Floating Body |
 
|
Floating Body |
|
The floating body coupled analysis capability was developed by Wood (formerly MCS), with the support of Chevron, ConocoPhillips and ExxonMobil, as part of a joint industry project on coupled analysis. The background to the initiative stemmed from remote deepwater developments, particularly West of Africa, that have demonstrated the limitations of traditional, uncoupled, design methodologies for the design of production and offloading systems.
The main features of the capability are:
•Nonlinear time domain and linearised frequency domain coupled analysis capabilities
•First and second order forces on multiple floating bodies
•Viscous damping modelling
•Hydrodynamic coupling between adjacent floating bodies
•Interface to the WaMIT hydrodynamic analysis program
More recently Flexcom has been successfully utilised in the optimisation of wave energy devices. The numerical modelling capabilities have been validated via a benchmarking study with published data from the U.S. Department of Energy (Connolly et al., 2018), and comparisons with empirical data derived from model-scale tank test facilities (Connolly & Brewster, 2017).
Further information on this topic is contained in the following sections:
•Applied Loading explains how each of the forces on the floating body are computed.
•Time Domain Analysis outlines the coupled analysis procedure in the time domain.
•Frequency Domain Analysis outlines the coupled analysis procedure in the frequency domain.
•Diffraction-Radiation Theory & Morison's Equation discusses the main differences between these hydrodynamic modelling approaches.
•Floating Body Modelling Detail discusses relatively simple (concentrated loads) and more complex approaches (distributed loads) for physically modelling the floating structure.
•Analysis Sequence presents a recommended sequence of steps for performing a floating body coupled analysis.
•WAMIT Interface describes the interface to the hydrodynamic radiation/diffraction analysis program WAMIT. Note that the WAMIT Interface is a legacy feature which has effectively been superseded by the newer Hydrodynamic Data Importer. This allows allows you to automatically import characteristic data relating to a Floating Body from a range of well-known hydrodynamic simulation packages.
•Input Formats describes the relevant input formats for the definition of force RAOs, the various force coefficients, added mass, radiation damping, viscous damping and hydrodynamic coupling coefficients.
•*FLOATING BODY is used to define a floating body and its associated properties.
•*ADDED MASS is used to define added mass for a floating body.
•*RADIATION DAMPING is used to define radiation damping for a floating body.
•*FORCE RAO is used to specify force RAOs for a floating body.
•*WIND is used to specify wind loading.
•*WIND COEFF is used to specify wind coefficients used to determine the wind loading on a floating body or moored vessel.
•*CURRENT COEFF is used to specify current coefficients used to determine the current loading on a floating body or moored vessel.
•*QTF is used to specify Quadratic Transfer Functions (QTFs) that allow the slow drift loads on a floating body or moored vessel to be determined.
•*QTF CALIBRATION FB is used to specify calibration coefficients used to scale the QTF coefficients for a floating body.
•*VISCOUS DRAG is used to define viscous drag for a floating body.
•*HYDRODYNAMIC COUPLING is used to define hydrodynamic coupling between adjacent floating bodies.
•*WAMIT is used to specify that Flexcom is to read floating body data from WAMIT output.
•*WAVE-GENERAL is used to specify miscellaneous parameters to wave loading. Specifically, the FLOAT_RAO_FORCES, FLOAT_QTF_FORCES and FLOAT_CONVOLUTION options are used to provide greater user control over the application of first order forces, second order forces, and the convolution integral procedure itself.
If you would like to see an example of how these keywords are used in practice, refer to E02 - CALM Buoy - Complex.