Scramjet intake and exhaust CFD studies for the HyShot scramjet flight experiment

Computational fluid dynamics calculations have been performed in support of the HyShot scramjet flight experiment, which will employ two symmetrically opposed intake/combustor/exhaust nozzles (one being fuel-on, the other fuel-off). Bleed ducts for removal of intake shocks and boundary and entropy layers are incorporated. The flight vehicle will spin on its axis at 4 to 6 Hz, and precess at 0.1 Hz at an angle that may (worst case) be as high as ± 4°. The CFD studies indicate that the intake/bleed duct configuration will perform well at 0° angle of attack, with successful capture of the unwanted flow features. Minor influences on the combustor entrance conditions from the effects of freestream Mach number variation and from the state of the boundary layer will be experienced. On the other hand, at the extreme values of angle of attack considered, there is a very strong effect on the combustor entrance conditions, with possible separation of the main intake wall boundary layer on the windward side. CFD studies of the exhaust nozzle flowfields indicate that the lift force generated by the flight experiment will always be directed from the fuel-on side towards the scramjet centreline, and will be greatest when the fuel-on side is the leeward side of the vehicle. Integration of this force over the vehicle spin period shows that the effective force experienced by the vehicle will always be directed towards the precession axis, thus damping the precession and assisting flight stability

Origin of the Nchanga copper–cobalt deposits of the Zambian Copperbelt

The Zambian Copperbelt forms the southeastern part of the 900-km-long Neoproterozoic Lufilian Arc and contains one of the world’s largest accumulations of sediment-hosted stratiform copper mineralization. The Nchanga deposit is one of the most significant ore systems in the Zambian Copperbelt and contains two major economic concentrations of copper and cobalt, hosted within the Lower Roan Group of the Katangan Supergroup. A Lower Orebody (copper only) and Upper Orebody (copper and cobalt) occur towards the top of arkosic units and within the base of overlying shales. The sulfide mineralogy includes pyrite, bornite, chalcopyrite, and chalcocite, although in the Lower Orebody, sulfide phases are partially or completely replaced by malachite and copper oxides. Carrollite is the major cobalt-bearing phase and is restricted to fault-propagation fold zones within a feldspathic arenite. Hydrothermal alteration minerals include dolomite, phlogophite, sericite, rutile, quartz, tourmaline, and chlorite. Quartz veins from the mine sequence show halite-saturated fluid inclusions, ranging from ~31 to 38 wt% equivalent NaCl, with homogenisation temperatures (ThTOT) ranging between 140 and 180°C. Diagenetic pyrites in the lower orebody show distinct, relatively low ? 34S, ranging from ?1 to ?17‰ whereas arenite- and shale-hosted copper and cobalt sulfides reveal distinctly different ? 34S from ?1 to +12‰ for the Lower Orebody and +5 to +18‰ for the Upper Orebody. There is also a clear distinction between the ? 34S mean of +12.1±3.3‰ (n=65) for the Upper Orebody compared with +5.2±3.6‰ (n=23) for the Lower Orebody. The ? 13C of dolomites from units above the Upper Orebody give ? 13C values of +1.4 to +2.5‰ consistent with marine carbon. However, dolomite from the shear-zones and the alteration assemblages within the Upper Orebody show more negative ? 13C values: ?2.9 to ?4.0‰ and ?5.6 to ?8.3‰, respectively. Similarly, shear zone and Upper Orebody dolomites give a ? 18O of +11.7 to +16.9‰ compared to Lower Roan Dolomites, which show ? 18O of +22.4 to +23.0‰. Two distinct structural regimes are recognized in the Nchanga area: a weakly deformed zone consisting of basement and overlying footwall siliciclastics, and a moderate to tightly folded zone of meta-sediments of the Katangan succession. The fold geometry of the Lower Roan package is controlled by internal thrust fault-propagation folds, which detach at the top of the lowermost arkose or within the base of the overlying stratigraphy and show vergence towards the NE. Faulting and folding are considered to be synchronous, as folding predominantly occurred at the tips of propagating thrust faults, with local thrust breakthrough. The data from Nchanga suggests a strong link between ore formation and the development of structures during basin inversion as part of the Lufilian Orogeny. Sulfides tend to be concentrated within arenites or coarser-grained layers within shale units, suggesting that host-rock porosity and possibly permeability played a role in ore formation. However, sulfides are also commonly orientated along, but not deformed by, a tectonic fabric or hosted within small fractures that suggest a significant role for deformation in the development of the mineralization. The ore mineralogy, hydrothermal alteration, and stable isotope data lend support to models consistent with the thermochemical reduction of a sulfate- (and metal) enriched hydrothermal fluid, at the site of mineralization. There is no evidence at Nchanga for a contribution of bacteriogenic sulfide, produced during sedimentation or early diagenesis, to the ores

The nature and genesis of marginal Cu-PGE-Au sulphide mineralisation in Paleogene Macrodykes of the Kangerlussuaq region, East Greenland

The Kangerlussuaq region of East Greenland hosts a variety of early Tertiary extrusive and intrusive igneous rocks related to continental break up and the passage of the ancestral Iceland plume. These intrusive bodies include a number of gabbroic macrodykes, two of which—the Miki Fjord Macrodyke, and the newly discovered Togeda Macrodyke—contain Cu–PGE–Au sulphide mineralisation along their margins. Sulphides occur as disseminated interstitial blebs and rounded globules of chalcopyrite and pyrrhotite with some Fe–Ti oxides and platinum-group minerals, comprising largely Pd bismuthides and tellurides. The globules are interpreted to have formed from fractionation of trapped droplets of an immiscible Cu- and Pd-rich sulphide melt and show geopetal indicators. Sulphur isotopes imply a local crustal source of S in these from pyritic sediments of the Kangerlussuaq Basin. Thus, generation of these sulphide occurrences was controlled by local country rock type. Low Ni/Cu and Pt/Pd ratios, also present in the Platinova reefs in the Skaergaard Intrusion, indicate that early fractionation of olivine may have depleted the magma of Ni and suggest the likely presence of a large magma chamber at depth. Xenoliths of Ni-rich olivine cumulates in the Miki Fjord Macrodyke may have been sourced from such a body. The location of thus far unidentified conduit or feeder zones to the macrodykes beneath the present day surface may represent potential targets for more massive sulphide orebodies

Simulation of hypersonic, reacting flow around reentry bodies - comparisons of numerical and experimental results

Results of an ongoing validation project for hypersonic flow prediction, which involves both numerical methods and experimental facilities, are presented. In the project, MBB provides the means for numerically simulating the flow around reentry bodies, whereas the Australian National University provides the means for experimentally simulating the flow. The general strategy for the comparisons is described and the results obtained for different parameters and different test gases are compared critically. A hyperboloid is chosen to be the test body. The results of the comparison provide confidence in both the numerical method and the modelling of high temperature physical and chemical effects. (orig.)Available from TIB Hannover: RR 2056(507) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Tomographic reconstruction of shock layer flows

The tomographic reconstruction of supersonic flows faces two challenges. Firstly, techniques used in the past, such as the direct Fourier method (DFM) (Gottlieb and Gustafsson in On the direct Fourier method for computer tomography, 1998; Morton in Tomographic imaging of supersonic flows, 1995) or various backprojection (Kak and Slaney in Principles of computerized tomographic imaging, vol. 33 in Classics in Applied Mathematics, 2001) techniques, have only been able to reconstruct areas of the flow which are upstream of any opaque objects, such as a model. Secondly, shock waves create sharp discontinuities in flow properties, which can be difficult to reconstruct both in position and in magnitude with limited data. This paper will present a reconstruction method, matrix inversion using ray-tracing and least squares conjugate gradient (MI-RLS), which uses geometric ray-tracing and a sparse matrix iterative solver (Paige and Saunders in ACM Trans. Math. Softw. 8(1):43-71, 1982) to overcome both of these challenges. It will be shown, through testing with a phantom object described in tomographic literature, that the results compare favourably to those produced by the DFM technique. Finally, the method will be used to reconstruct three-dimensional density fields from interferometric shock layer images, with good resolution (Faletič in Tomographic reconstruction of shock layer flows, 2005)