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Interfacial interactions and secondary flows in stratified two-phase flow
ANNUAL LITERATURE SURVEY 1996 in the simplified approach the perturbed interface is only the upper oil-gas interface. Both approaches include the viscous Kelvin-Helmholtz analysis in which the shear stresses are taken into account and the inviscid KH analysis where the shear stresses are neglected. Comparison with some experimental results suggests that the simplified method is a better predictor of the transition from stratified flow than the 'exact' approach, suggesting, perhaps, that the stability analysis on the upper interface alone is preferred. (Authors)
Interfacial interactions and secondary flows in stratified two-phase flow Line A., Masbernat L. & Soualmia A., Chemical Engineering Communications, 1996, 141-142/- (303-329). In English. In this paper are analyzed the interactions between a surface wave field and the kinematic structures above and below the waves, in gas-liquid stratified flow in a rectangular cross sectional channel. The analysis is based on experimental data both on the local structure of the flows and on the deformation of the gas-liquid surface. The basic phenomena that have been observed are: on the one hand, the wave that propagates over the liquid surface can exhibit a crosswise distribution of amplitude; on the other hand, secondary flows can be generated both in the gas and in the liquid. A theoretical attempt is developed to explain the distribution to wave amplitude; in fact, the waves propagate over a non uniform liquid current. The physical mechanisms which are based on the analysis of experimental results are also validated with numerical simulations. (from Authors) A proposal for treatment of turbulent mixing in a two-phase subchannel flow Sato Y., Kawahara A. & Sadatomi M., Chemical Engineering Communications, 1996, 141-142/- (399-413). In English. A practical method for the treatment of turbulent mixing rate in a two-phase subchannel flow in a hydrodynamic non-equilibrium state is proposed. Based on the assumption that the fundamental modes of the intersubchannel fluid transfer in such a state are turbulent mixing, void drift, and diversion cross flow, the turbulent mixing rate is considered to be equal to that in the hydrodynamic equilibrium state that the flow will attain. The applicability of the method is examined by experiments concerning the axial variation in tracer concentration in a non-equilibriumflow without diversion cross flow. A good agreement is seen between the calculations and the measurements. (Authors) Turbulent flow in a pipe with intermittent rough patches: an analogue of annular two-phase flow Jayanti S., Kandlbinder T. & Hewitt G.F., Chemical Engineering Communications, 1996, 141-142/- (237-259). In English. The response of turbulent pipe flow to sudden changes in wall roughness and flow cross-sectional area has been studied experimentally and numerically. Changes typical of those encountered by the gas phase in annular gasliquid flow have been considered. The results show that the flow field and the pressure field can be significantly distorted at these transitions. Good agreement has been obtained between the measured results and those calculated using the Harwell-FLOW3D computational fluid dynamics (CFD) code. (Authors) On the different forms of momentum equations and on the intra-and interphase interaction in the hydromechanics of a monodispersed mixture Nigmatulin R.I., Lahey Jr R.T. & Drew D.A., Chemical Engineering Communications, 1996, 141-142/- (287302). In English. Many different forms of the phasic conservation equations of two-phase flows have been presented in the literature. Unfortunately, there is still a lot of controversy as to 'best' form for two-fluid modeling. In addition, while there have been many attempts to conatitute the intraphase andinterfacialclosurelaws to achieve closure, ill-posed models are still the rule rather than the exception. The purpose of the paper is to show how various popular forms of the two-fluid model are related, and to summarize the current state-of-the-art in the modeling o finterfacial and intraphase closure laws. Moreover, new closure laws are proposed which attempt to account for the effect of dispersed phase (ie., inter-particle) interactions. It is hoped that this paper will help stimulate multiphase flow researchers to redouble this effort to achieve accurate, properly closed, two-fluid models which can used for the mechanistic predictions of multidimensional two-phase flows. (Authors) Shear and interfacial instabilities of oil-water flow in an inclined channel Tilley B.S., Bankoff S.G. & Davis S.H., Chemical Engineering Communications, 1996, 141-142/- (41-49). In English. A study of the linear stability of a laminar flow of an oil-water system in an inclinedchannel is presented. A novel shear-mode of instability, which is necessarily decaying in plane Poiseuille flow, is found to be the primary instability in certain situations. When the channel is sufficiently inclined, the long-wave mode can become unstable, regardless of the total volumetric flow rate of the fluids. The consequences to oil transport are discussed. (Authors) Experimental study of turbulent bubbly shear flows: group multiphase flows and group interfaces Lance M., 7 others & et al., Chemical Engineering Communications, 1996, 141-142/- (51-70). In English. This paper summarizes a set of experiments on bubbly shear flows. Homogeneous shear flows, plane mixing layer, boundary layer on a flat plate and sudden area expansion have been investigated, for low and moderate void fraction. Measurements of mean liquid velocity show that the main features of the corresponding single phase flow are conserved, in particular self-similarityof the mean velocity profiles. However, the turbulent field is strongly modified. The transverse interfacial momentum transfer has been evaluated, and proves to be dominated by instantaneous local forces, which are not usually taken into account in eulerian models. (Authors)
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Interfacial interactions and secondary flows in stratified two-phase flow Line A., Masbernat L. & Soualmia A., Chemical Engineering Communications, 1996, 141-142/- (303-329). In English. In this paper are analyzed the interactions between a surface wave field and the kinematic structures above and below the waves, in gas-liquid stratified flow in a rectangular cross sectional channel. The analysis is based on experimental data both on the local structure of the flows and on the deformation of the gas-liquid surface. The basic phenomena that have been observed are: on the one hand, the wave that propagates over the liquid surface can exhibit a crosswise distribution of amplitude; on the other hand, secondary flows can be generated both in the gas and in the liquid. A theoretical attempt is developed to explain the distribution to wave amplitude; in fact, the waves propagate over a non uniform liquid current. The physical mechanisms which are based on the analysis of experimental results are also validated with numerical simulations. (from Authors) A proposal for treatment of turbulent mixing in a two-phase subchannel flow Sato Y., Kawahara A. & Sadatomi M., Chemical Engineering Communications, 1996, 141-142/- (399-413). In English. A practical method for the treatment of turbulent mixing rate in a two-phase subchannel flow in a hydrodynamic non-equilibrium state is proposed. Based on the assumption that the fundamental modes of the intersubchannel fluid transfer in such a state are turbulent mixing, void drift, and diversion cross flow, the turbulent mixing rate is considered to be equal to that in the hydrodynamic equilibrium state that the flow will attain. The applicability of the method is examined by experiments concerning the axial variation in tracer concentration in a non-equilibriumflow without diversion cross flow. A good agreement is seen between the calculations and the measurements. (Authors) Turbulent flow in a pipe with intermittent rough patches: an analogue of annular two-phase flow Jayanti S., Kandlbinder T. & Hewitt G.F., Chemical Engineering Communications, 1996, 141-142/- (237-259). In English. The response of turbulent pipe flow to sudden changes in wall roughness and flow cross-sectional area has been studied experimentally and numerically. Changes typical of those encountered by the gas phase in annular gasliquid flow have been considered. The results show that the flow field and the pressure field can be significantly distorted at these transitions. Good agreement has been obtained between the measured results and those calculated using the Harwell-FLOW3D computational fluid dynamics (CFD) code. (Authors) On the different forms of momentum equations and on the intra-and interphase interaction in the hydromechanics of a monodispersed mixture Nigmatulin R.I., Lahey Jr R.T. & Drew D.A., Chemical Engineering Communications, 1996, 141-142/- (287302). In English. Many different forms of the phasic conservation equations of two-phase flows have been presented in the literature. Unfortunately, there is still a lot of controversy as to 'best' form for two-fluid modeling. In addition, while there have been many attempts to conatitute the intraphase andinterfacialclosurelaws to achieve closure, ill-posed models are still the rule rather than the exception. The purpose of the paper is to show how various popular forms of the two-fluid model are related, and to summarize the current state-of-the-art in the modeling o finterfacial and intraphase closure laws. Moreover, new closure laws are proposed which attempt to account for the effect of dispersed phase (ie., inter-particle) interactions. It is hoped that this paper will help stimulate multiphase flow researchers to redouble this effort to achieve accurate, properly closed, two-fluid models which can used for the mechanistic predictions of multidimensional two-phase flows. (Authors) Shear and interfacial instabilities of oil-water flow in an inclined channel Tilley B.S., Bankoff S.G. & Davis S.H., Chemical Engineering Communications, 1996, 141-142/- (41-49). In English. A study of the linear stability of a laminar flow of an oil-water system in an inclinedchannel is presented. A novel shear-mode of instability, which is necessarily decaying in plane Poiseuille flow, is found to be the primary instability in certain situations. When the channel is sufficiently inclined, the long-wave mode can become unstable, regardless of the total volumetric flow rate of the fluids. The consequences to oil transport are discussed. (Authors) Experimental study of turbulent bubbly shear flows: group multiphase flows and group interfaces Lance M., 7 others & et al., Chemical Engineering Communications, 1996, 141-142/- (51-70). In English. This paper summarizes a set of experiments on bubbly shear flows. Homogeneous shear flows, plane mixing layer, boundary layer on a flat plate and sudden area expansion have been investigated, for low and moderate void fraction. Measurements of mean liquid velocity show that the main features of the corresponding single phase flow are conserved, in particular self-similarityof the mean velocity profiles. However, the turbulent field is strongly modified. The transverse interfacial momentum transfer has been evaluated, and proves to be dominated by instantaneous local forces, which are not usually taken into account in eulerian models. (Authors)
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