Effective Stress, Composite Velocity & Porosity in Deformable Porous Media — Lesson 3

This lesson covers the concept of flow through deformable porous media, focusing on varying porosity and its relation to effective stress. It explains the continuity equations for both the solid and fluid phases, and the concept of interstitial velocities. The lesson also discusses how porosity changes over time, affecting the permeability of the porous medium. It introduces the concept of composite velocity and Darcy's law, and explains how the relative velocity of the liquid with respect to the solid follows this law. The lesson further delves into the relationship between excess stress and pressure, and how these factors affect the deformation gradient. It concludes by explaining how to solve the governing equation for the change in solid volume fraction with time, using appropriate initial and boundary conditions.

Video Highlights

00:44 - Introduction to composite velocity and Darcy's law
02:24 - Relationship between excess stress and pressure
07:04 - Solving the governing equation for change in solid volume fraction
17:21 - Explanation of boundary conditions and initial conditions

Key Takeaways

- The flow through deformable porous media is affected by varying porosity and effective stress.
- Two continuity equations, one for the solid phase and another for the liquid phase, are used to understand the flow.
- The composite velocity, which is the average velocity of the suspension, is a crucial concept in understanding the flow.
- Darcy's law explains the relative velocity of the liquid with respect to the solid.
- The governing equation for the change in solid volume fraction with time can be solved using appropriate initial and boundary conditions.