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  • Analytical Chemistry and Spectroscopy  (5)
  • Engineering  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Numerical analysis of the developing fluid flow in a circular duct rotating steadily about a parallel axis (1989)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 151-165 
    Details
    ISSN: 0271-2091
    Keywords: Numerical analysis ; Fluid flow ; Rotating circular duct ; Finite cell method ; Finite element method ; Swirl ; Inlet boundary conditions ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A numerical analysis of the flow pattern in the inlet region of a circular pipe rotating steadily about an axis parallel to its own is presented. Both finite cell and finite element methods are used to analyse the problem and they give qualitatively similar results which show that a swirling fluid motion is induced in the pipe inlet region. The analyses show that the direction of swirl is opposite to that of the pipe rotation when viewed along the flow axis and that its magnitude depends on the speed of pipe rotation and throughflow Reynolds number. Neither numerical analysis predicts the marked upturn in friction factor (or pressure drop) which has been observed experimentally. However, a dependence on the pipe inlet boundary conditions is demonstrated.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650090203
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  • 2
    Electronic Resource
    Electronic Resource
    CALCULATION OF STEADY AND OSCILLATING FLOWS IN TUBES USING A VORTICITY TRANSPORT ALGORITHM (1996)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 1241-1262 
    Details
    ISSN: 0271-2091
    Keywords: axisymmetric flow ; vortex method ; laminar flow ; entrance length ; steady and oscillating flows ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Steady and oscillating axisymmetric tube flows are modelled using a vorticity transport algorithm. The axisymmetric convective -diffusive Navier-Stokes equations are solved using a splitting technique. Axisymmetric ring vortex filaments are introduced on the walls and subsequently convected and diffused throughout the flow field. An axisymmetric equation similar to the Oseen diffusion equation is used to diffuse the ring vortex filaments. Vorticity is reflected from the tube walls using two techniques. Results are presented for the developing Poiseuille flow and for the developed flow in the form of the entrance length and the axial velocity and vorticity profiles. Good agreement is achieved with a finite difference method in the developing region of Poiseuille flow. The developed flow results are compared with the analytical solutions. The developed profiles of velocity and vorticity have errors of less than 0ċ3 per cent for both methods of dealing with reflection of diffusion at the bounding surfaces and similar accuracy is obtained for the velocity profiles in oscillating flow except at the wall. Oscillating flow is produced with a discretized sinusoidal piston motion. Velocity profiles, boundary layer thickness and entrance length are presented for oscillating flow. Good agreement is achieved for low-Womersley-number non-dimensional frequency. At higher values of this parameter, flows are inaccurately simulated, because the number of piston positions used to discretize the piston motion is inversely proportional to the non-dimensional frequency.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Parallel computation of incompressible flows with complex geometries (1997)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 24 (1997), S. 1321-1340 
    Details
    ISSN: 0271-2091
    Keywords: parallel flow simulation ; complex geometries ; mesh generation ; automobile ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: We present our numerical methods for the solution of large-scale incompressible flow applications with complex geometries. These methods include a stabilized finite element formulation of the Navier-Stokes equations, implementation of this formulation on parallel architectures such as the Thinking Machines CM-5 and the CRAY T3D, and automatic 3D mesh generation techniques based on Delaunay-Voronoi methods for the discretization of complex domains. All three of these methods are required for the numerical simulation of most engineering applications involving fluid flow.We apply these methods to the simulation of airflow past an automobile and fluid-particle interactions. The simulation of airflow past an automobile is of very large scale with a high level of detail and yielded many interesting airflow patterns which help in understanding the aerodynamic characteristics of such vehicles. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    On the accuracy of polynomial finite elements for crack problems (1981)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 17 (1981), S. 1835-1842 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A square tensile sheet with symmetric edge cracks is analysed by the finite element method to demonstrate the accuracy obtained with polynomial elements when the mesh patterns are chosen on the basis of the element's interpolation functions. Numerical results are provided for the accuracy of the total strain energy, the stress intensity factor, and the numerical condition of the global stiffness matrix. The stress intensity factor is determined to within 1.0 per cent accuracy using quadratic (linear strain) triangular elements with only 138 degrees-of-freedom.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620171208
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  • 5
    Electronic Resource
    Electronic Resource
    Frictionless geometrically non-linear contact using quadratic programming (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 127-144 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The successive quadratic programming (SQP) method is used with the finite element method (FEM) to solve frictionless geometrically non-linear contact problems involving large deformations of the elastica in the presence of flat rigid walls. To formulate the SQP problems, the potential energy (PE) is expanded in a Taylor series of second order in displacement increments about a configuration near a contact solution. The SQP problems consist of minimizing the Taylor expansion of the PE subject to the inequality constraints which represent contact. The quadratic programming (QP) method is made part of a Newton-Raphson (NR) search in which the QP corrections are made when a NR step does not satisfy the constraints. A revised simplex method developed by Rusin is used to solve the QP problems. The elastica is modelled with a total Lagrangian FEM developed by Fried. Solutions are obtained for the end loaded buckled elastica in point contact with a rigid wall and for a uniformly loaded elastica in regional contact with a rigid wall. The problems are also solved using a penalty method. The results obtained for the point contact problem are compared to an analytical solution. Calculations were made to obtain numerical information on maximum load step size and the number of inverse operations required for each load step. Cases in which the elastica stiffened substantially as a result of the initiation of contact are also discussed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620280110
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  • 6
    Electronic Resource
    Electronic Resource
    Fourier transform Raman spectroscopic study of hydrogen bonding in 2,5-dimercapto-1,3,4-thiadiazole using an environmental chamberThis paper is dedicated to Professor D. A. Long on the occasion of his 70th birthday. (1995)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 26 (1995), S. 617-622 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The bands at 2485 and 940 cm-1 observed in the Raman spectra of 2,5-dimercapto-1,3,4-thiadiazole represent the hydrogen-bonded ν(SH) stretching and δ(C-SH) in-plane bending modes, respectively. A quantitative study of the hydrogen bonding was carried out using intensity measurements of the bands assigned to the hydrogen-bonded and the free δ(C-SH) in-plane deformations at 940 and 919 cm-1, respectively, as a function of temperature. The Fourier transform (FT) Raman spectra were recorded over the temperature range 303-403 K using an environmental chamber fitted into the FT Raman sample compartment. The equilibrium constants between the free and the hydrogen-bonded molecules were determined over this temperature range and the average enthalpy for hydrogen-bond formation was obtained (ΔH° = -3.35 ± 0.2 kJ mol-1).
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250260806
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  • 7
    Electronic Resource
    Electronic Resource
    Applications of Raman spectroscopy to the study of polymers and polymerization processes (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 24 (1993), S. 475-483 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The application of Raman spectroscopy to polymers and polymerization processes is surveyed and the advent of recent advances in instrumental techniques to polymer analysis is highlighted. Some of the problems of the more widely-used infrared spectroscopic methods, for example in microstructural analysis of polydienes and copolymers, are discussed and the advantages of the Raman spectroscopic technique are explained. The use of near-infrared excitation and Fourier-transform Raman instrumentation for process monitoring and polymer composite studies is discussed. Raman microscopic and waveguide spectroscopic studies of small samples and polymer coatings on substrates are considered. Other applications are mentioned in the areas of polymer orientation, surface-enhanced Raman scattering, conducting polymers, biopolymers and time-resolved studies.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250240803
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  • 8
    Electronic Resource
    Electronic Resource
    Raman spectroscopic determination of the dissociation constants of an acetonitrile-zinc complex in aqueous solution and the enthalpy and entropy of complex dissociation (1991)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 22 (1991), S. 651-656 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dissociation constants for an acetonitrile-zinc complex, (CH3CN)Zn2+, were measured in aqueous solutions containing zinc salts (40-80%, w/w) and acetonitrile by Raman spectroscopy. Quantitative measurements of the intensity of the free and complexed ν(CN) Raman bands at 2264 and 2320 cm-1, respectively, were used to determine the average enthalpy and entropy of the complex dissociation to free acetonitrile in the temperature range 293-343 K for a 70% (w/w) solution of zinc chloride (0.052 mol) in an aqueous solution containing acetonitrile (0.024 mol); δH° and δS° values of 8.4 ± 0.5 kJ mol-1, respectively, were determined.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250221110
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  • 9
    Electronic Resource
    Electronic Resource
    Preparation and vibrational spectroscopic characterization of copolymers of 2,3-dimethylbutadiene and methyl methacrylate (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 24 (1993), S. 495-500 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The preparation and vibrational spectroscopic characterization of the hitherto unreported products of the copolymerization of 2,3-dimethylbutadiene and methyl methacrylate are presented. The polymers were prepared by free radical polymerization using α,α′-azobisisobutyronitrile as the initiator. Raman and Fourier transform infrared spectroscopic information on the 2,3-dimethylbutadiene-methyl methacrylate copolymer is presented for a range of copolymers differing in the 2,3-dimethylbutadiene to methyl methacrylate ratio. Quantitative information of the microstructure of the polymer and copolymer using the C=C stretching vibrations is provided by Raman spectroscopy. Evidence is presented for the splitting of the C=O stretching vibration, ascribed to aggregated syndiotactic and unaggregated syndio- and isotactic poly(methyl methacrylate) at 1734 and 1724 cm-1, respectively.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250240805
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  • 10
    Electronic Resource
    Electronic Resource
    Fourier transform Raman spectroscopic detector system for the analysis of polymers by gel permeation chromatography (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 24 (1993), S. 435-441 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An attempt was made to use a Fourier transform (FT) Raman spectrometer as a detector with a gel permeation chromatograph which was otherwise configured in the usual way for the measurement of molar mass distribution in polymers. A low-volume flow cell was constructed and the detector response tested both off-line and, in a preliminary way, in-line with the chromatograph. The particular objective was to establish whether it would be possible to measure the microstructural variation in polybutadiene with polymer molecular weight during the chromatographic process. The detector sensitivity was assessed for a range of polybutadienes with different cis-1,4-, trans-1,4- and vinyl-1,2- contents using tetrahydrofuran as solvent and eluent. Data obtained using visible Raman (488.0 nm) excitation and near-infrared (1064 nm) excitation were compared. Although it has been established that the Raman spectrometer is one of the best instruments for the evaluation of the microstructure of polybutadiene when used in a conventional way, it lacks the necessary sensitivity to provide quantitative information on polydienes which elute from a chromatograph. However, there is no reason in principle why an FT-Raman spectrometer should not be used as a concentration detector and for the simultaneous more detailed analysis of polymer composition or micro-structure during the chromatographic process, provided that the scattering intensity of the solute is high relative to the eluent. The potential advantages and the observed problems of what appears to be a novel experiment with an FT-Raman instrument are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250240709
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