Harmonic Boundary Conditions |
 
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Harmonic Boundary Conditions |
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Harmonic boundary conditions are used where the motions of nodes on the structure vary harmonically in a frequency domain regular wave analysis. They are defined in terms of a node number, degree of freedom, (optionally) static displacement, amplitude and phase. This option can be used in a regular wave analysis with one or many waves. The period of the motion is equal to the period of the regular wave. In an analysis with many regular waves, this means the period of the motion varies in the range of the analysis wave periods. The static displacement determines the mean displacement about which the harmonic motion takes place. So for example, if the preceding static analysis has a corresponding constant boundary condition with non-zero displacement, the static displacement should be consistent with this value. The phase angle is relative to the wave at the static offset position. By convention, a positive phase angle implies a phase lag, whereas a negative phase angle implies a phase lead.
•*BOUNDARY is used to define boundary conditions. Specifically, the TYPE=HARMONIC input is used to identify nodes on the structure whose motions vary harmonically in a frequency domain regular wave analysis.