Download or read book Vortex induced Waves and the Mechanism of Drop Entrainment in Transition from Stratified to Dispersed Oil water Pipe Flows written by Mohd Izzudin Izzat Bin Zainal Abidin and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents new insights on flow pattern transition from stratified to non-stratified of two-phase oil and water flows in horizontal pipes. A novel approach is implemented to facilitate investigation of drop entrainment which identifies onset of the particular transition, where a cylindrical bluff body is located transverse to flow direction to induce instabilities in the form of vortex-induced interfacial waves in stratified flows. Numerical investigations of two-dimensional single-phase flows performed with CFD code FLUENT shows that vortex shedding frequency increases with decrease in the cylinder diameter while the size of vorticity region expands with increase in cylinder diameter. From the findings, two cylinder diameters, 2 mm and 8 mm are selected for experimental investigation in two-phase flows to generate vortex shedding frequency in the range of 1 to 100 Hz. Findings of high-speed visualization on the flow patterns and interfacial wave characteristics showed that higher instabilities were achieved with increasing cylinder diameter where the transition boundaries were shifted towards lower mixture velocities and waves with higher amplitude were produced. This is attributed to the size of vorticity regions, which are attached to the interface to actuate the vortex-induced waves as demonstrated by the particle image velocimetry (PIV) results. Variations of the vortex shedding behavior achieved by various cylinder diameters were found to be reflected on the resulting vortex-induced waves. The cylindrical bluff body approach is further implemented for the investigations of drop entrainment using a cylinder diameter that corresponds to gap ratio of 0.656 as it provides high instabilities at minimum wall effects. The use of simultaneous PLIF and PIV was introduced to visualize the wave"s evolution with high spatial and temporal resolution while obtaining the velocity field around the waves at the same time. Drop entrainment was identified to occur through detachment of drop from interfacial waves and is formulated into a phenomenological model developed based on force balance. Further analysis of the deformed wave dynamics during drop detachment shows relation to the input flowrate ratio, r.

Download or read book Flow Pattern Transitions in Oil water Flows Past a Bluff Body written by Kyeong Hyeon Park and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this Thesis a novel approach is followed to facilitate the experimental investigations on the flow pattern transitions from separated to dispersed flows using a cylindrical bluff body in horizontal oil-water flows. A transverse cylindrical rod is used as a bluff body which is placed under the interface of the two immiscible liquids and near the test section inlet to passively generate interfacial perturbations and breaking waves. This approach was inspired from the use of hydrofoils in ships that reduce frictional drag via increased air entrainment. Studies are carried out using two flow facilities and high speed imaging combined with laser based measurements are performed at two axial locations along the test section, immediately after the cylinder and at large distance away from the cylinder. The effect of a confined geometry on the characteristics of the von Karman vortices and on the general flow behaviour immediately downstream of the cylinder are investigated in single phase water flows. It is found that the 3D pipe geometry does not affect significantly the vortex shedding behind the cylinder at least in the central plane of the pipe. The frequencies of the vortex shedding were comparable to those from a cylinder in an unconfined liquid. The results from two phase flows reveal that the cylinder reduces the mixture velocity for the transition separated to dispersed flows. It also actuates interfacial waves that are found to be non-linear and convective. In many cases the waves have the same frequencies as the von Karman vortices depending on the submergence depth of the cylinder underneath the oil-water interface and on the Froude number of the water layer. The observations suggest that strongly non-linear waves are responsible for forming thin ligaments that eventually break up into droplets.

Download or read book Transfer of Substance in Vortex and Wave Flows in One Component and Multi component Environment written by Tatiana Chaplina and published by Springer Nature. This book was released on 2023-06-02 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of vortex and wave flows is one of the traditional problems of fluid mechanics, the practical importance of which has grown significantly in recent years. Consideration of the processes of substance transfer in such complex systems as natural water bodies is fraught with many difficulties of a methodological and fundamental nature: the extreme complexity of conducting a full-scale experiment, the complexity and variability of hydrophysical fields of the ocean and hydrometeorological conditions during research, and also, in some cases, the complexity and the variability of the properties of the transferred substance. In this connection, it is of particular interest to study the transfer of markers in stationary vortex and wave flows, which can form in laboratory facilities with constant external conditions. In this case, it is possible to avoid problems associated with the spatial and temporal variability of natural sources of vortex formations and directly trace the dependence of the characteristic flow parameters or the characteristics of the movement of solid or other objects placed during. This book presents the results of experimental and theoretical studies of the dynamics and structure of multiphase vortex flows and the nature of the transfer of three types of markers: solid-state (ice, plastic), immiscible with water (oil, oil, diesel) and soluble (aniline dyes, uranyl). The results will be important, first of all, for a better understanding of the behavior of various impurities in the circulation flows and more accurate prediction of their distribution in natural conditions (in a stratified hydrosphere and atmosphere).

Download or read book Propagation Of Waves In Shear Flows written by A L Fabrikant and published by World Scientific. This book was released on 1998-10-20 with total page 305 pages. Available in PDF, EPUB and Kindle. Book excerpt: The state of the art in a theory of oscillatory and wave phenomena in hydrodynamical flows is presented in this book. A unified approach is used for waves of different physical origins. A characteristic feature of this approach is that hydrodynamical phenomena are considered in terms of physics; that is, the complement of the conventionally employed formal mathematical approach. Some physical concepts such as wave energy and momentum in a moving fluid are analysed, taking into account induced mean flow. The physical mechanisms responsible for hydrodynamic instability of shear flows are considered within the concept of negative energy waves. The phenomenon of over-reflection is analysed. A number of well-known theorems of the hydrodynamic theory of stability are interpreted in terms of the interaction of the waves having different energy signs. Attention is drawn to the plasma-hydrodynamic analogy, which is a powerful tool for physical analyses of general mechanisms of wave amplification and absorption in flows. Various wave-flow interaction problems are considered, for instance, sound generation in whistlers, wave scattering and amplification by vortices, methods of wave remote sounding, and some nonlinear dynamical and chaotic phenomena.The book is intended for researchers specializing in wave theory, aeroacoustics, geophysical and astrophysical fluid dynamics, and related fields. It may also be useful to graduate and post-graduate students as a supplement to standard lecture courses.

Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1987 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Phase Inversion in Dispersed Liquid liquid Pipe Flow written by K. H. Ngan and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the experimental and theoretical investigations on the development of phase inversion in horizontal pipeline flow of two immiscible liquids. It aims to provide an understanding on the flow development across the phase inversion transition as well as the effect on pressure drop. Experimental investigation on phase inversion and associated phenomena were conducted in a 38mm I.D. liquid pipeline flow facility available in the Department of Chemical Engineering at University College London (UCL). Two sets of test pipelines are constructed using stainless steel and acrylic. The inlet section of the pipeline has also been designed in two different configurations - (1) Y-junction inlet to allow dispersed flow to be developed along the pipeline (2) Dispersed inlet to allow formation of dispersion immediately after the two phases are joined. Pressure drop along the pipeline is measured using a differential pressure transducer and is studied for changes due to redistribution of the phases during inversion. Various conductivity probes (ring probes, wire probes, electrical resistance tomography and dual impedance probe) are installed along the pipeline to detect the change in phase continuity and distribution as well as drop size distribution based on the difference in conductivity of the oil and water phases. During the investigation, the occurrence of phase inversion is firstly investigated and the gradual transition during the process is identified. The range of phase fraction at which the transition occurs is determined. The range of phase fraction becomes significantly narrower when the dispersed inlet is used. The outcome of the investigation also becomes the basis for subsequent investigation with the addition of glycerol to the water phase to reduce the interfacial tension. Based on the experimental outcome, the addition of glycerol does not affect the inversion of the oil phase while enhancing the continuity of the water phase. As observed experimentally, significant changes in pressure gradient can be observed particularly during phase inversion. Previous literatures have also reviewed that phase inversion occurs at the maximum pressure gradient. In a horizontal pipeline, pressure gradient is primarily caused by the frictional shear on the fluid flow in the pipe and, in turn, is significantly affected by the fluid viscosities. A study is conducted to investigate on the phase inversion point by identifying the maximum mixture viscosity (i.e. maximum pressure gradient) that an oil-in-water (O/W) and water-in-oil (W/O) dispersion can sustain. It is proposed that the mixture viscosity will not increase further with an increase in the initial dispersed phase if the inverted dispersion has a lower mixture viscosity. This hypothesis has been applied across a wide range of liquid-liquid dispersion with good results. This study however cannot determine the hysteresis effect which is possibly caused by inhomogeneous inversion in the fluid system. A mechanistic model is developed to predict the flow characteristics as well as the pressure gradient during a phase inversion transition. It aims to predict the observed change in flow pattern from a fully dispersed flow to a dual continuous flow during phase inversion transition. The existence of the interfacial height provides a selection criterion to determine whether a momentum balance model for homogeneous flow or a two-fluid layered flow should be applied to calculate the pressure gradient. A friction factor is also applied to account for the drag reduction in a dispersed flow. This developed model shows reasonable results in predicting the switch between flow patterns (i.e. the boundaries for the phase inversion transition) and the corresponding pressure gradient. Lastly, computational fluid dynamic (CFD) simulation is applied to identify the key interphase forces in a dispersed flow. The study has also attempted to test the limitation of existing interphase force models to densely dispersed flow. From the study, it is found that the lift force and the turbulent dispersion forces are significant to the phase distribution in a dispersed flow. It also provides a possible explanation to the observed flow distribution in the experiments conducted. However, the models available in CFX are still unable to predict well in a dense dispersion (60% dispersed). This study is also suggested to form the basis for more detailed work in future to optimize the simulation models to improve the prediction of phase inversion in a CFD simulation.

Download or read book Swirling Flow Problems at Intakes written by J. Knauss and published by Routledge. This book was released on 2017-11-01 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamentals of vortex intake flow; Results theoretical & experimental work; Prediction of critical submergence; Modeling of vortices & swirling flows; Design; Intake structures; Pump sumps; Vortex-flow intakes. This volume forms an essential reference work for anyone involved in intakes, either as a practising design engineer or research worker. Water Power & Dam Constr., July 1988.The book is essential reading for postgraduate students & researchers alike and a very valuable aid to design engineers. Hydrol.Sc.Jrl., 33(3), 1988.

Download or read book Proceedings SPE Annual Technical Conference and Exhibition written by Society of Petroleum Engineers (U.S.). Technical Conference and Exhibition and published by . This book was released on 1996 with total page 910 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Vortex Flow in Nature and Technology written by Hans J. Lugt and published by Wiley-Interscience. This book was released on 1983 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Air Problems in Pipelines written by Manuela Escarameia and published by . This book was released on 2005-01-01 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Short wave Vortex Instabilities in Stratified Flow written by Luke Bovard and published by . This book was released on 2013 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: Density stratification is one of the essential underlying physical mechanisms for atmospheric and oceanic flow. As a first step to investigating the mechanisms of stratified turbulence, linear stability plays a critical role in determining under what conditions a flow remains stable or unstable. In the study of transition to stratified turbulence, a common vortex model, known as the Lamb-Chaplygin dipole, is used to investigate the conditions under which stratified flow transitions to turbulence. Numerous investigations have determined that a critical length scale, known as the buoyancy length, plays a key role in the breakdown and transition to stratified turbulence. At this buoyancy length scale, an instability unique to stratified flow, the zigzag instability, emerges. However investigations into sub-buoyancy length scales have remained unexplored. In this thesis we discover and investigate a new instability of the Lamb-Chaplyin dipole that exists at the sub-buoyancy scale. Through numerical linear stability analysis we show that this short-wave instability exhibits growth rates similar to that of the zigzag instability. We conclude with nonlinear studies of this short-wave instability and demonstrate this new instability saturates at a level proportional to the cube of the aspect ratio.

Download or read book Investigations on the Transition Between Stratified and Non stratified Horizontal Oil water Flows written by and published by . This book was released on 2006 with total page 694 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Instability of Finite Amplitude Waves written by Ali K. Cherri and published by . This book was released on 1997 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-phase flow--air flow over in viscid and incompressible wavy water--in a rectangular horizontal channel is analyzed to determine the characteristics of the transition from stratified to slug flow.

Download or read book Horizontal Oil water Flows in the Dual Continuous Flow Regime written by Jonathan Lovick and published by . This book was released on 2004 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt: The research presented in this thesis is concerned with the flow behaviour of two-phase, liquid-liquid, oil-water flow through horizontal pipes. The test liquids used were oil (density 828kg/rn3, viscosity 6x iO 3 Pa s) and water, with experiments carried out in a purpose built test facility with a stainless steel pipe (internal dia. 38mm, length 8m). Visual observation of the flow was possible at low mixture velocities through a lm transparent pipe at the end of the test section. At higher mixture velocities local probes were used for flow pattern identification. These local probes were a conductivity probe for identifying the continuous phase, and a high frequency impedance probe for measuring local phase distribution. A dual sensor impedance probe was also developed for measuring local drop velocity and also the drop chord length distributions. Pressure gradient was also measured using a differential pressure transducer, and in-situ phase fractions were obtained using Quick Closing Valves. Experimental results show that the dual continuous flow regime, where both phases retain their continuity while there is mixing at the interface, dominates at all input oil fractions at low mixture velocities and intermediate oil fractions at high mixture velocities. In general the pressure drop of the two-phase mixture is lower than that of single phase oil. At higher mixture velocities a minimum in pressure gradient appeared at high oil fractions perhaps as a combination of the drag reduction phenomenon and the relative fraction of the oil and water layers in the pipe. At the highest mixture velocity this minimum was at the boundary of fully dispersed oil continuous flow with dual continuous flow. Velocity ratios are shown to increase with increasing oil fraction at low mixture velocities, with this trend reversing at high mixture velocities. These trends in the pressure gradient and velocity ratio can be explained using the phase distribution diagrams, with the interfacial curvature greatly affecting velocity ratio. Local chord length data shows that, in general, drop sizes decrease with increasing distance from the interface and that oil drops tend to be slightly larger than water drops. Mixture velocity did not significantly affect the drop size of either phase in dual continuous flow. A modified version of the two-fluid model was suggested for dual continuous flow that treats the upper and lower layers as dispersions and uses experimental entrainment to calculate their properties. Better predictions were obtained when friction factors that accounted for the drag reduction phenomenon were used to calculate wall shear stresses.

Download or read book The Motion and Frequency of Large Disturbance Waves in Annular Two phase Flow of Air water Mixtures written by N. S. Hall-Taylor and published by . This book was released on 1962 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Entrainment and Deposition of Drops in a Dispersed Two phase Flow written by C. Langevin and published by . This book was released on 1983 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Wave Propagation in Dispersed and Gravity Stratified Gas liquid Flows written by D. Assimacopoulos and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: