remove the code of the IMPET ("decoupled") models

there was no interest in using them and the maintainance burden grew
pretty large as the Dumux and eWoms code-bases continued to diverge.

doc/handbook/tutorial.tex

@@ -4,43 +4,25 @@
 discretization in space and time and models that use a
 semi-implicit space and an explicit time discretization.
 
-The semi-implicit models work by first implicitly solving a mass
-balance equation for all conservation quaintites combined. This
-procedire yields a pressure field. Then, the conserved quantities are
-transported using an explicit post-processing procedure based on of
-the pressure field obtained in the implicit step. These models are
-usually refered to be based on the IMPES approach (\textbf{i}mplicit
-\textbf{p}ressure \textbf{e}xplicit \textbf{s}aturation) or, more
-generally, on the IMPET approach (\textbf{i}mplicit \textbf{p}ressure
-\textbf{e}xplicit \textbf{t}ransport).
-
-In contrast, the fully-implicit models describe the conservation
-quantities of a flow system as a system of strongly coupled partial
-differential equations which is directly using a non-linear
-solver. Physically, these conservation quantities are mass, momentum
-and energy; Although the momentum is usually not explicitly conserved
-in the context of flow models for porous media.
+Fully-implicit models as implemented by \eWoms describe the
+conservation quantities of a flow system as a system of strongly
+coupled partial differential equations which is directly using a
+non-linear solver. Physically, these conservation quantities are mass,
+momentum and energy; Although the momentum is usually not explicitly
+conserved in the context of flow models for porous media.
 
 In section \ref{box} a short introduction to the vertex centered
 finite volume scheme (VCFV or box method) used by \eWoms as the
-spatial discretization of the fully-implicit models is given. The
-decoupled models usually employ a cell-centered finite volume scheme
-which is quite similar to the VCFV discretization, except that this
-scheme does not require to construct a dual grid centered around the
-primary grid's vertices.
+primary spatial discretization is given.
 
-This chapter, first introduce how to solve flow problems using a
-fully-implicit model (section \ref{tutorial-coupled}) and then how to
-solve the same problem using a semi-implicit model (section
-\ref{tutorial-decoupled}). Being simple but representative case, an
+The purpose of this chapter is to introduce how flow problems can be
+solved in \eWoms.  Being a simple but representative case, an
 isothermal two-phase problem (i.e. two fluid phases, one solid phase)
 will be considered. The source code of these tutorials is shipped with
 the \eWoms source package and can be found in the \texttt{tutorial}
 directory.
 
 \input{tutorial-coupled}
-\input{tutorial-decoupled}
-%\input{tutorial-newmodel}
 
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