Radioss Implicit/Explicit

Altair Forum User

Hello,

 

I know that Radioss is a solver which has both Implicit and Explicit solving scheme. I want to know when I solve a problem in Radioss which scheme is being used. Is there any way to select the method i.e. implicit or explicit when solving a problem?

 

Thanks,

Datta 

Altair Forum User

Hi Datta,

In RADIOSS, both implicit and explicit time-integration schemes are available for the user. In an explicit scheme, velocities and displacements are obtained by direct integration of nodal accelerations. With this approach, the cycle time step is often small. Therefore, for static or slow dynamic computations where the duration of the study is long, many cycles are necessary to carry out the simulation. An alternative to explicit method in such cases is the implicit time-integration scheme.  Not all explicit features are available for implicit analysis. In loading only Concentrated load /CLOAD, pressure /PLOAD, and gravity load /GRAV are available.

The user should provide the required control cards to activate the implicit scheme. When the RADIOSS solver is running an implicit analysis it will be shown in the out file as  ** IMPLICIT OPTION USED **. The keywords required to launch a RADIOSS implicit analysis are defined in the Engine file and begin with /IMPL. In the Help Menu, please search for Activating an Implicit Analysis which will show the keywords required for an implicit analysis in RADIOSS. Examples are available in our Help Menu on implicit analysis. One tutorial and model files are attached along for your reference.

 

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Altair Forum User

Thank you Gopal and George for the reply. 

 

I want to see the difference between implicit and explicit. I have a model, where I have a chasis having an initial velocity striking RWALL. I am very confused how to activate the implicit analysis as there are so many cards  with /IMPL. 

Can you suggest me an appropriate card so that I can run an implicit analysis for my model?

 

Thank you,

Datta

Altair Forum User

Datta,

This simulation which is a chassis having an initial velocity striking the RWALL is an explicit analysis. 

In the Help Menu, please search for Activating an Implicit Analysis which will show the keywords required for an implicit analysis in RADIOSS based on the requirements of the user. A similar engine file is attached where control cards are activated for a nonlinear implicit analysis in RADIOSS. 

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Altair Forum User

Thank you for the reply George.