Application of Thermodynamics to Stability of Flow and Drag Reduction
Dimensionless numbers exist to describe the onset of secondary flows and the onset of turbulence, in various geometries. For example, in flow in bent pipes and in porous materials secondary flows suddenly begin to contribute to the pressure gradient when the Dean number L’ = 276; in Couette flow between coaxial cylinders (inner rotating) secondary flows suddenly contribute to the torque when the Taylor number Ta ≃ 3400; in flow through straight pipes the flow becomes turbulent when the Reynolds number Re < 1000.
KeywordsSecondary Flow Drag Reduction Couette Flow Coaxial Cylinder Taylor Number
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