466027 Scaleout of Pipeline Drag Reduction By Wall-Injected Polyox U310 Solutions to Marine Boundary Layers

Tuesday, November 15, 2016: 2:54 PM
Continental 1 (Hilton San Francisco Union Square)
Preetinder S. Virk, Nicholas Mannarino, Hannah Capponi, Moriel Levy and Veronica Wilson, Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA

Turbulent drag reduction by wall-injected Polyox U310 solutions was studied by simultaneous axial pressure profile and flow visualization measurements at Reynolds numbers from 40000 to 102000 in a transparent test pipe of ID 15.8 mm and L/D 430. Friction factors for solvent, deionized water, adhered to the Prandtl-Karman law for Newtonian fully-developed turbulent flow in smooth pipes, 1/√f = 4.0 log Re√f - 0.4, to within 0.5 units of 1/√f. The U310 Polyox, of MW ~ 10x106, was injected as a concentrated solution Cinj = 100 wppm through 6 equi-spaced 2.3 mm ID circumferential ports at friction-normalized injection velocities Vinj+ ~ 1 << pipeline mean velocity V+ ~ 25. Downstream polymer concentrations Cline varied from 0.05 to 2 wppm, exhibiting eventual fractional drag reductions DRline from ~ 0.03 to nearly the asymptotic maximum drag reduction DRMDR ~ 0.75 possible at the present Re. Polymer dissolution into the flow was assessed from the initial increase in fractional drag reduction towards the eventual downstream DRline, which provided a characteristic development distance (L/D)dr ~ 60, and also from flash photography which provided a characteristic distance (L/D)pv ~ 100 where red-dyed strands of the injected solution disappeared. Finally, an attempt was made to “scale-out” the pipeline drag reduction observations to a flat plate boundary layer by treating the latter as an equivalent pipe flow with UCL = Uo, the free-stream velocity, R+ = duτ/ν , with d thickness, uτ friction velocity and v kinematic viscosity at the boundary layer trailing edge L. Drag reduction from the present pipe flow results, measured by flow enhancement or slip S’line = (1/√fp – 1/√fn)Re√f, was translated to the classical HMS Highburton Polyox W301 ejection trials of Canham et. al (1971). This scale-out suggested that the present Polyox U310 might have provided their reported drag reductions at roughly 1/50 th their polymer expenditure rate per unit of hull wetted area.

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