Neumann boundary condition
In mathematics, the Neumann (or second-type) boundary condition is a type of boundary condition, named after Carl Neumann. When imposed on an ordinary or a partial differential equation, it specifies the values that the derivative of a solution is to take on the boundary of the domain. In engineering applications, the following would be considered Neumann boundary conditions:
- In thermodynamics, where a surface has a prescribed heat flux, such as a perfect insulator (where flux is zero) or an electrical component dissipating a known power.
For an ordinary differential equation, for instance:
the Neumann boundary conditions on the interval take the form:
where and are given numbers.
- For a partial differential equation, for instance:
where denotes the Laplacian, the Neumann boundary conditions on a domain take the form:
The normal derivative which shows up on the left-hand side is defined as:
It becomes clear that the boundary must be sufficiently smooth such that the normal derivative can exist, since for example at corner points of the boundary the normal vector is not well defined.
- Dirichlet boundary condition
- Mixed boundary condition
- Cauchy boundary condition
- Robin boundary condition