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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experiments in fluids 24 (1998), S. 141-150 
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  The convective heat transfer from a cylinder to a humid air stream flowing normal to the cylinder was investigated experimentally at atmospheric pressure over a range of variables which is relevant to the use of hot‐wire anemometry: air temperatures between 30 °C and 70 °C and velocities between 12 and 37 m/s. For molar fractions of water vapour up to 0.27, the heat transfer increased with increasing humidity. The ratio of heat transfer rates in humid air and dry air is a unique function of the molar fraction of water vapour, independent of the air temperature and flow velocity.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 18 (1995), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: O-Dealkylation of two series of fluorescent 7-alkoxy-coumarins and 7-alkoxyphenoxazones by plant cytochrome P450s was investigated in Helianthus tuberosus tuber tissues treated with prototype P450 inducers, environmental pollutants or agrochemicals. Methoxy-, ethoxy-, propoxy-and butoxycoumarins and methoxy- and ethoxyresorufins were metabolized by fplant microsomes. Dealkylation of pentoxy- and benzyloxyresorufins was not detected. All dealkylating activities were enhanced by aging plant tissues in the presence of xenobiotics, in some cases up to 20-fold relative to the activities detected in control tissues. Increases in total P450 in the same tissues never exceeded 3-fold. The isozymes induced by prototype P450 inducers clearly differed from those in mammalian liver. That multiple P450s with overlapping substrate specificities were involved in the metabolism of both alkoxycoumarins and alkoxyresorufins was demonstrated by (1) the differential induction of the activities in response to exposure to xenobiotics, (2) the differential inhibition of the activities by clotrimazole, paclobutrazole and tetcyclacis in aminopyrine and benzo(a)pyrene-treated tissues, and(3) the selective inhibition observed with antibodies raised against purified ethoxycoumarin deethylase fractions. Our results suggest that the measurement of the dealkylation of such fluorescent substrates in plants might be useful to monitor environmental pollution.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experiments in fluids 26 (1999), S. 208-214 
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  A successful application of the ultrasound velocity profile (UVP) measuring technique to investigations on the flow of magnetic fluids is described. The flow structure of a magnetic fluid in a concentric annular geometry with a large aspect ratio of 20 and a radius ratio of 0.65 was investigated for a inner cylinder rotation. Axial velocity distributions were measured using the UVP measuring technique. A non-uniform magnetic field was applied to the flow field using a permanent magnet located on the outside of the cylinders. The energy spectral density was calculated from the periodic axial velocity profiles. The critical Reynolds number was obtained for various magnetic field strengths, and the apparent viscosity caused by the applied magnetic field was estimated. The UVP method was demonstrated to provide useful information on the structure of Taylor vortex flow in a magnetic fluid.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experiments in fluids 26 (1999), S. 475-477 
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  A detailed numerical investigation on the corrections needed by hot-wire velocity measurements in wall vicinity was performed. In the case of a perfectly conducting wall the computed results agreed well with available experimental data. At first, the numerical results for the case of an adiabatic wall contradicted previous experimental observations. However, a precise evaluation led to a better understanding of the entire problem.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experiments in fluids 21 (1996), S. 110-117 
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The formation of water drops underneath nozzles was studied numerically to provide the basis for repeatable experimental drop formation. The drops detached from the nozzle and impacted on a free water surface forming vortex rings. Experimental results obtained through kinematographic studies of the penetration and growth of these vortex rings are presented. Variations of the penetration depth were measured, depending on the nozzle height above the water surface where the drops were formed. The experiments revealed that it is the state of oscillation at impact that defines the penetration length. Interesting variations of the vortex ring diameter with time were recorded. A good overall understanding of the behavior of the diameter variation was obtained when it was plotted as a function of the penetration depth.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Experiments in fluids 20 (1996), S. 178-188 
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Research and development work carried out to provide a method to measure accurately instantaneous flow rates in periodically operating injection systems is summarized. The instantaneous flow rate is reconstructed from axial velocity time series measured by a laser Doppler anemometer on the center-line of a capilary pipe flow. The theoretical background, on which the evaluation of the instantaneous flow rate is based is provided. It is shown that the axial mean velocity is sufficient to reconstruct the periodically varying flow rate and the pressure gradient. The application of the proposed method is described and an instrument is suggested that can be employed in many fields where fast, periodically varying flow rates occur and instantaneous information is needed.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A novel method is proposed that allows accurate estimates of the local wall shear stress from near-wall mean velocity data in fully developed pipe and channel flows. DNS databases are used to demonstrate the accuracy of the method and to provide the reliability requirements on the experimental data. To demonstrate the applicability of the method, near-wall LDA measurements in turbulent pipe and channel flows were performed. The estimated wall shear stress is shown to be accurate to within 1%. Streamwise mean velocity and turbulence intensity profiles normalized with the wall friction velocity at several Reynolds numbers are presented.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 137 (1999), S. 33-42 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary This paper reports a linear stability analysis of a non-Newtonian annular liquid sheet that is surrounded by nonviscous fluids in relative axial motion to it. It is shown that for a stress free basic flow the dispersion relation giving the absolute and convective instability mechanisms can be immediately obtained from the dispersion relation for a Newtonian sheet by introducing a wavenumber dependent “viscosity”. The stability behavior of the sheet is investigated numerically by a continuation algorithm, by which the solution branches of the dispersion relation, relevant for the stability information, can be traced. The results give a stability picture which covers the whole range of annular sheets from the cylindrical jet to the plane liquid curtain.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 21 (1995), S. 237-251 
    ISSN: 0271-2091
    Keywords: finite volume ; multigrid ; unsteady flow ; 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: This paper presents results of the numerical study of a piston-driven unsteady flow in a pipe with sudden expansion. The piston closes the larger-diameter pipe and moves between two limiting positions with strong acceleration or deceleration at the beginning and end of each stroke and constant velocity in between. The piston velocity in the exhaust stroke is about four times higher than in the intake stroke. Periodic piston movement in this fashion creates a complex unsteady flow between the piston head and the plane of sudden expansion. The numerical method is implicit and of finite volume type, using a moving grid and a collocated arrangement of variables. Second-order spatial discretization, fine grids and a multigrid solution method were used to ensure high accuracy and good efficiency. Spatial and temporal discretization errors were of the order of 1% and 0.1% respectively. The features of the flow are discussed and the velocity profiles are compared with experimental data, showing good qualitative and quantitative agreement.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 549-565 
    ISSN: 0271-2091
    Keywords: parallel computing ; multigrid method ; finite volume method ; block-structured grids ; incompressible flow ; 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: In this paper a parallel multigrid finite volume solver for the prediction of steady and unsteady flows in complex geometries is presented. For the handling of the complexity of the geometry and for the parallelization a unified approach connected with the concept of block-structured grids is employed. The parallel implementation is based on grid partitioning with automatic load balancing and follows the message-passing concept, ensuring a high degree of portability. A high numerical efficiency is obtained by a non-linear multigrid method with a pressure correction scheme as smoother.By a number of numerical experiments on various parallel computers the method is investigated with respect to its numerical and parallel efficiency. The results illustrate that the high performance of the underlying sequential multigrid algorithm can largely be retained in the parallel implementation and that the proposed method is well suited for solving complex flow problems on parallel computers with high efficiency.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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