$$ \newcommand{\uex}{{u_{\small\mbox{e}}}} \newcommand{\Aex}{{A_{\small\mbox{e}}}} \newcommand{\half}{\frac{1}{2}} \newcommand{\tp}{\thinspace .} \newcommand{\Oof}[1]{\mathcal{O}(#1)} \newcommand{\dfc}{\alpha} % diffusion coefficient $$

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Analysis of the Forward Euler scheme

$$ \begin{equation*} [D_t^+ u = \dfc D_xD_x u]^n_q \end{equation*} $$

Inserting $$ u^n_q = A^n e^{ikq\Delta x}$$ leads to $$ A = 1 -4F\sin^2\left( \frac{k\Delta x}{2}\right),\quad F = \frac{\dfc\Delta t}{\Delta x^2}\mbox{ (mesh Fourier number)} $$

The complete numerical solution is $$ u^n_q = (1 -4F\sin^2 p)^ne^{ikq\Delta x},\quad p = k\Delta x/2 $$

Key spatial discretization quantity: the dimensionless \( p=\half k\Delta x \)

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