A CHAOTIC ATTRACTOR IN A PERIODICALLY FORCED 2-PHASE FLOW SYSTEM

Motivated by the enhancement of heat transfer under oscillating flow conditions in single-phase heated channels and by stability problems in two-phase systems such as those in boiling water reactors, density-wave oscillations have been analyzed by numerically solving the nonlinear, variable delay, functional, ordinary integrodifferential equations that result from integrating the nonlinear partial differential equations for the single- and two-phase heated channel regions along characteristics and along channel length for axially uniform heat fluxes. The cases of constant pressure drop ΔPex across the channel (steady-state feed pump operation), exponentially decaying ΔPex (feed pump coastdown), and periodic ΔPex (feed pump oscillations) were studied. The nature of the strange attractor was analyzed quantitatively by calculating its correlation dimension - an estimate of its fractal dimension - and the dimension of the phase space in which it can be embedded. These calculations indicate that the change attractor is indeed a fractal object of fractional dimension 2.048±0.003 and embedding dimension 6.