Learning Forum

[Vaishnavi]

Hello Team!

I have completed few successful runs of wave-structure interactions. I can generate wave and get converged solution. I set a solution monitor for pressure on the surface where fluid ends - I called this as FSI (suppressed solid starts from this edge). My problem is that I repeated the same run with increasing and decreasing the number of time steps. The x-y plot of the value of pressure over the FSI interface shows a series of values which do not match at all if the time step is changed. Whats more surprising is that, when I tried getting the max. vertex values over the FSI surface over a period of time, it doesnt match either! I want to know if my simulation is completely wrong? how can changing time step alter the values completely! In one trial it is +3000 and another it is -2000 something. Pls help!!

 

 

This is my geometry, but the results that I have shown are from the 2D analysis. 

I intend to find the location of max pressure on the structure. any leads on this?

 

[DrAmine]

Forget about the FSI part: did you change the number of time steps or time step size?

[Vaishnavi]

Hi!

I added the number of time steps yes.

I havent altered the time step size.

I am writing the files of xy plot of total pressure. Should I also be looking at solution monitor of vertex/maximum of total pressure?

Whoch file should we be referring for observing the solution? My aim is to know the position and value of maximum pressure on a surface.

[Rob]

Check for convergence too. Also, how did you start the model?  Run without the structural part to see how it's behaving.  Taking facet maximum can be misleading with poor mesh/convergence as you can pick up rogue spikes that give weird results. 

[Vaishnavi]

hello rwoolhou,

 

The issue seems resolved. I require to see solution monitor for a longer duration of time and ignore the initial data as it is the flow development time.

I wish to get the value of force on the structure. So should I be selecting the vertex maximum of integral of pressure values? If I see solution monitor I get to see pressure wrt time on the surface. but when I see x-y plot, does this give average of pressure values when I click "Vertex or facet maximum" What should i select for obtaining correct results?

 

[DrAmine]

To get the force of the structure it is better to monitor/quantify the force. 

[Vaishnavi]

Okay. But then what do with get when we click on x-y plot under results under solution window? If I write or plot value of pressure against direction vector (x-0, y-1, z-0), does it mean I get the value of pressure (on selected surface) with Reference to y coordinate?

[DrAmine]

You get the value if pressure along that coordinate on the selected boundary. You can export the values of pressure and shear stress on the surface via generic ASCII export.