URANS simulations for a high-speed transom stern ship with breaking waves

An exploratory study of high-speed surface ship flows is performed to identify modelling and numerical issues, to test the predictive capability of an unsteady RANS method for such flows, to explain flow features observed experimentally, and to document results obtained in conjunction with the 2005 ONR Wave Breaking Workshop. Simulations are performed for a high-speed transom stern ship (R/V Athena I) at three speeds Froude number (Fr) = 0.25, 0.43 and 0.62 with the URANS code CFDSHIP-IOWA, which utilizes a single-phase level set method for free surface modelling. The two largest Fr are considered to be high-speed cases and exhibit strong breaking plunging bow waves. Structured overset grids are used for local refinement of the unsteady transom flow at medium speed and for small scale breaking bow and transom waves at high-speeds. All simulations are performed in a time accurate manner and an examination of time histories of resistance and free surface contours is used to assess the degree to which the solutions reach a steady state. The medium speed simulation shows a classical steady Kelvin wave pattern without breaking and a wetted naturally unsteady transom flow with shedding of vortices from the transom corner. At higher speeds, the solutions reach an essentially steady state and display intense bow wave breaking with repeated reconnection of the plunging breaker with the free surface, resulting in multiple free surface scars. The high-speed simulations also show a dry transom and an inboard breaking wave, followed by outboard breaking waves downstream. In comparison to an earlier dataset, resistance is well predicted over the three speeds. The free surface predictions are compared with recent measurements at the two lowest speeds and show good agreement for both non-breaking and breaking waves.     

Reactions of 1,1,3,3-tetrakis(dimethylamino)-1λ5,3λ5-diphosphete with diphenylchlorophosphane and methyl iodide

1,1,3,3-Tetrakis(dimethylamino)-1λ⁵,3λ⁵-diphosphete, 1, reacts with diphenylchlorophosphane to yield 1,1,3,3-tetrakis(dimethylamino)-4-diphenylphosphanyl-1,2-dihydro-3λ⁵-[1,3]diphosphetium chloride, 2, or, depending on the reaction conditions, the isomer compound 3. The cation of 2 is deprotonated by LiN[Si(CH₃)₃]₂ to give the diphenylphosphanyl-substituted derivative of 1, i.e., compound 4. Methyl iodide adds to 1 to form 1,1,3,3-tetrakis(dimethylamino)-4-methyl-1,2-dihydro-3λ⁵-[1,3]diphosphetium iodide, 6. Deprotonation of 6 with n-butyllithium leads to the monomethyl derivative of 1, i.e., compound 7. Physical properties, NMR spectra, and mass spectra of compounds 2–4, 6, and 7 are described. The results of the X-ray structural analysis of 6 are reported and discussed. © 1996 John Wiley & Sons, Inc.     

Di­aqua­tris­(pentane‐2,4‐dionato‐O,O′)­holmium(III) mono­hydrate and di­aqua­tris­(pentane‐2,4‐dionato‐O,O′)holmium(III) 4‐hydroxy­pentan‐2‐one solvate dihydrate

The structures of the title compounds, [Ho(C₅H₇O₂)₃(H₂O)₂]·H₂O and [Ho(C₅H₇O₂)₃(H₂O)₂]·C₅H₈O₂·2H₂O, both show an eight‐coordinate holmium(III) ion in a square antiprismatic configuration. The packing of these structures consists of an infinite two‐dimensional network of hydrogen‐bonded mol­ecules. In both structures, the same hydrogen‐bonded chain of Ho^III complexes is found.     

Lipase-Catalyzed Synthesis of Carboxylic Amides: Nitrogen Nucleophiles as Acyl Acceptor

 The lipase-catalyzed aminolysis of carboxylic esters is a fairly general reaction that has been performed with a wide range of esters and amines, generally in anhydrous organic media to avoid undesirable hydrolysis of the ester. Alternatively, carboxylic amides can be synthesized by lipase mediated condensation of carboxylic acids and amines if an excess of either reactant is avoided. Chiral carboxylic esters have been resolved by lipase-catalyzed aminolysis. In the majority of these resolutions, Candida antarctica lipase B has been employed as the catalyst. A range of chiral amines has been resolved by lipase mediated acylation, using mainly the lipases from C. antarctica (B type) and Pseudomonas species. The enantiorecognition was frequently found to depend critically on the acylating agent and the reaction medium.     

Surface-induced dissociation in tandem quadrupole mass spectrometers: A comparison of three designs

Three different devices that-can be used for surface-induced dissociation (SID) m tandem quadrupole instruments are compared here. The designs were compared by examining the fragmentation of several compounds including benzene, W(CO)₆, and (CH₃)₄N⁺. These studies show that SID can be readily implemented on a variety of tandem quadrupoIe instruments and that the spectra obtained with the in-line and 90° instruments are similar. Evidence is presented that confirms that high average internal energies and narrow distributions of internal energy are available by this technique. Efficiencies for fragmentation of odd-electron ions are on the order of those previously reported by others. The overall SID efficiency for even-electron ions is higher than that for odd-electron ions of similar structure.     

An Enlarged Data Base of Electron-Ionization Mass Spectra

The computer-searchable data base of reference mass spectra described earlier has been increased in size by 76%, so that it now contains 139,859 different spectra of 118,144 different compounds. The average number of peaks per spectrum is 53. All spectra were examined for errors by the Probability Based Matching (PBM) and the Quality Index (QI) algorithms and by human inspection. An improvement to the QI algorithm is based on the Terwilliger suggestion concerning saturated spectra. The number of different elemental compositions of compounds has increased by 64%. By using unknowns from the original data base with PBM, the probability that these incorrectly match a new spectrum is only 33% of that of incorrectly matching a spectrum in the original data base, further demonstrating that the variety of data in the library has been substantially expanded. Including additional reference spectra (measured under different conditions) of the same compound in the data base reduced the proportion of incorrect best-matching spectra by 42%.     

An accuracy analysis of mass matrix lumping for three-dimensional,unsaturated flow,finite element,porous media computations using analytical solutions

Lumping of the mass matrix for transient problems is the state of the practice for finite element groundwater programs. This improves nonlinear convergence where there is unsaturated flow, but the discovery was made that the accuracy of the results is reduced significantly for a test problem. This paper compares results from a recently derived transient three-dimensional (3-D) analytical solution for a given unsaturated flow test problem with those obtained from a standard parallel Galerkin 3-D finite element groundwater program with the mass matrix lumping option turned both on and off. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)