Dynamic dielectric response of electrorheological fluids in drag flow

TL;DR

This paper investigates the dynamic dielectric response of dilute electrorheological fluids in drag flow, deriving a new formula to estimate response time and comparing it with rheological measurements, highlighting the dielectric method's sensitivity.

Contribution

A new kinetic rate-based formula was developed to approximate the dielectric permittivity evolution in ER fluids, enhancing understanding of microstructure formation.

Findings

Dielectric response time aligns well with rheological response time.

Dielectric method detects transient microstructural changes more sensitively.

Saturation dielectric permittivity correlates with equilibrium microstructure.

Abstract

We have determined the response time of dilute electrorheological fluids (ER) in drag flow from the dynamic dielectric response. On the basis of a kinetic rate equation a new formula was derived to approximate the experimental time-dependent dielectric permittivity during the temporal evolution of the microstructure. The dielectric response time was compared to the standard rheological response time extracted from the time-dependent shear stress, and a good agreement was obtained. We found that the dielectric method is more sensitive to detect any transient during the chain formation process. The experimental saturation value of the dielectric permittivity corresponding to the equilibrium microstructure was estimated on the basis of formulas derived from the Clausius-Mossotti equation.