Hi all,

I need to analyze a toiletbowl. The problem is in setting the boundary regions. The inlets, where the water is flushed into the bowl, is okay - at least, that's what I think. The outlet is located just after the siphon. The problem is on how to indicate the open area (where our butt is). I was thinking of using pressure BC, since it is subjected to atmospheric pressure and temperature, but pressure and outlet BC cannot co-exist. How do I 'tell' star-cd that the area, which consist of atmospheric air? or in other words, how do I go about approching this problem. I am assuming that toiletbowl is quite common that everybody knows the general geometry and concepts on how it works. Your help is highly appreciated!

as far as i can remember

i'm sure pressure and outlet can co-exist in the same model/domain,

the outlet has to be fixed, ie. 1.5 kg/s not split (0.5) etc,

so choose a fixed outlet with the flowrate that you know and specify it, then use pressure boundary with pressure details / atmospheric etc

it should work fine, just make sure not to use split option of outlet

ted crilly

Thanks for your comment.

However, the flow rate at the outlet is not fixed and not known a priori - it is hope to know the value from the analysis. How else can I incorporate the atmospheric details in my analysis? Please advice.

hi ,

i would have thought the volume/mass of water is fixed, for example if your toilet has a 15Litre cistern, and it flushing in 15 seconds etc. This could be setup as a fixed outlet boundary @ 1 litre/second.

You other alternative i believe would be to use multiple pressure boundaries, if your flows are not fixed, you would need accurate pressures though to predict the flows correctly etc

-ted crilly