conditions at the location. The gate structure facilitates installing the spar and the wind turbine at the requisite site.

In the present paper, the heave response of a floating dock is to be studied using ANSYS AQWA software. This software considers only the radiation damping, which does not accurately estimate the structure's response. Hence, the viscous damping matrix (4) must be provided as an external damping matrix to the system. Free decay tests are conducted numerically, which provides the total damping matrix. The viscous damping matrix is obtained by subtracting the radiation damping matrix from the entire damping matrix. This matrix is then provided externally in the ANSYS AQWA analysis to receive the exact behavior of the system.

A floating dock of 60 m diameter is used to install a 5 MW wind turbine on a spar of 15 m diameter. The hydrodynamic response of the system is diagnosed when it is subjected to regular waves. For installing the spar foundation using the floating dock, the dock is wet towed to the site. When the dock reaches the site, the gates of the floating dock are closed. Later on, the gates are opened to facilitate the entry of spar inside it. Hence, during the spar installation, the system must be analyzed for two conditions, i.e., when the gates are closed and when the gates are opened. When the gates are opened, there are chances of instability. Hence, the system's behavior is analyzed and observed to behave quite effectively in both cases.

Keywords: Floating dock, viscous damping, hydrodynamic response, spar

References:

1. Jiang, Z., Li, L., Gao, Z., Halse, K. H., & Sandvik, P. C. (2018). Dynamic response analysis of a catamaran installation vessel during the positioning of a wind turbine assembly onto a spar foundation. Marine Structures, 61(August 2017), 1–24. https://doi.org/10.1016/j.marstruc.2018.04.010

2. Jiang, Z., Yttervik, R., Gao, Z., & Christian, P. (2020). Design, modeling, and analysis of a large floating dock for spar floating wind turbine installation. Marine Structures, 72(March), 102781. https://doi.org/10.1016/j.marstruc.2020.102781

3. Koo, B., Beyko, E., & Magee, A. (2016). Model Tests for Floatover Installation of Spar Topsides. 1–9.

4. Subbulakshmi, A., Jose, J., Sundaravadivelu, R., & Selvam, R. P. (2015). Effect of Viscous Damping on Hydrodynamic Response of Spar with Heave Plate. Aquatic Procedia, 4(Icwrcoe), 508–515. https://doi.org/10.1016/j.aqpro.2015.02.066

Presenting Author: Soumyashree Pani Indian Institute of Technology

Presenting Author Biography: I am currently pursuing my Ph.D. degree in the field of Floating Structural concepts at the
department of ocean engineering, Indian Institute of Technology Madras (IITM). My Ph.D.
dissertation is on 'Installation of Spar foundation using a Floating Dock'. Prior to IITM, I have done
my bachelor's and master's degree in Civil Engineering at College of Engineering & Technology (CET) Bhubaneswar, Odisha. My research interests include structural analysis, fluid-structure interactions,
hydrodynamics of deepwater platforms, coupled analysis.

Apart from academics, I also exhibited my interest in co-curricular and extracurricular
activities.

Authors:

Soumyashree Pani Indian Institute of Technology
Nilanjan Saha Indian Institute of Technology
R. Sundaravadivelu Indian Institute of Technology