[Cecco]

Hi,
I have simulated the flow into a centrifugal fan.
Now I have plotted the Eddy viscosity ratio (Eddy viscocity/dynamic viscosity) in order to get the thickness of the boundary layer (see the figure).
I surprised to watch that the EVR increase also outside the boundary layer.
I was expecting to see EVR=0 adjacent to the blade, then an increasing inside the boundary layer and then again EVR=0 ouside the boundary layer.

Is it strange? What do you think about? This would be that between two blades the flow is a continuing mixing?

Thanks in advance

[JuPa]

Curious: what value of eddy viscosity ratio will give you the thickness of the boundary layer?

The eddy viscosity ratio is simply the ratio of turbulent to laminar (molecular) viscosity. If you have values of eddy viscosity ratio outside of your boundary layer then it just indicates some sort of laminar or turbulent regime.

To be honest I don't see why this is strange.

[Lance]

As far as I know the eddy viscosity ratio should have its maxium value close to the middle of the boundary layer, at least for external flows. In the free stream the eddy viscosity is governed by the turbulence at the inlet, but it shouldnt necessarly be zero.

Also, your color range is [0,1] which is normally too low for RANS models. Try something on the order of [0,100] or more.

[Cecco]

@ RicochetJ:
I expected to see the same of this one: http://www.computationalfluiddynamic.../2013/04/2.png

probably it means this is laminar outside boundary layer, while mine is turbulent so explain the ratio doesn't come back to zero outside.

@Lance:
You can see image below with EVR btw [0;70]. I plotted [0;1] just to underline the bondary layer.

Thanks guys.

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I have no much experience in internal flows. Do you think it is a normal way to work (i mean in a turbulent regime) for a tangential blower (max volume flow rate 70 m3/h)?
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