Three-dimensional advective flows in a horizontal cylinder of square section with thermally insulated lateral boundaries

Three-dimensional advective flows in a horizontal cylinder of square section are numerically investigated under thermally insulated lateral boundaries and in the presence of a uniform longitudinal temperature gradient. The flow structure is shown to considerably depend on the Grashof number, the channel length, and the Prandtl number; depending on these parameters, the flow symmetrymode and its temporal behavior may be different. It is established that different cases of transition to oscillatory flow regimes are possible, namely, either with a preliminary violation of the flow symmetry (fork bifurcation) or without a change in the type of symmetry. The parameter range on which only the fork bifurcation is observable, while oscillatory flow patterns do not appear, is also determined.