[josephmp]

hi friends, when i applied periodic BC at the inlet and outlet of a 2D unitcell of a microchannel with specified mass flow rate, i got a seemingly unphysical pressure variation along the centre line with negative pressure towards the downstream end. But when i avoid the periodic BC and arrange unitcells in series with velocity inlet and pressure outlet BCs i get finite pressure drop. Why the periodic BC is not working? why the negative pressure? can you help me to solve this problem...?

[amin.z]

please attach some pic from your model...

[josephmp]

i m trying to model two type of 2D microchannels (the periodic module have dimensions around 0.2mm*0.6mm)
1.channel with noslip boundaries
2.channel with alternate slip and noslip boundaries at bottom surface
for both cases i applied periodic BC at inlet and outlet with a specified mass flow rate such that Re nearly equals 0.1

1.the pics numbered 5 gives the pressure variation for for 1st case with
periodic zone=inlet
shadow zone=outlet
pic 6 gives pressure variation for 1st noslip case with
periodic zone=outlet
shadow zone=inlet

2.the pics numbered 2-4 gives 2nd case with alternate slip and noslp boundaries
for the first case why am i getting negative pressures? is there any method to eliminate end effects?
for the 2nd case why the pressure varies like a zigzag manner? why i am not getting a pressure drop?
2.boundaries.pdf

4.axial pressure variation.jpg

5.pressure.jpg

6.preesure -noslip-periodic 2.jpg

3.mc_Fs 50.jpg

[josephmp]

if my problem description is having less clarity plz tell me ...i can clear it....