Hydrodynamic fluctuations and instabilities in ordered suspensions of self-propelled particles

Phys Rev Lett. 2002 Jul 29;89(5):058101. doi: 10.1103/PhysRevLett.89.058101. Epub 2002 Jul 15.


We construct the hydrodynamic equations for suspensions of self-propelled particles (SPPs) with spontaneous orientational order, and make a number of striking, testable predictions: (i) Nematic SPP suspensions are always absolutely unstable at long wavelengths. (ii) SPP suspensions support novel propagating modes at long wavelengths, coupling orientation, flow, and concentration. (iii) In a wave number regime accessible only in low Reynolds number systems such as bacteria, polar-ordered suspensions are invariably convectively unstable. (iv) The variance in the number N of particles, divided by the mean <N>, diverges as <N >(2/3 ) in polar-ordered SPP suspensions.

MeSH terms

  • Animals
  • Behavior, Animal
  • Cell Movement*
  • Leukocytes / cytology
  • Melanocytes / cytology
  • Models, Biological*
  • Movement