Numerical Approximation of Young Measure Solutions to Parabolic Systems of Forward-Backward Type

This paper is concerned with the proof of existence and numerical approximation of large-data global-in-time Young measure solutions to initial-boundary-value problems for multidimensional nonlinear parabolic systems of forward-backward type of the form $\partial_t u - \mbox{div}(a(Du)) + Bu = F$, where $B \in \mathbb{R}^{m \times m}$, $Bv \cdot v \geq 0$ for all $v \in \mathbb{R}^m$, $F$ is an $m$-component vector-function defined on a bounded open Lipschitz domain $Ω\subset \mathbb{R}^n$, and $a$ is a locally Lipschitz mapping of the form $a(A)=K(A)A$, where $K\,:\, \mathbb{R}^{m \times n} \rightarrow \mathbb{R}$. The function $a$ may have a nonstandard growth rate, in the sense that it is permitted to have unequal lower and upper growth rates. Furthermore, $a$ is not assumed to be monotone, nor is it assumed to be the gradient of a potential. Problems of this type arise in mathematical models of the atmospheric boundary layer and fall beyond the scope of monotone operator theory. We develop a numerical algorithm for the approximate solution of problems in this class, and we prove the convergence of the algorithm to a Young measure solution of the system under consideration.