ROSA is a special purpose interface to the PHOENICS CFD code.

It is an integrated software package for simulating the development of oil slicks and other spillages.

It has been validated against a number of hydraulic models and full scale river spillages, especially in Siberia where environmental concerns have become a major issue.

All the relevant physical phenomena (wind strength and direction, temperature, etc.) are taken into account.

• predict water quality in terms of pollutant concentration over time and space
• in the short-term, predict slick movements and formulate an emergency response
• in the long-term, predict deposition of pollutant and formulate a management and clean-up strategy

Modelling features of ROSA
ROSA comprises the following modules linked by a menu system:

• The river-current sub-models
• The oil-spill sub-models
• The data-entry module
• The visualisation module

Oil pollutants within the river are considered as consisting of:

• A surface slick floating on the water surface
• A mixed layer containing suspended oil fragments
• There is continuous exchange between the two layers and mass losses to the atmosphere
• The surface layer thickness is much less than that of the suspended layer which is equal to the flow depth

ROSA Validation
ROSA has been validated against a number of reliable laboratory and field measurements of velocity field and free surface elevations in two and three dimensions for open channels and river courses.

Free-surface flows in open channels
A number of free-surface flows have been simulated and validated against experimental data, including:

• flow in open turnaround channel,
• abrupt open channel expansion,
• flow impingement on bluff body,
• merging of streams,
• flows in channels with complex bed shapes and
• meandering open channel flows.

Good agreement has been achieved both for free surface elevation and velocity distributions.

Other capabilities

• ROSA is a modelling tool capable of simulating movement of oil and other pollutants on the surface of rivers, which flow at a constant rate.
• It has recently been extended, adding the capability to simulate flows that vary with time, i.e. tidal flows.
• This enables ROSA to be used to simulate the movement of oil in estuaries, along coastlines and on the open sea, greatly enhancing the usefulness of ROSA as a tool for predicting the spread of oil slicks.
• A further ROSA capability is the ability to simulate the movement of ice flows on oceans.