Drag reduction by surface treatment in turbulent Taylor-Couette flow

We use a Taylor-Couette facility to study the drag reducing effects of commercial surface products at high shear Reynolds numbers (Re-s) under perfect, couter-rotating conditions (r(i)omega(i) = -r(o)omega(o)). The correlation between torque contribution of the von Karman flow and shear Reynolds number is investigated. At this moment no significant drag changes are found for the commercial products. However, further research is needed to exclude uncertainties and errors from the torque measurements.