Home > Model Components > Lines > Winch Lines > Winch Properties
Winch properties
This tab allows to define a variable reference length for the Line. The reference length of the Line is the length that the Line would take when submitted to zero external loads. Most Lines will have a constant reference length over the simulation.
Setting a Variable Reference Length allows to define cables connected to winch, whose reference length can be changed either over quasi-static steps or time within time-domain dynamic simulations.
Warning
Most lines will have a constant reference length over the simulation. The use of variable reference length option must be restricted to cables connected to winches.
Note
Simulating installation analysis with the variable reference length option avoids to define several lines with different lengths to simulate the different stages of the installation.
Variable winch line length within static analysis
This allows to define how the reference length will change during the quasi- static analysis. To activate this option, select the Length variation (from static step 0) and press the Edit button. Select the path to the text file giving the length variation as a function of the static step.
Change in reference length can be defined as a function of Static analysis steps by activating the checkbox labelled Length variation (from step 0) and pressing the Edit button to point on the text file that contains the relationship between static step number and reference length change.
The text file can be given any file extension. The file format is illustrated below :
| Example 1 |
|
The reference length is increased by * +0.50 from step 0 to step 1 * +0.50 from step 1 to step 2 * +4.00 from step 2 to step 10 | |
| Example 2 |
|
The reference length is decreased by * -10.00 from step 0 to step 10 | |
| Example 3 |
|
The reference length is varied by * +10.00 from step 0 to step 10 * -10.00 from step 10 to step 2 * -5.00 from step 20 to step 30 |
Variable spring length within dynamic (time-domain) analysis
This feature allows to define how the reference length will change during the time-domain dynamic analysis.
Change in reference length can be defined as a function of time for time- domain dynamic analysis by selecting either Constant speed or Time-dependent option in the Dynamic frame.
You may either specify constant velocity rates (in m/s) or variable velocity rates (in m/s) in a text file. The velocity indicates the pay-out or pull-in rate.
The file format for variable velocity is illustrated below:
| Example 1 |
|
The payout velocity is specified as follows: * Positive payout velocity of 0.25m/s starting at time 0s The payout velocity will remain constant, equal to 0.25m/s for all times > 0s | |
| Example 1 |
|
The payout velocity is specified as follows: * Negative payout velocity of -0.10m/s starting at time 0s (decreasing length) The payout velocity will remain constant, equal to -0.10m/s for all times > 0s | |
| Example 2 |
|
The payout velocity is specified as follows: * Variable velocity from 0.0m/s at time 0s to 0.5m/s at time 20s. Linear interpolation of the velocity is used between discrete time values. * Constant velocity of 0.5m/s from time 20s to time 40s * Variable velocity from 0.5m/s at time 40s to 0m/s at time 60s. Linear interpolation of the velocity is used between discrete time values. * The payout velocity will remain constant, equal to 0.0m/s for all times > 60s | |
| Example 3 |
|
The payout velocity is specified as follows: * Variable velocity from 0.0m/s at time 0s to 0.15m/s at time 100s. Linear interpolation of the velocity is used between discrete time values. * Constant velocity of 0.15m/s from time 100s to time 500s * Variable velocity from 0.15m/s at time 500s to 0m/s at time 510s. Linear interpolation of the velocity is used between discrete time values. * Variable velocity from 0.00m/s at time 510s to -0.20m/s at time 520s. Linear interpolation of the velocity is used between discrete time values. * The payout velocity will remain constant, equal to -0.20m/s for all times > 520s |
Note
Negative values for variable reference length are allowed and correspond to pay-in.
