Analysis Type |
 
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Analysis Type |
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Clear can perform three types of interference analysis, all of course using the same basic procedure just outlined. In the first of these, the program produces a snapshot of minimum distance between structures, in the second a timetrace of minimum distance is produced, while the third analysis type calculates statistics of minimum distance. Each of these is now further described.
A Clear snapshot is just that, a snapshot of the minimum distance between two structures at a particular time you specify. Specifically, in a snapshot analysis Clear calculates for each point on the first element set the minimum distance between it and all of the points on the second element set. This is then plotted against distance along the first element set. A Clear snapshot analysis is normally used when postprocessing a Flexcom static run.
A Clear timetrace analysis on the other hand is normally used to postprocess the results of a Flexcom dynamic run. The output in this case is a time history of the minimum predicted distance between the two element sets. Specifically, at each analysis time Clear calculates the distance between each pair of points on the two element sets. The minimum of all of these distances is then the Clear output at that time.
A Clear timetrace analysis can be used with both regular wave and random sea Flexcom dynamic runs. However, for the random sea case the actual minimum distances may be of less interest than the statistics of minimum distance, and that is the rationale for the third Clear analysis type, the statistics analysis.
The procedure in a statistics analysis is as follows. For each point on the first element set, Clear calculates time histories of distance between it and all of the points on the second element set. From each of these time histories the program then calculates the mean value and the standard deviation of distance between the points.
The mean value and standard deviation are conveniently combined in a single quantity referred to here as the non-dimensional clearance. This is simply the ratio of the two parameters, or
The non-dimensional clearance can be used to determine the likelihood or probability of interference occurring between two points. The smaller the value of non-dimensional clearance, the more likely is interference between them, because the mean distance between the two points is small in comparison to their relative motions. So in a Clear statistics analysis, the program calculates for each point on the first element set the minimum non-dimensional clearance between it and all of the points on the second element set. This is then plotted against distance along the first element set (the same format as used in a snapshot plot). The output file in this case lists the minimum non-dimensional clearances together with the corresponding mean values and standard deviations.
•*ANALYSIS TYPE is used to specify the Clear analysis type and related parameters.