Two-Dimensional Simulation of Subcritical Flow at a Combining Junction: Luxury or Necessity?

Classically, in open-channel networks, the flow is numerically approximated by the one-dimensional Saint Venant equations coupled with a junction model. In this study, a comparison between the one-dimensional (1D) and two-dimensional (2D) numerical simulations of subcritical flow in open-channel networks is presented and completely described allowing for a full comprehension of the modeling of water flow. For the 1D, the mathematical model used is the 1D Saint Venant equations to find the solution in branches. For junction, various models based on momentum or energy conservation have been developed to relate the flow variables at the junction. These models are of empirical nature due to certain parameters given by experimental results and moreover they often present a reduced field of validity. In contrast, for the 2D simulation, the junction is discretized into triangular cells and we simply apply the 2D Saint Venant equations, which are solved by a second-order finite-volume method. In order to give an answer to the question of luxury or necessity of the 2D approach, the 1D and 2D numerical results for steady flow are compared to existing experimental data.     

Combining Contactless Inductive Flow Tomography and Mutual Inductance Tomography for Two-Phase Flow Measurements at a Continuous Casting Model

The flow structure in the mould of a continuous caster is of key importance for the quality of the final product.The use of most conventional flow measurement techniques is prevented by the high temperature of the liquid steel.For a downscaled physical model of the continuous casting process,we present combined measurements of the flow in the mould by Contacfless Inductive Flow Tomography(CIFT),and of the conductivity distribution in the submerged entry nozzle by Mutual Inductance Tomograpliy(MIT).In addition,we summarize an experiment with a magnetic stirrer around the submerged entry nozzle and its effects on the flow in the mould.Some new developments towards a robust implementation of CIFT at a real caster,including the use of pickup coils and gradiometric probes,are also discussed.     

An Experimental Study of a Bubble-Driven Liquid Metal Flow Under the Influence of a Rotating Magnetic Field

In this study we investigate the flow structure in a liquid metal cylinder while a bubble-driven flow is superposed with a rotating magnetic field(RMF).Argon gas is injected through a nozzle into a column of the eutectic alloy GalnSn.Without electromagnetic stirring the bubble plume in the centre region of the cylindrical vessel produces a recirculation with high velocities near the free surface while the fluid velocities in the bottom region remain rather low.The measurements revealed the potential of the RMF to control both the amplitude of the meridional flow and the bubble distribution and to provide an effective mixing in the whole fluid volume.Various periodic flow patterns were observed in a certain parameter range with respect to variations of the magnetic field strength and the gas flow rate.     

Characteristics of Flow around Open Channel 90° Bends with Vanes

Sharp open-channel bends are commonly encountered in hydraulic engineering design. Disturbances such as secondary flows and flow separation caused by the bend may persist for considerable distances in the downstream channel. A simple way of reducing these disturbances is through the insertion of vertical vanes in the bend section. A laser Doppler anemometry (LDA) unit was used to measure the three-dimensional mean and turbulent velocity components of flow in an experimental rectangular open-channel bend. Flow characteristics of the bend with no vanes are compared with those of bends having one or three vertical vanes. The size of the flow separation zone at the inner wall of the bend was determined from dye visualization data and confirmed with mean streamwise velocity data. Results show that the vertical vanes are effective in considerably reducing flow separation, intensity of secondary flows, and turbulence energy in the downstream channel. Furthermore, energy loss for bends with vanes is slightly less than for the no-vane case.     

CFD Predictions and Experimental Comparisons of Pressure Drop Effects of Turning Vanes in 90° Duct Elbows

This paper presents new results for numerical predictions of air flow and pressure distribution in two commonly used elbows: (1) 90° mitered duct elbows with turning vanes having 0.05 m radius, 0.038 m vane spacing and (2) 90° mitered duct elbows without turning vanes, in 0.2×0.2?m (8?in.×8?in.) duct cross section using the STAR-CD computational fluid dynamics (CFD) code. A k-ε turbulence model for high Reynolds number and k-ε Chen model were used for that purpose for comparative purposes. The simulation used 13 different Reynolds numbers chosen between the range of 1×105 and 2×106. To validate the CFD results, the results of two experimental papers using guided vanes were compared with simulated vane runs under the same condition. The first experimental study used a 0.6×0.6?m (24?in.×24?in.) square elbow with 0.05 m radius, 0.038 m vane spacing and air velocities at 2.54 m/s (500 fpm) and 25.4 m/s (5,000 fpm), the second experiment used a 0.81×0.2?m (32?in.×8?in.) rectangular elbow geometry with 0.05 m radius, 0.038 m vane spacing with air velocities from 10.16 m/s (2,000 fpm) to 13.97 m/s (2,750 fpm). For Reynolds numbers (1.00–2.00)×105 the pressure drop difference between vaned and unvaned elbows was found to be 35 Pa as compared to 145 Pa. The simulations also agreed reasonably well with published experimental results. For the 0.6×0.6?m (24?in.×24?in.) square elbow and 0.81×0.2?m (32?in.×8?in.) rectangular elbow with vanes, the difference in pressure drop was 3.9 and 4.1% respectively and indicates that CFD models can be used for predictive purposes in this important HVAC applications area.     

Vertical Vibration of Full-Scale Pile—Analytical and Experimental Study

This paper presents the results of vertical vibration tests on two full-scale single piles. The diameter of pile and embedded depth were 0.45 and 22 m, respectively. The soil samples were collected from three boreholes located at the site of investigation and it was explored to a depth up to 30.45 m below the ground level. The vertical vibration tests were conducted for different eccentricities to determine the frequency-amplitude response of the pile. Static load tests were also carried out on two single piles. A simple axisymmetric two-dimensional finite-element model was developed to predict the dynamic pile response. Novak’s plane strain model was also used for the prediction of the dynamic response of single pile. It was observed that the finite-element model predicted the natural frequency and peak displacement amplitude of pile reasonably well. However, prediction of dynamic response of the pile was found unsatisfactory by Novak’s plane strain model. Possible reasons for unsatisfactory performance of Novak’s model were investigated and presented.     

Thermodynamics of Calcium Ferrite Slags at 1200 and 1300°

Abstract

Oxygen isobars and liquidus isotherms of the system CaO-FeO-Fe₂O₃ at 1200 and 1300°C were determined by quenching samples equilibrated with CO₂–CO mixtures, The iron liquidus and the melt coexisting with two solids were carefully examined in terms of their composition as well as the equilibrium oxygen partial pressures, p _o2 . At 1200°C, p _o2 was 10^?7.70 atm when the slag coexisted with magnetite and dicalcium ferrite, At 1300°C, the melt region extends to the CaO–Fe₂O₃ join, where p _o2 was 10^?0.68 atm (air) or higher. Within the range of p _o2 from one order above that at iron saturation to 10^?4 atm, the slag composition, p _o2 , and the temperature T are related by the equation:

log (Fe^{+ + +} /Fe^{+ +} ) ? 0.170logp _O2 + 0.018 (wt% CaO) + 5500/T ? 2.52.

Activities of CaO(s), FeO(l), and Fe₃O₄ (S) in the slag were calculated from the p _o2 data by combining the available thermal data and/or by Gibbs-Duhem equation.

Résumé

Les isobares d'oxygene et les isothermes du liquidus du systeme CaO–FeO–Fe₂O₃ à 1200 et 1300°C ont été déterminées en trempant des échantillons équilibrés avec des mélanges CO₂–CO. Le liquidus du fer et le mélange coexistant avec deux solides ont été soigneusement étudiés en terme de composition et de pression partielle d'oxygène à l'équilibre, p _o2 . A 1200°C, p _o2 était de 10^?7.7 atm quand la scorie était en équilibre avec la magnétite et la ferrite de dicalcium. A 1300°C, le domaine du liquide s'étend jusqu'au joint CaO–Fe₂O₃ où p _o2 valait 10^?0.68 atm (air) ou plus. A l'intérieur du domaine de p _o2 qui s'étend d'un ordre au dessus de celle à la saturation en fer jusqu'à 10^?4 atm, la composition de la scorie, p _o2 et la température T sont reliées par l'équation:

log(Fe³⁺/Fe²⁺) ? 0.170logp _o2 + 0.018(pd %CaO) + 5500/T ? 2.52.

Les activités de CaO(s), FeO(l) et Fe₃O₄(S) dans la scorie ont été calculées a partir des valeurs de p _o2 en combinant les données thermodynamiques disponibles et/ou l'équation de Gibbs-Duhem.     

Theoretical and Experimental Study on Plug Shape Parameter of Press Piercing Mill

PPM ,theacronymofpresspiercingmill,hasbeenusedtoproducepiercedbilletfromcontinuoussquarebilletsince 1970s .The processcanreducecostandenergy ,andproducealloyedsteelpipe .Thistechnologyhasbeenwidelyadoptedinsomecompaniesrecently[1-3 ] .　　Becausethemetalflowisverycomplicateddur ingpresspiercing ,itisverydifficulttodeterminepiercingforceandplugshapewhichisrelatedtode formation .Ref [4 ]hascomparedtheplugswithdifferentshapesandpointedoutthatiftheplugconehasasharpangle ,thepiercingforcecanberedu…     

Chlorination Roasting of Oxidized Component Obtained from Dross at a Temperature of 1000°C

Metallurgist - Work is devoted to solution of the problem of processing dross obtained as a result of hot galvanizing of products, in particular, waste-free utilization of its oxidized component by...     

Interaction of Lanthanum,Lutetium, and Ytterbium Oxides at 1600°C

Powder Metallurgy and Metal Ceramics - Phase equilibria in the La2O3–Lu2O3–Yb2O3 system were studied by X-ray diffraction and electron microscopy for the first time at 1600°C over...     

Reaction of Cerium Oxide with Zirconium and Yttrium Oxides at 1250°C

Phase relationships in the ternary system ZrO₂ Y₂O₃ CeO₂ were investigated by x-ray diffraction analysis and electron microscopy for the first time, and phase relationships in the binary systems ZrO₂ CeO₂ and CeO₂ Y₂O₃ defined more accurately at 1250°C over the entire range of concentrations. The 1250°C isothermal section of the phase diagram for ternary system was constructed. Specimens were prepared from nitrate solutions by evaporation, drying, grinding, and subsequent annealing at 1250°C. The systems were characterized by the formation of broad solid solution ranges based on C -Y₂O₃, F-CeO₂, F-ZrO₂, and narrow based on T-ZrO₂ and -phase. No new phases were found in the systems. The path of isoparametric lines in the F-ZrO₂ solid solution field suggests that yttrium and cerium ions can substitute for each other without appreciable substitution of zirconium ions.     

Evolution and coarsening of Al2O3 dispersoids at 500 °C to 600 °C in a mechanically alloyed Al-Ti-O based material

The formation and coarsening of Al₂O₃ dispersoids have been investigated at 500 °C, 550 °C, and 600 °C in a mechanically alloyed (MA) extrusion of composition Al-0.35wt pct Li-1wt pct Mg-0.25wt pct C-10vol pct TiO₂ for times up to 1500 hours. In the as-extruded condition, the dispersed phases included Al₃Ti, Al₄C₃, MgO, cubic TiO (C-TiO), monoclinic TiO (M-TiO), TiO₂, and a small amount of Al₂O₃. However, numerous Al₂O₃ dispersoids (various polymorphs: η, γ, α, and δ) with “block-shaped” morphology were formed after heat treatment due to reduction of C-TiO, M-TiO, and TiO₂. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) showed conclusively the transformation of these phases to additional Al₂O₃ and Al₃Ti. High resolution TEM showed that the α-Al₂O₃ dispersoids exhibited some lattice matching with the α-Al matrix. Coalescence of the block-shaped Al₂O₃ dispersoids occurred after heat treatment, and Al₄C₃ also became attached to them. The length and width of the block-shaped Al₂O₃ dispersoids increased by a factor of ∼1.55 between 340 and 1500 hours at 600 °C.     

Leaching of lanthanide and yttrium from a Central Appalachian coal and the ashes obtained at 550–950 °C

In this work, we investigated leaching of lanthanide and yttrium (REY) from a Central Appalachian coal and its ashes obtained at 550–950 °C with the main purpose of understanding the impact of ashing temperature on REY leachability in water, ammonium sulfate, and hydrochloric acid. It is found that the coal contains a negligible amount of water-soluble REY, less than 1% ion-exchangeable REY, and about 28% of HCl-soluble REY. Ashing leads to dramatic changes in REY leachability in both ammonium sulfate and hydrochloric acid solutions, which is believed to be related to transformation and redistribution of organically-associated REY in coal during the ashing process. Ashing temperature significantly affects REY leaching from coal ashes; higher ashing temperature results in lower REY leachability in both solutions. Clay minerals may play a significant role in changing the leachability of REY after ashing. In addition, the results also suggest that the organic matter in the coal is relatively enriched in heavy REY.     

Deformation and strength behavior of two nickel-base turbine disk alloys at 650 °C

Two powder metallurgy nickel-base turbine disk alloys, RENE’95* and KM4, were studied for strength and deformation behavior at 650 °C. Two classes of microstructures were investigated: unimodal size distributions of γ′ precipitates with particle sizes ranging from 0.1 to 0.7 μm and commercially heat-treated structures with bimodal or trimodal size distributions of γ′ precipitates. The strength and deformation mechanisms were heavily influenced by the microstructure. In both alloys, deformation during compression tests consisted of a combination of a/2〈110〉 antiphase boundary (APB)-connected dislocation pairs and a/3〈112〉 partials creating superlattice intrinsic stacking faults (SISFs). In unimodal alloys, the fault density increased with decreasing particle size and decreasing strain rate. These trends, observed in compression testing, are consistent with earlier studies of similar alloys, which were tested in creep. As the γ′ size was reduced, the nature of the faults changed from being isolated within single precipitates to being extended across entire grains. Commercially heat-treated alloys, containing a bimodal distribution of γ′ particles, exhibited significantly more faulting than unimodal alloys at the same cooling γ′ size. This augmentation of the faulting in commercial alloys was apparently due to the presence of the fine, aging γ′ particles. The two typical commercial heat treatments (supersolvus and subsolvus) resulted in different deformation structures: the subsolvus behavior was similar to that of unimodal alloys with γ′ sizes between 0.2 and 0.35 μm, while the supersolvus deformation was similar to that of unimodal alloys with the 0.1 μm γ′ size. These differences were attributed to differences in the size of the fine, aging γ′ particles. Creep deformation in a commercially heat-treated material at 650 °C occurred solely by SISF-related mechanisms, resulting in a macroscopic slip vector of 〈112〉. The effects of alloy chemistry, APB energy, and microstructure on the deformation and mechanical behavior are discussed in detail, and possible effects of the faulting mechanisms on the mechanical behavior are explored. Finally, models for yield strength as a function of microstructure for bimodal alloys with large volume fractions of precipitates are found to be in need of development. RENE′95 is a trademark of General Electric Company, Fairfield, CT.