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Math 6410 • ODE

Fall 2016 • Question 8

Solve (and sketch the solution of) the differential equation \(u_t+uu_x=0\) on the domain \(-\infty <x<\infty \), \(t>0\) subject to initial data \(u(x,0)=u_0(x)\) where

  1. \begin{equation} u_0(x)= \begin {cases} 0, & x<0,\\ x, & 0<x<1,\\ 1, & x>1, \end {cases} \tag {2} \end{equation}
  2. \begin{equation} u_0(x)= \begin {cases} 1, & x<0,\\ 1-x, & 0<x<1,\\ 0, & x>1. \end {cases} \tag {3} \end{equation}

For which (if any) of these initial profiles does the solution of the problem \(u_t+uu_x=\epsilon u_{xx}\), \(\epsilon >0\), converge to a traveling wave profile? What is the speed of the traveling wave solution?

Raw LaTeX

Solve (and sketch the solution of) the differential equation \(u_t+uu_x=0\) on the
domain \(-\infty<x<\infty\), \(t>0\) subject to initial data \(u(x,0)=u_0(x)\) where
\begin{enumerate}
\item[(a)]
\begin{equation}
  u_0(x)=
  \begin{cases}
    0, & x<0,\\
    x, & 0<x<1,\\
    1, & x>1,
  \end{cases}
  \tag{2}
\end{equation}
\item[(b)]
\begin{equation}
  u_0(x)=
  \begin{cases}
    1, & x<0,\\
    1-x, & 0<x<1,\\
    0, & x>1.
  \end{cases}
  \tag{3}
\end{equation}
\end{enumerate}
For which (if any) of these initial profiles does the solution of the problem
\(u_t+uu_x=\epsilon u_{xx}\), \(\epsilon>0\), converge to a traveling wave profile?
What is the speed of the traveling wave solution?