What model to use when having both turbulent and laminar flow simultaneously in simulation domain

  • Last Post 03 June 2020
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AlexC posted this 03 June 2020

Please see the figure below. Hope the information is clear. 

Now imagine we have flow comes into a larger tube (Tube 1) from left, and then moves into a smaller tube (Tube 2) and exit Tube 2 from the right. By mass balance, we can easily find out that the Reynolds number between Tube 1 and Tube 2 is: 


So by picking the right D1 and D2, we can easily have laminar flow in Tube 1 and turbulent flow in Tube 2. In this case, what model should we use? Laminar model or turbulent model? It seems neither would work and I couldn't figure out how I should model this problem. 


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Kalyan Goparaju posted this 03 June 2020


Ansys Fluent has viscous models that are purpose built for computing flows that exhibit laminar-to-turbulent transition. The recommended approach is to select the SST k-w model and turn on 'Intermittency Transition Model'. 



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AlexC posted this 03 June 2020

Thank you Kalyan! That answers my question!