Effect of turbulence on Taylor dispersion for oscillatory flows

Experiments were carried out to explore the effect of the turbulence on Taylor dispersion for oscillatory tube flow. We found from measured velocity profiles that, while the velocity fluctuations exist over the parameter range in the present investigation, periodic conditional turbulent flow occurs and the turbulence intensity increases rapidly when the Stokes layer-based Reynolds number exceeds 535. The effective axial mass diffusivity for oscillatory flow deviate from the theoretical predictions corresponding to laminar flow as Reδ value increases, and the deviation becomes noticeable as Reδ increases to 235. It was also found that an ratio of effective diffusivity to theoretical value for laminar flow as large as 100 is available during turbulent oscillatory flows.