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My research interests currently include five major research areas:
- Fluid mechanics of drops and bubbles in confined geometries,
- Biological fluid dynamics: blood flow in arteries and vessels,
- Rheology of emulsions, foams and particulate flows,
- Rheology and mechanics of non-Newtonian drops - viscoelastic flows,
- Rheology of polymer solutions and melts.
These systems are encountered in a broad range of industrial, natural and physiological processes. Chemical engineering applications include enhanced oil recovery, coating operations, waste treatment and advanced materials processing. Pharmaceutical applications include emulsions which serve as a vehicle for the transport of the medical agent to the skin. Further applications constitute polishes, paints, agricultural sprays, cosmetics, ceramics and many foods. Abnormal blood flow is associated with several diseases including cardiovascular diseases (i.e. heart attacks and strokes) which are responsible for more than 50% of deaths in the Western world. Finally, beyond the wide variety of industrial applications, my particular interest in semiflexible polymers is motivated by the existence of important biopolymers such as DNA, actin filaments, microtubules and rod-like viruses.
The study of these systems is a problem of great technological and fundamental interest, and a scientific challenge. One major feature of these systems is the great variety of length scales associated with them. Depending upon the application, the relevant length scale may range from a few centimeters for large droplets, to a few micrometers for coal dust and red blood cells, to a few nanometers for colloidal particles, and finally to the atomic radius for macromolecules, where the ``particles'' consist of a few monomer units. Our goal is to predict the static and dynamic properties of such systems, their (micro)structure as well as their rheological behavior, such as shear dependent viscosity, normal stresses, viscoelasticity and yield stresses.
To achieve this objective and thus improve our fundamental understanding of these physical phenomena, my group applies novel computational and theoretical methods. The theoretical methods vary from simple scaling analysis based on physical arguments, to complicated perturbation techniques. Our computational research includes the utilization of novel, fast algorithms which permit the study of a large number of ``objects'' and the parallelization of these algorithms, so that we are able to exploit the recent availability of great computational power. These methodologies facilitate the investigation of large-scale dynamic simulations of suspensions of drops, bubbles, solid particles, artificial capsules, biological cells or polymer chains. Today, a vast array of more realistic and complicated problems, which in the past were regarded as unattainable, can be studied thoroughly. These computations are performed on local machines as well as on multiprocessor computers provided by the National Center for Supercomputing Applications (NCSA) at Urbana and the High Performance Computing Center (AHPCC) at Albuquerque.