1 Introduction

This paper, which sets down the equations solved by ROSA add-on of PHOENICS ( Zhubrin, 1995, 1996 ), meets a need often expressed by its current and potential users.

The purpose of this paper is to set down in a complete and orderly manner the equations solved in ROSA-EARTH.

In its current embodiment, ROSA uses Eulerian equations for the representation of both the river water and oil phases. These equations are listed in the present document, in which some details of the integration procedure are also given.

The most of the end users of ROSA do not need to be acquanted with the mathematics to be able to operate ROSA succesfully. The document is therefore provided as a reference for users who need to be concerned with mathematical basis of ROSA.