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verakurniawan

Assigning boundary condition in nodestring

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Hi

I am currently working on RMA2 numerical module to analyse whether there is any effect on water velocity and depth of waterbody near shore due to a bridge.

I tried to create a nodestring in one element (*I assume this one element is one of the bridge piers and would like to assign a boundary condition of zero velocity on the element). After creating a nodestring around the element, I could not assign the boundary condition.

There is always an error message popped out : "Selected string(s) not boundary string"

Anyone could help?

Thank you.

Regards

Vera Kurniawan

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RMA2 boundary conditions are intended to be use to tell how water moves into and out from the mesh. It isn't possible to define a boundary condition that is zero velocity in an element that is part of the mesh.

A couple alternatives are:

1. Change the material of the element to disable. This will force the element to be draw (unused) and all flow will move around the element.

2. Make the roughness in the material super high. This will cause a bunch of energy loss in the cell so that the velocity will be severely impeded. This option will show the element has having water in it but very little conveyance.

I hope this helps.

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Hi Jones

Thanks for your prompt reply. I really appreciate it.

So do you have any idea on how to intepret bridge piers in my mesh? Because my objective to use this RMA2 is to analyze whether there is any effect on the water velocity and depth due to the bridge existence.

I tried to follow your first suggestion, by choosing one element, and then I assign the material type as "disable". But somehow I could not run the model, this message appears "stop depth convergence exceeds 25.0".

I tried to enable the material that disabled before and rerun the model, I do manage to run the model.

I believe there is something that I miss out here.

I look forward to hearing from you. Thanks!

Cheers

Vera Kurniawan

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Hi,

The problem that you are having is that RMA2 is sensitive to wetting/drying issues. You can disable the element and use the steering module to try to get your run to converge or use a more stable numeric engine.

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Hi Jones

Do you have any tutorial on steering module that I can try on?

I refer to your last sentence on your last repy, are you saying that RMA2 is not stable enough to generate results for my problem? Any numeric model to recommend on analyzing the effect of bridge piers on water velocity and depth?

Thanks.

Merry Christmas and Happy New Year 2012!

Cheers

VeraKurniawan

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Hi,

I'm sorry I don't think we have a tutorial on the steering module. How to operate it should be in our help. If you are using SMS 10.1, the help is on the wiki (xmswiki.com). If you are using SMS 11.0, the help is distributed with SMS and you can get to it from the menu command (in web menu?).

RMA2 is likely stable enough to get the answer if you use the steering module or similar techniques. It is easier to get a solution to converge when running in steady state mode. However, there are more stable numeric engines available for SMS. My favorite numeric engine is TUFLOW. It is very stable even with rapid wetting/drying, runs in transient mode, has a very powerful model setup approach, very good error trapping and reporting, and is very versatile since you can use it in rivers, oceans, and even urban with storm drain systems. My second choice for this would be SRH2D which uses the generic model interface with SMS 10.1 (getting it setup to work with SMS 11.0 is currently in progress). SRH is a finite volume model that is very stable. You can learn more about these models by contacting our sales team.

I hope that this helps.

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Hi Jones

Unfortunately, I am still using SMS 8.1. Is there any difference on the steering module application between version 8.1 and version 10.1?

Can I still refer to xmswiki.com to learn how to use steering module in my SMS 8.1?

Thanks.

Cheers

Vera Kurniawan

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I don't remember what changes have taken place since SMS 8.1. That is quite an old version. I imagine most of the information on the steering module on the wiki would apply to SMS 8.1.

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