/SHSUB

Engine Keyword

/SHSUB - Activate New Sub-cycling

Description

Allows to activate new sub-cycling option, for which Isubcycle =2 in the /ANALY RADIOSS Starter option should be specified.

Format

/SHSUB/NSH print/NSH ctrl

Data

Description

NSH print

Defines the listing output frequency (in the output file or .out file in new extension) for the shell elements, over sub-cycles (that is to say over the only cycles for which internal forces of shell elements are computed).

NSH ctrl

In some cases where the sub-cycling time step falls down, shells may need to be computed each cycle and this process may require to be more CPU time-consuming than deactivating sub-cycling.

Default = 1000

Comments

1.	It is possible to make a run with sub-cycling and to switch after restart to a non sub-cycling (standard) computation, and reciprocally.

2.	NSH print defines the listing output frequency (in the output file .out in new extension) for the shell elements, over subcycles (that is to say over the only cycles for which internal forces of shell elements are computed).

With a negative value, the printing is also done to the standard output.

This additional output to the .out file for RADIOSS Engine will be written with frequency NSH_print over subcycles:

in case of /DT/SHNOD (nodal time step for SHELL and SH3N elements sub-cycling):

NC	T DTSUB NODE SUBCYCLE

•	NC = Current cycle number

•	T = Current time

•	DTSUB = Time step for sub-cycling

•	NODE = node_ID

•	SUBCYCLE = Sub-cycle number

At this time, the node_ID gives the time step for sub-cycling.

else:

NC	T DTSUB SHELL or SH3N SUBCYCLE

•	NC = Current cycle number

•	T = Current time

•	DTSUB = Time step for sub-cycling

•	SHELL or SH3N shell_ID or sh3n_ID

•	SUBCYCLE = Sub-cycle number

At this time, the shell_ID or sh3n_ID gives the time step for sub-cycling.

3.	NSH ctrl has been introduced with the /SHSUB keyword, since in case of the sub-cycling time step falls down, shells may need to be computed each cycle and this process may become some more CPU time consuming than deactivating sub-cycling.

Indeed, shells and 3-nodes shell elements are computed each Dt time step, corresponding to the Dt stability time step for shells: sub-cycling time step is a stability time step related to shells.

NSH ctrl: if NSH ctrl cycles are computed without sub-cycling, that is to say if shell elements are computed each cycle during NSH ctrl consecutive cycles, the sub-cycling method will be deactivated by RADIOSS Engine.

4.	Shells and 3-nodes shell elements are computed each Dt time step, corresponding to the Dt stability time step for shells: sub-cycling time step is a stability time step related to shells.

5.	In case of element time step (/DT/NODA is not specified in the RADIOSS Engine Input deck):

Dt = Tsca x minover_shells_and_3-nodes_shells (lc/c)

where, lc is the characteristic length and c is the sound speed of the related material.

Parameters of /DT/SHELL will be considered, especially for the value of (default value is 0.9). Parameters of the sub-options /DT/SHELL/Keyword3 will be normally considered.

6.	In case of nodal time step (/DT/NODA is specified in the RADIOSS Engine Input deck).

Dt = Tsca x minover_nodes_connected_to_shells sqrt(2 x m/Ksh)

where, m is the nodal mass, Ksh is the stiffness corresponding to the connected shells, and is the value given in /DT/NODA; but may be changed by using /DT/SHNOD.