Complex rheology

THINK Fluid Dynamix®

Complex rheology

Complex rheology refers to the study of fluids that exhibit non-Newtonian behavior, meaning their viscosity changes with applied stress or strain rate. Examples of such fluids include blood, polymers, slurries, and foams. CFD simulations, when combined with advanced rheological models, provide valuable insights into the flow behavior and performance of systems involving these complex fluids.

Complex rheological fluids pose unique challenges for engineers and scientists due to their non-linear and often time-dependent flow properties. This makes predicting their behavior in various applications and systems more complicated than for Newtonian fluids. CFD simulations, through the incorporation of appropriate rheological models, enable the accurate representation of these fluids‘ characteristics and behavior under different flow conditions.

In CFD simulations, the choice of a suitable rheological model is critical for capturing the relevant fluid behavior. Common models for non-Newtonian fluids include the Bingham plastic, power-law, Herschel-Bulkley, and Carreau-Yasuda models, among others. These models consider factors such as shear-thinning, shear-thickening, and viscoelastic properties, enabling the simulation of complex fluid dynamics in a wide range of applications.

Applications that benefit from CFD simulations of complex rheology include:

  • Biomedical engineering: Simulating blood flow in the cardiovascular system to inform the design of medical devices, such as stents and artificial heart valves, and to study disease progression.
  • Food processing: Analyzing the flow of complex food materials, such as dough, sauces, or dairy products, to optimize processing techniques and equipment design.
  • Polymer processing: Investigating the flow behavior of polymer melts and solutions during extrusion, injection molding, or film blowing to ensure optimal product quality and processing efficiency.
  • Slurry transport: Examining the flow of solid-liquid mixtures, such as mineral slurries or wastewater sludge, to optimize pipeline design and pumping strategies.

In our videos we introduce CFD solutions for complex rheology

CFD in the process industry: Mixing of highly viscous media.

These two CFD (Computational Fluid Dynamics) animations illustrate the contrasting characteristics of turbulent and laminar mixing, two different flow regimes that occur within fluid systems, playing critical roles in various applications.

The INVENT HYPERCLASSIC® Mixer shows remarkable features such as the uniformity of the flow generation, the energy input at the bottom and the creation of a „Virtual Wall“ between two mixers rotating in opposite directions.

In viscous, shear-thinning fluids, agitation tends to cause cavern formation. Boundary of the cavern can be defined as the surface where the local shear stress equals the fluid yield stress.