  We consider flows of Spin(7)-structures. We use local coordinates to describe
the torsion tensor of a Spin(7)-structure and derive the evolution equations
for a general flow of a Spin(7)-structure on an 8-manifold M. Specifically, we
compute the evolution of the metric and the torsion tensor. We also give an
explicit description of the decomposition of the space of forms on a manifold
with Spin(7)-structure, and derive an analogue of the second Bianchi identity
in Spin(7)-geometry. This identity yields an explicit formula for the Ricci
tensor and part of the Riemann curvature tensor in terms of the torsion.
