[DuFFman_EsP]

Hello,


I'm making an aerodynamic study in 2D Fluent on the profile of a truck (basically a couple of rectangles). I have meshed the geometry in Gambit and used the boundary layer utility to create the boundary layer from the value of y + I had previously calculated. (Characteristic length, length of the cab, speed 22.22 m / s). I have created the boundary layer with the first row obtained, 1.2 growth factor and so on. I have meshed the whole domain and then I move to Fluent.

The drag coefficient obtained seems to be valid, but no matter the different meshes or methods of calculation I used, I can not get a value of y + under 400 on the wall of the truck .....

Thank you in advance.

[SPH_CFD]

I think you can come back Gambit and decrease initial height of Boundary Layers. Y+ depends on distance from wall to first layer

Sent from my LG-F260S using CFD Online Forum mobile app

[oozcan]

Originally Posted by DuFFman_EsP

Hello,


I'm making an aerodynamic study in 2D Fluent on the profile of a truck (basically a couple of rectangles). I have meshed the geometry in Gambit and used the boundary layer utility to create the boundary layer from the value of y + I had previously calculated. (Characteristic length, length of the cab, speed 22.22 m / s). I have created the boundary layer with the first row obtained, 1.2 growth factor and so on. I have meshed the whole domain and then I move to Fluent.

The drag coefficient obtained seems to be valid, but no matter the different meshes or methods of calculation I used, I can not get a value of y + under 400 on the wall of the truck .....

Thank you in advance.

if you would like to see under a value under 400 for y+

please check regarding link and fomulas including y+

y+=y*ut/m ut=friction velocity m=viscosity. y= first layer thickness

Solution is that you should decrease first layer tickness, increasing layers (avoiding higher aspect ratio)

https://en.wikipedia.org/wiki/Law_of_the_wall

[DuFFman_EsP]

Thank you,

I will try again!

[DuFFman_EsP]

I tried once and y+ han not changed a lot. It is still more than 400.

[oozcan]

what did you give y+ for meshing?

[DuFFman_EsP]

I think that I have found the problem. I have y+=0,001. But I also have another wall (the floor) and probably its boundary layer could be giving me some problems.

I´m trying to create two boundary layers for both, truck and floor.

[DuFFman_EsP]

I´ve done it! and it works. Now, I have an y+=70 after calculating.

Thank you!

[oozcan]

Originally Posted by DuFFman_EsP

I´ve done it! and it works. Now, I have an y+=70 after calculating.

Thank you!

I am pretty good to be resolved it and How?

I was trying to post last night about boundary layer you were going to do. Life is busy!, well, probably, I think that you made boundary layer thickness give on interfaces of floor and truck in enclosure domain

[DuFFman_EsP]

I had forgotten to made a boundary layer for the floor (wall) and now I have y+=65-71 for different meshes.