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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experiments in fluids 18 (1995), S. 187-198 
    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 Particle concentration or mass flux measurements by phase-Doppler anemometry are based on counting the number of particles crossing the probe volume. In complex particulate flows this requires the knowledge of the particle size-dependent cross-section of the measurement volume perpendicular to the instantaneous particle velocity for each sample. A new method is presented which allows to estimate the instantaneous particle velocity using a one-component PDA-system with the aid of the integral value under the envelope of the Doppler signal. The envelope is reliably determined by a recently developed analogue burst detection electronic circuit using narrow band-pass filters and a synchro detector. The particle size-dependent measurement volume is obtained by the mean log-arithmic amplitude method introduced by Qiu and Sommerfeld (1992). The special signal processing requirements for realizing this method were implemented in a novel signal processor which additionally involves a burst detection based on an online estimation of the signal-to-noise ratio (SNR) and hence the data aquisition is only triggered for signals above a pre-set SNR level. The estimation of the signal frequency and phase is based on the calculation of the cross-spectral density using a hardware FFT (Fast Fourier Transform) chip. In order to demonstrate the accuracy of the novel method for particle concentration and mass flux determination, measurements were performed in a liquid spray and a particle laden swirling flow. Especially in the swirling flow, the particles exhibit random trajectories through the measurement volume and the powerfulness of the present method is demonstrated especially for this complex flow.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experiments in fluids 5 (1987), S. 197-200 
    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 Very narrow supersonic jets expanding from a small size convergent-divergent nozzle are visualized by the laser induced fluorescence method and simulated numerically using the piecewise linear method. Good agreement between the experiment and the numerical result is obtained in the jet structure, i.e. the shape of the barrel shock, the location of its reflection point on the axis, and the shape of the jet boundary.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experiments in fluids 6 (1988), S. 209-216 
    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 focusing of plane shock waves and spherical blast waves in water by parabolic and ellipsoidal reflectors is studied experimentally and numerically. The numerical computations are performed by a second order method based on an extension of Godunov's method, which is called piecewise-linear method. Tests of this method and a comparison with pressure measurements show a strong dependence of the maximum pressure attained in the focal region on the mesh size. Outside this focal region, however, good agreement between the pressure measurements and the result of the numerical computation is found. Furthermore it is shown by numerical computation, that non-linear effects in the focusing process may be partly avoided by an optimized reflector contour which depends on the strength of the incident shock wave. This modification provides that the maximum pressure is attained at the geometric focus and not at a location between reflector surface and geometrical focus.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Progress in Lipid Research 22 (1983), S. 221-233 
    ISSN: 0163-7827
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-8507
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The results of an experimental investigation of the effect of particles on decaying grid-generated turbulence in a downward vertical turbulent gas-particle flow are presented. The dispersed particles were glass spheres with a mean size of 700 μm. Titanium dioxide particles with a mean size of 2 μm were used as the particle-markers modeling the carrier-medium flow. The turbulence was generated by grids with square cells of two sizes (4.8 and 10 mm) and an impenetrability parameter equal to 0.49 at a mean flow velocity equal to 9.5 m/s. The grid Reynolds numbers were 3000 and 6300. The damping of turbulence by the particles, manifested in an increase in the turbulence decay rate (viscous dissipation) and a decrease in the turbulence energy in the power-consuming spectral band, was detected.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Experiments in fluids 13 (1992), S. 393-404 
    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 reliable method for the calibration of the measurement volume cross-section has been developed, in order to correct the particle size distribution measured by a phase-Doppler anemometer (PDA) with respect to the counting bias in favour of the large particles. Furthermore, this method allows the measurement of particle concentration or mass flux with high accuracy in two-dimensional two-phase flows. A comparison of the mass flow rate obtained by the integration of the mass flux measured in a water spray by applying this method with the global mass balance showed a difference of about 5%. The basis of the present method is the detection of the amplitude of the filtered Doppler signal in connection with the particle size measured by the PDA. The detection process is performed using an electronic circuit which validates the Doppler burst and has additionally the advantage that the highest amplitude portion of the burst can be selected for digitizing, acquisition and subsequent processing. Therefore, this method has the great advantage that the processed part of the burst has the highest signal-to-noise ratio which results in high accuracies for frequency and phase estimation.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Experiments in fluids 3 (1985), S. 197-206 
    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 shock wave which is incident onto a gas-particle mixture or initiated within such a mixture needs a certain distance to reach a constant velocity. This effect is due to the inertia and the heat capacity of the particles. In general the shock wave is decelerated and the frozen pressure jump is decaying. A vertical shock tube was used in order to produce a plane shock wave incident onto a homogeneous gas-particle mixture. In addition to measurements of the shock velocity and the pressure history along the total low pressure section, the particle velocity was measured within the relaxation zone far downstream of the diaphragm using a laser-Doppler-velocimeter. Thus a drag law describing the particle acceleration within the relaxation zone was derived from the measurements. To compare the experiments with theoretical results, calculations were performed by the random-choice method.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Shock waves 3 (1994), S. 299-311 
    ISSN: 1432-2153
    Keywords: Gas-particle flow ; Laser-Doppler anemometry ; Numerical predictions ; Underexpanded free jets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Underexpanded, supersonic gas-particle jets were experimentally studied using the shadowgraph technique in order to examine the influence of the dispersed particles on the shape of the free jet and the structure of the imbedded shock waves. The particle mass loading at the nozzle exit was varied between zero and one, and two sizes of particles (i.e. spherical glass beads) with mean number diameters of 26 and 45 μm were used. It was found that the Mach-disc moves upstream towards the orifice with increasing particle loading. The laser light sheet technique was also used to visualize the particle concentration distribution within the particle jet and the spreading rate of the particle jet. Furthermore, the particle velocity along the jet centerline was measured with a modified laser-Doppler anemometer. These measurements revealed that the particles move considerably slower than the gas flow at the nozzle exit. This is mainly the result of the particle inertia, whereby the particles are not accelerated to sonic speed in the converging part of the nozzle. In order to further explore the particle behavior in the free jet, numerical studies were performed by a combined Eulerian/Lagrangian approach for the gas and particle phases, including full coupling between the two phases. The numerical results showed that the application of different particle velocities at the nozzle exit as the inlet conditions, which were below the sonic speed of the gas phase has a significant influence on the free jet shape and the configuration of the shock waves. These results demonstrate that the assumption of equilibrium flow (i.e. zero slip between the phases) at the nozzle exit which has been applied in most of the previous numerical studies is not justified in most cases. Furthermore, the numerical calculations of the free jet shape and the particle velocity along the jet axis were compared with the measurements. Although correlations for rarefaction and compressibility effects in the drag coefficient were taken into account, the particle velocity along the center line was considerably overpredicted.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Archives of environmental contamination and toxicology 34 (1998), S. 6-11 
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. The partitioning of the widely used gasoline additive methyl tert-butyl ether (MTBE) between liquid growth media and gaseous phase was measured daily under laboratory conditions to determine how closely dissolved MTBE concentrations matched nominal concentrations. Total (gaseous and dissolved) MTBE averaged across 6 days for 29.6, 503.2, and 1005.7 mg L−1 MTBE treatments were 89.9, 90.3, and 73.0% of nominal, respectively, and mean dissolved MTBE in these same treatments were 74.6, 73.8, and 69.6% of total MTBE, respectively. This suggests that dissolved MTBE concentrations can vary substantially from nominal. The effect of MTBE on the growth of selected algae was also evaluated under laboratory conditions. Three unicellular algae, Selenastrum capricornutum (Chlorophyta), Navicula pelliculosa (Bacillariophyta), and Synechococcus leopoliensis (=Anacystic nidulans, Cyanophyta = Cyanobacteria), representative of three taxonomic groups, were used as test organisms. Toxicity tests were acute and increase in cell number was used as an indicator of growth. Algal species were exposed by injection of MTBE into sealed vessels containing defined liquid growth media. The growth of N. pelliculosa and S. leopoliensis was negatively affected at nominal 2400 mg L−1 MTBE, whereas the growth of S. capricornutum was negatively affected at nominal 4800 mg L−1 MTBE and positively affected at nominal 600 mg L−1 MTBE. The differential sensitivity of the growth of these representative species suggests that MTBE may alter algal community composition in the natural environment.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied phycology 9 (1997), S. 19-24 
    ISSN: 1573-5176
    Keywords: Chaetoceros ; growth ; neutral lipid ; total lipid ; nitrogen deprivation ; Nile Red
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chaetoceros muelleri (Schütt) was cultured on a thermal gradient plate, subjected to two media types with a range of specific conductances, and evaluated for growth and neutral lipid accumulation. Growth was measured directly by daily changes in cell numbers and indirectly by changes in optical density at 750 nm. C. muelleri exhibited a growth rate of at least two doublings day-1 over broad temperature (20 to 35 °C) and conductance ranges (10 to over 60 mS cm-1) and the optimum growth rate approached 4.0 doublings day-1 at 30 °C and a conductance of 25 mS cm-1. Intracellular neutral lipid storage was evaluated with fluorometry and epifluorescent microscopy using the fluorochrome Nile Red. Gravimetric analysis revealed a total lipid content in nitrogen-depleted cultures of C. muelleri of over 400 mg L-1, five to seven times that observed in nitrogen-replete cultures. Based on its high growth rate, tolerance to a broad range of temperatures and specific conductances, and large quantity of intracellular lipid, C. muelleri may have potential for exploitation as a renewable precursor to liquid fuels or as a lipid source.
    Type of Medium: Electronic Resource
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