Range graphs show results as a function of arc length along a line or a turbine blade. Three different forms of range graph are available, as described below.
Envelope range graphs
These show the values the variable took, during a specified part of the simulation. In particular:
- The graph shows the minimum, mean and maximum values that the variable took during the specified part of the simulation, with the exception that the line clearance range graphs only show the minimum value. Static state graphs show the value of the variable in statics. For frequency domain dynamics, the output is based on synthesised time histories.
- Effective tension range graphs have extra curves showing the segment Euler load and the allowable tension value (as specified on the line types data form).
- Bend moment range graphs have an extra curve showing the maximum permitted bend moment (EI / minimum bend radius specified on the line types data form).
- Curvature range graphs have an extra curve showing the maximum permitted curvature (the reciprocal of the minimum bend radius specified on the line types data form).
- Bend radius range graphs have an extra curve showing the minimum bend radius specified on the line types data form.
- Stress range graphs show the allowable stress (as specified on the line types data form).
- Range graphs for code check results have an extra curve showing the maximum allowable value.
- A standard deviation curve can also be added to a range graph – to do this edit the graph's properties (by double clicking on the graph) and set the standard deviation curve's visible property (by default the curves are not visible). Two curves are then drawn, at $\textrm{Mean}\pm x\sigma$, where $x$ is a user chosen value and $\sigma$ is the standard deviation. The standard deviation is calculated from all the samples that lie in the simulation period chosen for the graph.
Std. dev. range graphs
These show the standard deviation of the result, as a function of arc length along the line or turbine blade. These graphs are available for both time domain and frequency domain dynamics. For time domain, the standard deviation is calculated from the time history over the specified period. For frequency domain, the standard deviation is calculated as the square root of the zeroth moment of the result spectrum.
Extremes range graphs
These show the most probable maximum (MPM) of the dynamic part of the result occurring in the storm duration, as a function of arc length along the line. These graphs are available for frequency domain dynamics only.
To obtain a range graph:
- Select the range graph result type.
- Select the desired range graph type. This can be envelope, std. dev. or extremes.
- Select the object, which must be a line or turbine object.
- For a turbine object, select the turbine blade.
- Select the arc lengths. This can be the entire line or turbine blade, a selected arc length range, or a selected section range.
- Select the period.
- Select the variable.
- For the frequency domain extremes range graph type, set the storm duration required.
- Click the show button.
Time domain range graphs are displayed in graph windows and they are updated during the simulation. You can therefore set up one or more graph windows at the start of a simulation and watch the graphs develop as the simulation progresses.
For both time and frequency domain analyses, when you reset the simulation the curves are removed but the graph windows remain. This means that you can adjust the model, re-run the simulation and the graphs are updated with the data from the new simulation. Graphs are automatically deleted if the object to which they refer is removed, for example by loading a new model.
Range jump suppression
For time domain results, OrcaFlex applies range jump suppression for range graphs of angles.
Special considerations for lines that use line feeding
The behaviour of range graphs for lines that use line feeding depends upon the requested period:
- The static state and instantaneous value periods are both associated with a single instant in time. Accordingly, results for nodes on the instantaneously active line are shown on the range graph. The arc lengths shown on the x-axis of the range graph correspond to the node actual arc lengths.
- For any period that represents a time duration, e.g. whole simulation or a specified period, points are shown on the range graph for any node that remains at its reference arc length for the whole of that duration. Results for nodes whose actual arc length differs from its reference arc length during this time period are not shown because the arc length serves as an independent x-axis value that cannot be allowed to vary in the period over which the y-axis values are calculated.
