Running a Mathematica's notebook, I hear a beep. What does it means?

Questions
, ,
1

Hi everybody.
I want to find a numerical solution for Laplace equation in a rectangular domain, so I’ve created this code:

xfinale = 5;
yfinale = 5;
\[CapitalOmega] = Rectangle[{0, 0}, {xfinale, yfinale}];
solNumericaLaplace = 
  NDSolve[{Inactive[Laplacian][u[x, y], {x, y}] == 0, u[0, y] == 0, 
    u[x, yfinale] == 0, u[x, 0] == 0, 
    u[xfinale, y] == Sin[n*Pi*y/yfinale]}, 
   u, {x, y} \[Element] \[CapitalOmega]];

When I try to evaluate notebook, I hear a beep, but there isn’t an error message. So I click on “Help → Why the Beep?..” and I see this message on the screen: The kernel Local has quit (exited) during the course of an evaluation.

What does it means? How can I fix the problem?
Thanks for your suggestions.

2

Near-duplicate of Why the heat equation doesn't work with NDSolve? .