Physics 345 - Unruly Matter: Flow, Instability, and Turbulence

Fluids-air, water, plasmas, and soft biological media-are ubiquitous in nature, shaping
phenomena from the motion of cells and blood to weather systems, oceans, stars, and galaxies.
This course explores the physics of fluids as dynamical systems, with a focus on how smooth,
orderly flows become unstable, nonlinear, and turbulent. Beginning with the continuum
description of matter and the fundamental conservation laws of mass, momentum, and energy,
we develop the Euler and Navier–Stokes equations and use them to understand a wide range of
physical phenomena.
 

Topics include vorticity and circulation, boundary layers and drag, flow instabilities, the
transition from laminar to turbulent motion, as well as highly viscous flow and diffusion.
Throughout the course, emphasis is placed on scaling arguments, nondimensionalization, and
approximation techniques-core tools that allow us to reason quantitatively about complex
systems that cannot be solved exactly.
 

Applications are drawn broadly from astrophysical and space plasmas, geophysical and
oceanographic flows, engineering and industrial systems, biological transport and locomotion at
cellular and organismal scales, and fluid dynamics in the human body. By highlighting the shared
physical principles underlying these seemingly disparate systems, the course presents fluid
mechanics as a unifying framework connecting physics, applied mathematics, engineering, and
the life and Earth sciences.

Fall semester. Professor Loinaz