Roll-waves in bi-layer flows
  In this paper, we derive consistent shallow water equations for bi-layer flows of Newtonian fluids flowing down a ramp. We carry out a complete spectral analysis of steady flows in the low frequency regime and show the occurence of hydrodynamic instabilities, so called roll-waves, when steady flows are unstable. 
Marc Boutounet (INSA Toulouse), Pascal Noble (ICJ), Jean-Paul Vila   (IMT)
physics.flu-dyn