[hamed.majeed]

Hi guys,
I used immersed solid approach in CFX for a flat plate to predict the boundary layer formation over it. I compared my results with a general case of flat plate, i.e. without using immersed solid domain. Although I know immersed solid under-predicts the boundary layer formation, however that is what I needed to find out.
This post is the gist of my analysis.
Earlier I have validated flow over a flat plate in cfx
http://www.cfd-online.com/Forums/cfx...lysis-cfx.html

The flow parameters and references are same as defined in above link. I needed to change the geometry so that I could compare both the results.

Flow over a flat plate (general case)
Here is the model created.

Meshing

Then I applied the boundary conditions, the fluid domains need to be joined together by fluid fluid domain interface. Also wall b.c., inlet b.c. and symmetry b.c. are specified. At the exit i applied the outlet boundary condition.
This the the velocity contour I obtained.

Finally, I plotted the velocity vs Y plot, to see the boundary layer. The boundary layer thickness comes out to be 0.8 m. Which is quite good compared with the empirical value of 0.84m.


Flow over a flat plate as an immersed solid
I have done this part just to see how much the immersed solid approach under predicts the boundary layer.

# of iterations 100, variable variation 1e-4
I used ANSYS CFX v 14.0, so I used all the options related to Momentum source scaling factor and Boundary Model.
I used a range of Momentum source scaling factors and boundary models, these are the best results I could obtain.


The solution converged.
The velocity profile seems to be fairly accurate.



Finally, I calculated the velocity vs Y plot, which gives boundary layer thickness to be 0.105 m. The empirical value as stated earlier is 0.84 m.





Remarks
I have not done the mesh independency test yet, I shall soon post it.
The boundary layer is under predicted if immersed solid is used. This is clearly the case.




I plotted the friction coefficient vs length plot but they are very inaccurate, i problem I need to counter far.



Any comments and suggestions are appreciated.