Rigid Seabed Profiles |
 
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Rigid Seabed Profiles |
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Rigid seabed profiles may be either flat or sloping, or defined via an arbitrary 2D bathymetry. In the default case of a flat seabed, the seabed is coincident with a plane at zero datum (the global YZ plane). If the sloping seabed option is invoked, a uniformly sloping seabed is modelled which passes through the global origin of co-ordinates. The seabed slope is specified in degrees, and a positive slope defines a seabed sloping upwards in the positive global Y direction, while a negative slope gives a seabed sloping in the opposite direction. For the most general case, Flexcom allows you to define a 2D seabed profile. This is done by specifying an external ASCII data file which contains information on the profile of the seabed surface.
Note that the Elastic Seabed model is the recommended option in Flexcom. Rigid seabed contact involves the application of boundary conditions in a direction normal to the seabed to prevent nodal penetration. In situations where intermittent contact occurs, such as in the touchdown zone of a steel catenary riser, the application and removal of restraints can result in high frequency noise with a consequent requirement for small simulation time steps. Rigid seabed contact is also further complicated by issues of Seabed Penetration and Negative Contact Reactions. In summary, the elastic seabed contact model is the preferred option, except in cases of exceptionally high contact stiffness.