Fluid Mechanics
Transition from laminar flow to turbulent flow is aided by the

Surface roughness and curvature (i.e.sharp corners)
Pressure gradient and the compressibility of the flowing medium
All of these
Vibration

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Fluid Mechanics
Turbine impeller

Does not produce tangential current
Is effective over wide range of viscosities
Produces only radial current
Produces only tangential current

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