\section{Summary} \label{s.summary}

In the preceding sections we argue that external irradiation in a
close massive star binary will not appreciably alter the shapes of the
components, but instead will drive steady flows across their
surfaces. We explore these flows using first an analytic model, and
then a numerical model based on the \glados\ code. The principal
observational signature of the flows is deeper line profiles when a
star is approaching the observer, as compared to when the star is
receding. This is the same behavior as seen in the Struve-Sahade
effect, and thus our surface flows formalism seems a promising
explanation for the effect. Further investigation is clearly required.

