# Surface Roughness Problem

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December 15, 2014, 04:23
Surface Roughness Problem
#1
New Member

RoyDaniel
Join Date: Oct 2014
Location: Taiwan
Posts: 9
Rep Power: 4
Dear All Flow 3D Modellers ,

Now I am creating models of simple open Channel which its length is 200 m with various Surface Roughness. To input Surface roughness, I just used the equation which is mentioned in the users manual "FLOW-3D Documentation, Release 10.1.0" page 409. the input symbol is k which is derived from manning's , Rh (Hydraulic adius) and Dh (Hydraulic Diameter). As my mannings are 0.035 and 0.05 and my channel size is 25.5 m width and 10 m depth, hence it yields k = 0.5886 ( for n = 0.035) and k=2.602 ( for n = 0.05). Then , I have make running for those two value of k ( surface roughness), but unfortunately both results show the same value of water depth ( please see figures on attachment files), according to my knowledge in open channel they should have different water depth result. Could anyone help me to give some comment that I may have made some mistakes in this model?
Thank you so much

Best Regards,
Roy
Attached Images
 Picture1.jpg (38.5 KB, 19 views) Picture2.jpg (45.5 KB, 15 views) Result 1.jpg (32.6 KB, 16 views) Result 2.jpg (34.4 KB, 15 views)

 December 15, 2014, 07:19 #2 New Member   Serhan Aldogan Join Date: Dec 2014 Location: Turkiye Posts: 1 Rep Power: 0 Dear Roy, Is it possible that something with physics is wrong?

 December 15, 2014, 09:29 Dear Sehran #3 New Member   RoyDaniel Join Date: Oct 2014 Location: Taiwan Posts: 9 Rep Power: 4 Dear Sehran, I think you're correct, it may have mistake with Viscosity and turbulence. Let me check first , then I will let you know. Thank you so much Sehran .. Cheers Roy,

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