LAUNCH SIMULATION LAUNCH SIMULATION

To initiate a launch analysis, the following command must be issued:


     LAUNCH, -OPTIONS

where the available options are:


     -RESTART, RESTART_TIME

     -MAXTIME, MAX_TIME

     -MAXOSCILLATIONS, NUM_OSCILLATIONS

     -TSTEP, DT0, DT1, DT2

     -WINCH, V0

     -QTIP

     -QSEP

     -NOYAW

     -NO_CAPSIZE, YES/NO

     -SAVE, SAVE_INCREMENT

     -STORE, STORE_INCREMENT

     -OLD, YES/NO

If -RESTART is specified then this is a continuation of a previous launch analysis and integration will be restarted at RESTART_TIME. Four of the options control the termination of launch simulation. For the options -MAXTIME and -MAXOSCILLATIONS, MAX_TIME is the final simulation time, and NUM_OSCILLATIONS is the number of oscillations allowed after separation. The time step increment during the simulation is controlled with the -TSTEP option, where DT0, DT1, and DT2 is the increment during sliding, tipping and after separation, respectively (defaults are 0.75 seconds for all 3). The -WINCH option is used to specify V0, the initial winch velocity, in feet or meters/second (default=1 feet/second). -QTIP causes the simulation to quit after the jacket begins to tip, and -QSEP causes the simulation to quit after the jacket separates from the barge(s). The simulation will terminate if any of the above conditions are met, whichever one occurs first. Using -NOYAW provides an additional force applied at the trailing end of the jacket to eliminate any relative yaw between the barges and the jacket until the jacket tips.

Normally, if a body has a roll or pitch angle greater than 90 degrees, the program will stop the simulation anticipating that something occurred that was not intended. If the -NO_CAPSIZE, YES option is used, no checking for capsizing will be performed.

During the computation of a time domain simulation, the data is stored in the database. The user has some control over this data storage with the options -SAVE and -STORE. The state of a configuration will be written to the database at STORE_INCREMENT increments of computed steps. If the option -STORE is omitted, the data will be written every computed time step. In other words, a default of STORE_INCREMENT equal to 1 will be used. Even though the data is stored in the database, it will be inaccessible unless the database itself has been saved. Control over how often the database is saved is provided by the -SAVE option. If this option is omitted, the database will be saved fifteen times during the time domain simulation. If the option is used, the database will be saved at SAVE_INCREMENT increments during the time domain. In other words, if -SAVE 30 is used, the database will be saved once every 30 computed time steps.

Historically, launch has used a predictor/corrector integration scheme. With Rev 7.07, this scheme is used until separation and then the integration is changed to a Newmark method. To keep the old method, one can use the -OLD YES option.