Wave Theory Indicator
Specifies which wave theory to use to compute the water particle velocities and accelerations. The wave theories available are:
Standard Airy Wave
This is also known as linear wave theory. Discussion of this theory can be found in the previously mentioned references.
Modified Airy Wave
This is a modification of the standard Airy theory which includes the free surface effects due to the wave. The modification consists of determining a depth scaling factor equal to the depth divided by the depth plus the surface elevation. Note that this scale factor varies as a function of the location in the wave train.
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Standard Stokes 5th Wave
This is a 5th order wave theory, also discussed in the previously mentioned references.
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Modified Stokes 5th Wave
This is a modification of the standard Stokes 5th theory. The modification is the same as applied to the Airy theory.
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Stream Function Wave
This is Dean’s Stream Function theory, also discussed in the previously mentioned references.
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Modified Stream Function Wave
This is Dean’s Stream Function theory, modified to directly consider current in the wave solution.
Stream Function Order
When the Stream Function theory is activated, the solution order must be defined. Typical values for the stream function order range from 3 to 13, and must be an odd value (see API-RP2A figure).
Water Depth
Defines the vertical distance (in units of length) from the still water level the surface to the sea bed.
Wave Height
Defines the height of the incident wave. The height is the vertical distance in units of length from the wave crest to the wave trough.
Wave Period
Defines the time span (in seconds) for two successive wave crests to pass a fixed point.
Wave Kinematic Factor
Because the two-dimensional wave theories do not account for spreading, a reduction factor is often used for the horizontal particle velocity and acceleration. Wave kinematic measurements support values in the range of 0.85 to 0.95. Refer to the applicable offshore codes before using this item.
Wave Direction Cosines
Define the direction of wave travel. These fields are unit-less and follow the standard software global axis convention.
Wave Phase Angle
Defines the position of the wave relative to the starting node of the piping system. The phase angle is a measure (in degrees) of position in the wave train, where 0 is the wave crest, 180 is the wave trough, and 360 is the following crest. Because the wave propagates over the piping structure, each point in the structure experiences all possible wave phase angles. One analysis technique specifies the wave phase at the system origin, and then the phase at each node point in the model is determined. From these exact phase locations, the water particle data is computed from the wave theory.
Alternatively, a conservative engineering approach is to use the same phase angle usually zero for all points in the model. This technique produces higher loads; however, the extra conservatism is warranted when given the unknowns in specifying environmental data.