[Libmesh-users] Applying Traction Boundary Condition by Using site_time_Derivative or Penalty Method

[Nikrouz <nik...@gm...>]

Dear All libMesh uses,

I want to apply traction boundary condition on two of the surfaces of my 
geometry. As far as I know, There are two methods

for defining such a boundary condition: *Using penalty method* and 
*side_time_derivative method*. I have a couple of questions:


1- Which method is more straightforward for defining boundary 
condition(traction) in libMesh?

2- I have searched different examples in libMesh and I could not find 
any case that has used side_time_derivative method(for example defined 
in fem-ex3). Is there any example illustrates how can I call the 
mentioned method in the code? Where should I call it?How?

In the example fem3 example, the method need two inputs:

*bool ElasticitySystem::side_time_derivative (bool request_jacobian,**
**                                             DiffContext & context)*

*FEMContext & c = cast_ref<FEMContext &>(context);

   // If we're on the correct side, apply the traction
   if (c.has_side_boundary_id(BOUNDARY_ID_MAX_X))
     {
*

*......*


How and where should I use this method in the code to have a traction 
boundary condition?

Thank you everybody!