[nhhamidsa]

hello.
i want to simulate a of flow over a 3D dynamic wind turbine airfoil. i'm using LES method for viscosity. generally i know that there is a fluctuate behaviour in lift numbers vs angle of attack.my problem is that i couldn't validate the problem with 2D study . the 3D used mesh is the swiped mesh of 2D mesh. (e.g 0.0001*chord length). the front and back surface is set to periodic. and the mesh size in the Z direction is 1. is it true that i'm used just 1 cell in the Z direction for mesh??

[FMDenaro]

Originally Posted by nhhamidsa

hello.
i want to simulate a of flow over a 3D dynamic wind turbine airfoil. i'm using LES method for viscosity. generally i know that there is a fluctuate behaviour in lift numbers vs angle of attack.my problem is that i couldn't validate the problem with 2D study . the 3D used mesh is the swiped mesh of 2D mesh. (e.g 0.0001*chord length). the front and back surface is set to periodic. and the mesh size in the Z direction is 1. is it true that i'm used just 1 cell in the Z direction for mesh??

No, you have to let a spanwise lenght Lz such that it is larger than the characteristic integral lenght scale. Using only one cell you are forcing a 2D-like case

[nhhamidsa]

Originally Posted by FMDenaro

No, you have to let a spanwise lenght Lz such that it is larger than the characteristic integral lenght scale. Using only one cell you are forcing a 2D-like case

so why it can't validate with 2D study? i'm just used one mesh size in Z direction
and what is characteristic integral length

[FMDenaro]

Originally Posted by nhhamidsa

so why it can't validate with 2D study? i'm just used one mesh size in Z direction
and what is characteristic integral length

You can do a RANS simulation in 2D, if you perform LES it must be done in 3D

[nhhamidsa]

Originally Posted by FMDenaro

You can do a RANS simulation in 2D, if you perform LES it must be done in 3D

as i said my simulation is 3D , and i want to do this by LES simulation. but my main question is that is it true for 1 mesh size in Z direction

[FMDenaro]

Originally Posted by nhhamidsa

as i said my simulation is 3D , and i want to do this by LES simulation. but my main question is that is it true for 1 mesh size in Z direction

No, that's false

[nhhamidsa]

Originally Posted by FMDenaro

No, that's false

thanks dear friend

[nhhamidsa]

even for very short length in Z direction (e.g 0.01 chord length)

[FMDenaro]

Originally Posted by nhhamidsa

even for very short length in Z direction (e.g 0.01 chord length)

There is not enough physical extension to let a 3D field developing, thus LES would be not a physical approach.