Multizone contaminant dispersal analysis using an element assembly approach.

An element-assembly formulation of multi-zone contaminant dispersal analysis theory is described. In this approach a flow system is idealized as an assemblage of mass transport elements that model specific instances of contaminant mass transport in the flow system. Equations governing the mass transport phenomena modeled by each element are expressed in terms of contaminant concentration variables, the nodal concentration variables, that approximate the contaminant concentration at discrete points, the system nodes, in the flow system. The imposition of conservation of mass allows these element equations to be assembled to form spatially discrete but temporally continuous equations that govern the system as a whole. These system equations may then be solved to determine the response of the system to contaminant excitation. At its most general level this approach makes no limiting assumptions about the nature of the mass transport phenomena modeled (beyond the assumption of mass conservation) and is, therefore, not limited, in principal, to the well-mixed zone idealization, although, it includes the well-mixed multi-zone theory as a special case. Element equations for; a) well-mixed zones, b) instantaneous flow transport (with and with out filtering), c) mass transport phenomena governed by first order kinetics, and d) mass transport phenomena governed by the one-dimensional convection diffusion equation are presented. Solution options are outlined, examples of application are presented, and the CONTAM family of programs, that provide one implementation of the theory, is briefly described.