Magneto-hydrodynamics

H. Alfven (Stockholm) discoveries in magneto-hydrodynamics with fruitful applications in different parts of plasma physics. L. Neel (Grenoble) discoveries concerning antiferromagnetism and ferrimagnetism which have led to important applications in solid state physics. 

Cesium Picrate. C6H2(N02)30Cs, mw 361.01, N 11.64%, yel needles explds with moderate violence at 277—87°. It has been used to surface seed RDX charges used in expl driven magneto-hydrodynamic generators (Ref 3)... 

Figure 2.48 The top shows the schematic design of a magneto-hydrodynamic mixer with equally spaced electrodes arranged In a micro channel and an external magnetic field oriented along the z-axis. On the bottom theoretical results for the evolution of two parallel liquid lamellae as a function of dimensionless time are shown [146].

Figure 2.49 The left side shows the schematic design of an annular magneto-hydrodynamic mixer. On the right, the evolution of the interface between two liquids, as described in [147], is depicted.

Gleeson, ). P., West, )., Magneto-hydrodynamic mixing, in Proceedings of the 5th International Conference on Modeling and Simulation of Microsystems, San )uan, Puerto Rico, 22-25 April 2002, Computational Publications, Boston, pp. 318-321 (2002). 

Nuclear and magneto-hydrodynamic electric power generation systems have been produced on a scale which could lead to industrial production, but to-date technical problems, mainly connected with corrosion of the containing materials, has hampered full-scale development. In the case of nuclear power, the proposed fast reactor, which uses fast neutron fission in a small nuclear fuel element, by comparison with fuel rods in thermal neutron reactors, requires a more rapid heat removal than is possible by water cooling, and a liquid sodium-potassium alloy has been used in the development of a near-industrial generator. The fuel container is a vanadium sheath with a niobium outer cladding, since this has a low fast neutron capture cross-section and a low rate of corrosion by the liquid metal coolant. The liquid metal coolant is transported from the fuel to the turbine generating the electric power in stainless steel... 

The first simulations of the collapsar scenario have been performed using 2D Newtonian, hydrodynamics (MacFadyen Woosley 1999) exploring the collapse of helium cores of more than 10 M . In their 2D simulation MacFadyen Woosley found the jet to be collimated by the stellar material into opening angles of a few degrees and to transverse the star within 10 s. The accretion process was estimated to occur for a few tens of seconds. In such a model variability in the lightcurve could result for example from (magneto-) hydrodynamic instabilities in the accretion disk that would translate into a modulation of the neutrino emission/annihilation processes or via Kelvin-Helmholtz instabilities at the interface between the jet and the stellar mantle. 

External energy sources for active mixing are, for example, ultrasound [22], acoustic, bubble-induced vibrations [23,24], electrokinetic instabilities [25], periodic variation of flow rate [26-28], electrowetting induced merging of droplets [29], piezoelectric vibrating membranes [30], magneto-hydrodynamic action [31], small impellers [32], integrated micro valves/pumps [33] and many others, which are listed in detail in Section 1.2. 

The jets seem to be launched in the central region of the objects, either by the star itself or by the disk surface close to the star and it is thought that magnetic fields are responsible for the collimation of the thin jets. The detailed processes underlying the phenomenon are not well understood because of the inherent difficulties of treating magneto-hydrodynamic problems. 

Munger, D., Vincent, A., A level set approach to simulate magneto hydrodynamic instabilities in aluminium reduction cells. Journal of Computational Physics, 217, pp. 295-311, 2006. 

Safa, Y., Flueck, M., Rappaz, J., Numerical simulation of thermal problems coupled with magneto hydrodynamic effects in aluminium cell. Applied Mathematical Modelling, 33, pp. 1479-1492, 2009. 

The microphysics in the field generation and particle acceleration described here is clearly beyond the reach of the magneto hydrodynamic approximation. A parameter study utilizing a PIC code working from first principles is necessary to fully understand the interdependence between the relative bulk Lorentz factors of the colliding plasma shells, the power law index of the non-thermal electron population, eb and in a broader sense the detailed evolution and structure in collisionless shocks. 

Qian, S. and Bau, H.H. (2005) Magneto-hydrodynamic stirrer for stationary and moving fluids, Sensors and Actuators B, Chemistry, 106, 859-870... 

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