The addition of particles to liquids alters their physical properties, such as effective density, viscosity, and thermal conductivity. Base fluids like water or oil typically exhibit Newtonian behavior, meaning shear stress is proportional to shear rate. In contrast, suspensions show significantly more complex rheological behavior. Currently, the effective viscosity and thermal conductivity of suspensions are preferably determined experimentally, as numerical simulations in this context are associated with greater uncertainties.

Many liquid products such as paints, inks, beverages, pharmaceuticals, slurries, and shower gels contain various types of particles to achieve desired end-product properties or to adjust processing characteristics.

The objective of the project is the development of numerical methods for calculating the effective viscosity and thermal conductivity of suspensions. The flow field around the particles as well as the temperature field inside and outside the particles are resolved spatially. High-precision simulation of the relevant physical processes at the microscopic level enables characterization and optimization of the rheological and thermal behavior of suspensions. A well-established method for simulating many moving particles in a flowing fluid is the immersed boundary method, which is also applied in this project.

• Implementation of an immersed boundary method for moving particles
• Validation simulations for fixed single particles in laminar flow
• Implementation of shear-periodic boundary conditions
• Simulations to determine the effective viscosity and thermal conductivity of suspensions
• Investigation of mono- and polydisperse mixtures
• Development of regime maps based on the simulation data

The development of a suitable method opens up a wide range of application possibilities, particularly in three areas: (a) numerical simulations complement the experimental characterization of suspensions to capture their rheological and thermal behavior; (b) simulations can be used to optimize the composition of suspensions to achieve desired properties; (c) macroscopic correlations for effective material properties such as viscosity and thermal conductivity are to be derived for use in flow simulations with commercial software.