Diffusion in Fluids: Understanding Mass Transport

This lecture introduces the concept of diffusion, focusing on the transport of small particles, molecules, and dye in a fluid at rest. The instructor begins by explaining the fundamental definition of diffusion and its significance in fluid mechanics. The discussion includes the mathematical formulation of diffusion, highlighting the diffusion equation and its relationship to mass transport. The instructor emphasizes the importance of understanding diffusion in practical applications, such as mixing in chemical processes. The lecture also covers the similarities between chemical diffusion and heat conduction, clarifying common misconceptions. The instructor presents a microscopic view of diffusion, illustrating how thermal fluctuations lead to the random movement of particles. The derivation of the diffusion equation is approached from both macroscopic and microscopic perspectives, demonstrating how random walks of particles result in the diffusion equation. The lecture concludes with a discussion on estimating diffusion coefficients and their relevance in real-world scenarios, setting the stage for further exploration of fluid dynamics.