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Andrew Chapman

Pit channel flows

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Hi,

I'm testing a proposed flood mitigation pipe and want to maximise inflow from the 2D domain to reach pipe capacity. I want the pipe to control the flow and not the pit channel. Would it be sufficient to simply specify the pit channel with an area larger than the pipe?

I realise this can easily be tested in TUFLOW, but am wanting to understand how flow into a circular or rectangular pit is calculated.

Regards,

Andrew

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Hi Andrew

An alternative approach would be to connect a SX point (within the 2d_BC layer of your model) to the 1d pipe.

The sx connection will allow flows to enter the pipe from the 2d domain with the pipe controlling the discharge and not any pit channel.

Hope this helps

Thanks

David

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Hi Andrew,

If you connect the pipe manholes directly to the 2D, you may find water does not enter the system if the manholes are located near the centre crown of the road (ie, the inlet is elevated above the gutters).

For the lateral pipes connecting the pits to the trunk, don't make the diameter too large as you will introduce too much storage into the system and attenuate flow.

For the pits themselves, you will need to increase the width and height, but also increase the inlet capacity chart (eg, orifice coefficient to 1, depending on how you model pits) so that they inject flow.

I've found that it is sometimes hard to get flow to the pits from 2D due to gutter definition. What I do is buffer pits by a 3m radius, then burn this circle into the grid, lowering the z-pts by 200mm around the pit.

Cheers,

Paul.

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Hi Paul,

With regards to "burning" the 3 m radius circle, is this applied to all pit inlets regardless of width or number?

Also, what would you set the "Conn_No" attribute to?

I'm trying to model a network consisting of "R" pit types, but the flows appear to be small at some particular locations.

Regards,

Danny

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