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-   -   Total dynamic viscosity in turbulence models (http://www.cfd-online.com/Forums/flow-3d/113336-total-dynamic-viscosity-turbulence-models.html)

faisalbhat February 18, 2013 06:17

Total dynamic viscosity in turbulence models
 
Hi everyone,
I am doing a free surface simulation of a spillway, for which I worked out the value of ROUGH = 1.35m from the stricker-manning's corelation given in the Flow-3D manual, corresponding to Hydraulic Mean Depth of 2.5m.

I used a value of TLEN = 0.2m corresponding to 7% of 2.5m.

However, after running the simulation, the values of dynamic viscosity(max.) are in the range of 300-400 Pa-s (i.e 3x10^5 times viscosity of water).

I later tried reducing the value of TLEN, and found that a value of 5 mm limits the dynamic viscosity to 10 Pa-s. But this seems to have greatly underestimated the possible eddies that could be expected.

On the other hand, reducing the value of ROUGH to 0.2m and using TLEN =0.1m, resulted in a value of dynamic viscosity(max.) = 120 Pa-s.

I can't think of any further adjustments to ROUGH & TLEN.
Please suggest something.


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