Introduction to the Physics of Granular Matter (WS 20/21)

Prof. Dr. Matthias Sperl

Matthias dot Sperl at dlr.de

Dr. Philip Born

Philip dot Born at dlr.de

Dr. Till Kranz

kranz at thp.uni-koeln.de

News

Course Description

Granular matter is an example for a physical system far from equilibrium: Dissipative collisions among the constituent particles break time reversal symmetry and a constant energy input is necessary to establish a non-equilibrium steady state. The course shall give an overview of the current understanding of the physics of granular materials comprising theory, computer simulation as well as laboratory and microgravity experiments. Beyond the current state of the art, open research questions shall be reviewed as well as implications for applications.

Topics include

Granular Phenomena in Nature
Sand Piles; Avalanches; Formation and Migration of Dunes, etc.
Granular Packings
Mechanical Properties; Critical Behavior; Non-Destructive Techniques
Granular Fluids
Kinetic Theory; Rheology; Computer Simulation; Experiments in Microgravity

Lecture (online only)

Tuesday

10:00 – 11:30

New video lectures may appear around this time

Thursday

9:15 – 10:00

We will be live on Zoom for questions and comments and later in the semester for the seminar presentations

The password for both the videos and Zoom can be found on Ilias
  1. Lecture November 3
    1. Welcome & Organization (pdf)

    2. Teaser & Outline

    3. Some numbers & Terms

    4. Some (more) numbers & Terms

  2. Lecture November 5

    Dissipation & Friction

  3. Lecture November 10
    1. Forces in Granular Packings & Stress Birefringence

    2. Force Chains & Heterogeneities

  4. Lecture November 12

    Sound Propagation in Granular Matter

  5. Lecture November 17
    1. Granular Plasticity & Mohr's Circle (featuring a beautiful & exclusive experiment)

    2. Mohr's Circle & The Coulomb Yield Criterion

  6. Lecture November 19

    The Mohr-Coulomb Failure Analysis

  7. Lecture November 24
    1. Consequences of the Failure Analysis

    2. Angle of Repose (featuring two(!) beautiful & exclusive experiments)

  8. Lecture November 26

    The Angle of Repose in Nature

  9. Lecture December 1
    1. The Janssen Effect

    2. Hour Glass Theory

  10. Lecture December 3

    Subtleties of the Granular Constant

  11. Lecture December 8
    1. The Hunt for a State Variable

    2. The Jamming Transition

  12. Lecture December 10

    Examples of Granular Flow

  13. Lecture December 15
    1. Conservation of Mass & Diffusion

    2. The Navier-Stokes Equation

  14. Lecture December 17

    The Temperature Field

  15. Lecture December 22
    1. Inelastic Collisions

      The whiteboard is frozen for part of this video. Apologies for that

    2. Solving for the postcollisional Velocities

    3. The Inelastic Collapse

    4. Bonus: Calculate π by colliding blocks

  16. Lecture Januar 12
    1. Excursion: The Isothermal Fluid

    2. Hydrodynamic Modes

  17. Lecture January 14

    Estimating the Viscosity & Kinetic Theory

  18. Lecture January 19
    1. The Liouville Operator

    2. The BBGKY hierarchy & the Boltzmann Equation

  19. Lecture January 26
    1. Haff's Law & The Collision Frequency

    2. The Velocity Distribution & The Homogeneous Cooling State

  20. Lecture February 2
    1. Stability of the Homogeneous Cooling State

    2. From the Boltzmann Equation to the macroscopic Balance Equations

    3. Sheared Granular Fluids & Bagnold Scaling

  21. Lecture February 9
    1. The μ(I)-rheology

      (Audio only, due to a technical glitch. Please refer to the Mural for written notes)

    2. Integration Through Transients

  22. Lecture February 11

    Deriving the the μ(I)-Law

    (Apologies for the simultaneous teaching by Philip & Till towards the end)

Recommended Reading

Lecture Notes

Seminar

The seminar takes place on Thursdays 9:15 – 10:00. The dates are according to individual agreement. Questions should be addressed to Matthias Sperl

Januar 7
The Brazilnut Effect
January 21
A Minimal Model for Dunes
January 28
Wet Granular Matter
February 4
Stress Dip under a Sand Pile

Suggested Topics

Phenomena

Experiments

Experimental Techniques

A variety of imaging and tracking techniques could be discussed

Simulation

Theory