Computational techniques and validation of 3-dimensional viscous/turbulent codes for internal flows

Computational techniques and codes developed for the prediction of three-dimensional turbulent flows in internal configurations and rotor passages are described. Detailed calibration and validation of the flow fields in 90° curved ducts, cascades, end-wall flows and turbomachinery rotors are presented. Interpretation and comments on accuracy, level of agreement with various turbulence models and limitations of the codes are described. The single pass space-marching code is found to be efficient for curved duct and two-dimensional cascade flows. Multipass space-marching, time-marching and zonal methods are found to be accurate for complex situations. The efficiency and accuracy of a zonal technique, with considerable saving in computational time, is demonstrated. Paper presented atagard Symposium “Validation of Computational Fluid Dynamics,” May 2–5, 1988, Lisbon, Portugal The research work on computation was sponsored by the David Taylor Naval Ship Research and Development Center with Dr D Fuhs as the technical monitor, and NASA Lewis Research Center with Dr P Sockol as the technical monitor.     

An unconventional approach to integrated ground and surface water development

The conjunctive use of surface water with groundwater development in the Ganga Basin is considered more desirable due to unacceptable environmental conditions created by using all the low flows and the limited possibilities of surface storages. There are several ways to increase infiltration during the monsoon season. One method is to create groundwater storage by pumping during the non-monsoon period. A procedure for estimating the extent and the rate of pumping such that it is replenished in 120 days of the monsoon season and equilibrium is achieved, is outlined in this study. The areas in the Ganga Basin suitable for such groundwater storage schemes have been marked out and the economic aspects of the scheme have also been studied. It is concluded that with this scheme of underground storage of flood water the total potential irrigation in the Ganga Basin may be limited by the area of irrigable land rather than the water supply. It is suggested that this potentially advantageous scheme should be systematically studied and investigated in detail and factors like sediment transportation which may reduce the infiltration rate, the possible hazards of subsidence due to lowering of the water table, the possible ecological effects, and other relevant issues should also be considered.     

Reduction of Fatty Acid Methyl Esters with Sodium Borohydride-t-Butanol-Methanol

Methyl esters of undecenoic, oleic, erucic, linoleic, gorlic, ricinoleic, 12-hydroxystearic, 9,10-dihydroxystearic, 12-ketostearic and 9,10-epoxystearic acids were reduced to alcohols by refluxing with sodium borohydride in t-butanol-methanol. The products were found by chromatographic and spectral techniques to consist of mainly alcohols and small quantities of unreduced esters. Methyl undecenoate and gorlate also yielded minor proportions of corresponding wax esters. Olefinic unsaturation was not affected. Keto and epoxy groups were reduced faster than ester groups, hydroxy esters faster than nonhydroxy esters and shorter-chain esters faster than longer-chain esters.     

Incorporation of eicosapentaenoic and docosahexaenoic acids into groundnut oil by lipase-catalyzed ester interchange

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were incorporated into groundnut oil by interesterification with a 1,3-specific lipase fromMucor miehei. The resultant EPA and DHA concentrations of the groundnut oil were 9.5 and 8.0%, respectively.     

Changes in lipid class and fatty acid compositions during maturation ofHibiscus esculentus andHibiscus cannabinus seeds

The major lipid classes and their constituent fatty acids were analyzed in maturing seeds ofHibiscus esculentus andH. cannabinus. The seeds matured in 40 and 45 days, respectively. The active accumulation period was from the 13th to 25th and 15th to 30th day after flowering, respectively. While a continuous increase in the content of triacylglycerols (TAG) was noticed inH. esculentus, TAG was at its peak inH. cannabinus on the 20th day after flowering. The contents of polar lipids were high in the immature seeds but decreased during maturation. The major fatty acids in both species were palmitic, oleic and linoleic. Cyclopropane fatty acids were present only in TAG of both species throughout maturation period. Cyclopropene and epoxy acids appeared in TAG in traces at the final stages of seed maturation. Oleic and linoleic acids were preferentially esterified at the secondary positions of TAG. The contents of palmitic and stearic acids at the secondary positions were sharply reduced as TAG accumulated.     

Surface and Internal Lipids of Calotropis gigantea L. Leaves

The surface and internal lipids of Calotropis gigantea L. (Ascelepiadaceae) leaves analysed. The surface lipids (0.8%, dry wt.) consisted of hydrocarbons (22.2%), ester waxes (20.7%), aldehydes (7.9%), triacylglycerols (4.6%), fatty acids (20.0%), sterols (13.2%), diacylglycerols (3.3%), monoacylglycerols (2.9%) and unidentified components (5.2%). The internal lipids (8.3%, dry wt.) contained 52.8, 21.7 and 25.5% non-polar, glyco- and phospholipids, respectively. The internal non-polar lipids were made up of pigments (13.5%), hydrocarbons (6.4%), ester waxes (6.2%), fatty acids (6.7%), sterols (5.7%), diacylglycerols (2.5%) and monoacylglycerols (2.3%). The glycolipids comprised esterified sterylglycosides (2.4%), monogalactosyldiglycerides (8.4%), sterylglycosides (1.7%), cerebrosides (2.3%). digalactosyldiglycerides (4.2%) and sulfoquinovosyldiglycerides (2.7%). The phospholipids were composed of cardiolipin (2.8%), phosphatidylglycerol (5.6%), phosphatidylethanolamine (4.0%), phosphatidylinositol (3.6%), phosphatidylcholine (8.3%) and phosphatidylserine (1.2%). All the internal lipid classes had high contents of linolenic, palmitic and linoleic acid whereas the surface lipids contained palmitic and stearic acids as major components.     

Synthesis of seven-link two-freedom linkages with sliding inputs and output using identical link positionsSynthese sielbengliedriger getriebe mit zwei freiheitsgraden und chubantrieb unter benutzung identischer Schwingenlagen

Two-freedom seven-bar linkages with sliding inputs and output are especially compact as two-variable function generators. When two of the sliders, appropriately chosen, have parallel directions the method of identical link positions[6] is shown to split up the synthesis of the linkage into that of a double slider and a slider-crank while as many as 11 precision points are obtained.     

Photochromic films prepared by solid state processing of disentangled ultrahigh molecular weight polyethylene and photochromic dyes composites

Disentangled ultrahigh molecular weight polyethylene (DPE) is a special grade of polyethylene (molecular weight, >10⁶ Da) which can be processed by an environment friendly solid state process on counter rotating two roll mill (TRM) below the melt temperature of the polymer. This unique processing property of DPE was utilized to develop smart DPE photochromic films. Photochromic dye like 'Spirooxazine' or 'Spiropyran' has been mixed with DPE resin powder prior to film formation without altering the DPE properties. These films could change their optical appearances on exposure to UV-light of wavelength 365 nm and the color change phenomenon of the films could also be replicated by sunlight. The color change observed is found to be reversible, that is, films could return to colorless form either spontaneously in dark or by thermal stimuli. Such smart property was imparted to DPE even at very low concentration (2,000 ppm) of photochromic dyes. Spectrophotometric studies were used to measure the rate of forward reaction with UV radiation and the rate of backward reaction in dark. In fact, DPE powder and photochromic dye composite was used to produce the compression molded disc to understand the color change phenomena. Moreover, it was observed that the photo-degradation rate of dye, could be retarded ~30% by using amphoteric Zinc phthalate salt. TGA and DSC studies confirmed that the characteristics of DPE film remained almost unaltered even after with preparation of film photochromic dyes.     

Inorganic-organic hybrid membranes with anhydrous proton conduction prepared from tetramethoxysilane/methyl-trimethoxysilane/trimethylphosphate and 1-ethyl-3-methylimidazolium-bis (trifluoromethanesulfonyl) imide for H2/O2 fuel cells

Anhydrous proton-conducting inorganic-organic hybrid membranes were prepared by sol-gel process with tetramethoxysilane/methyl-trimethoxysilane/trimethylphosphate and 1-ethyl-3-methylimidazolium-bis (trifluoromethanesulfonyl) imide [EMI][TFSI] ionic liquid as precursors. These hybrid membranes were studied with respect to their structural, thermal, proton conductivity, and hydrogen permeability properties. The Fourier transform infrared spectroscopy (FT-IR) and ³¹P, ¹H, and ¹³C nuclear magnetic resonance (NMR) measurements have shown good chemical stability, and complexation of PO(OCH₃)₃ with [EMI][TFSI] ionic liquid in the studied hybrid membranes. Thermal analysis including TG and DTA confirmed that the membranes were thermally stable up to 330 °C. Thermal stability of the hybrid membranes was significantly enhanced by the presence of inorganic SiO₂ framework and high stability of [TFSI] anion. The effect of [EMI][TFSI] ionic liquid addition on the microstructure of the membranes was studied by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) micrographs and no phase separation at the surfaces of the prepared membranes was observed and also homogeneous distribution of all elements was confirmed. Proton conductivity of all the prepared membranes was measured from −20 °C to 150 °C, and high conductivity of 5.4 × 10⁻³ S/cm was obtained for 40 wt% [EMI][TFSI] doped 40TMOS-50MTMOS-10PO(OCH₃)₃ (mol%) hybrid membrane, at 150 °C under anhydrous conditions. The hydrogen permeability was found to decrease from 1.61 × 10⁻¹¹ to 1.39 × 10⁻¹² mol/cm s Pa for 40 wt% [EMI][TFSI] doped hybrid membrane as the temperature increases from 20 °C to 150 °C. For 40 wt% [EMI][TFSI] doped hybrid membrane, membrane electrode assemblies were prepared and a maximum power density value of 0.22 mW/cm² at 0.47 mA/cm² as well as a current density of 0.76 mA/cm² were obtained at 150 °C under non-humidified conditions when utilized in a H₂/O₂ fuel cell.     

Characterization of a continuous CO<Subscript>2</Subscript> laser-welded Fe-Cu dissimilar couple

Continuous CO₂ laser welding of an Fe-Cu dissimilar couple in a butt-weld geometry at different process conditions is studied. The process conditions are varied to identify and characterize the microstructural features that are independent of the welding mode. The study presents a characterization of the microstructure and mechanical properties of the welds. Detailed microstructural analysis of the weld/base-metal interface shows features that are different on the two sides of the weld. The iron side can grow into the weld with a local change in length scale, whereas the interface on the copper side indicates a barrier to growth. The interface is jagged, and a banded microstructure consisting of iron-rich layers could be observed next to the weld/Cu interface. The observations suggest that solidification initiates inside the melt, where iron and copper are mixed due to convective flow. The transmission electron microscopy (TEM) of the weld region also indicates the occasional presence of droplets of iron and copper. The microstructural observations are rationalized using arguments drawn from a thermodynamic analysis of the Fe-Cu system.