Stretching of Macromolecules in Turbulent Flows.
Abstract
We have investigated the behavior of dilute polymer solutions in flows which are strong in sense that they can induce a significant deformation of the macromolecules. The rationale for this approach is that since turbulent flows are laminar on sufficiently small scales (such as the size of a polymer). The stretching of polymers by elongational flow bursts within the turbulent fluid can be studied by examining the behavior of polymers in simple (laminar) elongational flows. The stretching, in turn, is a necessary condition for the flow to be significantly affected by the addition of minute quantities of polymer; this is true regardless of the details of the mechanism leading to drag reduction (DR) and is a consequence of the observation that flow modification appears when the volume fraction of the polymers exceeds unity, i.e., when the polymers are strongly overlapping (in a dilute solution this condition is satisfied only for stretched polymers). We investigated the stretching of polymers (the so-called coil stretching transition) in elongational flows using a combination of 'physical' (scaling type) and 'chemical' (molecular level description in terms of local conformational states) techniques. This report summarizes the ones that are the most important in the context of DR, and flow modification in general. Keywords: Polymers in elongation flow; Coil stretching transition; Rotational isomerism; Energy storage.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 15, 1985
- Accession Number
- ADA161800
Entities
People
- Frank S. Henyey
- Yitzhak Rabin