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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Annals of biomedical engineering 28 (2000), S. 431-441 
    ISSN: 1573-9686
    Schlagwort(e): Particle image velocimetry ; Heart valve ; Cavitation ; Regurgitation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract High density particle image velocimetry, with spatial resolution of O(1 mm), was used to measure the effect of occluder rebound on the flow field near a Bjork–Shiley Monostrut tilting-disk mitral valve. The ability to measure two velocity components over an entire plane simultaneously provides a very different insight into the flow compared to the more traditional point to point techniques (like Laser Doppler Velocimetry) that were utilized in previous investigations of the regurgitant flow. A picture of the effects of occluder rebound on the fluid flow in the atrial chamber is presented. Specifically, fluid velocities in excess of 1.5 m/s traveling away from the atrial side were detected 3 mm away from the valve seat in the local low pressure region created by the occluder rebound on the major orifice side where cavitation has been observed. This analysis is the first spatially detailed flow description of the effects of occluder rebound on the flow field past a tilting-disk mechanical heart valve and further reinforces the hypothesis that the rebound effect plays a significant role in the formation of cavitation, which has been implicated in the hemolysis and wear associated with tilting-disk valves in vivo. © 2000 Biomedical Engineering Society. PAC00: 8719Uv, 8780-y, 8719Hh, 4755Bx
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 2013-2027 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In this paper, a simple procedure based on fast and slow reaction asymptotics has been employed to derive first-order closure models for the nonlinear reaction terms in turbulent mass balances from mechanistic models of turbulent mixing and reaction. The coalescence-redispersion (CRD) model, the interaction by exchange with the mean (IEM) model, the three-environment (3E) model, and the four-environment (4E) model have been used to develop closure equations. The closure models have been tested extensively against experimental data for both single and multiple reactions. The closures based on slow asymptotics for the CRD, 3E and 4E models provide very good predictions of all of the experimental data, while other models available either in the literature or derived here are not adequate. The simple new closure equations developed in this paper may be useful in modeling systems involving turbulent mixing and complex chemical reactions.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 277-280 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 26 (1980), S. 165-168 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 29 (1983), S. 320-329 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A new mathematical model (the four environment model) to describe turbulent flow chemical reactors with complex reactions and separate reactant feed streams is developed. The feed stream residence time distributions, the batch chemical kinetics, and a single turbulent micromixing parameter, which may be estimated from direct turbulence theory, are required as input information to the model. The model is computationally efficient as it involves only ordinary differential equations.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 29 (1983), S. 329-337 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The four environment model, which was developed in Part I, has been compared with three extensive sets of experimental data from plug-flow and stirred-tank reactors with unmixed feedstreams and a single chemical reaction. The data sets have been accurately reproduced with a single value of the micromixing parameter (RS), and the “best fit” value of RS for each data set was close to the value estimated from the Corrsin-Rosensweig turbulent mixing theory. This lends support to the turbulence analogy suggested in Part I. Simulations of competing reactions of the parallel-consecutive type are used to discriminate between the four and three environment models with the four environment model providing much more realistic predictions.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 28 (1982), S. 302-311 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A mathematical model of nitric oxide (NO) formation during pulverized coal combustion was developed from a proposed kinetic mechanism involving 12 overall chemical reactions. Most significantly, the model describes the complex conversion of coal bound nitrogen compounds to NO during combustion. The predictions of the model compare favorably with literature data obtained in well defined laboratory combustors firing gaseous fuels doped with organic nitrogen additives, as well as with data obtained in laboratory coal combustors. The predictions of the model are in qualitative agreement with trends observed in practical coal combustors.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 1089-1101 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: An experimental study of the effect of turbulent mixing on the selectivity of a parallel-consecutive reaction system (A + B → R; R + B → S) has been carried out in an unmixed feedstream (multijet) tubular reactor. Fluid mechanical characterization of the reactor by pulsed ultrasound Doppler velocimetry reveals that the mean and rms velocity fields are nearly constant over eight-ninths of the reactor length. Axial profiles of mean product concentration (R and S) have been measured spectro-photometrically with a fiber-optic probe under constant hydrodynamic conditions but with variable feed concentration conditions. The concentration profiles (particularly the S profile) show very large deviations from the perfect mixing (classical plug flow reactor) limit. These data provide a good basis for discriminating among the many models of mixing and reaction available in the literature. This is demonstrated with two examples: the four-environment model, which fits the data well, and the interaction by exchange with the mean model, which does not.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    ISSN: 1573-9686
    Schlagwort(e): Heart valves ; Artificial heart ; Laser Doppler velocimetry ; Velocity ; Reynolds stress ; Regurgitant jets
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract Laser Doppler velocimetry, with a high temporal resolution (1 ms time windows), was used to measure the flow field in two regions (major and minor orifices) near the aortic and mitral valves (Bjork Shiley™ monostrut Nos. 25 and 27, respectively) of the Penn State artificial heart. The motion of each valve was also investigated using a 1000 frame/s video camera in order to estimate the valve's closing velocity. Fluid velocities in excess of and opposite to valve closing velocity were detected near the valve, providing evidence of “squeeze flow.” Maximum Reynolds shear stresses of approximately 20,000 dyn/cm2 and time-averaged Reynolds shear stresses of approximately 2000 dyn/cm2 were observed during the regurgitant flow phase. These elevated Reynolds shear stresses suggest that regurgitant jets play a role in the hemolysis and thrombosis associated with tilting disk heart valves in an artificial heart environment. © 1998 Biomedical Engineering Society. PAC98: 8745Hw, 4727Wg, 4279Qx
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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