Detailed studies of the movement of liquid steel (hydrodynamics) on a real object are practically impossible. The solution to this problem are physical modelling carried out on water models and ...numerical modelling using appropriate programs. The method of numerical modelling thanks to the considerable computing power of modern computers gives the possibility of solving very complex problems. The paper presents the results of model tests of liquid flow through tundish. The examined object was model of the twonozzle tundish model. The ANSYS Fluent program was used to describe the behavior of liquid in the working area of the tundish model. Numerical simulations were carried out using two numerical methods of turbulence description: RANS (Reynolds-Averaged Navier-Stokes) – model k-ε and LES (Large Eddy Simulation). The results obtained from CFD calculations were compared with the results obtained using the water model.
This work reviews the advances in the development of CECO, a wave energy converter (WEC) of the floating oscillating bodies subgroup that has its motions and power take-off system (PTO) restricted to ...an inclined direction. For this purpose, the review is conducted on the basis of the Technology Readiness Levels (TRLs), the most frequently used metric to assess the maturity of a technology. The main conclusions and milestones of each stage are also presented along with an introduction to the ongoing works and a general picture of future research lines.
The minimisation of the duration of ladle furnace treatment on the ladle furnace station and transferring part of the technological operations to the tundish might intensify the steel production ...process. The present paper reports results concerning a new method of feeding alloy additions intended to be used during the continuous casting process. For continuous casting tundishes, it seems possible and rational to correct the chemical composition of steel or to feed low melting point microalloys and non-metallic inclusion modifiers. The object of investigation was a single strand tundish. Computer simulation of the liquid steel flow and alloy addition behaviour in turbulent motion conditions was done using the Ansys-Fluent computer program. The numerical model employed in the computations was verified by industrial (non-isothermal conditions) and laboratory (isothermal conditions) tests. In all tundish equipment variants, except for variant no. 3, a reduction in the mixing time was achieved as against the tundish currently used in industrial conditions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The formation of the cast strands’ primary structure is a very complex process in terms of the thermodynamics and physicochemical. It occurs during solidification and crystallization of the liquid ...steel in the crystallizer and in the secondary cooling zone of the CC device. On the basis of the experience gained in the industry and knowledge arising from theory of metals and alloys solidification it can be concluded, that substantial influence on the shape of cast strands primary structure have the temperature of overheating of the liquid steel above liquidus temperature and solidification velocity. A proper control of those casting parameters allows to obtain the cast strands with desired primary structure. In the one and two-way symmetric devices regulation like this is not problematic, in the multi-way devices - specially in the asymmetric - causes a series of problems. In those devices can occur a major temperature difference in each outlet zone of the tundish working space caused by i.e. the distance length diversity of liquid steel stream from the inlet to each outlet and by disadvantageous layout of liquid steel flow zones (turbulent flow zone, plug flow and dead zones) in working area of tundish. Particularly high values of those diversity can be expected in the asymmetric tundishes.
The article presents results of laboratory research - model and industrial regarding impact of the liquid steel overheating temperature, but also heterogeneity of the temperature fields in the tundish on primary structure of the cast strands.
Comparative experiments were conducted between uniform and non-uniform stepped spillway profiles in a large-size laboratory facility. For each stepped configuration, the air concentration ...distributions matched the advective diffusion equation and the interfacial velocity was well correlated with a power law. A comparison of the air-water flow properties showed small differences in terms of number of entrained air bubbles, chord sizes and turbulence characteristics between the different configurations. For the non-uniform steps, larger flow instabilities and stronger variation in the air-water flow properties were observed. Further some non-intrusive measurements were performed with acoustic displacement metres to characterize the free-surface profiles, free-surface fluctuations and free-surface wave celerity in both non-aerated and aerated flow regions. The experiments highlighted a close agreement between experimental data and theoretical predictions in the non-aerated flows and with conductivity probe data in the aerated flows. The non-intrusive technique was suitable for measuring the free-surface characteristics on stepped chutes, especially in the non-aerated flow region.
X-ray Compton scattering tomography Webber, James
Inverse problems in science and engineering,
10/2016, Letnik:
24, Številka:
8
Journal Article
Recenzirano
Odprti dostop
We lay the foundations for a new fast method to reconstruct the electron density in X-ray scanning applications using measurements in the dark field. This approach is applied to a type of machine ...configuration with fixed energy sensitive (or resolving) detectors, and where the X-ray source is polychromatic. We consider the case where the measurements in the dark field are dominated by the Compton scattering process. This leads us to a 2D inverse problem where we aim to reconstruct an electron density slice from its integrals over discs whose boundaries intersect the given source point. We show that a unique solution exists for smooth densities compactly supported on an annulus centred at the source point. Using Sobolev space estimates, we determine a measure for the ill posedness of our problem based on the criterion given by Natterer ("The mathematics of computerized tomography" SIAM 2001). In addition, with a combination of our method and the more common attenuation coefficient reconstruction, we show under certain assumptions that the atomic number of the target is uniquely determined. We test our method on simulated data-sets with varying levels of added pseudo random noise.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Validated SILVACO physical models were exploited to optimise electrical and optical characteristics of 1.5 µm wavelength InAlAs–InGaAs Avalanche photodiodes and InGaAs PIN diodes. Optimised SILVACO ...models were created by selectively thinning down the absorption layers to further reduce the carrier transit time. Further optimisation was accomplished by scaling the light window aperture and mesa area sizes with the aim of reducing the device capacitances. The optimised PIN diode provides a maximum opto-electric bandwidth of 35 GHz with a current responsivity of 0.4 A/W under −5 V bias voltage and 10 µW incident optical power. At 1 µW incident optical power, the maximum opto-electric bandwidth and current responsivity of the optimised avalanche diode is 21 GHz and 1.4 A/W under −21.5 V bias voltage. The optimised APD and PIN photo-detectors are capable of working at a data rate of up to 25 and 40 Gb/s, respectively.
Thin-plate weirs are commonly used as measuring devices in flumes and channels, enabling an accurate discharge measurement with simple instruments. The calibration formulae of such devices rely upon ...some empirical coefficients and there is a need to obtain new accurate physical data to complement the existing evidence. In the present study, the discharge calibration of a large 90° V-notch thin plate weir was performed using an unsteady volume per time technique. The V-notch weir was initially closed by a fast-opening gate. The sudden opening induced an initial phase of the water motion dominated by the free-falling motion of a volume of fluid in the vicinity of the weir, followed by a gradually-varied phase, during which some seiche was observed in the tank. The relationship between water discharge and upstream water elevation was derived from the integral form of the continuity equation. The results yielded a dimensionless discharge coefficient Cd=0.58 close to previous experiments for 90° V-notch weirs. The findings showed that the unsteady discharge calibration of the V-notch weir yielded similar results to a more traditional calibration approach based upon steady flow experiments, allowing a rapid testing over a broad range of flow rates.
► Unsteady discharge calibration was performed with a 90° V-notch weir. ► The sudden gate opening induced an initial phase dominated by a free-falling motion. ► This was followed by a gradually-varied phase with some seiche in the tank. ► The results yielded a dimensionless discharge coefficient Cd=0.58. ► The unsteady discharge calibration yielded similar results to a more traditional calibration approach.
This paper presents a study of the effects of a potential landslide in La Yesca Reservoir, Jalisco-Nayarit, Mexico. The main purpose of the paper is to predict the maximum wave amplitude, wave ...run-up, and dam overtopping. The landslide is formed by an unstable slope of more than 24 Mm
3
that is partially submerged for the range of the reservoir operation levels. The dynamics of the sliding mass were obtained in detail considering that it moves over a pair of failure surfaces with the potential rupture of a third surface. The paper presents results of a physical model of the reservoir based on Froude similitude (scale 1:200). Impulse waves are produced with a solid wedge shape slide as it moves on rails. The movement was calibrated to reproduce the dynamics of the landslide. Also, numerical modelling of the event was performed with a 2D implicit model that solves the two-dimensional shallow water equations. In this case, the impulse waves were generated at each time increment with the variation of the ground elevation (obtained from the dynamics of the landslide) for the mesh points where the landslide passes. The results of both studies are similar.
Modern tundishes have evolved as vessels to serve as the final step in refining of molten steel by removing inclusions and promoting thermochemical homogeneity. In this study the flow behaviour in a ...four-strand tundish was investigated by means of a 1/2-scale water model as well as numerical modelling. The numerical and physical models were used to characterize residence time distribution and calculate properties pertaining to tundish flow regime. Three different tundish configurations were investigated: a bare tundish with no flow control devices, a tundish with a turbulence inhibitor, and a tundish with both a turbulence inhibitor and a dam. The physical and numerical models showed that a tundish without flow control devices is prone to significant short-circuiting. A tundish with a turbulence inhibitor was shown to be successful in preventing short-circuiting and provided surface-directed flow that might assist the removal of inclusions from the melt. However, it was also observed that the upward-directed flow caused the maximum turbulence kinetic energy near the surface to increase dramatically. The potential for slag entrainment should therefore be considered during the design and operation of tundishes with turbulence inhibitors.
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