[sourav90]

I can easily visualise the flowType in a nozzle geometry like in the attached figure 3. When I searched on this topic (extensional flow or extensional stress), there are important practical implications like in -

• polymer mixing: https://www.sciencedirect.com/scienc...64391X00800641
• red blood cell deformability: https://www.researchgate.net/profile...crochannel.pdf

There is a functionObject called flowType that comes with both OpenFOAM-v2012 & OpenFOAM-8. The v8 provides the description:

PHP Code:

> foamInfo flowType
File
    /opt/OpenFOAM/OpenFOAM-8/src/functionObjects/field/flowType/flowType.H

Description
    Calculates and writes the flowType of a velocity field.

    The flow type parameter is obtained according to the following equation:
    \verbatim
                 |D| - |Omega|
        lambda = -------------
                 |D| + |Omega|

        -1 = rotational flow
         0 = simple shear flow
         1 = planar extensional flow
    \endverbatim

Examples: cannot find any tutorials using "flowType" 


On this topic there are a few threads, but nothing very illuminating.

• flowType
• does anyone know what does flowType do?

The polymer mixing example used a software called BEMflow that provides the "particle flow number" in the range 0 to 1 (rotational, shear, elongation), through (probably) a particle tracking method. In contrast, OPenFOAM provides the flowType that ranges between -1 to +1 (rotational, simple shear, planar extensional). For my application (3D bio-printing i.e. flowing hydrogel with living cells through nozzles), it would be very nice to know what portion of the fluid is experiencing how much of stress (shear & extension).

Now, my question is –
Is there a way to decouple extensional stress and shear stress & quantify these two parameters individually in OpenFOAM?


I'm not sure if this is the correct forum (maybe in programming & development?) but any kind of input would be very welcome