Selected Animations


  • Turbulent Drag Reduction
  • Shear-Induced DNA Migration
  • Populations of Swimming Microorganisms
  • Swimming Organism with Multiple Flexible Flagella
  • Dynamics of Cells under Flow
  • Also, see us on YouTube: How to swim in corn syrup.


    Turbulent Drag Reduction


    Animation of an "exact coherent state", a three-dimensional, traveling-wave solution to the Navier-Stokes equation in pressure-driven channel flow. Our group uses these solutions to study how polymer additives affect turbulent flows (e.g. Stone, P. A. et al., Phys. Rev. Lett., 89, 208301 (2002)).


    Shear-Induced DNA Migration

     


    Animation of a single DNA molecule in solution during simple shear flow near a single wall. Our group has studied the mechanisms responsible for the migration of this long flexible polymer away from the wall. (see e.g. Jendrejack, R. M. et al., Phys. Rev. Lett., 91, 038102 (2003)).


    Populations of Swimming Microorganisms

     


    Simulation of microorganisms swimming in a thin film of fluid. Very often, the model organisms are seen swimming in pairs, a result of the fluid motions generated by the organisms as they move though the fluid. (see e.g. Underhill, P. T. et al., Phys. Rev. Lett., 100, 248101 (2008)).


    Swimmimng Organism with Multiple Flexible Flagella

     


    A swimming cell, modeled as a spherical body with two rotating flagella in a viscous fluid. The flagella, modeled as thin flexible helical filaments rotate counterclockwise, and in response the cell body rotates clockwise as it swims.


    Dynamics of Cells under Flow

     


    Simulation of model cells colliding during shear flow.  The dynamics of collisions are important for the distribution of red blood cells in the circulation.


    How to Swim in Corn Syrup

    Everyone enjoys the sight of a beautiful fish waving its tail back and forth to propel itself through the water. Not as easily visible, but equally fascinating, are the swimming motions of microorganisms, with their beating patterns of cilia or their twisting flagella. But why don't microorganisms have a tail like a fish -- what could be simpler for evolution to design than a simple flapping tail? Well, for a microorganism, even water is a highly viscous fluid (like corn syrup to a fish), and as you'll see below, it turns out that a flapping tail won't propel a fish-sized swimmer in corn syrup.

            Many years ago, the great 20th century fluid dynamicist G. I. Taylor developed simple models to demonstrate the principles of swimming. As part of an NSF-supported educational outreach project, we recreated his model swimmers and produced the movies shown below, which you can find on YouTube.

    This is a rubber band-powered swimmer which uses a common flapping mechanism for swimming in water. This is a great system for swimming at a high Reynolds number. As the back flaps it pushes water back in vortices.



    This is the same rubber band-powered swimmer used in the previous video but in corn syrup.



    This is a rubber band-powered swimmer in corn syrup that uses rotating helical wires to produce thrust by the difference in drag along and perpendicular to the wire. There are many microorganisms such as E. coli that use helical flagella to propel themselves in much the same way.