Have a software that solves Helmholtz equation, can I use it for Poisson?

[Amani_lama112]

I only took one class of PDE and even though I do remember the relationship between Laplace and Poisson I really do not recall Helmholtz at all. Anyways, I am trying to figure out if my software (a software I found online, FISKPACK) that solves Helmholtz equation can be used to solve Poisson equations? I mean, I understand that with Poisson, the function to the right is not necessarily related to the function itself but can we say Helmholtz is a subset of Poisson?
Any one here can advice about a software that solves Poisson equations? I found FIShPACK and I am trying to understand it enough to use it.
Thank you

 

[SteamKing]

I only took one class of PDE and even though I do remember the relationship between Laplace and Poisson I really do not recall Helmholtz at all. Anyways, I am trying to figure out if my software (a software I found online, FISKPACK) that solves Helmholtz equation can be used to solve Poisson equations? I mean, I understand that with Poisson, the function to the right is not necessarily related to the function itself but can we say Helmholtz is a subset of Poisson?
Any one here can advice about a software that solves Poisson equations? I found FIShPACK and I am trying to understand it enough to use it.
Thank you

According to this website:

http://people.sc.fsu.edu/~jburkardt/f77_src/fishpack/fishpack.html

FISHPACK can be used to solve Poisson equations, since the parameter lambda can be taken to be equal to zero. Note that these are two-dimensional equations only.

 

[Amani_lama112]

Thank you Steamking, my issue is if lambda is zero, wouldn't that reduce to Laplace instead of Poisson?
Thanks again

 

[SteamKing]

Thank you Steamking, my issue is if lambda is zero, wouldn't that reduce to Laplace instead of Poisson?
Thanks again

The Poisson equation is the same as the Laplace equation, except the RHS is not equal to zero.

 

[Amani_lama112]

Thank you again SteamKing, I understand that, however if I need to solve a Poisson equation (with non zero RHS) wouldn't making lambda = 0 not be it?

 

[SteamKing]

Thank you Steamking, my issue is if lambda is zero, wouldn't that reduce to Laplace instead of Poisson?
Thanks again

Look at the first page of the link to the FISHPACK routines. They are designed to solve Laplace, Poisson, and Helmholtz type equations.

As I tried to say, the Laplace equation is ∇²φ = 0 and the Poisson equation is ∇²φ = f(x,y)

It's the RHS of the equation which determines whether you have a Laplace or a Poisson type equation.