Laminar flow transition threshold

A recent investigation of the Tilling of CNTs with nonpolar liquids found that reducing the diameter of the CNT reduces the solid liquid interfacial tension. From theoretical considerations, the authors calculated the surface tension of the CNT to be 50 mN m , close to experimental values found in literature (28-45 mN m ). A transition between Poiseuille laminar flow and ballistic flow inside a CNT below a nm diameter threshold was also obtained from theoretical calculations. 

The ratio of t/t, which is characteristic of the possibility of vortices, does not depend on the micro-channel diameter and is fully determined by the Reynolds number and L/d. The lower value of Re at which f/fh > 1 can be treated as a threshold. As was shown by Darbyshire and Mullin (1995), under conditions of an artificial disturbance of pipe flow, a transition from laminar to turbulent flow is not possible for Re < 1,700, even with a very large amplitude of disturbances. 

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