1 Generalized Integral Plume Model for Simulations of Marine Discharges istein Johansen, Henrik Rye and Ismail Durgut SINTEF Materials and Chemistry Trondheim, Norway oistein.johansen@sintef.no Abstract The present paper describes the development of a 3D multi-component integral plume model for simulations of marine discharges from point sources, such as produced water discharges (formation water with dissolved chemicals and dispersed oil droplets), and discharges from offshore drilling operations (drilling mud and cuttings). The model is based on a Lagrangian concept, in which the plume is divided into segments which are advected vertically by buoyancy and inertia and horizontally by ambient currents. Changes in buoyancy are accounted for in terms of volumetric expansion of gas with reduced pressure and possible separation of bubbles, droplets or solid particles from the plume in cross flow. Separation of gas bubbles, liquid droplets or mineral particles from the plume is seen as an important feature of model, both in terms of loss of buoyancy, and as a source for spreading in the far field. Radial outflow of entrained water subsequent to surfacing or bottoming of the plume is another feature that is included to provide initial conditions for far field spreading. 1 Introduction The multi-component plume model described in this paper was originally developed for simulations of releases of oil and gas from oil exploration and production in deep waters. The main features of that model (DeepBlow) are described in a previous paper by one of the authors (Johansen 2000). The DeepBlow model was also developed as a multi-component integral plume model, and included phase transformation (dissolution of gas and formation of gas hydrates) and the corresponding loss of buoyancy by removal of free gas. In the present model, mineral particles (with negative buoyancy) are included as a fourth component (in addition to gas, oil and water), and bottoming of plume have thus been taken into account. The main issues in the present paper will be the handling of separation of bubbles, droplets and solid particles from plumes deflected by strong cross-flows, and the radial outflow of entrained water in surfacing or bottoming plumes. The methods used for integration of the plume model in near field advection-diffusion models are also presented, and example applications are shown to demonstrate some major features of the multi-component model. 2 Plume model In most plume models, the equations for continuity of mass, momentum and scalar properties (e.g., temperature and salinity) are defined for control volumes bounded by cross-sections normal to the trajectory of the plume. The models may be either Eulerian, where the control volumes are fixed in space, or Lagrangian, where the control volumes are moving with the plume. In Lagrangian models, the plume is represented by a series of non-interfering elements. Each element, which can be thought of as a cylinder or section of a bent cone, is characterized by its mass, location, width (radius), length (thickness), average velocity, composition (mass fraction of gas, oil, particles), temperature and salinity. These parameters will change as the element moves