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-   -   on the validity of poisson eq's solution (http://www.cfd-online.com/Forums/main/3634-validity-poisson-eqs-solution.html)

 yfyap June 22, 2001 13:32

on the validity of poisson eq's solution

i am solving a poisson equation with neumann boundary conditions: d^2[phi]/dx^2+d^2[phi]dy^2=S define: delta=d^2[phi]/dx^2+d^2[phi]dy^2-S after i obtained the solution, i computed delta(as defined) for the entire domain. is the solution still valid if the magnitude of one of the deltas reaches 0.02 as it should be far smaller than that(approaches 0)? any opinion or advice is welcomed. thanks regards, yfyap

 John C. Chien June 23, 2001 17:16

Re: on the validity of poisson eq's solution

(1). If the Left-hand side Is Equal to the Right-hand side, then obviously the solution is valid because it satisfies your equation. (2). If the Left-hand side Is Not Equal to the Right-hand side, then your definition of delta will be Non-zero. Thus, the equation is Not Satisfied. That also means you are not getting the right solution to satisfy your equation.

 Kike June 25, 2001 06:22

Re: on the validity of poisson eq's solution

Dear YFYAP

This is not a simple question. My suggestions is: Check it with experimental data or another numerical results (another code or researcher).

2% error is maybe good enough for your case but it could be dramatic for the Challenger, that depends on your case's requirements.

You can have 0.01% error and your results can become useless becuase your definition of the RHS (ie. S in your eq.) do not match with the physical model that your case need.

Regards

Kike

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