Gravitational flooding of a very hot horizontal surface by water resul
ts in a two-phase flow with very interesting flow properties The purpo
se of this work is to demonstrate some properties of such flows by ana
lysing the properties of the mathematical model describing the flow. W
ith some simplifications the problem can be reduced to a system of thr
ee hyperbolic partial differential equations. Eigenvalues, eigenvector
s and canonical form are obtained. The criticality condition is obtain
ed from the system describing the steady state. The system of partial
differential equations is made dimensionless, and physical scaling cri
teria are obtained.