User's guide of Proceessing Modflow 5.0

Processing Modflow 183
The retardation factor R is defined by
R ' 1 % D b
n @K d
v x1 ' Q x1 /(n@)y@)z)/R
v x2 ' Q x2 /(n@)y@)z)/R
v y1 ' Q y1 /(n@)x@)z)/R
v y2 ' Q y2 /(n@)x@)z)/R
v z1 ' Q z1 /(n@)x@)y)/R
v z2 ' Q z2 /(n@)x@)y)/R
(4.8)
where D is the bulk mass density of the porous medium, n is the effective porosity, and K is the
b d
distribution coefficient. A detailed description of these parameters can be found in the literature,
e.g., Freeze and Cherry (1979). The retardation factor was first applied to groundwater problems
by Higgins (1959) and Baetsle (1967). Baetsle indicated that it may be used to determine the
retardation of the center of mass of a contaminant moving from a point source while undergoing
adsorption. PMPATH uses the retardation factor to modify the average pore velocity of the
groundwater flow. The velocity vectors in equation (4.3a)-(4.3f) become
Erase particle
(4.9a)
(4.9b)
(4.9c)
(4.9d)
(4.9e)
(4.9f)
You can only erase particles located in the current layer. The current layer is shown in the tool
bar. Change it first, if you need to erase particles in another layer.
< To delete particles
1. Click the Erase particle button .
2. Move the mouse cursor to where you want a corner of the "Erase" window.
3 Drag the mouse cursor until the window covers the particles which will be deleted.
4. Release the mouse button.
Zoom In
By default, PMPATH displays the entire model grid. Zoom in is useful, if you want to view a
part of the model domain in greater detail or if you want to save plots of a certain part of the
model area (see Sec 4.4 for how to save plots).
4.2 PMPATH Modeling Environment