Publikationen

We consider liquid metal flow in a square duct with electrically insulating walls under the influence of a magnetic point dipole using three-dimensional direct numerical simulations with a finite-difference method. The dipole acts as a magnetic obstacle. The Lorentz force on the magnet is sensitive to the velocity distribution that is influenced by the magnetic field. The flow transformation by an inhomogeneous local magnetic field is essential for obtaining velocity information from the measured forces. In this paper we present a numerical simulation of a spatially developing flow in a duct with laminar inflow and periodic boundary conditions.

The motion of a conductor in a magnetic field induces eddy currents whose interaction with the field produces Lorentz forces opposing the motion. One can determine the velocity of the conductor from the force on the magnet system since the latter is equal but opposite to the Lorentz force on the conductor. This contactless method is known as Lorentz force velocimetry (LFV). We study an idealized configuration of LFV, i.e. a rotating solid cylinder interacting with a point dipole. The understanding of parameter influences in this setup can be helpful for more realistic configurations. We use a purely kinematic approach appropriate for low magnetic Reynolds numbers. Numerical results for small and large distances between dipole and cylinder have been obtained with the commercial software COMSOL Multiphysics.

The pulse tube engine is a simple prime mover based on the pulse tube process. It has high potential to be applicable in waste heat usage. In the present work a simulation model is used to design a pressurized experimental pulse tube engine employing helium as working fluid. The measurd engine characteristics are comparred with the calculated predictions. Using the model and the experimental test rig, the engine performance is studied for different heat input temperatures, filling pressures and operating frequencies. The energy conversion process based on a broken thermodynamic symmertry and a thermal lag occurring in the pulse tube is proven theoretically. Fundamental characteristics and application limiations of the pulse tube engine are disclosed experimentally. The obtained engine behavior provides suggestions for its further development.

We present a RANS numerical model for calibrating LFF. Two common metallurgy industry flow types: duct flow and open-channel flow have been studied with this model. For duct flow, the computing calibration constant demonstrates coincide with accuracy of 3.4% with an experimental model. For open-channel flow, a multiphase model is built to take free surface into account. The free surface deformation, magnetic field optimization and characteristics of the realistic flow in an open channel can be simulated by this numerical model.