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DHW Pond Flow Test 050710


More tests on the foam board flow distribution.

All at 2.5 gpm.  Edge dams 1 inch high for all.









Text Box: Previous test -- slots had lids.







First Test - Full Depth Slots:

Configuration is identical to the last (050709) test, except that all of the slots have been cut to full depth.

See sketch above.






Text Box: on this test, the slots were cut to full depth as shown above.
Text Box: Foam Board

The end result was very similar to the 050709 test.

The flooding on the top of the foam board happens in the W first, followed by a slow advance of the water toward the E.  The progression toward the E might have  been a little faster, but this could be because the top of the foam board was damp.


The end depths are deeper on the W end just as for the 050709 test.


Final Depths:

E        0.5 inch

W        0.8 inch (almost over edge dam in places)

S        0.4 inch

N        0.4 inch


This is the same as previous test -- deepest on W, deep on E, with a hump in the middle at the N and S positions.



Second Test -- Add Slots in W dam:

Same setup as above, but added two full depth slots in the W dam edge (where the water depth has been the greatest, and where the first flooding occurs).


This did result in a shorter time to flood the full foam board -- about 4 minutes, rather than as much as 10 minutes.

It also resulted in the final depth on the W end being slightly less:


W dam            0.75    inch

SW               0.625

S                0.25

Se               0.5

NE               0.5

N                0.25

NE               0.5


While this lowered the water a bit on the W dam, it also lowered it at the N and S points.


Its also bothersome to me that the "fix" (W end slots) are aimed at fixing the specific symptoms of this foam board -- another board might be different.  I suppose I should have tried adding slots on both the E and W ends, which would have been symetric.


Third Test -- Moved pump outlet toward E:

On the previous tests, the pump outlet was a bit toward the W end of the board.  I wanted to see if moving it closer to the E end would make it flood the E end first.



The results was that the E end did indeed tend to flood first, but by the time the whole surface was flooded and in equilibrium, it was back to being deeper in the W end as before.  That is, the offset pump outlet was not causing the deeper flooding in the W end -- it must have to do with the distortions in the foam board itself.





Fourth Test -- Four Spout Hub:



This is my cut at your suggestion to change the pump outlet so that its in the center of the foam board and has four outlets, one aimed toward each quadrant of the board.


This definitely results in a more uniform initial flooding process.

The end water depth distribution is ends up being similar to previous tests -- deep in W, fairly deep in E, and shallow in the N - S middle line.


The flow pattern seems to be pretty good -- as bit slow on the ends.


Overall the best so far.


Tried a variation with a 6 lb weight on the hub to see if this would take the hump out.  Did not seem to have much effect -- perhaps a very slight increase in depth at the N and S slots.




The fairly vigorous jets tend to get the flow moving, and create circular patterns that keeps the water on top somewhat mixed up, except at the E and W ends which have slower flow.

Hub is made from a short piece of 4 inch ID Schedule 40 PVC -- cap is MDO and is glued on with PU glue.






This configuration is the best so far, and it might be OK.  But, its bothersome that it still has an uneven depth of water in the pond on top the foam board.  This seems to be due to some warping of the foam board.  In this case the warping is not bad enough to keep it from working, but who knows what it might do over time?  Or, how the next piece of foam board might warp.  It would be very frustrating to get the thing all put together, and then take a look at it a month later and find that the foam board has warped more or differently, and needs to be re-configured.

It would be nice to find something more robust.

Text Box: slots







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