Fictitious domain method

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In mathematics, the Fictitious domain method is a method to find the solution of a partial differential equations on a complicated domain , by substituting a given problem posed on a domain , with a new problem posed on a simple domain containing .

General formulation[edit]

Assume in some area we want to find solution of the equation:

with boundary conditions:

The basic idea of fictitious domains method is to substitute a given problem posed on a domain , with a new problem posed on a simple shaped domain containing (). For example, we can choose n-dimensional parallelepiped as .

Problem in the extended domain for the new solution :

It is necessary to pose the problem in the extended area so that the following condition is fulfilled:

Simple example, 1-dimensional problem[edit]

Prolongation by leading coefficients[edit]

solution of problem:

Discontinuous coefficient and right part of equation previous equation we obtain from expressions:

Boundary conditions:

Connection conditions in the point :

where means:

Equation (1) has analytical solution therefore we can easily obtain error:

Prolongation by lower-order coefficients[edit]

solution of problem:

Where we take the same as in (3), and expression for

Boundary conditions for equation (4) same as for (2).

Connection conditions in the point :

Error:

Literature[edit]

  • P.N. Vabishchevich, The Method of Fictitious Domains in Problems of Mathematical Physics, Izdatelstvo Moskovskogo Universiteta, Moskva, 1991.
  • Smagulov S. Fictitious Domain Method for Navier–Stokes equation, Preprint CC SA USSR, 68, 1979.
  • Bugrov A.N., Smagulov S. Fictitious Domain Method for Navier–Stokes equation, Mathematical model of fluid flow, Novosibirsk, 1978, p. 79–90