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diffusion coefficient not constant?

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Old   August 24, 2017, 05:09
Default diffusion coefficient not constant?
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Hello everybody,

I just simulate the residence time distribution of tubes (laminar flow).

I am using OpenFoam and the scalarTransportFoam solver (Here is the diffusion coefficient (DT) the moluḱular diffusion coefficient divided by the fluid density).

If I compare my simulations results with measurements I find out that the diffusion coefficient (DT) is not constant. With a larger volumetric flow i need a larger diffusion coefficient (DT) to fit the two curve. Is the diffusion coefficient a function of the velocity? I have not found a model in the literature which describes this effect.

Anyone a idea or some literature?

best regards
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