flopy.mt3d.mtadv module

class Mt3dAdv(model, mixelm=3, percel=0.75, mxpart=800000, nadvfd=1, itrack=3, wd=0.5, dceps=1e-05, nplane=2, npl=10, nph=40, npmin=5, npmax=80, nlsink=0, npsink=15, dchmoc=0.0001, extension='adv', unitnumber=None, filenames=None)[source]

Bases: flopy.pakbase.Package

MT3DMS Advection Package Class.

Parameters:
  • model (model object) – The model object (of type flopy.mt3d.mt.Mt3dms) to which this package will be added.
  • mixelm (int) – MIXELM is an integer flag for the advection solution option. MIXELM = 0, the standard finite-difference method with upstream or central-in-space weighting, depending on the value of NADVFD; = 1, the forward-tracking method of characteristics (MOC); = 2, the backward-tracking modified method of characteristics (MMOC); = 3, the hybrid method of characteristics (HMOC) with MOC or MMOC automatically and dynamically selected; = -1, the third-order TVD scheme (ULTIMATE).
  • percel (float) – PERCEL is the Courant number (i.e., the number of cells, or a fraction of a cell) advection will be allowed in any direction in one transport step. For implicit finite-difference or particle-tracking-based schemes, there is no limit on PERCEL, but for accuracy reasons, it is generally not set much greater than one. Note, however, that the PERCEL limit is checked over the entire model grid. Thus, even if PERCEL > 1, advection may not be more than one cell’s length at most model locations. For the explicit finite-difference or the third-order TVD scheme, PERCEL is also a stability constraint which must not exceed one and will be automatically reset to one if a value greater than one is specified.
  • mxpart (int) – MXPART is the maximum total number of moving particles allowed and is used only when MIXELM = 1 or 3.
  • nadvfd (int) – NADVFD is an integer flag indicating which weighting scheme should be used; it is needed only when the advection term is solved using the implicit finite- difference method. NADVFD = 0 or 1, upstream weighting (default); = 2,central-in-space weighting.
  • itrack (int) – ITRACK is a flag indicating which particle-tracking algorithm is selected for the Eulerian-Lagrangian methods. ITRACK = 1, the first-order Euler algorithm is used. = 2, the fourth-order Runge-Kutta algorithm is used; this option is computationally demanding and may be needed only when PERCEL is set greater than one. = 3, the hybrid first- and fourth-order algorithm is used; the Runge-Kutta algorithm is used in sink/source cells and the cells next to sinks/sources while the Euler algorithm is used elsewhere.
  • wd (float) – is a concentration weighting factor between 0.5 and 1. It is used for operator splitting in the particle- tracking-based methods. The value of 0.5 is generally adequate. The value of WD may be adjusted to achieve better mass balance. Generally, it can be increased toward 1.0 as advection becomes more dominant.
  • dceps (float) – is a small Relative Cell Concentration Gradient below which advective transport is considered
  • nplane (int) – NPLANE is a flag indicating whether the random or fixed pattern is selected for initial placement of moving particles. If NPLANE = 0, the random pattern is selected for initial placement. Particles are distributed randomly in both the horizontal and vertical directions by calling a random number generator (Figure 18b). This option is usually preferred and leads to smaller mass balance discrepancy in nonuniform or diverging/converging flow fields. If NPLANE > 0, the fixed pattern is selected for initial placement. The value of NPLANE serves as the number of vertical ‘planes’ on which initial particles are placed within each cell block (Figure 18a). The fixed pattern may work better than the random pattern only in relatively uniform flow fields. For two-dimensional simulations in plan view, set NPLANE = 1. For cross sectional or three-dimensional simulations, NPLANE = 2 is normally adequate. Increase NPLANE if more resolution in the vertical direction is desired.
  • npl (int) – NPL is the number of initial particles per cell to be placed at cells where the Relative Cell Concentration Gradient is less than or equal to DCEPS. Generally, NPL can be set to zero since advection is considered insignificant when the Relative Cell Concentration Gradient is less than or equal to DCEPS. Setting NPL equal to NPH causes a uniform number of particles to be placed in every cell over the entire grid (i.e., the uniform approach).
  • nph (int) – NPH is the number of initial particles per cell to be placed at cells where the Relative Cell Concentration Gradient is greater than DCEPS. The selection of NPH depends on the nature of the flow field and also the computer memory limitation. Generally, a smaller number should be used in relatively uniform flow fields and a larger number should be used in relatively nonuniform flow fields. However, values exceeding 16 in two-dimensional simulation or 32 in three- dimensional simulation are rarely necessary. If the random pattern is chosen, NPH particles are randomly distributed within the cell block. If the fixed pattern is chosen, NPH is divided by NPLANE to yield the number of particles to be placed per vertical plane, which is rounded to one of the values shown in Figure 30.
  • npmin (int) – is the minimum number of particles allowed per cell. If the number of particles in a cell at the end of a transport step is fewer than NPMIN, new particles are inserted into that cell to maintain a sufficient number of particles. NPMIN can be set to zero in relatively uniform flow fields and to a number greater than zero in diverging/converging flow fields. Generally, a value between zero and four is adequate.
  • npmax (int) – NPMAX is the maximum number of particles allowed per cell. If the number of particles in a cell exceeds NPMAX, all particles are removed from that cell and replaced by a new set of particles equal to NPH to maintain mass balance. Generally, NPMAX can be set to approximately two times of NPH.
  • interp (int) – is a flag indicating the concentration interpolation method for use in the MMOC scheme. Currently, only linear interpolation is implemented.
  • nlsink (int) – s a flag indicating whether the random or fixed pattern is selected for initial placement of particles to approximate sink cells in the MMOC scheme. The convention is the same as that for NPLANE. It is generally adequate to set NLSINK equivalent to NPLANE.
  • npsink (int) – is the number of particles used to approximate sink cells in the MMOC scheme. The convention is the same as that for NPH. It is generally adequate to set NPSINK equivalent to NPH.
  • dchmoc (float) – DCHMOC is the critical Relative Concentration Gradient for controlling the selective use of either MOC or MMOC in the HMOC solution scheme. The MOC solution is selected at cells where the Relative Concentration Gradient is greater than DCHMOC. The MMOC solution is selected at cells where the Relative Concentration Gradient is less than or equal to DCHMOC.
  • extension (string) – Filename extension (default is ‘adv’)
  • unitnumber (int) – File unit number (default is None).
  • filenames (str or list of str) – Filenames to use for the package. If filenames=None the package name will be created using the model name and package extension. If a single string is passed the package will be set to the string. Default is None.

Notes

Examples

>>> import flopy
>>> m = flopy.mt3d.Mt3dms()
>>> adv = flopy.mt3d.Mt3dAdv(m)
classmethod load(f, model, ext_unit_dict=None)[source]

Load an existing package.

Parameters:
  • f (filename or file handle) – File to load.
  • model (model object) – The model object (of type flopy.mt3d.mt.Mt3dms) to which this package will be added.
  • ext_unit_dict (dictionary, optional) – If the arrays in the file are specified using EXTERNAL, or older style array control records, then f should be a file handle. In this case ext_unit_dict is required, which can be constructed using the function flopy.utils.mfreadnam.parsenamefile.
Returns:

adv – Mt3dAdv object.
Return type:

Mt3dAdv object

Examples

>>> import flopy
>>> mt = flopy.mt3d.Mt3dms()
>>> adv = flopy.mt3d.Mt3dAdv.load('test.adv', m)
write_file()[source]

Write the package file

Returns:
Return type:None