# problem with bondary condition for RANS case for NACA0012 using FLUENT

Member

I am running RANS simulation for NACA0012 aerofoil to use the RANS result as initial solution for incompressible LES simulation. My simulation domain is 3 c upstream, 7 downstream and 3 c to upper and lower boundaries. The simulation is using k-w SST and i run it for angle of attack 10.8. I used two boundaries as inlet (velocity inlet) and i define the velocity components ( ucos(10.8),usin(10.8),0) and other two as pressure outlet, while the front and back are periodic.

the velocity contours and outlet velocity profile are shown below

and the outlet pressure boundary

has anyone face the same problem at the outlet boundary as shown in the velocity profile at the outlet boundary?

• UKForum Coordinator
edited July 3

What are you expecting to see in the result? Which boundaries are pressure? Why are you preventing reverse flow?

• Member
edited July 3

i was expecting velocity profile at the outlet to be close to the free stream velocity (71.3m/s),i set the boundary on the left side and bottom one as inlet (velocity inlet) and the outlet and top boundaries as pressure outlet

• UKForum Coordinator
edited July 3

Turn off the prevent reverse flow and set reverse flow direction from neighbouring cell. The wake from the aerofoil looks about right, and the odd velocity near the bottom may be a result of the anti-reverse flow and back flow setting.

• Member
edited July 6

I had turn off the prevent reverse flow and set reverse flow direction from neighbouring cell, but still i have the same flow behaviour at the outlet and it is not changed

• Forum Coordinator
edited July 6

Regards,

Keyur

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• Member
edited July 6

yes i set the residuals to 10e-5 and the solution is converged

• UKForum Coordinator
edited July 6

Plot velocity vectors, they may help explain what's going on.

• Member
edited July 7
• UKForum Coordinator
edited July 7

Why is the velocity lower at the bottom on the inlet?

• Member
edited July 7

at the inlet the velocity is constant