Effects of polymer addition on transition and length scales of flow structures in transitional channel flow

The effect of polymer addition on transition to turbulence in a two-dimensional water-flow channel was experimentally investigated by flow visualization using reflective flakes. entering the test section maintains high disturbance level expanding laterally after reaching Reynolds number upstream section. In order obtain intermittency factor (turbulence fraction), visualized images were classified into non-turbulent and turbulent regions, streamwise scale streaks appearing region estimated from autocorrelation coefficient computed shifting direction. results show that similar pure water case, intermittent with patch-like distribution areas clustered is observed. at which increases shifts toward higher numbers increasing concentration, indicating delay transition. elongate concentration. At concentrations, straight elongated penetrate through suggesting affects stability streaks. These changes streak behavior indicate not only but also structure during process.