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Differences between HX, HXi and HXe

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We are currently reviewing an ESTRY/TUFLOW model and the question has come up when should a modeller be using 2d_bc_hx, or 2d_bc_hxe and 2d_bc_hxi.  As on this occasion the modeller has chosen to use 2d_bc_hxi thorough out the model and now has several hundred "Check 2231" messages, we know this occurs because there are no zpt points on some of the HXi lines.

So the questions we have are:

  1. When do we use these different hx types?
  2. What the benefits of each type?

 Thanks

Fil

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Hi Fil,

HXi and HXe are just different naming conventions that modellers can use to distinguish between Internal and External boundaries. HX is just if you don't mind when they're internal or external boundaries in the same layer.

Thus, it does not matter whether you call your boundaries HX, HXi or HXe, some people just like to group them separately.

The part in the 2d_bc layer that is important is the boundary type, as specified in the first attribute of the GIS layer. You can see the attributes of the layer in table 4.33 of the 2010 manual and the different types of boundaries in table 4.32.

Table 4.32 has substantial discussion on how the different boundary types work, but if you have more questions on how to use them or what to use where, just let me know.

 

You're right in saying that the check is because there are no ZP points found at those locations. In regards to how to fix this, I would investigate the Read GIS Z HX Line in the .tgc file. If you don't want to use ZP points, then remove this line. If you do want to use ZP points, then you will need to append points to those HX lines.

There is a good example on how to use ZH points on in tutorial 4 on the TUFLOW wiki.

 

I hope that helps, let me know if you need more information.

Thanks,

Rachel

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...

HXi and HXe are just different naming conventions that modellers can use to distinguish between Internal and External boundaries. HX is just if you don't mind when they're internal or external boundaries in the same layer.

...

Interestingly, I've always seen it as HXi = Isis links and HXe = Estry links! Which would be backwards from how you have it... :) Good job I don't differentiate such things in my own bc layer names.

Anyway, exactly as already said, the differentiation stops with the file names, the HX lines do the same thing either way. They apply water levels from the linked 1D model nodes to some selected 2D cells so that water may flow into (or out of) the 2D domain.

PHA

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Thanks all, just interesting to see how the HX layers naming conventions are used. Its always strange how we modellers assume that everyone uses layers in the same way. We have seen a few models that seem to use HXi with Zpts applied and then use HX without Zpts. Maybe that's how they differentiate between applying Zpts?  Although its nice to know that we are not missing something.

Thanks

Fil

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