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1.
2.
Capillary driven surface oscillations of liquid argon (Tsat = 87.3 K at 1,013 hPa) have been investigated in a partly filled right circular cylinder under non-isothermal boundary conditions. The oscillations take place during the reorientation from the normal gravity surface position towards a new position upon step reduction of gravity. The situation is similar to the end of thrust in a rocket tank when the cold propellant moves along the warmer tank wall driven by capillary forces. The aim was to investigate the influence of the temperature difference between the slightly subcooled cryogenic liquid and the superheated cylinder wall on the oscillations and their characteristics in a single-component, two-phase system. Axial wall temperature gradients of averaged 0.15 K/mm ? 1.93 K/mm above the normal gravity surface position were implemented. A general dependence of the reorientation behavior on the gradient value was observed, concerning the apparent contact line behavior, the frequency and damping of the oscillations of the free surface center point, and the apparent contact angle. The behavior of the ullage pressure was found to follow the behavior of the contact line. 相似文献
3.
C.E. Dreyer W.V. Chiu R.H. Wagoner S.R. Agnew 《Journal of Materials Processing Technology》2010,210(1):37-47
The warm formability of three sheet magnesium alloys was measured using the OSU formability test adapted for testing at elevated temperatures under isothermal conditions. The adapted test is shown to reliably enforce plane strain tension over a significant fraction of the sample, thus providing an assessment of FLD(0), typically the minimum major strain value on a forming limit diagram. By mathematically modeling the strain as a function of punch displacement, a case is made that the punch displacement itself provides an expedient approach to ranking the relative formability of sheet metals. Combined with knowledge of the constitutive behavior of the material, the punch displacement–strain relationship provides an explanation for the observed shape of the punch load versus displacement curves. OSU formability test results show that a new magnesium sheet alloy, yttrium-containing ZW41, is significantly more formable than traditional magnesium alloys AZ31 and ZK10. The improvement is linked to a more random texture in the new alloy, which diminishes the tendency for gross, catastrophic shear instability typical of the strongly textured traditional alloys. 相似文献
4.
Dennis Haake Joerg Klatte Aleksander Grah Michael E. Dreyer 《Microgravity science and technology》2010,22(2):129-138
An open capillary channel is a structure that establishes a liquid flow path when the capillary pressure caused by surface
tension forces dominates in comparison to the hydrostatic pressure induced by gravitational or residual accelerations. To
maintain a steady flow through the channel the capillary pressure of the free surface has to balance the pressure difference
between the liquid and the surrounding constant pressure gas phase. Due to convective and viscous momentum transport the pressure
along the flow path of the liquid decreases and causes the free surface to bend inwards. The maximum flow rate through the
channel is reached when the free surface collapses and gas ingestion occurs near the outlet. This stability limit depends
on the geometry of the channel and the properties of the liquid. In this paper we present an experimental setup which is used
in the low-gravity environment of the Bremen Drop Tower. Experiments with convective dominated systems have been performed
where the flow rate was increased up to the maximum value. In comparison to this we present a one-dimensional theoretical
model to determine important characteristics of the flow, such as the free surface shape and the limiting flow rate. Furthermore
we present an explanation for the mechanism of flow rate limitation for these flow conditions which is similar to the choking
problem for compressible gas flows. 相似文献
5.
6.
Study on the efficiency of thermal refurbishment of residential buildings in Vienna. In the framework of the Kyoto Protocol Austria has committed to reduce its greenhouse gas emissions until 2008/2012 by 13% on the base of 1990. Therefore the Federal Government as well as the provincial governments have implemented programs for the protection of climate including several measures to reduce the emission of hazardous greenhouse gases mainly CO2. Regarding the enormous potential reduction activities were mainly focused on residential buildings. The refurbishment of the building envelope reduces the heating costs as well as the carbon dioxide emissions and improves the indoor climate. Several investigations were taken to check the utility of thermal refurbishment under structural and physical conditions. Plenty of data available in the line of several expertises of existing residential buildings were analysed and completed by additional investigations. The economic efficiency of thermal insulations is pointed out as well as the period of repayment or the influence of the thickness of insulation on the heating energy demand or possible CO2‐reductions. 相似文献
7.
A SOUnding Rocket Compere Experiment (SOURCE) is prepared for launch in spring 2008 and shall deliver approximately 360 s of microgravity time. The experiment is intended to partially fulfill the scientific objectives of the European Space Agency Microgravity Applications Program project AO-2004-111 (Convective boiling and condensation). One of the tasks of this experiment is the investigation of capillary dominated flow at a heated wall. The SOURCE experiment will also serve the needs of the COMPERE research group whose mandate is to investigate the behavior of propellant in spacecraft tanks. SOURCE is a benchmark type of experiment on fluid behavior in tanks to test hypotheses and numerical predictions (quantitative results on a tank scale). Several work packages have been distributed to the Center of Applied Space Technology and Microgravity (ZARM) to manage a part of the preparation of this experiment. Since ZARM acts also as a principal investigator, the subject of surface tension driven flows is one of the main topics. It includes the design of the experimental setup to study free surface behavior as well as the numerical predictions to quantify the heat transfer at a non-isothermal boundary condition in the absence of gravity. 相似文献
8.
The surface evolver (SE) algorithm is a valued numerical tool for computations of complex equilibrium interfacial phenomena. In this work, an iterative procedure is implemented such that SE can be employed to predict steady-state flows along capillary channels of arbitrary cross-section. As a demonstration, a one-dimensional stream filament flow model is solved that approximates the pressure changes inside the channel. Despite its simplicity, the precision, stability, and speed of the method affirm it as an efficient and unique design tool for a variety of capillary flow problems. The procedure is ideally suited for slender column flows such as open wedge channel flows, several of which are validated herein via parabolic flight and drop tower experiments. 相似文献
9.
Two types of single-site heterogeneous catalysts have been designed so as to facilitate either the side-chain oxidation or
ring-hydroxylation of toluene in O2 (solvent-free) or by employing aqueous (H2O2) or organic (cumene hydroperoxide) hydroperoxides in high yield. The use of H2O2 and cumene hydroperoxide in particular, facilitates the ring-hydroxylation of toluene when zeolite-encapsulated metal complexes,
such as perhalogenated or tetra-nitro-substituted phthalocyanines, are used as catalysts. Nanoporous, redox molecular sieves,
display a higher tendency for the side-chain oxidation of toluene with air as an oxidant, with benzoic acid as the predominant
product. 相似文献
10.
Dreyer David L. Jones Kenneth C. Molyneux Russell J. 《Journal of chemical ecology》1985,11(8):1045-1051
Journal of Chemical Ecology - The feeding deterrency of a series of pyrrolizidine, indolizidine, and quinolizidine alkaloids and selected derivatives was measured against the pea aphid... 相似文献