Changes between Version 6 and Version 7 of u/erica/PoissonSolver
- Timestamp:
- 08/19/13 12:36:43 (11 years ago)
Legend:
- Unmodified
- Added
- Removed
- Modified
-
u/erica/PoissonSolver
v6 v7 5 5 Elliptic equations can be thought of as being the steady state limit of the diffusion equation, 6 6 7 [[latex($u_t = (\kappa u_x)_x + (\kappa u_y)_y + \psi$)]]7 [[latex($u_t = (\kappa u_x)_x + (\kappa u_y)_y + f$)]] 8 8 9 when both the 1) boundary conditions and 2) the source (or forcing term) [[latex($\psi$)]] are time-independent. Under these conditions, the time-dependent terms vanish as the system relaxes to steady state (in the limit t [[latex($\rightarrow \infty$)]]), and we are led to the elliptic equation (here in 2D),9 when both the boundary conditions and the source (or "forcing") term are time in-dependent. Under these conditions, the time dependent terms vanish as the system relaxes to steady state (in the limit t [[latex($\rightarrow \infty$)]]), and we are led to the elliptic equation (here in 2D), 10 10 11 11 [[latex($(\kappa u_x)_x + (\kappa u_y)_y = f $)]] 12 12 13 where u is the dependent variable we are solving for, and heref is the forcing term.13 where u is the dependent variable we are solving for, and f is the forcing term. 14 14 15 Th is equation needs to 1) be satisfied by all points within a bounding region and 2) satisfy the boundary conditions on that region. This then can be interpreted as an instantaneous constraint on thesystem, much different than the wave-like solutions of hyperbolic equations which travel with finite speed.15 The solution to this equation needs to simultaneously 1) satisfy this equation at all points within a bounding region and 2) satisfy the boundary conditions on that region. This then can be interpreted as an instantaneous system, much different than the wave-like solutions of hyperbolic equations which travel with finite speed. 16 16 17 Some special cases for elliptic equations are when [[latex($\kappa = 1$)]]. When f is non-zero, we have the Poisson equation,17 Some special cases for elliptic equations occur when [[latex($\kappa = 1$)]]; when f is non-zero, we have the Poisson equation, 18 18 19 19 [[latex($\triangledown ^2 u = f$)]]