Rheology of Dendrite-Like Particles in Suspension

During solidification of metals, millions of tinny snowflake-like crystals form. Like in a snowstorm, these crystals can move, pile up in front of an obstacle, whirl around and even form avalanches. The law for describing the motion of a single snowflake-like crystal in a liquid is known quite a while. However, for the collective motion of ensemble of snowflake-like crystals in a liquid the laws of motion are questionable. Collisions and interlocking of individual crystals or crystal ensembles are becoming more and more signif- icant when the crystal number density increases. By using a modern 3D printer, we plan to produce over 100.000 crystals that are only micrometres in size and resemble snowflakes. A suspension containing these particles will be stirred under well-defined con- ditions. From the measured forces, conclusions will be drawn about the laws that govern the collective motion. Such investigations using different spherical particles are well known. However, snowflake-like particles will definitely behave different and thus new insights into the dynamic of their collective motion are to be expected. Additionally to the experimental work, computer simulations will help to interpret the measurements. Here, new modelling approaches will be necessary to describe phenomena that are characteristic for the motion of ensembles of snowflake-like particles. Those modelling approaches will finally enable to improve computer simulations of solidification process and with that a quality improvement of cast products will be possible.

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