Session: 01-03-01 Hydrodynamics

Paper Number: 79718

79718 - Hydrodynamic Coefficients of Generic Subsea Modules in Forced Oscillation Tests – Importance of Structure Parts 

Preparing for the installation of a subsea module, necessary vessel- and crane capacity, as well as the limiting sea‐state for the operation must be assessed. Hydrodynamic coefficients for the structure of interest can be estimated through model tests, numerical / CFD simulations or estimations based on experience. In most cases, the coefficients are estimated manually, based on published data for similar structures and/or idealized structure elements, leading to uncertainties and rough estimates.

 

A systematic study of the hydrodynamic coefficients' behaviour for simplified subsea modules has been performed, to support the project engineers in the estimation process. Hydrodynamic coefficients are assessed by use of a nearly two-dimensional test setup. The tests are performed in forced oscillations at various amplitudes and periods, representing the forces on the module while lowered through the water column.

 

In this paper, the importance of each of the key components of the subsea modules – mudmat, protection roof and the different shapes of the process equipment inside the modules are studied at fully submerged condition. Results for the individual module elements, variety of generic contents and different combinations of these elements are presented.

 

The main findings are that for the tested modules, damping is generally the dominating hydrodynamic force. However, the presence of the content inside the modules will generally increase the importance of added mass.

 

Estimation of the hydrodynamic coefficients by summation of the coefficients for the individual structure elements generally overestimates the damping, compared to the coefficients measured for the complete modules. For added mass, estimation based on summation gives generally good results for the modules consisting of a mudmat and a protection roof, with and without the internal content. For the structures without a roof or a mudmat, the added mass estimated by summation will be underestimated.

Presenting Author: Mia Abrahamsen Prsic SINTEF Ocean

Authors:

Mia Abrahamsen Prsic SINTEF Ocean
Frøydis Solaas SINTEF Ocean
Trygve Kristiansen Norwegian University of Science and Technology (NTNU)