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-   -   Void Array Index Warning (https://www.cfd-online.com/Forums/flow-3d/81724-void-array-index-warning.html)

jfasl November 4, 2010 15:21

Void Array Index Warning
 
I'm trying to run a casting simulation but keep getting this message in the warnings and errors...

warning: void array index exceeds maximum nvor = 28467
at cycle = 12938, time = 0.20113E+01
void region volumes and pressures may be incorrect

I have noticed that my fluid volumes are really off in my casting, anyone know why this happens and what to do to alleviate it?

MuxaB November 4, 2010 23:54

It looks like it is going unstable. Can you look at the results? Does the flow look reasonable?

what version are you running?

By itself this message is not critical, just telling you that it cannot keep track of all voidss in the domain and will join some of them to stay within the maximum allowed number of voids. But the fact that you have so many of them is an indication of a severe breakup of the fluid.

jfasl November 5, 2010 10:11

I can look at the results, they look reasonable flow wise, but the volumes I'm getting are way off for filling. I'm running version 9.4.1.

MuxaB November 6, 2010 20:39

Quote:

Originally Posted by jfasl (Post 282311)
I can look at the results, they look reasonable flow wise, but the volumes I'm getting are way off for filling. I'm running version 9.4.1.

How can flow look reasonable but volume be way off? They must both be off.

What kind of filling problem is it? high-pressure die casting, gravity?

jfasl November 8, 2010 16:16

It is a gravity casting, the flow PATTERN looks fine, but I used force windows to measure the volume in each cavity of my mold, and the volumes that the windows are showing are not at all what they should be. Basically, the graphics are showing the cavities full, but after calculating the volume of each cavity and comparing it to what the force window says it is, they dont matchup at all. I was wondering if that error had something to do with it.

MuxaB November 8, 2010 23:13

Quote:

Originally Posted by jfasl (Post 282663)
It is a gravity casting, the flow PATTERN looks fine, but I used force windows to measure the volume in each cavity of my mold, and the volumes that the windows are showing are not at all what they should be. Basically, the graphics are showing the cavities full, but after calculating the volume of each cavity and comparing it to what the force window says it is, they dont matchup at all. I was wondering if that error had something to do with it.

I don't think it is an error in the force window integration of fluid volume. What about the total volume in the domain? Does it make sense?

jfasl November 9, 2010 11:09

I'm getting extra volume residing above the cavities after they fill. I tried to measure and match the fluid volume at the beginning (using the preprocessor and the "report" message "fluid at time zero") to the volume of the cavities, but even after doing that I'm getting extra slop on top after the simulation has completed.

MuxaB November 15, 2010 13:31

Quote:

Originally Posted by jfasl (Post 282759)
I'm getting extra volume residing above the cavities after they fill. I tried to measure and match the fluid volume at the beginning (using the preprocessor and the "report" message "fluid at time zero") to the volume of the cavities, but even after doing that I'm getting extra slop on top after the simulation has completed.

You mean it overfills? Assuming you are using the velocity bc and the flow rate is constant, there may be a couple of reasons your estimate of the filling time is off. One is the cumulative volume error - the loss or gain of total fluid volume due to the approximations of the numerical scheme. The total volume error is reported during the simulation. You can extract it from the flsgrf file too (in general history data).

The second reason is that not all cells m ay be100% full. If the F-packer is on (default), then most cells should be at least 99% full. However, some may have much less fluid, e.g., the last cells in the cavity to fill. The f-packer tries to 'pack' them but it takes some time during which fluid can spill.

Another possible reason is the open area at the inlet is not what you think it is. The pre-processor reports open areas at mesh boundaries in prpout.


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