Hanns Walter Müller

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Thermal convection in binary liquid mixtures is investigated in the limit where the solutal diffusivity is weak, but the separation ratio is large. Representative examples are colloidal suspensions such as ferrofluids. With a grain size being large on molecular length scales, the particle mobility is extremely small, allowing to disregard the concentration(More)
We investigate in detail the initial susceptibility, magnetization curves, and microstructure of ferrofluids in various concentration and particle dipole moment ranges by means of molecular dynamics simulations. We use the Ewald summation for the long-range dipolar interactions, take explicitly into account the translational and rotational degrees of(More)
The damping of sound waves in magnetized ferrofluids is investigated and shown to be considerably higher than in the nonmagnetized case. This fact may be interpreted as a field-enhanced, effective compressional viscosity-in analogy to the ubiquitous field-enhanced shear viscosity that is known to be the reason for many unusual behaviors of ferrofluids under(More)
In a wide variety of natural and laboratory magnetized plasmas, filaments appear as a result of interchange instability. These convective structures substantially enhance transport in the direction perpendicular to the magnetic field. According to filament models, their propagation may follow different regimes depending on the parallel closure of charge(More)
Colloidal suspensions of ferromagnetic nanoparticles, so-called ferrofluids, are shown to be suitable systems to demonstrate and investigate thermal ratchet behavior: By rectifying thermal fluctuations, angular momentum is transferred to a resting ferrofluid from an oscillating magnetic field without net rotating component. Via viscous coupling the noise(More)
The complete magnetodissipative structure of ferrofluid dynamics is derived from general principles, without reference to the angular momentum of the ferromagnetic grains. The results are independent of most microscopic details, and easily interpret two previous experiments. Both the Debye theory and the effective-field theory by Shliomis are shown to be(More)
Part of the field dependent dissipation in ferrofluids occurs due to the rotational motion of the ferromagnetic grains relative to the viscous flow of the carrier fluid. The classical theoretical description due to Shliomis (Zh. Eksp. Teor. Fiz. 61, 2411 (1971) [Sov. Phy JETP 34, 1291 (1972)]) uses a mesoscopic treatment of the particle motion to derive a(More)
A radially movable probe has been developed for studies of filamentary transport in ASDEX Upgrade during edge localized modes (ELMs) by means of Langmuir tips and magnetic pickup coils. The probe is permanently installed at the low field side in the ASDEX Upgrade vacuum vessel and is not subject to limitations in probe size, as, for example, probes on a(More)
Measurements at different experiments have shown that a few 10% of the energy loss from the confined plasma during an ELM cycle is deposited to non-divertor components. Usually, these components are not designed to receive high heat loads. The measurement and the extrapolation of these non-divertor loads to a next step fusion reactor are essential for the(More)