The Layered Darcy’s Law Interface
The Layered Darcy’s Law (ldl) interface (), found under the Porous Media and Subsurface Flow branch () when adding a physics interface, is used to simulate flow within layered porous materials which are defined on boundaries within a 3D model domain. It is only available for 3D simulations and is only active on all boundaries where a layered material is defined.
A layered material can be defined on the boundaries by adding one of the following nodes:
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 Single Layer Material
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 Layered Material Link, together with a Layered Material node
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 Layered Material Stack, together with one or several Layered Material nodes
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 Material, with the Layer thickness property specified
See Layered Material, Layered Material Link, Layered Material Stack, Layered Material Link (Subnode), and Single Layer Materials in the COMSOL Multiphysics Reference Manual for details on the definition of layered materials.
The physics interface uses a variant of Darcy’s law and can be used for stationary and time-dependent analysis. Although the layered material is represented as a boundary in the model, the through-thickness variation of the pressure is accounted for. In addition, a single boundary may represent several layers with different properties varying through the thickness of the layered material. This uses the Extra Dimension tool which defines the equations on the product space between the boundary and the additional dimension for the thickness of the layered material.
When this physics interface is added, the following default nodes are also added to the Model Builder: Fluid and Matrix Properties, No Flow (the default edge condition), and Initial Values. Then, from the Physics toolbar, add other nodes that implement, for example, edge conditions and mass sources. You can also right-click Layered Darcy's Law to select physics features from the context menu.