Observation of channel turbulence accompanying a rarefaction flow of a Bose-Einstein condensate

Understanding turbulence is one of the great challenges in modern hydrodynamics research. In a superfluid, the emergence of solitons and quantized vorticity in regions of turbulence leads to particularly interesting dynamics, yielding an effective viscosity in a nominally dissipationless fluid. In our previous work, we have employed a quantum mechanical piston geometry to generate a region of turbulence in a trapped Bose-Einstein condensate, and have showcased the interplay of vortices and shocks leading to an effective viscosity in the system. Here, we expand on this work and demonstrate the emergence of channel turbulence from a considerably simpler geometry: expansion into a wet-channel accompanied by rarefaction waves. This geometry provides a method for the highly repeatable and controllable generation of turbulence, allowing us to conduct detailed studies of system parameters determining the onset of turbulence. Our experimental results are corroborated by matching numerical studies. This approach to generate channel turbulence in a superflow provides important benchmark data for theoretical modeling, and opens new avenues for research, such as the merging of two turbulent regions which we also demonstrate in prototypical experiments.