Learning Forum

[Luigi0]

Hi,

I am trying to simulate laminar flow in microchannel. My analysis is a 2.5 D analysis, with one element along the width (Z axis).

The dimension are: Length (along X) = 3 mm; Height (along Y) = 150 um; width (along Z) = 15 um. Boundary conditions are mass-flow inlet, pressure-outlet. I expect that the profile of the velocity (X component) should be parabolic, but at the inlet it seems not. Why?

1) Velocity X contour (inlet)

[Karthik Remella]

Hi,nYou will not get a parabolic profile because the flow is not yet fully developed. When you apply a mass flow rate BC at the inlet, it will assume a uniform velocity at this boundary (except at the walls), which is what you are seeing in your plots. If you wish to input a parabolic profile at the inlet, I suggest that you use the Fluent expressions at the inlet and specify the inlet velocity likewise.nThank you.nKarthikn

[Luigi0]

Thanks nI am working with ansys 19.1, so the expression option is not present. The only possibility is to use a udf.nThanksn

[DrAmine]

So use and UDF for that. The manual does contain good examples how to accommodate this via DEFINE_PROFILE.n

[Karthik Remella]

To add - you could also run a streamwise periodic case on a small section of your pipe with your exact inlet diameter. You can write the profile files for your inlet conditions and use these profile files. Just wanted to throw this idea into the pool.nThanks.nKarthikn