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  • 1
    Electronic Resource
    Electronic Resource
    Numerical Models for Two-Phase Turbulent Flows (1996)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 28 (1996), S. 11-43 
    Details
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.fl.28.010196.000303
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  • 2
    Electronic Resource
    Electronic Resource
    The influence of particles on the spatial stability of two-phase mixing layers (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1839-1845 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A modified Rayleigh equation has been derived for the study of spatial instability of gas–particle two-phase mixing layers. The particles are assumed to have a material density much greater than the carrier fluid. The mathematical model is based on the assumptions that the mean flow profile can be approximated as that of the particle-free single-phase mixing layer and that the two phases are in dynamic equilibrium at the start of the perturbation. The resulting eigenvalue problem was solved numerically. The major finding from the analysis is that the presence of the particles enhances the stability of the two-phase flow and decreases the amplification rate of perturbations in the flow. The results show that the stability of the flow is enhanced with increased particle loading and decreased free-stream velocity ratio. For a given free-stream velocity ratio, the most amplified growth rates decrease almost linearly with the particle loading. The most amplified growth rate, however, occurs near the same angular frequency as that of the particle-free flow. The effect of particle on the perturbation phase velocity is most significant for smaller values of the angular frequency. However, the presence of particles does not change the phase velocity at the angular frequency corresponding to the most amplified rate for the single-phase flow. The phase velocity of the perturbations is slower compared to particle-free flows for modes with frequencies below the maximum amplified frequency, while it is the opposite for modes at frequencies above the maximum amplified frequency. The profiles of streamwise and cross-stream velocity fluctuations are also modified by the existence of particles. The magnitude of effects is related closely to the particle loading. For temporal instability of a two-phase mixing layer, the growth rate in time decreases linearly with increasing particle loading, which is consistent with the spatial instability results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857657
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  • 3
    Electronic Resource
    Electronic Resource
    Self-organizing particle dispersion mechanism in a plane wake (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2244-2251 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental and numerical results concerning solid particle motion in a plane wake are presented that demonstrate the importance of large-scale vortex structures in self-organizing dispersion processes. Previous studies have demonstrated that a time scale ratio involving the aerodynamic response time of the particles and a characteristic time of the vortex structures is an important parameter for indicating the qualitative and quantitative nature of the dispersion process. A stretching and folding mechanism associated with vortex development and merging interactions has been suggested as a description for characterizing particle dispersion in plane mixing layers at intermediate time scale ratios. For plane wakes where large-scale vortex mergers rarely occur, a highly organized particle dispersion process focuses intermediate time scale ratio particles along the boundaries of the large-scale vortices. The fractal correlation dimension associated with chaotic systems is found to be a useful parameter for quantifying the relative organization of the dispersion patterns as a function of the particle time scale ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858465
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  • 4
    Electronic Resource
    Electronic Resource
    The linear stability of an oscillatory two-phase channel flow in the limit of small Stokes numbers (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 7 (1995), S. 1510-1512 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of particles on the linear stability of an oscillatory two-phase plane channel flow are examined for small Stokes numbers. The results in this note are valid for the condition that the dimensionless oscillation frequency is of the order of unity or smaller. The particles are found to have a destabilizing effect at all flow oscillation frequencies except in the high-frequency region and the extent of the destabilization increases with increasing particle mass fraction. The critical Reynolds number for a gas–particle flow may be significantly changed by the flow oscillation. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868537
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  • 5
    Electronic Resource
    Electronic Resource
    Laminar condensation heat and mass transfer to a moving drop (1981)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 27 (1981), S. 372-377 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents numerical solutions to the nonlinear, coupled boundary-layer equations governing laminar condensation heat and mass transfer in the vicinity of the forward stagnation point of a spherical cold water droplet translating in a saturated mixture of three components. The environment surrounding the droplet is composed of a condensable (steam), a noncondensable and nonabsorbable (air), and a third component which is noncondensable but absorbable (Elemental Iodine, for example). The dispersed and the continuous phases have been treated simultaneously. Results obtained here show excellent agreement with experimental results where available. An important conclusion is that for laminar condensation on a freely falling droplet, for a given thermal driving force and noncondensable gas concentration in the bulk, the dimensionless heat transfer decreases with increasing saturation temperature of the outside medium.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690270306
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    The effects of surfactants on the motion and transport mechanisms of a condensing droplet in a high reynolds number flow (1985)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 1149-1156 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The motion and transport mechanisms of a condensing droplet initially contaminated with insoluble monolayer surfactant material are examined through a theoretical approach. The surface tension gradient force induced by the surfactant and the shear stress from the relative motion between droplet and its ambient vapor are evaluated on the droplet surface as major forces affecting the internal motion of the droplet. The strength of the internal motion ranges from one order of magnitude smaller than the free stream velocity for slight surfactant contamination to almost a complete stop in motion for high surfactant concentration.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690310713
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  • 7
    Electronic Resource
    Electronic Resource
    Simulation of particle dispersion in a two-dimensional mixing layer (1988)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 946-954 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Particle dispersion in a two-dimensional mixing layer is analyzed numerically by calculating the particle trajectories in a free shear layer simulated by discrete vortices. Important global and local flow quantities reported in experimental measurements are reasonably simulated.The particle dispersion results demonstrate that the extent of particle dispersion depends strongly on the Stokes number St, the ratio of particle aerodynamic response time to the characteristic time of the mixing layer flow. Particles with relatively small St values are dispersed at approximately the fluid dispersion rate. Particles with large St values are dispersed at a rate that is less than the fluid rate. Particles with intermediate values of St may get flung outside of the vortex structures in the mixing layer and therefore get dispersed at a higher rate than the fluid. This result is in agreement with some previous experiments in plane and axisymmetric jets. It is also found that a higher dispersion rate is associated with the particles introduced to the flow from the low-speed side and from near the middle of the mixing layer.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690340607
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Momentum transport in a turbulent mixing layer (1989)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 23-41 
    Details
    ISSN: 0271-2091
    Keywords: Momentum transport ; Turbulent mixing layers ; Discrete vortex method ; Time-dependent momentum fluctuations ; Comparison with experiments ; Large-scale structures ; 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: The turbulent momentum transport phenomena in a two-dimensional mixing layer are investigated numerically by a discrete vortex method. The numerical model and calculations are verified through a comparison with existing numerical simulations and experimental measurements. The main emphasis is placed on the exploration of the detailed time-dependent instantaneous local momentum fluctuations and on the comparison of numerical results with available experimental measurements. The current simulations confirm qualitatively the various trends in the turbulent momentum flux and fluctuating components of the velocity in the mixing layer found with several experimental results. The study shows that similarity exists in turbulent momentum quantities along the axial direction of the mixing layer. The calculations also show a definite correlation between the passage of a large-scale structure and a burst in the turbulent momentum flux. The probability density functions of the fluctuating quantities are shown to be mostly Gaussian-like, with only a few exceptions.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650090104
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  • 9
    Electronic Resource
    Electronic Resource
    MIXED TRANSFORM FINITE ELEMENT METHOD FOR SOLVING THE NON-LINEAR EQUATION FOR FLOW IN VARIABLY SATURATED POROUS MEDIA (1997)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 24 (1997), S. 441-455 
    Details
    ISSN: 0271-2091
    Keywords: finite elements ; Richards equation ; porous flow ; 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: A new computational method is developed for numerical solution of the Richards equation for flow in variably saturated porous media. The new method, referred to as the mixed transform finite element method, employs the mixed formulation of the Richards equation but expressed in terms of a partitioned transform. An iterative finite element algorithm is derived using a Newton-Galerkin weak statement. Specific advantages of the new method are demonstrated with applications to a set of one- dimensional test problems. Comparisons with the modified Picard method show that the new method produces more robust solutions for a broad range of soil- moisture regimes, including flow in desiccated soils, in heterogeneous media and in layered soils with formation of perched water zones. In addition, the mixed transform finite element method is shown to converge faster than the modified Picard method in a number of cases and to accurately represent pressure head and moisture content profiles with very steep fronts. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.501
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