[hunt_mat]

Originally Posted by LuckyTran

Oh sorry, that's right you have only a diffusive flux in the lagrangian formulation. Now just keep in mind that you can set the flux to 0 without invoking any differencing scheme. This is the way.


The other way is to set the du/dx to zero and then interpolate it onto the face flux. This way introduces discretization errors and inconsistencies.

I sort have done that. I've simply set the first and second equal, and that's fixed that little issue.

[hunt_mat]

As you can see a lot of the issues I've had have gone away after my rather crude fix the issue at h=0 is now working. The issue is now twofold: The value at h=1 seems to be erratic. I use a stress-free condition at h=1, but there still seems to be a spike.

The other issue is about parametrisation.

[FMDenaro]

How do you introduce the Neumann BC into the scheme?

[hunt_mat]

Originally Posted by FMDenaro

How do you introduce the Neumann BC into the scheme?

Via the flux.

[FMDenaro]

Originally Posted by hunt_mat

Via the flux.

In your figure I see only the density, I need to check also the velocity plot and all the details about your BC.

[hunt_mat]

Originally Posted by FMDenaro

In your figure I see only the density, I need to check also the velocity plot and all the details about your BC.

The velocity looks wrong as it should be zero at h=0. I could force this in the algebraic equations.

This is graph is for the edges, rather than the cells. I used interp1 in Matlab to obtain the values, and I got a NaN at h=0 for some reason.

[hunt_mat]

I have the majority of the problems sorted but one issue I think is the length of the rod in question. The way I calculate it is by using the mass in each cell as being constant. and if dh represents the mass of a typical cell, then I use:

where dX represents the new length after compression. The new cell locations are then given as

X=[0 cumsum(dX)]

Then the length of the rod is given as X(end).

As you can see, it hasn't gone down much and I wondered if this was the code or just a poor choice of parameters.