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Model ID: 500

Variable Saturated Flow

This example utilizes the Richards’ Equation application mode to assess how well geophysical irrigation sensors see the true level of fluid saturation in variably saturated soils. Andrew Hinnell, Alex Furman, and Ty Ferre from the Department of Hydrology and Water Resources at the University of Arizona brought the example to us. Originally worked out in the PDE modes in COMSOL Multiphysics, we share their elegant model reformulated in the Richard’s Equation application modes.

The challenge to characterizing fluid movement in variably saturated porous media lies primarily in the need to describe how the capacity to transmit and store fluids changes as fluids enter and fill the pore space. Experimental data for these properties are difficult to obtain. Moreover, the properties that change value as the soil saturates happen to be equation coefficients, which makes the mathematics notoriously nonlinear.

The Richards’ Equation application mode provides interfaces that automate the van Genuchten and the Brooks and Corey relationships for fluid retention and material properties that vary with the solution.

COMSOL Multiphysics solution for effective saturation (surface), pressure head (contours), and velocity (arrows) at 30 minutes.

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