Models for the evolution of magnetic fields of neutron stars are constructed, assuming the field is embedded in the proton superconducting core of the star. The rate of expulsion of the magnetic flux out of the core, or equivalently the velocity of outward motion of flux-carrying proton-vortices is determined from a solution of the Magnus equation of motion for these vortices. A force due to the pinning interaction between the proton-vortices and the neutron-superfluid vortices is also taken into account in addition to the other more conventional forces acting on the proton-vortices. Alternative models for the field evolution are considered based on the different possibilities discussed for the effective values of the various forces. The coupled spin and magnetic evolution of single pulsars as well as those processed in low-mass binary systems are computed, for each of the models. The predicted lifetimes of active pulsars, field strengths of the very old neutron stars, and distribution of the magnetic fields versus orbital periods in low-mass binary pulsars are used to test the adopted field decay models. Contrary to the earlier claims, the buoyancy is argued to be the dominant driving cause of the flux expulsion, for the single as well as the binary neutron stars. However, the pinning is also found to play a crucial role which is necessary to account for the observed low field binary and millisecond pulsars.

The spinning down (up) of a superfluid is associated with a radial motion of its quantized vortices. In the presence of pinning barriers against the motion of the vortices, a spin-down may be still realized through "random unpinning" and "vortex motion," as two physically separate processes, as suggested recently. The spin-down rate of a pinned superfluid is calculated, in this framework, by directly solving the equation of motion applicable to only the unpinned moving vortices, at any given time. The results indicate that the pinned superfluid in the crust of a neutron star may as well spin down at the same steady-state rate as the rest of the star, through random unpinning events, while pinning conditions prevail and the superfluid rotational lag is smaller than the critical lag value.

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This study concerns dynamics of a two-phase flow around a rotating solid body. Under consideration is a model of a gear wheel in a gearbox which rotates and is partially submerged in oil. The flow of interest is complex and involves effects of free surface dynamics, rotation, and formation of bubbles and drops. Occurring flow regimes include laminar, transitional and turbulent. The major focus of the investigation is on details of the developed flow, and the purpose is validation of numerical methods developed for design and optimization of such components. Current experiments are performed in a test rig which is modelling a generic simplified gearbox with a single isolated rotating wheel. The flow measurements are carried out by using particle image velocimetry (PIV) and the test rig is specially designed for this purpose with the optical access maximized. The flow similarity with respect to a real gearbox is fully maintained and the working fluid is a transparent mineral oil. The PIV measurements are performed at four different rotation speeds for two different wheel configurations in order to cover a spectrum of operational conditions needed for numerical modelling. The emphasis is on the result of experiments on a smooth wheel. The measurements are providing velocity distribution around the wheel and details on bubble and drop distribution.

The observed large rates of spinning down after glitches in some radio pulsars have been previously explained in terms of a long-term spin-up behavior of a superfluid part of the crust of neutron stars. We argue that the suggested mechanism is not viable; being inconsistent with the basic requirements for a superfluid spin-up, in addition to its quantitative disagreement with the data. Hence, the observed post-glitch relaxations may not be interpreted due only to the effects of the stellar crust.