Soot formation in a turbulent swirling flow

The qualitative understanding of soot formation in simple models of gas turbine primary-zone combustors is summarized. Soot formation in flame radiation and air pollution was investigated. Results are presented, namely: (1) if the fuel is premixed with air in approximately stoichiometric proportions, the sequence of states that a fluid element undergoes as it burns is quite different from the sequence when liquid or vapor fuel is injected into an air-flow; (2) swirling flows, as are typical or swirl-can combustors, when burning, can amplify small aerodynamic disturbances upstream of the swirl vanes; and (3) different fuels form significantly different amounts of soot. Each of these effects makes major changes in the amount of soot formed in a given combustor

Euler-Lagrange relationship for random dispersive waves Scientific report

Euler-Lagrange relationship for random dispersive wave

Wake of the Moon

Lunar wak

Euler-Lagrange relationship for random dispersive waves

Euler-Lagrange relationship for random dispersive wave

Laboratory measurements in a turbulent, swirling flow

Measurements of soot inside a flame-tube burner using a special water-flushed probe are discussed. The soot is measured at a series of points at each burner, and upon occasion gaseous constitutents NO, CO, hydrocarbons, etc., were also measured. Four geometries of flame-tube burners were studied, as well as a variety of different fuels. The role of upstream geometry on the downstream pollutant formation was studied. It was found that the amount of soot formed in particularly sensitive to how aerodynamically clean the configuration of the burner is upstream of the injector swirl vanes. The effect of pressure on soot formation was also studied. It was found that beyond a certain Reynolds number, the peak amount of soot formed in the burner is constant

Fast optimal transition between two equilibrium states

We demonstrate a technique based on invariants of motion for a time-dependent Hamiltonian, allowing a fast transition to a final state identical in theory to that obtained through a perfectly adiabatic transformation. This method is experimentally applied to the fast decompression of an ultracold cloud of Rubidium 87 atoms held in a harmonic magnetic trap, in the presence of gravity. We are able to decompress the trap by a factor of 15 within 35 ms with a strong suppression of the sloshing and breathing modes induced by the large vertical displacement and curvature reduction of the trap. When compared to a standard linear decompression, we achieve a gain of a factor of 37 on the transition time.Comment: 5 pages, 4 figures, an error in Eq. (2) has been correcte

Two-Dimensional Magnetic Resonance Tomographic Microscopy using Ferromagnetic Probes

We introduce the concept of computerized tomographic microscopy in magnetic resonance imaging using the magnetic fields and field gradients from a ferromagnetic probe. We investigate a configuration where a two-dimensional sample is under the influence of a large static polarizing field, a small perpendicular radio-frequency field, and a magnetic field from a ferromagnetic sphere. We demonstrate that, despite the non-uniform and non-linear nature of the fields from a microscopic magnetic sphere, the concepts of computerized tomography can be applied to obtain proper image reconstruction from the original spectral data by sequentially varying the relative sample-sphere angular orientation. The analysis shows that the recent proposal for atomic resolution magnetic resonance imaging of discrete periodic crystal lattice planes using ferromagnetic probes can also be extended to two-dimensional imaging of non-crystalline samples with resolution ranging from micrometer to Angstrom scales.Comment: 9 pages, 11 figure

Mud mound / ?diapiric features in the Faroe - Shetland Channel

Various high resolution and conventional multi-channel exploration seismic profiling (1966-2002) at the northern end of the Faroe - Shetland Channel (FSC) have identified several large sea bed mounds with a possible diapiric form, originally named the Pilot Whale Diapirs. Some mounds rise over 70 m above the surrounding sea bed and are 2 - 3 km across. The profiles show that the sea bed examples are just a tiny fraction of more extensive subsurface features, covering more than 2000 km2, with less than 10% disturbing the sea bed. The subsurface features occur principally at two levels with a migration northwestwards from deep to shallow. The seismic profiles identifythe host deposits as part of the thick Neogene to Quaternary sequence infilling much of the FSC. The latter includes the North Sea Fan (up to 1 km thick) comprising extensive debrites and some catastrophically emplaced megaslide debrites, two of which abut the mud mounds. The mounds and related subsurface features display various morphologies and seismic facies, and a range of processes may be involved in their development, including mud volcanism, subsurface injection of soft sediment and diapirism. The features are developed above the crest and NW-flank of a NNE trending symmetrical anticline that is expressed at the stratigraphic level of top Palaeogene lavas and they appear to be broadly aligned with the axial trace of this structure. This anticline appears to have continued developing at least into the Pliocene. Material comprising the mounds and related subsurface features appears to have been derived from the subsurface evacuation hollows developed within the ?Eocene to Miocene succession. The formation of these features is thought to be associated with tectonic compression, overpressuring of older sediments due to rapid loading or fluid release upon diagenesis or some combination, including movement on NW-SE trending lineaments. The location of the mounds above a Cenozoic inversion dome and at the margin of a thick sediment wedge (the North Sea Fan) is similar to the setting of large mud mounds observed offshore Norway

Magnetic field independence of the spin gap in YBa_2Cu_3O_{7-delta}

We report, for magnetic fields of 0, 8.8, and 14.8 Tesla, measurements of the temperature dependent ^{63}Cu NMR spin lattice relaxation rate for near optimally doped YBa_2Cu_3O_{7-delta}, near and above T_c. In sharp contrast with previous work we find no magnetic field dependence. We discuss experimental issues arising in measurements of this required precision, and implications of the experiment regarding issues including the spin or pseudo gap.Comment: 4 pages, 3 figures, as accepted for publication in Physical Review Letter