Modelling of transient gas-liquid flow and pigging in pipes

More and more transient gas-liquid operations in pipes are being successfully applied in the oil and gas industry. Pigging in two-phase pipelines, to remove liquid accumulation or for cleaning purposes, is an important transient operation. Another important operation is the injection of (-)-as to transport the accumulated liquid in the pipeline to process facilities. Analysis of such transient two-phase flow in a pipeline is necessary not only for designing the liquid and (Yas handling facilities, but also for safe operating procedure. In pipeline-fiser system such operations cause even more severe changes in flow conditions. A two-fluid model has been developed to determine the transient behaviour of fluids during these operations.T he derived one-dimensionasl et of equationsf or each flow pattern describet he flow of fluids in all regions. Semi-implicit finite difference schemes were used to solve the initial and boundary value problem for each phase of the process- gas/pig injection, gas shut-in, slug production and gas flow out of the system. An extensive experimental program has been carried out to acquire two-phase transient flow and pigging data on a 67 m long, 0.0525 m diameter, 9.9 m high pipeline-riser system. A computer based data acquisition system has been utilised to obtain rapidly changing and detailed information of the flow behaviour during the transient tests. The model results compare well with the experimental data for characteristics such as inlet pressure, hold-up and pig velocity

Born-Infeld magnetars: larger than classical toroidal magnetic fields and implications for gravitational-wave astronomy

Magnetars are neutron stars presenting bursts and outbursts of X- and soft-gamma rays that can be understood with the presence of very large magnetic fields. Thus, nonlinear electrodynamics should be taken into account for a more accurate description of such compact systems. We study that in the context of ideal magnetohydrodynamics and make a realization of our analysis to the case of the well-known Born-Infeld (BI) electromagnetism in order to come up with some of its astrophysical consequences. We focus here on toroidal magnetic fields as motivated by already known magnetars with low dipolar magnetic fields and their expected relevance in highly magnetized stars. We show that BI electrodynamics leads to larger toroidal magnetic fields when compared to Maxwell's electrodynamics. Hence, one should expect higher production of gravitational waves (GWs) and even more energetic giant flares from nonlinear stars. Given current constraints on BI's scale field, giant flare energetics and magnetic fields in magnetars, we also find that the maximum magnitude of magnetar ellipticities should be $10^{-6}-10^{-5}$. Besides, BI electrodynamics may lead to a maximum increase of order $10\%-20\%$ of the GW energy radiated from a magnetar when compared to Maxwell's, while much larger percentages may arise for other physically motivated scenarios. Thus, nonlinear theories of the electromagnetism might also be probed in the near future with the improvement of GW detectors.Comment: 8 pages, no figures, accepted for publication in The European Physical Journal C (EPJC

Registro de introduções de plantas de cultura pré-colombiana coletadas na Amazônia brasileira.

Registro de introduções do material coletado nas viagens realizadas de 1984 a 1988. Principais características das plantas matrizes: timbó, dao, acai, tucuma, cupuaçu, biriba, condessa, graviola, araticum, palmeiras do gênero oenocarpus, pupunha, urucu, taperebá, cutite, cajarana, cacau, plantas medicinais, boldo.bitstream/item/63464/1/CPATU-Doc58.pd