User's guide of Proceessing Modflow 5.0

68 Processing Modflow
3.4 The Grid Menu
Mesh Size
Allows you to generate or modify a model grid. See Section 3.1 for how to use the Grid Editor.
Layer Type
Select Layer Type to open the Layer Options dialog box (Fig. 3.14). The elements of this dialog
box are described below.
< Type
The numerical formulations, which are used by the Block-Centered-Flow (BCF) package to
describe groundwater flow, depend on the type of each model layer. The layer types are:
Type 0 The layer is strictly confined. For transient simulations, the confined storage
3.4 The Grid Menu
coefficient (specific storage × layer thickness) is used to calculate the rate of change
in storage. Transmissivity of each cell is constant throughout the simulation.
Type 1 The layer is strictly unconfined. The option is valid for the first layer only. Specific
yield is used to calculate the rate of change in storage for this layer type. During a flow
simulation, transmissivity of each cell varies with the saturated thickness of the
aquifer.
Type 2 A layer of this type is partially convertible between confined and unconfined.
Confined storage coefficient (specific storage × layer thickness) is used to calculated
the rate of change in storage, if the layer is fully saturated, otherwise specific yield will
be used. Transmissivity of each cell is constant throughout the simulation. Vertical
leakage from above is limited if the layer desaturates.
Type 3 A layer of this type is fully convertible between confined and unconfined. Confined
< Anisotropy factor
storage coefficient (specific storage × layer thickness) is used to calculate the rate of
change in storage, if the layer is fully saturated, otherwise specific yield will be used.
During a flow simulation, transmissivity of each cell varies with the saturated
thickness of the aquifer. Vertical leakage from above is limited if the layer desaturates.
The anisotropy factor is the ratio of transmissivity or hydraulic conductivity (whichever is being
used) along the I-direction to transmissivity or hydraulic conductivity along the J-direction. The