We consider optimal control of a parabolic differential equation, mode
ling one-dimensional fluid flow through a soil-packed tube in which a
contaminant is initially distributed. A fluid is pumped through the tu
be to remove the contaminant. The convective velocity due to the fluid
pumping is the nonlinear control action. The goal is to minimize a pe
rformance criterion which is a combination of the total contaminant at
the final time and the cost of the control. The optimal control is ch
aracterized by an optimality system.