How to mention neuman boundary condition for velocity at the outlet or inlet??
 

Hi all


I am modeling 2d axi-symmetric laminar pipe flow with ferrohydrodymaic source terms.

Now,the problem is very simple.I want to specify du/dx=0 at the boundaries(inlet ,outlet where ever I want,if its a part of extremely long piping network the flow can be fully developed at both ends.) instead of specifying u=1 m/s ,0.2 mm/sec 3 m/sec.... blah,blah etc.

I know there are define_profile macros which can set velocity profile(nothings but sets the value of velocity at the boundary for non uniform radial variation)

But how can I set the velocity gradient =0 at the boundary(i.e the cell_face at the extreme ends)????

Any help is greatly appreciated.