Suspension of viscoelastic particles in Newtonian and yield stress fluids: Rheology and microstructure evolution via homogenization
Abstract
Suspensions of deformable particles are of great industrial and scientific interest. Prominent examples of these fluid systems inclu de microgel suspensions, filled polymers, pastes, drilling fluids and lubricants, as well as blood and mucous. The evolution of thei r microstructure under large deformations gives rise to complex rheological behaviors, such as shear thickening/ thinning and normal stress differences, whose understanding is crucial not only to engineer fluids with desired rheological properties, but also to pro vide guidance for the design of pumps, filling stations, liquid-based body armor and novel medical devices. While there has been a h uge amount of work for colloidal and non-colloidal suspensions of rigid particles, much less is known about suspensions of deformabl e particles, beyond certain generalizations of Einstein s estimates for dilute particle volume fractions. The primary objective of this project is to fill this gap by the development and application of homogenization techniques to generate general classes of rheo logical models for non-dilute suspensions of particles undergoing finite deformations and rotations under Stokes flow conditions. Th e models will be able to account for hydrodynamic and certain non-hydrodynamic particle interactions, in a way that reproduces exact ly classical and more recent estimates for dilute suspensions. The models will be able to handle geometric nonlinearities arising fr om the deformation and rotation of randomly oriented ellipsoidal particles leading to `tumbling, `trembling and `tank-treading mo tions, as well as from flow-induced changes in the angular dependence of the two-point correlation function for the particle-center distribution. The particles can be nonlinear viscoelastic solids or fluids, while the suspending fluid can be Newtonian or elasto-vi scoplastic, including yield-stress fluids. The homogenization techniques to be developed will be based on variat red by the PI, which treat elastic stresses as polarizations in the context of Hashin-Shtrikman variational approximations for appro priately defined pseudo-dissipation potentials, combined with the PI s `linear comparison methods to account for nonlinearity and n on-uniformity of these polarizations. As such, they will be able to account for complex rheological behavior for the matrix and par ticles, such as shear thickening/ thinning, normal stress differences, `back stresses, shear banding and thixotropy, as well as ele ctrostatic, magnetic and other non-hydrodynamic interactions between the particles, under general oscillatory loading conditions. Ac curate and reliable models for suspension rheology are of crucial importance in numerous applications of interest to the Navy. These include the development of liquid body armor vests, which remain in the liquid state while a soldier stands still, moves or runs, b erties of the turbulent boundary layer and thus reducing skin friction. The models can also be useful in the design and development of cardiovascular and drug delivery medical devices by accounting for the non-Newtonian rheology of the relevant fluids. More genera lly, these rheological models that are capable of accounting for the microstructure and its evolution will be of great value in the design of complex fluids with optimized rheological properties by providing a viable alternative to expensive full-scale computation al fluid dynamics simulations. These models will also serve to greatly reduce the number of required experimental tests, prior to fi nal characterization via rheological techniques, such as Large Amplitude Oscillatory Shear (LAOS).Approved for Public Release
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 20, 2021
- Source ID
- N000142112772
Entities
People
- Pedro Ponte-castaneda
Organizations
- Office of Naval Research
- United States Navy
- University of Pennsylvania