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-   -   Viscous resistance coefficient in physical v-model (http://www.cfd-online.com/Forums/fluent/50054-viscous-resistance-coefficient-physical-v-model.html)

AL December 15, 2008 15:52

Viscous resistance coefficient in physical v-model
 
Hi,

According to FLUENT 6.1 user's guide when we use physical velocity model then, FLUENT assumes that the inputs for the resistance coefficients are based upon well-established empirical correlations that are usually based on superficial velocity. Therefore, FLUENT automatically CONVERTS the inputs for the resistance coefficients into those that are compatible with the physical velocity formulation. Now, suppose that we have a material with permeability of 1e-5 and porosity of .1, what is the input for the resistance coefficient (1/alpha) when using physical velocity model? I made a simple example of flow through a simple porous channel (1mm*70 mm) with velocity inlet (4m/s) and pressure outlet (0pa) boundary conditions. Alpha was presumed 1e5 and porosity (.1). What is so surprising is the report of pressure at the inlet-mid. For the physical model I get 2384 pa and for superficial model 105 pa. I think for the same pressure drop with physical velocity model I should change inputs for alpha( but how). Could any one give me an idea and also answer to my first question? Regards.



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