Secondary flows of viscoelastic liquids in straight tubes

The unsteady flow of the Green–Rivlin fluids in straight tubes of arbitrary cross-section driven by a pulsating pressure gradient is investigated. The non-linear constitutive structure defined by a series of nested integrals over semi-infinite time domains is perturbed simultaneously with the boundary of the base flow through a novel approach to domain mapping. The dominant primary component of the flow, the longitudinal field, and the much weaker transversal field arise at the first and the second orders of the analysis, respectively. The secondary field is driven by first-order terms stemming from the linearly viscoelastic longitudinal flow at the first order. The domain mapping technique employed yields a continuous spectrum of unconventional closed cross-sectional shapes. We present longitudinal velocity profiles and transversal time-averaged, mean secondary flow streamline patterns for a specific fluid and for representative cross-sectional shapes in the spectrum the triangular, square and hexagonal shapes.