Brandon Lindley, University of North Carolina
Viscoelastic Fluid Layers in Large Amplitude Oscillatory Strain: Normal
Stress Communication and Peak Frequency Selection Criteria.
Abstract:
In this poster, we explore linear and nonlinear stress communication
through viscoelastic layers in large amplitude oscillatory shear
(LAOS) imposed at one interface. Motivated by questions concerning
biological layers, we are led to focus on stress signals arriving at
either interface, the driven or opposing. In doing so, we identify a
remarkable structure in boundary normal and shear stress signals,
presented first in terms of a frequency sweep and then generalized
to a scaling law with respect to all control parameters (material
properties and experimental controls). The structure consists of
peaks in the maximum stress signals versus any parameter sweep,
indicating a clear selection mechanism with robust redundancy for
communicating shear and normal stress across biological layers. In
this poster, we restrict to a single mode upper convective Maxwell
model, where analysis and simulations reveal a transparent
explanation of the phenomenon. The upper convected nonlinearity is
common to all the nonlinear continuum mechanical models, and thus
the normal stress communication mechanism revealed here is
fundamental.
Note: This work was done jointly with two undergraduates the presenter mentored this summer, Breannan Smith, and Eddie Lee Howell who are also presenting posters on closely related results at this Cha-Cha Days.
Advisor: Greg Forest (UNC)