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RMA2 - Triangular vs recatangular elements


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I'm developing an RMA-2 model of a river reach and will be simulating large flood events in steady state. The river is approximately 3000 feet wide and has levees on each side to contain flood waters. We would be simulating the model in steady state. Question is, what are the advantages and disadvantages of using triangular elements versus rectangular elements?

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That is a good question and I'll do my best to answer it.

One of the issues to consider is runtime. A quad in one element can cover the space of two triangles with the same output locations (roughly). The fewer elements will execute quicker.

I understand but I don't have any papers or proof that QUADs run more stable than triangles. I'm not sure what situations this applies to.

Another issue is stability. RMA2 can be sensitive to wetting and drying. If you have a well defined bank, you can easily align quads in the direction of the bank. This makes it possible for the wetting/drying algorithm to peel off layers that are thin parallel to the bank.

I generally aim to use quads if the direction of flow is well defined and align them with the direction of flow and use triangles in areas where the flows are not as well defined.

Cheers,

Rusty

I'm developing an RMA-2 model of a river reach and will be simulating large flood events in steady state. The river is approximately 3000 feet wide and has levees on each side to contain flood waters. We would be simulating the model in steady state. Question is, what are the advantages and disadvantages of using triangular elements versus rectangular elements?

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