No abstract

In this paper we report experiments on the growth of dry foams and their rise in vertical pipes of different circular cross-sectional radii with length over diameter ratios in the interval 25 ≤ h/D ≤ 80 for applications in the study of fracture stimulation in enhanced oil recovery processes. Air injection at the bottom of the pipes is performed at a constant flow rate by means of a single capillary tube. The formation and rising of the foam was investigated for two different cases: 1) when the top cap of the vertical pipes is open and 2) when it is closed. We find that the position and velocity of the foam front as well as the foam dispersivity are both dependent on the pipe diameter and on whether its top end is open or capped. When the top is open, the foam column grows faster compared to the case when it is sealed. In pipes with h/D ≥ 30, the growth rate is non-linear and faster than in pipes with h/D < 30 in which cases the foam rises at an almost constant rate. As the diameter of the pipe increases, the size of the produced bubbles also increases. In closed-top pipes the foams tend to be more homogeneous than in open top pipes. The experimental observations indicate that under foam drainage driven by gravity, the liquid flow velocity across the Plateau borders is indicative of a drainage model based on a plug-like flow in channels with fully mobile interfaces, where viscous dissipation occurs only in the nodes.

In this paper we report experiments on the growth of dry foams and their rise in thin vertical pipes of different circular cross-sectional radii. Air injection at the bottom of the pipes is performed at a constant flow rate by means of a single capillary tube. The formation and rising of the foam was investigated for two different cases: (a) when the top cap of the vertical pipes is open and (b) when it is closed. We find that the position and velocity of the foam front as well as the foam dispersivity are both dependent on the pipe diameter and on whether its top end is open or capped. When the top is open, the foam column grows faster compared to the case when it is sealed. In pipes of small diameters, the growth rate is nonlinear and faster than in pipes of large diameters in which cases the foam rises at an almost constant rate. As the diameter of the pipe increases, the size of the produced bubbles also increases. In closed-top pipes the foams tend to be more homogeneous than in open top pipes. The experimental observations indicate that under foam drainage driven by gravity, the liquid flow velocity across the Plateau borders is indicative of a drainage model based on a plug-like flow in channels with fully mobile interfaces, where viscous dissipation occurs only in the nodes.

This paper reports the production of intermetallic microrods and microtubes from the decomposition of an intermetallic compound in an AlTiFe system. The intermetallic compound was obtained by mechanosynthesis of elemental powders of Al, Ti and Fe over 300 h at 400 rpm, sintering from compacted powder particles at 300 MPa per minute and at 900 °C for 3600 s in an argon atmosphere. The milled and sintered samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The intermetallic AlTi3 and Fe3Al phases were obtained during the milling process. After sintering, a decomposition of these intermetallic phases was found—Al3Ti0.75Fe0.25, Al3Ti, FeTi, AlTi3, Ti9Al23, Fe2Ti, Al86Fe14 and Al0.4Fe0.6. As a result of the decomposition, we observed the formation of hexagonal rods with intercalated phases of AlTi3 and Fe2Ti.

No abstract