# Problem with phase changes viscosity layering

**URL:** <https://community.geodynamics.org/t/problem-with-phase-changes-viscosity-layering/3291>\
**Category:** General\
**Created:** [February 27, 2024, 12:38pm UTC](https://community.geodynamics.org/t/problem-with-phase-changes-viscosity-layering/3291 "2024-02-27T12:38:19Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![vladycm](https://avatars.discourse-cdn.com/v4/letter/v/b5a626/32.png) [@vladycm](https://community.geodynamics.org/u/vladycm)\
**Post date:** [February 27, 2024, 12:38pm UTC](https://community.geodynamics.org/t/problem-with-phase-changes-viscosity-layering/3291/1 "2024-02-27T12:38:19Z")

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Hello.

I am currently using version 2.5.0 of ASPECT and am trying to include several phase transitions in a test model. In my test model I use only one compositional field and several phase transitions. I use the tests/latent\_heat\_viscosity.prm file for testing.  
This model works ok, I can see the viscosity layering correctly in Paraview:  
set Viscosity = 1e20  
…  
set Phase transition depths = all:400000|600000|800000|1000000  
…  
set Viscosity prefactors = 1, 5, 10, 100, 1000  
but this one does not display correctly the viscosity layering (for the same transition depths as above):  
set Viscosity prefactors = 1, 5, 0.1, 100, 1000  
In this model, the viscosities of the last two layers get switched, the 100x1e20 is like 5e22, and the lowermost layer instead of 1000x1e20 is 1e22.

I am not sure if I do something that is not ok or not.  
Please advice.

Thanks.  
V.