add PRT section to readme, update prt.tex

README.md

@@ -67,12 +67,14 @@ Instructions for building definition files for new packages are summarized in [d
 
 MODFLOW is a popular open-source groundwater flow model distributed by the U.S. Geological Survey.  For 30 years, the MODFLOW program has been widely used by academic researchers, private consultants, and government scientists to accurately, reliably, and efficiently simulate groundwater flow.  With time, growing interest in surface and groundwater interactions, local refinement with nested and unstructured grids, karst groundwater flow, solute transport, and saltwater intrusion, has led to the development of numerous MODFLOW versions.  Although these MODFLOW versions are often based on the core version (presently MODFLOW-2005), there are often incompatibilities that restrict their use with one another.  In many cases, development of these alternative versions has been challenging due to the underlying MODFLOW structure, which was designed for the simulation with a single groundwater flow model using a rectilinear grid.
 
-MODFLOW 6 is the latest core version of MODFLOW. It synthesizes many of the capabilities available in MODFLOW-2005, MODFLOW-NWT, and MODFLOW-LGR. MODFLOW 6 was built on a new object-oriented framework that allows new packages and models to be added, and allows any number of models to be run simultaneously in a single simulation.  Model may be coupled sequentially, such as for flow and transport, or the models may be tightly coupled at the matrix level, such as for multiple flow models. MODFLOW 6 presently contains two types of hydrologic models, the Groundwater Flow (GWF) Model and the Groundwater Transport (GWT) Model.
+MODFLOW 6 is the latest core version of MODFLOW. It synthesizes many of the capabilities available in MODFLOW-2005, MODFLOW-NWT, and MODFLOW-LGR. MODFLOW 6 was built on a new object-oriented framework that allows new packages and models to be added, and allows any number of models to be run simultaneously in a single simulation.  Model may be coupled sequentially, such as for flow and transport, or the models may be tightly coupled at the matrix level, such as for multiple flow models. MODFLOW 6 presently contains three types of hydrologic models, the Groundwater Flow (GWF) Model, the Groundwater Transport (GWT) Model, and the Particle Tracking (PRT) Model.
 
 The Groundwater Flow (GWF) Model was the first model to be released in MODFLOW 6. It supports regular MODFLOW grids consisting of layers, rows, and columns, but it also supports more flexible grids that may conform to irregular boundaries or have increased resolution in areas of interest. The GWF Model consists of the original MODFLOW stress packages (CHD, WEL, DRN, RIV, GHB, RCH, and EVT) and four advanced stress packages (MAW, SFR, LAK, and UZF), which have been distilled from their predecessors to contain the most commonly used capabilities. MODFLOW 6 contains a new Water Mover (MVR) Package that can transfer water from provider packages to receiver packages. Providers can be many of the stress and advanced stress packages; receivers can be any of the advanced stress packages. This new capability makes it possible to route water between lakes and streams, route rejected infiltration into a nearby stream, or augment lakes using groundwater pumped from wells, for example. To modernize user interaction with the program, the MODFLOW 6 input structure was redesigned. Within package input files, information is divided into blocks, and informative keywords are used to label numeric data and activate options. This new input structure was designed to make it easier for users to adjust simulation options in an intuitive manner, reduce user input errors, and allow new capabilities to be added without causing problems with backward compatibility.
 
 The GWT model for MODFLOW 6 simulates three-dimensional transport of a single solute species in flowing groundwater. The GWT Model solves the solute transport equation using numerical methods and a generalized CVFD approach, which can be used with regular MODFLOW grids or with unstructured grids. The GWT Model is designed to work with most of the new capabilities released with the GWF Model, including the Newton flow formulation, unstructured grids, advanced packages, and the movement of water between packages. The GWF and GWT Models operate simultaneously during a MODFLOW 6 simulation to represent coupled groundwater flow and solute transport. The GWT Model can also run separately from a GWF Model by reading the heads and flows saved by a previously run GWF Model. The GWT model is also capable of working with the flows from another groundwater flow model, as long as the flows from that model can be written in the correct form to flow and head files.
 
+The Particle Tracking (PRT) Model simulates the three-dimensional trajectory of particles in flowing groundwtaer. The PRT Model solves an explicit solution for DIS and DISV grids. The PRT Model can operate simultaneously with a GWF model via an exchange, or can consume GWF outputs via Flow Model Interface (FMI).
+
 
 ## How to Cite MODFLOW 6
 

doc/mf6io/prt/prt.tex

@@ -1,20 +1,20 @@
-The PRT Model performs three-dimensional particle tracking in flowing groundwater. ...  
+The PRT Model performs three-dimensional particle tracking in flowing groundwater.
 
 This section describes the data files for a \mf Particle Tracking (PRT) Model.  A PRT Model is added to the simulation by including a PRT entry in the MODELS block of the simulation name file.  There are currently two types of spatial discretization approaches that can be used with the PRT Model: DIS and DISV.  The input instructions for these three packages are not described here in this section on PRT Model input; input instructions for these three packages are described in the section on GWF Model input.
 
-The PRT Model is designed to permit input to be gathered, as it is needed, from many different files.  Likewise, results from the model calculations can be written to a number of output files. ...  Details about the files used by each package are provided in this section on the PRT Model Instructions.
+The PRT Model is designed to permit input to be gathered, as it is needed, from many different files.  Likewise, results from the model calculations can be written to a number of output files. Details about the files used by each package are provided in this section on the PRT Model Instructions.
 
 The PRT Model reads a file called the Name File, which specifies most of the files that will be used in a simulation. Several files are always required whereas other files are optional depending on the simulation. The Output Control Package receives instructions from the user to control the amount and frequency of output.  Details about the Name File and the Output Control Package are described in this section.
 
-For the PRT Model, ``flows'' (unless stated otherwise) represent particle mass ``flow'' in mass per time, rather than groundwater flow.  In this implementation, each particle is assigned unit mass, and the numerical value of the flow can be interpreted as particles per time.
+For the PRT Model, ``flows'' (unless stated otherwise) represent particle mass ``flow'' in mass per time, rather than groundwater flow.  Each particle is currently assigned unit mass (configurable mass is planned but not yet implemented), and the numerical value of the flow can be interpreted as particles per time.
 
 \begin{enumerate}
 
-\item The PRT Model simulates transport of ...; however, because \mf allows for multiple models of the same type to be included in a single simulation, ... can be represented by using multiple PRT Models.
+\item The PRT Model simulates particle trajectories through flowing groundwater, and requires simulated groundwater flows as input. Flows can be routed to a PRT Model from a GWF Model in the same simulation via a GWF-PRT Exchange.  Alternatively, a PRT Model can read binary flow and head files saved by a previously run GWF Model via Flow Model Interface.
 
-\item The PRT Model requires simulated groundwater flows as input. Simulated flows from the GWF Model can be passed in memory to the PRT Model in the same simulation via a GWF-PRT Exchange.  Alternatively, the PRT Model can read binary flow and head files saved by a previously run GWF Model.  The current implemention of the PRT Model does not support particle tracking through the advanced stress packages or the Water Mover Package.
+\item Particle tracking is not yet supported for the advanced stress packages or the Water Mover Package.
 
-\item Although there is GWF-GWF Exchange, a PRT-PRT Exchange has not yet been developed to connect multiple particle-tracking models, as might be done in a nested grid configuration.  
+\item A PRT-PRT Exchange is planned but has not yet been developed. This exchange will connect multiple particle-tracking models, e.g. for nested grid configurations 
 
 \end{enumerate}
 
@@ -25,7 +25,7 @@ \subsection{Particle Mass Budget}
 A summary of all inflow (sources) and outflow (sinks) of particle mass is called a mass budget.  \mf calculates a mass budget for the overall model as a check on the acceptability of the solution, and to provide a summary of the sources and sinks of mass to the flow system.  The particle mass budget is printed to the PRT Model Listing File for selected time steps.  In the current implementation, each particle is assigned unit mass, and the numerical value of the flow can be interpreted as particles per time.
 
 \subsection{Time Stepping}
-In \mf time step lengths are controlled by the user and specified in the Temporal Discretization (TDIS) input file.  When the particle-tracking model and transport model are included in the same simulation, then the length of the time step specified in TDIS is used for both models.  If the PRT Model runs in a separate simulation from the GWF Model, then ....  Instructions for specifying time steps are described in the TDIS section of this user guide; additional information on GWF and PRT configurations are in the Flow Model Interface section.  
+In \mf time step lengths are controlled by the user and specified in the Temporal Discretization (TDIS) input file.  When the flow model and particle-tracking model run in the same simulation, the time step length specified in TDIS is used for both models.  If the PRT Model runs in a separate simulation, the time discretization may differ.  Instructions for specifying time steps are described in the TDIS section of this user guide; additional information on GWF and PRT configurations are in the Flow Model Interface section.  
 
 
 

src/Solution/ParticleTracker/Method.f90

@@ -21,7 +21,7 @@ module MethodModule
   !! domain. A domain can be a model, cell in a model, or subcell in
   !! a cell. Tracking proceeds recursively, delegating to a possibly
   !! arbitrary number of subdomains (currently, only the three above
-  !! are recognized). A tracking method is responsible for advecting
+  !! are recognized). A tracking method is responsible for advancing
   !! a particle through a domain, delegating to subdomains as needed
   !! depending on cell geometry (implementing the strategy pattern).
   !<