Turbulence, in multiphase flow

It is rather difficult to establish a reasonably accurate mathematical model of a gas-liquid-liquid three-phase reactor for biphasic hydroformylation, because of the complexity in formulating all the necessary mechanisms such as phase dispersion and distribution, multiphase flow, interphase mass transfer, micromixing, and the hydroformylation reaction. Besides, the task is further complicated by turbulence in multiphase flow and the complex domain of stirred-tank reactors. 

Velocity measurement of the dispersed phase in multiphase flow is possible using both PIV and LDV. In PIV, the particles can be masked according to size, and the velocity for each size fraction can be estimated [7]. The turbulent properties, for example, granular temperature, are more difficult to measure because of the low number of particles in the measured volume. With LDV it is also possible to obtain the velocity and size for the dispersed phase, but the turbulent properties for the dispersed phase are still difficult to measure accurately, owing to the low number of particles and also because the position of the particles is not exactly the same aU the time. 

Lahcy, R. T, Jr., 1988, Turbulence and Phase Distribution Phenomena, in Transient Phenomena in Multiphase Flow, ICHMT Int. Seminar, N. H. Afgan, Ed., Hemisphere, New York. (3)... 

Lahey, R.T. (1987), Turbulence and phase distribution phenomena in two-phase flow. ICHMT International Seminar on Transient Phenomena in Multiphase Flow, Dubrovnik, Yugoslavia, May 24-30. 

Deutsch E, Simonin O (1991) Turbulence modification in multiphase flow. ASME FED 1 34-42... 

Marie JL, Moussali E, Lance M (1991) A First Investigation of a Bubbly Stress Measurements. International Symposium on Turbulence Modification in Multiphase Flows, ASME/JSME Annual Meeting, Portland, Oregon, USA, 23-27 June... 

The focus of this review has been on mass transfer in laminar, single-phase flows. Significant work is necessary for the rigorous analysis of current distribution in turbulent flows. Progress is also required for the analysis of current distribution in multiphase flows, especially in porous media relevant to fuel cell or battery applications. 

In single-phase flow, flow pattern means whether the flow is laminar or turbulent or whether flow separation or secondary flow exists. In multiphase flow, flow pattern refers to the internal geometry of the flow, i.e., the relative location of interfaces between the phases, such as stratified and dispersed. 

Fukano, T. Utsumi, R., Ousaka, A., and Sakamoto, T., Behavior of the Liquid Film Flowing Concurrently with High Speed Gas Flow, FED-Vol. 110, Turbulence Modification in Multiphase Flows, ASME pp. 81-88 (1991). 

Several flow patterns exist in multiphase flows. It must be noted that the flow is seldom homogeneous and, in most cases, different velocity and phase fractions exist at any given location within the pipe. This is fundamentally different from single-phase flow. Also, in most cases, the flow is turbulent. 

G.Gouesbet, P.Desjonqu res, A.Berlemont. Eulerlan and Lagranglan approaches to turbulent dispersion of particles. S mlnalre International Transient Phenomena In Multiphase Flow, ICHMT, Dubrovnik, 1987. 

In the same way that relative length scales of eddies and blobs affect the breakup of blobs, in multiphase flows the relative response times of particles and eddies determine how particles interact with eddies (Tang et al., 1992). Although we do not discuss this issue in detail, it is important to recognize two things (1) the relevant length scales for multiphase flows can be much more difficult to scale accurately because of the complicated interactions between turbulence and particles and (2) where tracer particles are used in experiments, the scales of motion that can be observed are a function of the particle size and characteristic response time. 

In Section 5-6.2, methods of plotting several common solution variables, such as velocity, stream function, and species concentration, were discussed. Plots of turbulent kinetic energy and dissipation are also of interest in turbulent flows, especially if other processes, such as chemical reactions, are to take place. In multiphase flows, the volume fraction of the phases is the most useful tool to assess the distribution of the phases in the vessel. In this section, three additional quantities are reviewed that are derived from the velocity field. These can provide a deeper understanding of the flow field than can plots of the velocity alone. 

Zun I (1987) Transition from wall void peaking to core void peaking in turbulent bubbly flow. Invited lecture, ICHMT international seminar on transient phenomena in multiphase flow, Dubrovnik, Yugoslavia, 24-29 May In Afgan NH (ed) Proceedings of transient phenomena in multiphase flow. Hemisphere Publ Corp, pp 225-245, 1988... 

It is the author s conviction that in many (turbulent) dispersed multiphase flows—except probably in very dense multiphase flow systems—the origin of mesoscale structures is in the fluid—particle interaction, with a secondary role for particle-particle interaction (coUisions, coalescence, breakup). Clustering of particles is believed to be intimately connected with the chaotic dynamics of fluid accelerations, as particles converge toward each other where and when the divergence of the acceleration field is positive (Goto... 

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