[LiquidFlow] Aperture size for inclined element

Inclined element represents apertures (or fractures) in the rock mass. In the existing implementation of the integration over inclined element, the aperture size (i.e. thickness of 2D element or cross section area of 1D element) is not considered. This MR fixes this issue by introducing a Parameter type variable to the process data struct to store the aperture sizes. In the initialization of the local assembler, the numerical integration weights are directly multiplied by the aperture sizes. Therefore, the aperture sizes are assumed to be independent of time.

All three existing tests for inclined element are modified to test the new feature:

• 2D fracture in 3D space: element thicknesses are randomly assigned with MeshElement type Parameter variable.

  

• 2D fracture in 3D domain: element thicknesses are assigned with Group type Parameter variable with material IDs.

  

• line in 3D space: homogeneous element area is assigned to all line elements with Constant type Parameter variable.

Since the apertures sizes are homogeneous, the test solutions of this test are not changed at all.

1. Feature description was added to the changelog
2. Tests covering your feature were added?
3. Any new feature or behavior change was documented?