Starting Conditions - Defaults

The default starting slow position is the position of the structure as originally defined by the user in Data Categories 1 to 4. The default starting slow velocity is zero in all 6 degrees of freedom.

The fast position and velocity are calculated by the program and added to the slow position and velocity to form the total position and velocity. If any two structures are connected by an articulation this calculation is omitted for those structures, the fast position and velocity are zero and the total position and velocity are the same as the slow position and velocity.

Starting Conditions with the RDEP option, but NONE in Data Category 15

If the RDEP option (Administration and Calculation Options for the Aqwa Suite) is used with a filename given on the RESTART data record (e.g FILE01), then the position in the file FILE01.EQP will override the default slow position. However, if the slow position is defined in Data Category 15 this will in turn override the data in the .EQP file. The default starting slow velocity is zero in all 6 degrees of freedom.

The fast position and velocity are calculated by the program and added to the slow position and velocity to form the total position and velocity. If any two structures are connected by an articulation this calculation is omitted for those structures, the fast position and velocity are zero and the total position and velocity are the same as the slow position and velocity.

SLP* or SLV* specified, but not POS* or VEL*

The SLP* (The SLP* Data Record - Slow Starting Positions) and SLV* (The SLV* Data Record - Slow Starting Velocities) data records define the slow position and velocity respectively. The SLP* data record will overwrite any values read in from an EQP file.

The fast position and velocity are calculated by the program and added to the slow position and velocity to form the total position and velocity. If any two structures are connected by an articulation this calculation is omitted for those structures, the fast position and velocity are zero and the total position and velocity are the same as the slow position and velocity.

This is the most usual starting condition for this analysis type

POS* or VEL* specified, but not SLP* or SLV*

The POS* (The POS* Data Record - Starting Positions) and VEL* (The VEL* Data Record - Starting Velocities) data records define the total position and velocity respectively.

If the RDEP option is used the slow position will be read from the specified EQP file, otherwise the slow position is the same as the total position. The slow velocity is the same as the total velocity.

Both POS* and SLP* or VEL* and SLV* specified

The slow position is as specified on the SLP* data record. The RDEP option is ignored.

The total position is as specified on the POS* data record.

The slow velocity is as specified on the SLV* data record.

The total velocity is as specified on the VEL* data record.

The initial values of fast position and velocity are calculated from the difference between the slow and total values.

Initial Reactions

It is not possible to specify the initial articulation reactions in Aqwa-Drift. If the positions are correct the articulation reactions will reach equilibrium in the 1st time step.