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cameronParticipant
in 5.0.4 you will be able to do so.
cameronParticipantIn your case it is probably best to set it to pressure/weir for high flow. Energy would be ok if the bridge is overtopped by a lot of water or if you have a perched bridge where the overbank area is a lot lower than the top of bridge.
cameronParticipantThat depends on the situation. You don’t want the active flow area of each cross-section changing significantly from one cross-section to the next as it causes a shock to the system. For unsteady modeling it is a lot more difficult to deal than than steady and can require multiple ineffective areas.
Water cannot expand faster than 2:1 to 3:1 and can’t contract faster than 1:1. This is important around bridges and other areas that expand or contract quickly.
cameronParticipantThe orientation of the cells can make a difference to the results. I have tested this and found it does impact results, but can take a lot of time to get the cells in the correct orientation. One thing to note that you get one N value per cell face so if a cell covers both channel and overbank, it might using the overbank and not the channel n value.
Each study is different so you would need to test to see how much of a change you can get.
Simple answer:
If the cells are left North-South, the model should run faster as HEC-RAS solver simplifies some things. Once you change the cell shape, HEC-RAS solver cannot simplify things and calculations take longer.cameronParticipantWhat does the profile of the lateral weir look like and what are the ground elevations where the mesh starts? Since the flow is going into a 2D mesh, the terrain in the 2D mesh is controlling the tailwater conditions.
I would think that an all 2D model would be far more stable than a 1D/2D model for a dam breach.
cameronParticipantcheck the time step you are using and the flow area change between cross-sections.
cameronParticipantCheck your ineffective areas. You don’t want the active top width changing between cross-sections to rapidly as that will also cause models to blow up.
February 28, 2018 at 4:54 am in reply to: Using Lateral Weirs with Dam Breach and 2D Flow Areas #11219cameronParticipantTake a look at the example 2D models that come with HEC-RAS. There are multiple dam breach examples where they do all 2D, 1D/2D, and storage area to 2D.
cameronParticipantYou could also set a minimum flow so the cross-sections don’t dry out. What do your htab parameters look like?
February 28, 2018 at 1:23 am in reply to: Using Lateral Weirs with Dam Breach and 2D Flow Areas #11217cameronParticipantYou can do an all 2D model with a dam breach and no 1D cross-sections. Why do you need a 1D model through the dam breach?
cameronParticipantThe lidded cross-section approach would cover multiple cross-sections so you would control the slope through it.
cameronParticipantEach grid cell has to have their property tables calculated before running the model for the first time. If any changes are made to the mesh, the tables need to be updated and will do so when you try to run it again.
cameronParticipantgo and delete the hdf file it is trying to create and then run it again.
You could also try upgrading to 5.0.3
February 10, 2018 at 12:07 am in reply to: Difference between “depth max extent (max)” and “depth (max)” #11177cameronParticipantdepth max extent causes any cell that gets wet to appear as fully wet. All dry parts of the cell get the threshold depth that you specified when you created the depth max extent.
cameronParticipantSwitch over to full momentum it you get a lot of errors your timestep is too high. One minute timestep is high. In general, your timestep should be small enough that water from one cell does not skip the next cell during the timestep.
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