I have tried to explore the information but still not very clear on the exact difference between diffusion, convection and advection. Can anyone help me out to clear my concept?
Answer
Convection is the collective motion of particles in a fluid and actually encompasses both diffusion and advection.
- Advection is the motion of particles along the bulk flow
- Diffusion is the net movement of particles from high concentration to low concentration
We typically describe the above two using the partial differential equations: \begin{align} \frac{\partial\psi}{\partial t}+\nabla\cdot\left(\mathbf u \psi\right)&=0\tag{advection}\\ \frac{\partial\psi}{\partial t}&=\nabla\cdot\left(D\nabla\psi\right)\tag{diffusion} \end{align} where $\psi$ is the quantity in consideration, $\mathbf u$ is the fluid velocity and $D$ the diffusion coefficient (sometimes called the diffusivity).
There are some nuances to the combined effect for convection (e.g., forced, natural, gravitational mechanisms), but the general definition for it is the total motion.
No comments:
Post a Comment