[firavia]

Hello,

I am simulating a flow inside a pipe that has 8 blades, I used the cut cell mesh and after the simulation was completed I checked the Y plus value on the blade wall and the Y plus value was in the range of 30 to 60 for 80 % of the cells but 20 % of the cells near the wall were far from the acceptable range, does that mean that my simulation will be inaccurate or would that mean that at 80 % of blade wall the standard wall function will work okay but at 20 % of the cells the solution will be inaccurate ?

I used K -Epsilon method
Standard wall function
Fluid: Water
Mesh type: Cut cell.

I would be very grateful if you answer my inquiry, thanks.

[firavia]

Please can anyone answer this question above , I am sure it is simple, I just want to know whether all the cells 100 % should be in the correct range of y plus near the wall for the solution to be accurate or if 80 % of the cells near the wall are in the right range that means 80 % of the dissipation equation will be solved correctly and project an accurate solution at 80 % of the wall and bad inaccurate result at 20 % of the wall.

[Zaktatir]

what does it mean far from the range? bigger than 300?

[firavia]

10% of the wall cells are below 20 down to 8 and 10 % are between 60 and 100 and the rest are in the safe range. What i am scared of is the low values (below 20).

[Zaktatir]

then use the scalable wall functions which no matter how you mesh is fine only use a min value of 11.26 for your yplus if the real values are below that

[Vidyanand Kesti]

in this condition use enhanced wall treatment it should take care of bondary layer

[macfly]

I suspect that Raef is not geting the answers he was looking for.

I think the initial question was: if some cells have a y+ outside of the desired range (let's say 30-100), will it propagate some error to other cells around, or to the whole domain?

[firavia]

Yesss macfly thats my question exactly , thanks !

[Zaktatir]

overproduction of turbulent energy this leads in some regions to strong acceleration or deceleration

This the problem if using the worng turb model and the wrong wall modeling.

However thanks dissipation this may be reduced somewhat: that is why problem dependent.

Carry out the result analysis and then make a sensitivity analysis with other wall modeling approach. It is normal to do not match the yplus range. That is why i use scalable wall functions when i am not interested in resolving the viscous layer and omega based models or enhanced wall treatment when i am INTENDING to resolve the near wall region (Ret< 200 / yplus to 5)

Carry On