We report experiments conducted in Taylor-Couette and plane Couette flows considering both the transition from laminar to turbulent flow and the reverse transition from turbulent to laminar flow. In the first case, the transition is dis?continuous and is characterized by laminar-turbulent coexistence. The transition is controlled by the existence of finite amplitude solutions. In the second case, unexpectedly, the transition is continuous and leads to a periodical stripes pattern whose wavelength is large compared to the shear scale. This pattern can even be described in a generalized noisy Ginzburg-Landau formalism. In this context, the intermittent and disordered laminar-turbulent coexistence can be seen as the ultimate stage of the modulation of the turbulent flows.
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