# GfsBcNavier

### From Gerris

**GfsBcNavier** is used to impose a Navier slip condition (for velocity or Robin boundary condition for a tracer) of the form

*v*_{boundary}=*v*_{0}+*λ*∂_{n}*v*_{boundary}

where *∂ _{n}* is the derivative normal to the boundary and

*and*

*v*_{0}*are parameters.*

*λ***Note**: the normal points toward the inside of the domain (in contrast to GfsBcNeumann).

The syntax in parameter files is

[ GfsBc ] V0 LAMBDA

where `V0`

and `LAMBDA`

are the parameters. Both `V0`

and `LAMBDA`

are GfsFunctions.