The Planted Tank Forum - View Single Post - How do you calculate the height of water over a baffle?
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Old 05-13-2019, 01:38 PM Thread Starter
Michael Chan
Algae Grower

Join Date: Jul 2018
Posts: 54
How do you calculate the height of water over a baffle?

As the subject indicates, I'm interested in whether anyone knows how to calculate how high water will be, if flowing over a baffle / weir. I've attached an image describing the problem.

In this example, water enters the sump via the yellow pipe on the left, at a flow rate of Q cubic meters per second. It passes over two baffles, and is pumped out of the sump at the same rate.

The water in the first chamber rises to height x1. The height of the first baffle is x2. The height of the water over the sump is thus h = x1 - x2.

Assuming the depth of the sump is D, I need to calculate h.

After doing a little research online I came across Bazin's formular (http://www.aquatext.com/calcs/weir%20flow.htm) for a sharp edged weir. Does anyone with experience know if this formula is appropriate for the problem as described? The numbers is calculated seemed to be reasonable (on the order of 1.5 cm for 1000 gallons per hour over a 20 cm wide baffle). How should the discharge coefficient be selected?