ask for setting a drain node constraint?

Hi, I got a question, please let me know how to set a drain node constraint? Since I do know how to set, now water is only removed from the groundwater flow system. in fact, I put drain in 1st kind (head) constraint value, max & min as drain's max elevation & min elevation, after running it shows very high water level.

Anyboday can give a suggestion? Thanks

Hi,
As far as I know, if you're using 1st kind boundaries (head), then they can only be constrained by flux, so putting the min and max elevations in the constraint won't make sense.  To set up the 1st kind boundary as a drain (outflow only) then set the head value at the drain elevation and set up the constraints so that the qmax = 0.  This should ensure the boundary allows water only to flow out of the model, not in.  If the calculated head at this node becomes lower than the head you have specified for the drain, then it will become inactive.

A quicker way to do this is to input the boundary as a seepage face type - that does the same thing.  You need to change first kind BCs to seepage face via the boundary condition options.

Hope that helps,

Gemma

Thanks Gemma, Would you please show the direction of setting seepage face? Thanks~

Hi Mingo88,

To set up a seepage face boundary, you need to get into the "Flow Boundaries" menu.  You need to change the option below the mesh inspector to "options" instead of "assign".  If you then click on the "Head (1st kind)" button in the top left then you can choose the option "seepage face".  You'll need to switch back to "assign" again, before you can start adding the seepage face nodes to the model.

Hope that helps.  If it doesn't make sense then let me know and I can send a screenshot to explain it.

Gemma

Dear Gemma, Thanks alot for the help. Would you please send me a screen shot to email:duckula1204@hotmail.com. Thanks in advance!