Rarefied Gas Dynamics and Trans-sonic Microflows

In the main field of research the frontiers of classical flow descriptions are investigated. High Knudsen numbers

lead to a molecular, non-continuous fluid behavior. As a consequence, high Knudsen numbers deny the description of a flow by a continuous approach and additional statistical models have to be defined. In this case, a quasi-continuous transport model for dispersed systems based on transport equations for statistical moments is used. A further example is the relation between flow behavior and Reynolds number. High Reynolds numbers

result in the flow leaning away from a laminar and towards a turbulent behavior. When critical velocities with very low specific shear forces are reached, the stability of laminar flows disappears and a transient turbulent flow is developed. Finally, for high Mach numbers

we no longer speak about incompressible, but compressible flows. The scale-independent investigation of the interaction of these three dimensionless values is one of the main scientific fields of research in the domain of thermofluid dynamics.