OrcaFlex Manual - Orcina

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User Interface, Results
remain, so you can adjust the model and re-run the simulation and the graphs will then be redrawn. Graphs are
automatically deleted if the object that they refer to is removed, for example by loading a new model.
Range Jump Suppression
Just as it does for Time History and XY Graphs, OrcaFlex applies range jump suppression for range graphs of angles.
3.9.10 Offset Graphs
These graphs are available only after a multiple statics calculation has been done and only for the offset vessel. The
following variables are plotted against offset distance:
Restoring Force
The magnitude of the horizontal component of the total force applied to the vessel by the attached Lines or other
objects. Note that this force is not necessarily in the offset direction.
Vertical Force
The vertically downwards component of the total force applied to the vessel by the attached Lines or other objects.
Yaw Moment
The moment, about the vertical, applied to the vessel by the attached Lines or other objects.
Worst Tension
The largest tension in any segment of any Line connected to the vessel.
To obtain an Offset Graph:
� Select Offset Graph on the Results form.
� Select the offset vessel.
� Select the offset direction required.
� Select the variable required.
� CLICK the Graph button.
3.9.11 Spectral Response Graphs
These graphs are available only if you have run a response calculation wave. The graph is only available once the
simulation has been completed.
The graph plots the calculated RAO for the selected variable on the Y axis and wave frequency on the X axis.
To obtain a Spectral Response Graph:
� Select Spectral Response Graph on the Results form.
� Select the object required.
� Select the variable required (see Selecting Variables). More than one variable can be selected.
� CLICK the Graph button.
3.9.12 Extreme Value Statistics Results
There is often a requirement to predict the extreme responses of a system, for example to determine the likelihood
of a load exceeding a critical value that may lead to failure. Such values are needed when using standards such as
DNV-OS-F201 and API RP 2SK.
OrcaFlex can estimate extreme values for any given result variable by analysing the simulated time history of the
variable using extreme value statistical methods. You may, for instance, perform a mooring analysis in an irregular
sea-state and then estimate the maximum mooring line tension for a 3-hour storm.
The statistical theory for this estimation is well-established and is described in the theory section. The procedure is
essentially this:
� You select the statistical distribution to be used to model the distribution of extremes. See Data below.
� OrcaFlex estimates the distribution model parameters that best fit the simulation time history of the variable.