The Activity field allows you to set the suppression state of the Ocean Environment object. Set it to Suppressed if you want to exclude the object from the analysis.

The ocean geometry is defined by the Ocean Mean Water Level (mean water surface Z position with respect to the global origin) and the Ocean Depth (vertical distance from the Ocean Mean Water Level to the seabed).

Figure 8.28: Ocean Geometry

The material properties of the seawater are defined by the Ocean Density and Ocean Viscosity. The latter is only used where the global structural coefficients are set to vary by Reynolds number (see Structural Coefficients). The default values of Ocean Density and Ocean Viscosity are set to 1025 kg/m³ and 0.00108 Pa s, respectively, which are applicable for seawater at a temperature of 20°C and a salinity of 0.035 kg/kg.

The vertical acceleration due to gravity is defined by the Gravitational Acceleration property, which defaults to the standard value of 9.80665 m/s².

These coefficients apply to all submerged line bodies in the Geometry.

Default Member Flooding controls whether tubular line bodies are considered to be flooded by the surrounding seawater or not. (An internal fluid for tubular line bodies can also be defined with Component-Based Variation or Pipe-in-Pipe objects.)

Added Mass Coefficient in Y (CaY) and Added Mass Coefficient in Z (CaZ) control the ratio of added mass to displaced mass, where the added mass is the mass of seawater that moves with the line body in a dynamic analysis, in the two directions perpendicular to the line body axis.

Buoyancy Force Ratio can be used to adjust the buoyancy of line bodies relative to the buoyancy force based on the line body displacement and the defined Ocean Density. This may be useful when accounting for external pipe features that are not explicitly modelled.

Drag and inertia coefficients are also defined for all submerged line bodies. These coefficients can be set to vary by vertical Z position, or by the Reynolds number of the relative fluid flow around the line body; set Tabular Input Options to Z Level for the former, or Reynolds Number for the latter.

Depending on your selection, you can then set Coefficients by Depth or Coefficients by Reynolds Number using the tabular data input. The independent variable is entered in the first column, followed by the Drag Coefficient in Y (CdY), Drag Coefficient in Z (CdZ), Drag Coefficient in X (CtX), Inertia Coefficient in Y (CmY) and Inertia Coefficient in Z (CmZ). All coefficients are defined in the local line body axes. Click the   icon to add more rows to the table. Duplicate entries of Z Level or Reynolds Number are ignored.

You can choose to Include Soil-Pile Interaction. Setting this option to Yes allows you to specify a Soil-Pile Data File, which may be a Mechanical APDL macro (.mac) file or some other APDL code snippet. The specified file is included in the solver input file via the /INPUT command.

Examples of soil-pile interaction macros may be obtained through a Service Request on the Ansys customer site.

The following options are used to define wave and current conditions for the simulation.

Wave Theory

In Static Structural and Transient Structural analyses, you can define a Wave Theory to be used in the calculation. The available options are:

A more complete description of these wave theories is provided in Hydrodynamic Loads in the Mechanical APDL Theory Reference .

In a Modal analysis, or where the imported Geometry contains only solid bodies, water motion is not permitted. In a Harmonic Response analysis, the wave information is entered via the Harmonic Wave Load object. Harmonic Response analyses are restricted to periodic waves (Airy, Wheeler, Stokes, Stream Function or User Defined Wave).

For Static Structural and Transient Structural analyses, if the imported Geometry does not contain any line bodies but does contain surface bodies, you can only choose between No Water Motion or Diffracted. If the imported Geometry does contain line bodies, you are free to select from any of the wave theories listed above.

Wave Spectrum

Where the Wave Theory is selected as Random, Shell New Wave or Constrained, an additional Wave Spectrum option is shown. This is used to select a wave spectrum to which the combination of linear waves is fitted. The available options are:

Wave Case Definition

For any Wave Theory other than No Water Motion, the Wave Case Definition tabular data input is used to define the current and/or wave properties for the calculation. The number of rows in the Wave Case Definition table will match the Number of Steps defined in the Static Structural or Transient Structural Analysis Settings; a separate load case may be defined for each step of the analysis.

Figure 8.29: Wave Case Definition Tabular Data Input

All wave theories require a Current Definition at every step. Use the drop-down menu to select from any of the Ocean Current objects that you have defined in your analysis, or choose Disable Current to exclude current effects for that step.

For all wave theories that include wave motion, a Wave Direction may be defined at each step. This sets the direction that the incident wave travels towards, relative to the direction of the global X axis.

For wave theories of Airy, Wheeler, Stokes, Stream Function, Diffracted and User Defined Wave, the wave properties are specified by the Wave Period, Wave Height and Phase Shift. Setting the Wave Period or Wave Height to zero will disable the wave motion for a given step. For a Stream Function wave, the Stream Function Order may also be defined; for a User Defined Wave, the Wave Length may be defined.

For Random, Shell New Wave and Constrained waves, the wave property definitions depend on the selected Wave Spectrum. These are summarized in Table 1.

Where applicable, in the User Defined Spectrum column of the Wave Case Definition table, you should use the drop-down menu to select from any of the User Defined Spectrum objects that you have defined in your analysis.

Additional Options

For periodic waves (Airy, Wheeler, Stokes, Stream Function or User Defined Wave) the Force Application option allows you to set the position/orientation of elements relative to the wave surface for the force calculation. The available options are:

The Wave Details Output option indicates that a description of the defined wave should be written to the Solution Information. For non-periodic waves, this includes details of the wave components.

For Airy, Wheeler, Stokes and Stream Function waves, the MacCamy-Fuchs Adjustment option allows you to include or exclude a correction to the structural inertia coefficients to account for diffraction effects. This is relevant for larger diameter line bodies in shorter wavelength waves.

For Random, Shell New Wave and Constrained waves:

For Random and Constrained waves:

For Shell New Wave and Constrained waves, the Time Offset and Position Offset set the time and position offsets at which the maximum wave crest will occur.

For Shell New Waves the Wave Spread Angle is used to compute a wave spreading factor to modify the horizontal wave kinematics for near-unidirectional seas, while the Use Evolving Wave option may be used to modify the component wave phase angles over the simulation.

Where the Wave Theory is set to Diffracted, additional pressure mapping options are displayed. Use the Hydrodynamic Data File selection dialog box to choose an Aqwa-generated hydrodynamic database (.ahd) file, which will be used to determine hydrodynamic loads on line body elements. Where the imported Geometry includes surface bodies, use the Scoping Method and Geometry/Named Selection options to define the surfaces onto which the hydrodynamic pressures will be transferred.