News from Peace Heaven, the professional DRA (Drag-Reducing Agents) supplier

Addition of small amounts of polymers to a fluid undergoing fully developed turbulent channel or pipe flow can yield significant increase in the mass flow for a given pressure gradient. This phenomenon is referred to as polymer induced turbulent drag reduction (DR). DR has been successfully used for crude-oil transport and has potential application for surface-water and under-water transports. The DR project is supported by DARPA and is in collaboration with faculties in the Naval Architecture and Marine Engineering Department. The ultimate goal is to develop new and feasible technologies for fast ocean transport by reducing power requirement. A phase modulated flow birefringence method is being used to quantify polymer chain orientation and deformation in a drag reducing turbulent channel flow. Chain orientations are measured at different heights of the channel to study the contribution of different layers for reducing the drag.

One of the complexities encountered during polymer induced drag reduction is degradation or scission of polymer chains which hamper their effectiveness as a drag reducing agent. The second project is aimed at studying conditions and mechanisms for flow induced polymer chain scission. Chain scission or polymer degradation (as it is commonly referred to) is an important aspect of many technological applications such as polymer drag reduction, melt processing and recently sequencing strategies for DNA.

We are experimentally investigating polymer chain scission in turbulent and extensional flows. Our scission studies in turbulent flows have enabled us to identify a new upper limit for polymer drag reduction that is determined by chain scission rather than the maximum drag reduction asymptote. We are now focusing on studying chain scission in purely extensional flows. The figures below show two cross-slot devices that will be used to study chain scission in inertial and viscous (creeping flow limit ) planar elongational flows. The results from these studies would be used to validate scission theories.