[Luis Partida]

You need to have a look at the HTab parameters of the structure, the internal and bounding manning’s values as well. By adding any information in the Htab parameters that states (recommended), this helps dial in a smooth convergence at the structure

[Luis Partida]

To all who are interested in actual definitions see the below youtube video released the other day entirely about Ineffective Flow. As Chris said, this is a very subjective topic in modeling.

[Luis Partida]

I saw your response to the topic previously posted but i will respond here. I would digitize a reach in ArcMap and try importing it into RAS Mapper just to see if the process works. If this doesnt work, try multiple things such as building a new model, adding a new geometry with a different name. Make sure your reach being imported has a simplified geometry. Meaning, if your reach has 5 million vertices then of course it will hang up on you. Try simplifying your input reach in a GIS platform then reimport within RAS

[Luis Partida]

Steven,

That is up to you as the modeler to determine. To answer your question, no, not within RAS or a HEC-18 spreadsheet can you do this. But if you receive a D50 at a depth of 10 ft and the calculated scour = 12 ft, then you must obtain a new D50 from a range greater than the depth calculated until it no longer supersedes your D50 sample depth.

[Luis Partida]

The optimization process should have gotten you there. The rule when using optimization is that you are supposed to take the resultant flows from the optimized flow file in Standard table-1 and enter those as flows in the steady state flow editor. THEN you have to turn optimization OFF with the new flows and re run the model. If this doesnt work and you know the amount of flow diverting in the original model you could just add them as static reductions within the steady state flow editor

[Luis Partida]

You can complete this in RAS Mapper as your first step in a geometry build.

Open RAS Mapper and on the left expand Geometry. Then select your geometry right click and edit. Then expand the geometry until you see “Reach” then right-click on this and you will see and import option

[Luis Partida]

This is most likely the user entered “distance to US cross section and deck”. In full 2D the bridge will generate 2 dotted red lines representing cross sections 1 and 4 in a typical bridge modeling rules. In practice, for 2D bridges, I like to place the distance as close to my bridge as possible OR at least make sure that the dotted line ends up at a cell triangulation (this can be done via breaklines)

[Luis Partida]

I am not sure I know of any modeling scenario that would benefit from that small of cell sizes both resultant-wise and efficiency-wise

[Luis Partida]

You just have to know based on the computations options and tolerances what is an unacceptable error and stop it when you see that. Remember though the error that is showing is JUST the error at 1 specific location (XS/Cell) and that specific time. There are times when i will see an error go above 1.0 and i let it continue because globally that error may be just fine.

[Luis Partida]

If it is 1D, I would increase the roughness coefficient of the US and DS cross sections. If it is 2D I would also adjust the associated cells roughness coefficient assuming they were small enough to not impact adjacent cells.

Another option could be to model the weir as a cross section with Lids. In this instance you could correlate an exact cross section with a weir and associated roughness coefficient. You could also add a minor loss coefficient to the model in the Table of the geometry data editor.

[Luis Partida]

The corps put out a 2 page document on this exact question.

https://www.hec.usace.army.mil/confluence/rasdocs/r2dum/latest/optimize-your-computer-for-fast-computations

[Luis Partida]

Ah so this is a 2D model…I think the direction of flow in terms of the structure and cell faces can be easily fixed with breaklines. Similar to the methods in Harris county requiring a breakline be placed at the edge of the 1D2D interface which will not actually enforce a cell break but it will orient cell faces perpendicular to the structure. As far as which equation to use, I have always had the understanding that unless you are predicting excessive variances in velocities i.e. a damn breach analysis hence the removal of the convective terms in the simplified equation

[Luis Partida]

The easiest way to import gridded data is to use HEC MetVue to convert the .nc file to a DSS file and using that file for use in HEC-RAS

[Luis Partida]

That means your station number does not fall in line with the upstream and downstream cross section ID’s. The number selected must be in between. i.e. US XS = 50 DS XS =49 Inline Structure must be something like 49.5 or any number between the two

[Luis Partida]

Hey Scott, the first thing that comes to mind for me is to model the slat fence as a cross section with lids and either add contraction and expansion losses or add a minor loss to the cross section. This is of course assuming it is perpendicular to flow

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