The ability of a polymer solution to reduce the drag within a turbulent flow is dependent on the polymer type, its molecular weight and the polymer concentration. Within a turbulent boundary layer, the local molecular weight and polymer concentration are dependent on polymer degradation and polymer diffusion, respectively. Given a local polymer concentration and molecular weight, the velocity profile is modified from the Newtonian via polymeric stresses redistributing the momentum in the near-wall region, which results in drag reduction. Consequently, examination of the near-wall velocity profile modifications relative to the Newtonian condition is primarily dependent on the drag reduction. In the classical view, it is exclusively determined based on the level of drag reduction, but recent computational and experimental results have shown that particularly at high drag reduction (HDR; \>40%) the modifications are influenced by flow and polymer properties. This past work provided evidence that at HDR there is some evidence that the behavior is Reynolds number dependent. However, since that work focused on a single flow configuration (turbulent boundary layer), an inability to fully collapse the data indicates that polymeric properties must also be considered in examining modifications to the near-wall velocity profile in the HDR regime.

 

There has been recent work that studied the impact of polymer drag reduction on coherent structures and the near-wall velocity profiles within a homogeneous polymer concentration. The uniform concentration was achieved by creating polymer oceans with a steady-state molecular weight sufficiently high that it still produced significant drag reduction. The current study will compare these recent works with the more well established findings of near-wall velocity profiles modified with injection of drag-reducing polymer solution within a developing turbulent boundary layer. This is particularly interesting given the recent findings from both high-Reynolds number experiments and DNS simulations that the classical view of how the inertial range is modified with polymer solution is not accurate. The sensitivity to the drag reduction regime (low drag reduction (LDR) versus high drag reduction (HDR)), Reynolds number, and polymer properties (Weissenberg number, viscosity ratio, and length ratios) will be discussed. This will also review past literature and assess if degradation was expected, and if so, an estimate of the local polymer properties. There will also be recent experimental results presented from polymer drag reduction studies within a custom designed recirculating water tunnel that can achieve speeds up to 10 m/s.


Comparison of Turbulent Boundary Layer Profiles Modified With Injection or Uniform Concentration of Drag-Reducing Polymer Solution

Division / Sponsors: 
Heat Transfer Division (HTD), Fluids Engineering Division (FED)

Heat Transfer Summer Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/HT/HT2020/volume/83709

18th International Conference on Nanochannels, Microchannels, and Minichannels
Paper Proceedings: https://asmedigitalcollection.asme.org/ICNMM/ICNMM2020/volume/83693

Fluids Engineering Division Summer Meeting
Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2020/volume/83716

HT-ICNMM2020 - Virtual Conference, SHTC - Virtual Conference, FEDSM2020 - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.