EDEM

Bulk Data Entry Defines the parameters required to activate coupling between OptiStruct and EDEM.

Format


(1)	(2)	(3)	(4)	(5)
EDEM	`ID`
	`CONTROL`	`PERIOD`	`FILTER`
	`COUPLING`	`TYPE`	`ID`	`LABEL`

Example


(1)	(2)	(3)	(4)	(5)
EDEM	100
	`CONTROL`	0.1	0.15
	`COUPLING`	SURF	2	Surf_2

Definitions


Field	Contents	SI Unit Example
`ID`	EDEM coupling definition identification number. No default (Integer > 0)
`CONTROL`	Flag indicating that the coupling control parameters are to follow.
`PERIOD`	OptiStruct-EDEM coupling time-step. This is the simulation time between two consecutive synchronization points between OptiStruct and EDEM. 6 <Blank, 0 < Real < TTERM> Default = TTERM/100.0
`FILTER`	Filtering interval by a time period. This indicates the filtering interval for smoothing the imported forces from EDEM. <Blank, Real > PERIOD> Default = PERIOD
`COUPLING`	Coupling interface flag indicating that parameters to define the coupling interface are to follow (this continuation line can be repeated as required to define multiple coupling surfaces).
`TYPE`	Entity type used to define the coupling interface. SURF The coupling interface is defined using a surface (SURF) and the corresponding Surface ID is input via the `ID` field. No default
`ID`	Identification number of the entity defined in the preceding `TYPE` field. No default (Integer > 0)
`LABEL`	Label of the coupling surface geometry which is generated by OptiStruct and sent to EDEM during the initialization step (optional). Default = coupling_<edemid>_interface_<surfid> (Character String)

Comments

OptiStruct-EDEM coupling allows coupling the advanced structural analysis capabilities of OptiStruct with bulk and granular material interaction capabilities of EDEM. You can simulate and analyze the interaction of materials such as coal, soils, grains, and so on with deformable surfaces. It is currently only supported with Explicit Dynamic Analysis (NLEXPL) subcases.
OptiStruct transmits nodal coordinates and velocity to EDEM, while EDEM sends nodal forces to OptiStruct during the coupling, which occurs at each synchronization point after a time defined as the coupling time-step specified by the PERIOD field.
It is important to make sure that the Unit Systems defined in both OptiStruct and EDEM are consistent. For OptiStruct-EDEM coupling runs, it is mandatory in OptiStruct to define the UNITS Subcase Entry to identify the model units. It is your responsibility to make sure that this identified units system is consistent with the units system defined in EDEM.
The coupling interface surface is defined only in OptiStruct and the first equipment material data defined in the EDEM model is used as the material data for all coupling surfaces defined by OptiStruct. The coupling surface(s) defined by OptiStruct are exported to the EDEM model during the initialization of coupling. Additionally, the particle type, material, interaction physics data should be defined in the EDEM model.
In OptiStruct, the interface surface material data is used to calculate the deformation behavior of surface, while in EDEM, the interface surface material data (defined under Equipment Material) is used to calculate the contact forces during the interaction between the particles and the surface.
To initiate an OptiStruct-EDEM coupling run, the Coupling Server should be started in the EDEM GUI, and the EDEM model should be loaded into the EDEM Creator GUI. Then check to make sure that the “Current Time” is set to 0.0 in EDEM Creator GUI. Subsequently, before the OptiStruct run, include the path to *\EDEM\lib in the EDEM installation location to $PATH environment variable. Then run the OptiStruct model which contains the EDEM Subcase and Bulk Data Entries.
The coupling between OptiStruct and EDEM involves synchronizing the simulation at specific intervals to exchange relevant data (OptiStruct provides the Nodal coordinates and Nodal velocities to EDEM, and EDEM provides the Forces to OptiStruct at synchronization points). The figure below provides more information on how the synchronization takes place.

DT_user

User-defined time between synchronization points specified in the PERIOD field, also identifies the OptiStruct-EDEM coupling time-step

DT_os

OptiStruct time-step

DT_edem

EDEM time-step

DT

Actual coupling time-step during the run

t_n

The time at the n^th synchronization point

F

Forces provided by EDEM

X

Nodal coordinates provided by OptiStruct

V

Nodal velocities provided by OptiStruct

1-9

Numbers represent the steps which take place sequentially.

Figure 1.

The user-defined PERIOD value is DT_user, which requests the synchronization points. For each solver OptiStruct and EDEM, the synchronization occurs at the OptiStruct and EDEM time-steps that are closest to and immediately after the requested synchronization point (requested by DT_user).
Note:
- The actual value of DT can be slightly different between OptiStruct and EDEM (as the individual time-steps of each solver can be different from each other).
- The value of DT can also vary slightly during the course of the analysis within each solver (as the time-steps of each solver can vary adaptively during the course of the solution).
- It is not recommended to have the value of PERIOD (DT_user) lower than either of the individual solver time-steps (DT_os or D_edem). In case the value of PERIOD is set lower than one or both of the individual time-steps, it is reset by OptiStruct at cycle 2 of the Explicit run based on the below formula:
  DT_user = max (DT_user, 2*DT_os, 2*DT_edem)
  This reset is performed only once during the coupling run, and in the rare case that the value of DT_user falls below the value of either of the individual solver time-steps subsequently during the course of the coupling run, the synchronization occurs at the next/upcoming solver time-step.