History

The Evolution of MOHID

The development of the Mohid model started back in 1985, passing since this time through continuously updates and improvements due to its use during different projects of scientific research and engineering projects. Initially the Mohid water modeling system was a bi-dimensional hydrodynamic model, called Mohid 2D (Neves, 1985). This model was used to study estuaries and coastal areas using a classical finite difference approach.

In the following years, a bi-dimensional eulerian and lagrangian transport model were included in this model. The first three-dimensional was introduced by Santos (1995), which used a vertical double Sigma coordinate. This version was called Mohid 3D.

The limitations of the double Sigma coordinate revealed the necessity to develop a model which could use a generic vertical coordinate, permitting the user to choose the type of vertical coordinate, depending on the study area. Due to this necessity the concept of finite volumes was introduced with the version Mesh 3D by Martins (1999). In the Mesh 3D model were included a three dimensional eulerian transport model, a three dimensional lagrangian transport model (Leitão, 1996) and the zero-dimensional water quality model (Miranda, 1999). Since the introduction of the finite volumes approach, this discretization remains in the model Mohid.

 With the growing model complexity, it was necessary to introduce a new way in the organization of the information of the Mohid model. In 1998 the whole code was submitted to a complete rearrangement, using the new feature of programming languages and also the capacities of the computer to reprogram the whole Mohid model. The main goal of this rearrangement was to turn the model more robust, reliable and protect its structure against involuntary programming errors, so it would be more easily “grow able”. To achieve this goal, objected oriented programming in FORTRAN was introduced to the Mohid model, although FORTRAN is not an object oriented language. This migration began in 1998, implementing object oriented features like those described in Decyk [8] with significant changes in code organization. This migration resulted in an object oriented model for surface water bodies which integrates scales and processes.

 The philosophy of this new Mohid model, further on simple designated Mohid,  permits to use the model in any dimension (one-dimensional, two-dimensional or three-dimensional). The whole model is programmed in ANSI FORTRAN 95, using the objected oriented philosophy. The subdivision of the program into modules, like the information flux between these modules was object of a study by the Mohid authors.

The object oriented modular design of this model was the base to build the present MOHID Water Modelling System, which is a set of several numerical tools. Actually MOHID Water Modelling System is composed by over 40 modules which complete over 240 000 code lines.