4. Diffusion

Try these first

1. 1.

   Define diffusion in terms of concentration.

   Hint

   Think about how smells spread in a room.

2. 2.

   What is the primary factor affecting effective diffusivity?

   Hint

   How open is the material?

3. 3.

   What drives the process of diffusion?

   • Concentration gradient
   • Temperature
   • Pressure

   Hint

   It's about where something is more and less present.

4. 4.

   True or False: The local equilibrium assumption holds true for all flow velocities.

   • True
   • False

   Hint

   At high speeds, processes change quickly.

5. 5.

   Describe a real-world scenario where the local equilibrium assumption may fail. What implications would that have for modeling diffusion?

   Hint

   Consider factors like time and speed in response to diffusion.

6. 6.

   Using Fick's laws, derive the mathematical expression for effective diffusivity in a soil-water system, incorporating porosity.

   Hint

   Start with diffusion equations and how they relate to porous media.