  The flow of viscoelastic wormlike micellar solutions (WLMs) in porous media
is encountered in many practical applications like enhanced oil recovery or
groundwater remediation. To understand the flow dynamics of these complex
fluids in porous media, a model porous media consisting of a straight
microchannel with micropore throats present in it, is very often used. In this
study, we perform an extensive numerical investigation to understand the flow
dynamics of wormlike micellar solutions based on the two-species
Vasquez-Cook-McKinley (VCM) model for micelles through such model porous media.
We find the existence of an elastic instability once the Weissenberg number
exceeds a critical value; likewise, it was seen in many prior experimental and
numerical studies dealing with polymer solutions. However, for the present case
of a WLM solution, we observe that this elastic instability is greatly
influenced by the breakage and reformation mechanisms of the wormlike micelles.
In particular, we notice that the intensity of this instability (characterized
by the fluctuating flow fields) increases as the Weissenberg number increases;
however, beyond a critical value of it, this elastic instability and/or the
flow field fluctuation is suppressed because of the breakage of long micelles.
This is in contrast to the polymer solutions for which the flow field gradually
transits to a more chaotic and turbulent-like state (or the so-called elastic
turbulence state) as the Weissenberg number gradually increases. Additionally,
we observe that the flow dynamics of these WLM solutions are strongly dependent
on the type of micropore throat, the number of pore throats, and the spacing
between two consecutive pore throats. An extensive discussion on the pressure
drop and apparent viscosity is also presented in the present study.
