Orientation of normal vectors for embedded boundaries

[maikel]

Do normal vectors on the embedded boundary point into the body or into the fluid?

Note: For the implicit function that defines the geometry we read in the documentation

Define an implicit function of position which describes the surface of the embedded object. Specifically, the function class must have a public member function that takes a position and returns a negative value if that position is inside the fluid, a positive value in the body, and identically zero at the embedded boundary.

[WeiqunZhang]

They point into the body, which is consistent with the sign of the implicit function.