#jsDisabledContent { display:none; } My Account |  Register |  Help

# Mixed boundary condition

Article Id: WHEBN0002784886
Reproduction Date:

 Title: Mixed boundary condition Author: World Heritage Encyclopedia Language: English Subject: Collection: Publisher: World Heritage Encyclopedia Publication Date:

### Mixed boundary condition

Green: Neumann boundary condition; purple: Dirichlet boundary condition.

In mathematics, a mixed boundary condition for a partial differential equation defines a boundary value problem in which the solution of the given equation is required to satisfy different boundary conditions on disjoint parts of the boundary of the domain where the condition is stated. Precisely, in a mixed boundary value problem, the solution is required to satisfy a Dirichlet or a Neumann boundary condition in a mutually exclusive way on disjoint parts of the boundary.

For example, given a solution u to a partial differential equation on a domain Ω with boundary ∂Ω, it is said to satisfy a mixed boundary condition if, consisting ∂Ω of two disjoint parts, Γ
1
and Γ
2
, such that ∂Ω = Γ
1
∪ Γ
2
, u verifies the following equations:

\left. u \right|_{\Gamma_1} = u_0          and          \left. \frac{\partial u}{\partial n}\right|_{\Gamma_2} = g,

where u
0
and g are given functions defined on those portions of the boundary.[1]

The mixed boundary condition differs from the Robin boundary condition in that the latter requires a linear combination, possibly with pointwise variable coefficients, of the Dirichlet and the Neumann boundary value conditions to be satisfied on the whole boundary of a given domain.

## Contents

• Historical note 1
• Notes 3
• References 4

## Historical note

M. Wirtinger, dans une conversation privée, a attiré mon attention sur le probleme suivant: déterminer une fonction u vérifiant l'équation de Laplace dans un certain domaine (D) étant donné, sur une partie (S) de la frontière, les valeurs périphériques de la fonction demandée et, sur le reste (S′) de la frontière du domaine considéré, celles de la dérivée suivant la normale. Je me propose de faire connaitre une solution très générale de cet intéressant problème.[2]
— Stanisław Zaremba, (Zaremba 1910, §1, p. 313).

The first boundary value problem satisfying a mixed boundary condition was solved by Stanisław Zaremba for the Laplace equation: according to himself, it was Wilhelm Wirtinger who suggested him to study of this problem.[3]

## Notes

1. ^ Obviously, it is not at all necessary to require u
0
and g being functions: they can be distributions or any other kind of generalized functions.
2. ^ (English translation) "Mr. Wirtinger, during a private conversation, has drawn to my attention the following problem: to determine one function u satisfying Laplace's equation on a certain domain (D) being given, on a part (S) of its boundary, the peripheral values of the sought function and, on the remaining part (S′) of the considered domain, the ones of its derivative along the normal. I aim to make known a very general solution of this interesting problem."
3. ^ See (Zaremba 1910, §1, p. 313).

## References

• . domains in fairly general elliptic operators selfadjoint for the mixed boundary value problem involving a general second order uniqueness theorems and existence" (English translation of the title), Gaetano Fichera gives the first proofs of Existential analysis of the solutions of mixed boundary value problems, related to second order elliptic equation and systems of equations, selfadjoint. In the paper "
• Guru, Bhag S.; Hızıroğlu, Hüseyin R. (2004), Electromagnetic field theory fundamentals (2nd ed.), Cambridge, UK – New York: .
• .
• , translated from the Italian by Zane C. Motteler.
• .
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.

Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.