What does mean 'gamma2' ?

[free]

I don't konw what the 'gamma2' mean is?

I found 'gamma2' is Slipperiness variable, either 1.0 (free slip) or -1.0 (no slip). What's the mean ?

In the 'u2dbc_im'

Code: Select all

!
!  Southern edge, closed boundary condition: free slip (gamma2=1)  or
!                                            no   slip (gamma2=-1).
!
#  ifdef EW_PERIODIC
#   define I_RANGE IstrU,Iend
#  else
#   define I_RANGE Istr,IendR
#  endif
        DO i=I_RANGE
          ubar(i,Jstr-1,kout)=gamma2(ng)*ubar(i,Jstr,kout)
#  ifdef MASKING
          ubar(i,Jstr-1,kout)=ubar(i,Jstr-1,kout)*                      &
     &                        GRID(ng)%umask(i,Jstr-1)
#  endif
        END DO

What's that mean ?

[kate]

Free-slip means the boundary has no friction and no slip means the boundary has friction so that the flow goes to zero right at the wall. In the code you show, u at the southern boundary has values just inside the domain and just outside the domain. The outside value is provided by the boundary conditions, in this case equal to the inside value for free-slip and opposite the inside value for no-slip. The value at the wall is the average of the inside and outside values, zero for no-slip.