Steady vs Unsteady flow results

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Steady vs Unsteady flow results

Arthur Barboza
Hi everybody,

I am having a little trouble while running steady and unsteady flow simulation.

In the steady state, my results match with observed WS elevations all along the reach. But, if I run an unsteady simulation (constant flow and boundary condition exactly the same as in steady state), two "waterfalls" appears in the middle of the reach, giving me WS elevations way higher than observed data.

Does somebody have a clue about what might be happening? I know HEC-RAS solve steady/unsteady simulation with different routines and equations, but I wouldn't expect such a big difference in Froude number and others hydraulic properties that affects the WS elevation.

Thanks,

Arthur

 
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Re: Steady vs Unsteady flow results

cameron
Did you adjust the Htab parameters?  Are there any structures in the model? Do the hydrographs at any of the structures look funny?  Have you tested different timesteps?  Do you get any errors when running in unsteady?
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RES: Steady vs Unsteady flow results

Arthur Barboza

Thanks a lot Cameron! I solved it by adjusting the HTab Parameters, they were default.

 

Thanks,

 

Arthur Prado Barboza

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De: cameron [via HEC-RAS Help] [mailto:[hidden email]]
Enviada em: Wednesday, June 14, 2017 12:36 AM
Para: Arthur Barboza <[hidden email]>
Assunto: Re: Steady vs Unsteady flow results

 

Did you adjust the Htab parameters?  Are there any structures in the model? Do the hydrographs at any of the structures look funny?  Have you tested different timesteps?  Do you get any errors when running in unsteady?


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