Rectangular Canal with kinks (local energy losses)

[Anonymous]

Hello

I am not sure, whether HEC Ras is the right instrument for what I’m trying to do but I think it should be possible. My system is quite simple: I have a bending rectangular canal, it has 4 45° kinks. Now I did create the canal and run the simulation (Fr is slightly above 1 so supercritical). What Im not able to simulate are the 4 kinks. I expect an energy loss of about 0.1 x velocity head each 45° angle (this is my assumption).

How can I add the local energy loss to my model? (Also, do you think 0.1 x veloctiy head is a valid assumption?)

Thanks a lot 🙂

Carmen

[Anonymous]

For steady flow:

From the flow data editor under options select known changes in WS and EG. You can add an extra loss that is a coefficient multiplied by the velocity head. I would suppose you would want to use at least 0.1.

If you wanted more accuracy you could use 2D flow.

[Anonymous]

Hi Jarvus

Thank you so much, it works!

One more question you might be able to answer: I have supercritical flow. I understand, that the disturbancies (I have several, 4 kinks as mentioned) then only affect the downstream part. But: when I run the simulation with supercritical flow only the last local energy loss is taken into account at all. Is this a mistake of the program or do I misunderstand the hydraulics?

Do I need to enter a time series in order to run it 2D? (I only need a constant flow of 45m3/s.)

Best wishes, Carmen

[Anonymous]

For super critical flow the effect of the extra energy loss should be visible immediately downstream.

If you only see a change at the very downstream end that seems questionable.

Make your coefficients a little bigger and check if you are getting a difference immediately downstream of each kink. If you are not then you may have a data mistake.

I have not used the coefficients with super critical flow but I would presume they should work.

For 2D flow you can just do a long time series with a constant flow. A bigger issue is that you will have to create a terrain. If you are brand new to this that could be some work.

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