The dynamics of ultradilute polymer solutions in transient flow: Comparison of dumbbell-based theory and experiment

Flexible Polymer Chains in Elongational Flow

“…The recirculation vortex shrinks with increasing inertia and good agreement between flow visualization (Fig. 193 To compare results obtained at different flow rates and orifice diameters, it is advantageous to convert data into dimensionless parameters defined by the following relations: dimensionless axial coordinate x' = xlra dimensionless flow velocity v: = vxlvav dimensionless strain-rate Exx = Exxl( vaulro) In agreement with previous contraction flow simulations [30,42], the strainrate distributions in Fig. 8.5).…”

“…Birefringence results in opposed-jet flow are discussed elsewhere in this book [50]. Recent results obtained from this same group have additionally confirmed the adequacy of the Chilcott-Rallison dumbbell model when applied to a transient extensional flow, such as during start-up and cessation of flow in a four-roll mill [193]. Recent results obtained from this same group have additionally confirmed the adequacy of the Chilcott-Rallison dumbbell model when applied to a transient extensional flow, such as during start-up and cessation of flow in a four-roll mill [193].…”

“…The breadth of this transition was much greater than could be accounted for by polymer dispersity alone [58]. The gradual chain orientation reported in the two and four-roll mill experiments, and during flow around a corner, was successfully explained with the FENE-CR model [191][192][193]. The gradual chain orientation reported in the two and four-roll mill experiments, and during flow around a corner, was successfully explained with the FENE-CR model [191][192][193].…”

How dilute are dilute solutions in extensional flows?

“…Consequently polymer-polymer interactions are possible even at concentrations c/c* < O(1). The improper use of a nearequilibrium definition to characterize dynamic changes in conformation and the associated rheological responses to deformation has lead to the recent introduction of the term "ultradilute" solution to describe polymer solutions that remain truly dilute even when the polymer chains are deformed well beyond their equilibrium state (Harrison et al 1998).…”

Lubricated cross-slot flow of a low density polyethylene melt

“…It has been used for complex mixed flows in slide coating [37], in eccentric rotating cylinder [38], two-roll mill [39][40][41] or cross-slot [42] geometries. In order to test the performances of constitutive modeling in various flow situations, we have selected three streamlines involving different mixtures of simple shear and planar elongation as shown in Fig.…”