Learning Forum

[S.Shrestha-4]

Hi!

I am new to Ansys Fluent. The simulation is of liquid water in the serpentine microchannel, velocity inlet around 6 m/s and a pressure outlet using laminar viscous model with energy equation on. This is the pathlines I see. Why are there no pathlines in the curved part? 

[Rob]

Plot a velocity vector field too, plot on the centre plane, so same view as you have now. Also remember that pathlines follow the flow, so if the lugs don't interact with the centre flow the pathlines will bypass them.  

[S.Shrestha-4]

 

Thank you for your reply. What did you exactly mean by lugs? I did plot the velocity along the mid-plane, and get this. Does this mean there is a thick boundary layer? How shall I approach to solve this?

 

 

[Rob]

Lugs - the wavy bits.  It's not a thick boundary layer, it's that the flow has no reason to go into the lugs. 

Ansys staff aren't able to offer engineering advice, so please talk to your Prof and report back. It's all part of the fun working with fluidic devices. 

[S.Shrestha-4]

 

Hi! I did fix the dimensions and now the path lines looks better. Although laminar flow model was used, there seems to be some eddy, when looking at the velocity profile. Does that mean the flow is not laminar, although Reynolds number is small around 500? Should I have used a turbulent model? If it’s not an eddy, what is it? 

Thank you!

 

[Rob]

You can have separation and eddies in laminar flow. The only people who define those flows as turbulent are medics and geologists: please don't encourge them! ;) 

[S.Shrestha-4]

Thanks for your answer. How can we remove the flow separation in Fluent? 

[Rob]

Are you sure that's not what is happening? At least for the fluid and flow rate you have in your model.