Shock / boundary-layer interaction control using three-dimensional bumps for transonic wings

Three-dimensional bumps have been developed and investigated, aiming at the two major objectives of shock-wave / boundary-layer interaction control, i.e. drag reduction and suppression of separation, simultaneously. An experimental investigation has been conducted for a default rounded bump in channel now at University of Cambridge and a computational study has been performed for a spanwise series of rounded bumps mounted on a transonic aerofoil at University of Stuttgart. Observed in both cases are wave drag reduction owing to A-shock structures produced by three-dimensional surface bumps and mild control effects on the boundary layer. The effects of rough surface and tall extension have been investigated as well as several geometric variations and multiple bump configurations. A double configuration of narrow rounded bumps has been found to best perform amongst the tested, considerably reducing wave drag through a well-established A-shock structure with little viscous penalty and thus achieving substantial overall drag reduction. Counter-rotating streamwise vortex pairs have been produced by some configurations as a result of local flow separation, but they have been observed to be confined in relatively narrow wake regions, expected to be beneficial in suppressing large-scale separation under off-design condition despite increase of viscous drag. On the whole a large potential of three-dimensional control with discrete rounded bumps has been demonstrated both experimentally and numerically, and experimental investigation of bumps fitted on a transonic aerofoil or wing is suggested toward practical application.

Zeitschrift für angewandte mathematik und mechanik

Ing. Holger Steeb, Dr.-Ing. Fehmi Cirak, Prof. Dr.-Ing. Ekkehard Ramm, University of Stuttgart, Department of Civil Engineering, Institute of Structural ...

Numerical analyses of tunnel-induced settlement damage to a masonry wall

Settlements due to underground construction represent a risk for the architectural heritage, especially in The Netherlands, because of the combination of soft soil, fragile pile foundation and brittle, un-reinforced masonry façade. Modelling of soil-structure interaction is fundamental to assess the risk of building damage due to tunnelling. This paper presents results of finite element analyses carried out with different models for a simple masonry wall. Focus is paid on the comparison between coupled, uncoupled and semi-coupled analyses, in which the soil-structure interaction is represented in different ways. In particular, the implementation of a soil-structure interface model in the numerical analyses is analysed, in order to asses its validity. The aim of the research project is the development of a damage classification system for different building typologies.

1.55-mu m resonant cavity enhanced photodiode based on MBE grown Ge quantum dots

Self-assembly Ge quantum dots (QD) on Si and Si/Ge mutli-quantum-wells (MQW) are grown by MBE. The island size and island density was investigated by atomics force microscopy. Ten-layer and twenty-layer MQW were selected for photodiode device fabrication. In photoluminescence (PL), a broad peak around 1.55-mu m wavelength was observed with higher peak intensity for the 10-layer MQW which had less defects than the 20-layer sample. Resonant cavity enhanced (RCE) photodiodes were fabricated by bonding on a SOI wafer. Selected responsivity at 1.55 mu m was successfully demonstrated. (c) 2005 Elsevier B.V. All rights reserved.

A Facile One-pot Synthesis of Substituted Pyridine-2,4(1H,3H)-diones from α-Acyl-α-carbamoyl Ketene-S,S-acetals

A facile and efficient one-pot synthesis of substituted pyridine-2,4(1H,3H)-diones has been developed. Subjected to N,N-dimethylformamide dimethyl acetal (DMFDMA) in N,N-dimethylformamide at 120 ˚C, a series of acyl(carbamoyl)ketene S,S-acetals were converted into the corresponding substituted pyridine-2,4(1H,3H)-diones in high yields.

Ring-Opening/Recyclization Reactions of (Dimethylamino)propenoyl-Substituted Cyclopropanes: Facile Synthesis of Halogenated Pyridin-2(1H)-ones

A facile and efficient synthesis Of Substituted pyridin-2(1H)-ones has been developed by the reaction of readily available 1-carbamoyl-]-[3-(dimethylamino)propenoyl]cyclopropanes with phosphoryl chloride or phosphorus tribromide in dichloromethane at room temperature.

A Facile and Practical One-Pot Synthesis of beta-Oxo Thioamides from beta-Oxo Amides and Isothiocyanates

A facile and practical one-pot synthesis of beta-oxo thioamides from beta-oxo amides has been developed. By treatment with isothiocyanates in ethanol in the presence of potassium carbonate, a series of beta-oxo amides was converted, under reflux, in high yields into the corresponding beta-oxo thioamides.

Efficient synthesis of substituted tetrahydrothiopyrano[2,3-b]thiopyran-4,5-diones by a double annulation strategy from dialkenoylketene dithioacetals

An efficient synthetic procedure for substituted 2,3,6,7tetrahydrothiopyrano [2,3-b] thiopyran-4,5 -diones by a double annulation strategy is described. The ring systems are made in good yields from readily available dialkenoylketene dithioacetals in the presence of either sodium sulfide nonahydrate/N,N-dimethylformamide (DMF) or a sodium hydride/DMF/amine system.

One-pot synthesis of substituted isothiazol-3(2H)-ones: Intramolecular annulation of alpha-carbamoyl ketene-S,S-acetals via PIFA-Mediated N-S bond formation

A facile and efficient synthetic route towards; highly substituted isothiazol-3(2H)-ones 2 from readily available U.-carbamoyl ketene-S,S-acetals 1 is presented. The key step features the formation of an N-acylnitrenium ion, generated from the oxidization of substituted amides with the hypervalent iodine reagent phenyliodine(III) bis(trifluoroacetate) (PIFA), and its succeeding intramolecular amidation to form a new N-S bond affording the title compounds.

Synthesis and applications of 3-[6-(hydroxymethyl)pyridin-2-yl]-1,1 '-bi-2-naphthols or 3,3 '-bis[6-(hydroxymethyl)pyridin-2-yl]-1,1 '-bi-2-naphthols

A series of new 1,1'-bi-2-naphthol (BINOL) derived ligands, 3-[6-(hydroxymethyl)pyridin-2-yl]-BINOLs or 3,3'-bis[6(hydroxymethyl)pyridin-2-yl]-BINOLs, bearing one or two chiral pyridinylmetlianols attached to a binaphthyl skeleton, have been synthesized using the Suzuki cross-coupling reaction. The resulting compounds have been used as ligands in the enantioselective addition of diethylzinc to aldehydes; the products were obtained with up to 96% ee.

Synthesis of new bis-BINOLs linked by a 2,2 '-bipyridine bridge

A series of new G-symmetric chiral ligands 8, 9, 11 and 12, consisting of two binaphthyl units linked by a 2,2'-bipyridine bridge, has been synthesized via Suzuki cross-coupling reactions.