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Mark Prater

specifying weirs in ADCIRC

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I have several inane questions about specifying weirs using SMS (my current version is 10.0.6).

* Is a "weir" in SMS the same as an "interior barrier boundary" in ADCIRC?

* How to I create an ADCIRC weir? I could not find any information in the xmswiki pages.

My attempts to create a pair of closely aligned feature arcs, distributing equal numbers of vertices in each, and trying to assign the "weir" attribute have all resulted in the error message "Weirs can only be created between two nodestrings with equal number of nodes. 2118386775 nodestrings selected." So, I gather that my approach is incorrect.

Thanks in advance for any suggestions.

-- Mark

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Hi Mark,

I'm not sure how weirs relate to interior barrier boundaries.

Weirs have to be defined in the mesh module on nodestrings rather than feature arcs in the map module. Sorry about the confusion. You create one at each side of the weir and they have to have the same number of segments.

The fact that it reports 2118386775 nodestrings selected sounds like a bug. I'll have my QC team look into this and see if we can get some documentation on using ADCIRC weirs.

Cheers,

Rusty

I have several inane questions about specifying weirs using SMS (my current version is 10.0.6).

* Is a "weir" in SMS the same as an "interior barrier boundary" in ADCIRC?

* How to I create an ADCIRC weir? I could not find any information in the xmswiki pages.

My attempts to create a pair of closely aligned feature arcs, distributing equal numbers of vertices in each, and trying to assign the "weir" attribute have all resulted in the error message "Weirs can only be created between two nodestrings with equal number of nodes. 2118386775 nodestrings selected." So, I gather that my approach is incorrect.

Thanks in advance for any suggestions.

-- Mark

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Hi,

There are a number of issues associated with the use of wiers in ADCIRC. They are internal barriers but with the addition of pipes running through them so that whenever the pipes are submerged a flux passes through them related to the head across the barrier. This is obviously what you want :) Unfortunately, unless this has been updated in the most recent versions of ADCIRC, the code used to generate the flux is incorrect. The flux that ADCIRC calculates is L^3/T and then it applies this at each node and then integrates along the element edge which results in a total flux of L^4/T, which is clearly wrong. I inserted a parameter which is based on the element length which basically divides the calculated flux by this length so that after integration it is about right, although obviously not perfect. As a simple test I ran a model that had a wier with 3, 1m diameter, pipes in a simple box of 40kmx10km. The wier split the box into 2 20kmx10km regions and I forced one end with an M2 tide of about 3m. The enclosed basin bit managed to have an M2 of about 2m. Those pipes were moving a large amount of water. The grid of course was course and therefore each pipe was moving a lot of water.

I hope that I have made it clear(ish). The problem can be overcome but it will require a bit of tinkering with the code. Also if you want to run it in parallel and you use adcprep then check that adcprep actually accepts wiers, IBTYPE=5,25, as he version that I had, v46.19, didn't.

If you have any other questions on wiers then just ask and I will try and answer them, especially as whenever I ask questions on them no-one else seems to know and I have spent about 18 months messing about with them. It would be good to have some-one else using them :)

Ian

PS Incidently Rusty, who would know, is right about setting wiers up. You just create 2 nodestrings and then select the two and choose wier as the boundary condition. Make sure you check the bathymetric depths along each node so that you don't put the pipe too low.

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