[kongl1986]

I am simulating a 2D gas-solid flow in CFB rectangle riser.
Now my question is that:
When I using standard wall function, with the Y+ is around 8to 14, and the aspect ratio of the mesh is 40.
the volume fraction of radius direction of the CFB is accepable.
However. when I use enhanced wall treadment with Y+=1.2.
aspect ratio is either 39 or 46,
the solid volume fraction of radius derection of the CFB is not good.
It fluctuates a lot and in the near wall area, it increases and decreases as showed in the pic.
Cound you tell me why this fluctuant and decreasing stucture happens near the wall.

Is it related to the aspect ratio of the boundary lay and the Y+?
The only difference i can found is these.


The reason i cannot use standard wall function with good Y+ value is that my cfb riser is very thin, if so, the first grid near the wall is too big, amost 1/3 of the radius.

p.s: i am using transient module , the result under standard wall fucntion as i described is acceptable but i just want to control the y+ in a good value, so i change it to enhanced wall treatment and the problem occurs
thank you

[kongl1986]

the riser is 10m x 0.0381m rectangle