July 15, 2024
Virtual Flume
Ven Te Chow’s book “Open Channel Hydraulics” is arguably the gold-standard book for hydraulic engineers-especially those of us who model open channel flow.
Wormhole Island – “What’s the Best Shape for a Wormhole Culvert?”
A recent question was posted on the HEC-RAS blog regarding the optimal shape of the SA/2D Area Connection alignment for a wormhole culvert – in particular, whether a “Z” shape or “S” shape would be preferable. My apologies in advance for the drawn-out response, but I’ve had this question come up a number of times in class and thought I’d post some of my whiteboard sketches along with some random thoughts on the topic:
“Z” or “S”?
If you draw a “Z” shape, the order in which the vertices are entered will determine the direction of flow (always oriented from left to right looking downstream in HEC-RAS). The following image shows four different ways to draw a “Z”-shaped connection along with the associated orientation of flow that will be assumed in HEC-RAS. In the case of a wormhole culvert, flow could enter the “wormhole” at any of the green arrows (or at any point along each of the adjacent faces) and exit along any of the faces indicated by the red arrows. Wormhole culvert inlets and outlets typically wouldn’t be located along the diagonal segment of the “Z”, but directional arrows are shown along those segments to illustrate how the orientation of flow is preserved along the entire shape:
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Comments
Heidi Lane
on June 1, 2017We have been working on a model that is over 650 square miles. We randomly keep getting an error that we cannot seem to figure out. We are under a time crunch and I am hoping you can help me. the model takes 18 hours to run, so when we get the error, we lose another day of work while we are trying to calibrate. The error is "Error renaming file: XXXX.p66.tmp.hdf to XXXX.p66.hdf… Path/File access error" Has anyone seen this before or have a solution where I do not have to run the model again? It says it finished the simulation and then gives that error. I cant figure out why or when or what is different. Please help! Thanks!!
Chris Goodell
on June 1, 2017Not saying this is the cause of your error, but I have seen that error before when RAS projects are saved deep in your file directory structure (i.e. you have a really long directory path). Suggest moving your RAS project to a new folder much closer to the root of the drive you are using and see if that helps.
Anonymous
on June 3, 2017I have seen this happen on simulations that take a long time to run and are placed on server and not the local machine. I also place long simulations on the local machine.
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