Session Ch - Convection & Buoyancy.
ORAL session, Sunday, November 23
308, Moscone Center
Multiple solutions are common in fluid mechanics, from either the quadratic nature of the Euler or Navier-Stokes equations, or nonlinear terms associated with convection, free interfaces, or Non Newtonian effects. But problems where many solutions are steady and stable for identical boundary conditions are relatively rare. Many recent examples have been found in oceanic climate problems in which two states are both steady and completely stable. A number have been reproduced in the laboratory. If convection is driven by both heat and salinity differences, for instance, a convection cell is readily constructed that is driven principally by either temperature or salinity difference for the same forcing conditions. If convective motion is opposed by surface stress, an analog device can be made using pressure difference instead of stress, and air instead of heat, which possesses two stable, steady states. Multiple state effects are found in by a broad class of circulation and estuary models such as a coastal current of fresh water in salty rotating water and convection cooled from above when the water is salt stratified. The simplified equations for these types of examples will be discussed, and their probable occurrence in other areas of fluid mechanics, such as ventilation, combustion, and geophysics will be mentioned.