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DHW Pond Flow Test 050709


The edge dams are 1 inch high (2 layers of half inch MDO).  The slots are only in the lower layer of MDO, so they are half an inch high.  There are 9 slots on S and 9 on N edges.  When the pond depth on top the FB gets over 1/2 inch, the slots become submerged orifices. 

It would be easy to cut the slots through so they are full depth, and repeat the test.

No slots in E or W edges.


The sequence of pictures shows the filling of the pond on top of the FB over several minutes.



7:07 pm -- filling at 2.5 gpm


7:08 -- filling at 2.5 gpm


7:10 pm -- filling


77:12 -- filling

7:13 -- just wetting the entire basin. 

There is flow out all slots at this point -- a first!

Some slots are flowing faster, but all are flowing.

This is the best flow distribution so far, and it might be satisfactory if its repeatable over time (time meaning months or years).



Water depths at 7:16 pm

W end           7/8 + inch

N mid            3/8    inch

NE                 1/2    inch

SE                  3/8   inch

S mid             3/8   inch

SW                 3/4   inch


The dominant flow pattern is four circles -- one each quadrant of the FB.

The NW one turns CCW

       SW                  CW

       NE                   CW

       SE                   CCW


This flow pattern is evidently caused by the "jets" from the two branches of the T flowing N and S.  I put jet in quotes because they are very leisurely "jets".

There is no apparent flow pattern toward the slots, but since they are all flowing, some of the flow has to be out the slots.   


I guess this kind of flow pattern might be OK.  The big circles keep everything stirred up, and all the time some water is exiting the slots.  The only reservation here might be that the part of the flow near the E-W centerline moves very slowly.


As you can see from the pictures the filling process first fills the W end, and then the puddle gradually works its way to the E end -- taking about 10 minutes until the whole basin is filled.  Even after its filled, it remains deeper on the W end, and seems to have no inclination to make a uniform depth.

I am unclear on whether the wetting of the whole basin would take less time if there were slots in the E and W ends or not.  End slots would allow the FB to dump more water on the deep end as its filling, and this might tend to level the FB more, and encourage filling of the high end.  On the other hand, its the increasing depth of the water in the flooded end that eventually creeps into the dry end, and slots would reduce this depth.




























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