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Using the Interpolation Function to Pass Boundary Conditions

Posted Jul 19, 2011, 4:09 p.m. EDT Computational Fluid Dynamics (CFD), Microfluidics, Modeling Tools & Definitions, Parameters, Variables, & Functions Version 4.2 1 Reply

Erin Koksal
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I am a new COMSOL user, and I was hoping to understand how to properly use the interpolation function to transfer boundary conditions between models. I am working on a microfluidic model which is too large to mesh and solve in a single step, and so I need to break the model into segments, solve them individually, and pass the solution values from the outlet of model 1 to the inlet of model 2. (etc.)

After creating a global interpolation function, I set the inlet velocity values of a second model (with the exact same geometric dimensions) to the outlet values exported from the first model. The model runs and solves, but the solution is unexpected for several reasons:

1) The average velocity over the outlet surface of model 1 is more than 1000x greater than the average velocity over the inlet surface of model 2.

2) The highest velocity magnitude for model 2 was in the lower left corner of the conduit, not centered as in model 1.

A very simple model and the data file used for interpolation are both attached (the excel file was saved as a tab-separated text file). The data file was creating by exporting the velocity data from the outlet surface of model 1.

Any advice would be tremendously appreciated.

Thank You!
1 Reply Last Post Jul 20, 2011, 1:37 p.m. EDT
Erin Koksal
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Posted: 1 decade ago Jul 20, 2011, 1:37 p.m. EDT
In the model Geometry settings, the Length Unit needs to be set to meters (not mm, not feet, not angstroms, just m) for the Interpolation Function to work correctly.

The units can still be defined as desired when creating geometry by adding the units in brackets: for example, to create a 1.5 mm width block, set "Width: 1.5 [mm]"

Many thanks to COMSOL Support!
In the model Geometry settings, the Length Unit needs to be set to meters (not mm, not feet, not angstroms, just m) for the Interpolation Function to work correctly. The units can still be defined as desired when creating geometry by adding the units in brackets: for example, to create a 1.5 mm width block, set "Width: 1.5 [mm]" Many thanks to COMSOL Support!

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