Thermocapillary flow without return flow–linear flow

The experimental realization of thermocapillary flow without return flow is reported. This type of flow (linear flow) was proposed and analyzed theoretically by Smith and Davis (J. Fluid Mech., 132:119–144, 1983). We suppressed the return flow by providing channels and side channels with lower flow resistance compared to that of the return flow. Cooling the layer with linear flow from above results in the Marangoni instability of longitudinal rolls as the most dangerous mode. Strong linear flow stabilizes the system against longitudinal rolls. We report preliminary results on the threshold and on the wavelength of the longitudinal rolls.     

Extensional flow —a mathematical perspective

Extensional flow has been studied extensively for less than half the lifetime of the word rheology, although measurement of viscosity from extensional flow experiments can be traced back to the beginning of this century. In recent years extensional flow has, however, attracted a great deal of attention in conferences, workshops and special issues of journals. This has coincided with interest, both scientific and industrial, in elasticoviscous fluids, notably polymer solutions and molten polymers. The particular success of specialized, carefully targetted or focussed, workshops is highlighted.A personal reflection is offered here on some of the issues in extensional flow from the point of view of an applied mathematician. The state of the art, as far as extensional viscosity is concerned, is briefly surveyed. Both theoretical and practical aspects of the task of obtaining useful extensional flow properties are outlined, drawing heavily on a recent review by James and Walters. Particular attention is paid to spinning experiments, drawing heavily on recent theoretical investigations by the author. The merits of defining a spinning viscosity, in addition to the formally defined tensile viscosity, are advanced. The idea of general approximations for extensional flows is reviewed and some aspects of this are highlighted, particularly in connection with Metzner's idea of extensional primary field (EPF) approximations. Finally qualitative investigations of the behaviour of model fluids (in model flows) are illustrated and a new result on the boundedness of solutions for unsteady uniaxial extension of a FENS-P dumbbell model is presented.Presented as a keynote lecture at the 4the European Rheology Conference, September 4–9, 1994, Seville, Spain     

The flow pattern map of a two-phase non-Newtonian liquid–gas flow in the vertical pipe

A map for the determination of flow pattern for two-phase flow of gas and non-Newtonian liquid in the vertical pipe has been presented. Our own experimental data confirm applicability of such a map.     

Investigation of two-phase flow pattern,liquid holdup and pressure drop in viscous oil–gas flow

An experimental investigation was carried out on viscous oil–gas flow characteristics in a 69 mm internal diameter pipe. Two-phase flow patterns were determined from holdup time-traces and videos of the flow field in a transparent section of the pipe, in which synthetic commercial oils (32 and 100 cP) and sulfur hexafluoride gas (SF₆) were fed at oil superficial velocities from 0.04 to 3 m/s and gas superficial velocities from 0.0075 to 3 m/s.     

K-ε-T model of dense liquid-solid two-phase turbulent flow and its application to the pipe flow

To predict the characteristics of dense liquid-solid two-phase flow, K-ε-T model is established, in which the turbulent flow of fluid phase is described with fluid turbulent kinetic energy K_f and its dissipation rate ε_f, and the particles random motion is described with particle turbulent energy K_p and its dissipation rate ε_p and pseudothermal temperature T_p. The governing equations are also derived. With K-ε-T model, numerical study of dense liquid-solid two-phase turbulent up-flow in a pipe is performed. The calculated results are in good agreement with experimental data of Alajbegovic et al. (1994), and some flow features are captured.     

Transient growth in turbulent particle-laden channel flow

Linear transient growth of optimal perturbations in particle-laden turbulent channel flow is investigated in this work.The problem is formulated in the framework of a Eulerian-Eulerian approach,employing two-way coupling between fine particles and fluid flow.The model is first validated in laminar cases,after which the transient growth of coherent perturbations in turbulent channel flow is investigated,where the mean particle concentration distribution is obtained by direct numerical simulation.It is shown that the optimal small-scale structures for particles are streamwise streaks just below the optimal streamwise velocity streaks,as was previously found in numerical simulations of particle-laden channel flow.This indicates that the optimal growth of perturbations is a dominant mechanism for the distribution of particles in the near-wall region.The current study also considers the transient growth of small-and large-scale perturbations at relatively high Reynolds numbers,which reveals that the optimal large-scale structures for particles are in the near-wall region while the optimal large-scale structures for fluid enter the outer region.     

On the Euler flow in ℝ2

We give a global existence and uniqueness theorem for the Euler flow in ² for suitable initial velocity fields, possibly diverging at infinity.     

Q-consciousness: where is the flow?

What can recent research on quantum-consciousness (Q-consciousness) tell us about the connection between quantum level phenomena and human consciousness? Q-consciousness theorists propose and experimenters purport to show evidence linking quantum mechanisms of one kind or another to changes in biologically important atomic and molecular processes that produce and shape 'consciousness.' Several mechanisms are identified. In the studies reviewed, consciousness is not operationally defined. How Q-level events influence or are responsible for the complex performance of consciousness in its environment is not specified. Several problems with specifying causality within and between different temporalities at the biological and quantum level are not addressed. The morphogenic rules that govern the origin, continuous or discontinuous, and spontaneous presenting of an organized consciousness are missing. The literature reviewed shows that there are causal links between quantum events and molecular changes that affect biological processes such as photosynthesis and bird migration. Even so, the connections between the quantum level of reality, biological processes, mind and the diverse flow of consciousness are not well and consistently defined, or characterized and understood in ways useful for conducting research of the morphogenesis of consciousness. No overall experimental direction is Q-consciousness research is discernable. Finally, the preponderance of limited experimental evidence does not point toward a particular Q-consciousness theory. Suggestions are made about how recasting cell doctrine, thinking of consciousness as 'performance,' and nonlinear and complexity theory may provide some guidance relevant to the possible flow of Q-consciousness.     

Review on vertical gas–liquid slug flow

Vertical slug flow is characterized by the rise of long bullet-shaped gas bubbles with a diameter almost matching that of the tube - Taylor bubbles. Liquid slugs separate consecutive Taylor bubbles, which may interact and coalesce if the distance between them is small. Slug flow has numerous industrial applications, being also observed on physiological and geological systems. In spite of the contribution of the development of non-intrusive experimental techniques to a deeper understanding of slug flow features, the complexity of this flow pattern requires the combined use of numerical approaches to overcome some of the optical problems reported in experimental methods, and other limitations related to the flow aperiodic behavior.The need to systematize the large amount of data published on the subject and to understand the limitations of the techniques employed constitutes the motivation for this review. In the present work, literature on vertical gas–liquid slug flow, with Newtonian fluids, from 1943 to 2015, covering theoretical, experimental and numerical approaches, is reviewed. Focus is given to single and trains of Taylor bubbles rising through stagnant and co-current liquids.It should be emphasized, however, that further research still needs to be conducted in some particular areas, namely the hydrodynamics of the liquid film surrounding the Taylor bubbles, the interaction between consecutive bubbles, and a more detailed approach to the flow of Taylor bubbles through co-current liquids.     

Investigation on effect of drag models on flow behavior of power-law fluid–solid two-phase flow in fluidized bed

In this study, a Eulerian-Eulerian two-fluid model combined with the kinetic theory of granular flow is adopted to simulate power-law fluid–solid two-phase flow in the fluidized bed. Two new power-law liquid–solid drag models are proposed based on the rheological equation of power-law fluid and pressure drop. One called model A is a modified drag model considering tortuosity of flow channel and ratio of the throat to pore, and the other called model B is a blending drag model combining drag coefficients of high and low particle concentrations. Predictions are compared with experimental data measured by Lali et al., where the computed porosities from model B are closer to the measured data than other models. Furthermore, the predicted pressure drop rises as liquid velocity increases, while it decreases with the increase of particle size. Simulation results indicate that the increases of consistency coefficient and flow behavior index lead to the decrease of drag coefficient, and particle concentration, granular temperature, granular pressure, and granular viscosity go down accordingly.     

Advantageous swirling flow in 45° end-to-side anastomosis

The effects of swirling flow on the flow field in 45° end-to-side anastomosis are experimentally investigated using a particle image velocimetry technique to reveal fluid dynamic advantages of swirling flow in the vascular graft. Non-swirling Poiseuille inlet flow unnecessarily induces pathological hemodynamic features, such as high wall shear stress (WSS) at the ‘bed’ side and large flow separation at the ‘toe’ side. The introduction of swirling flow is found to equalize the asymmetric WSS distribution and reduces the peak magnitude of WSS. In particular, the intermediate swirling intensity of S = 0.45 induces the most uniform axial velocity and WSS distributions compared with weaker or stronger swirling flows, which addresses the importance of proper selection of swirling intensity in the vascular graft to obtain optimum flow fields at the host vessel. In addition, swirling flow reduces the size of flow separation because it disturbs the formation of Dean-type vortices in secondary flow and inhibits secondary flow collision. The beneficial fluid dynamic features of swirling flow obtained in this study are helpful for designing better vascular graft suppressing pathological hemodynamic features in the recipient host vessel.     

Effect of heat flow on heat‐transfer characteristics for a supersonic spatial flow around a spherically blunted cone

Heattransfer processes for a supersonic spatial flow around a spherically blunted cone were studied by solving direct and inverse threedimensional problems taking into account heat flow along the longitudinal and circumferential coordinates. It is shown that highly heatconducting materials can be used to advantage to decrease the maximum temperatures on the windward side of streamline bodies.     

Viscosity-stratified flow in a Hele–Shaw cell

A hierarchy of mathematical models describing viscosity-stratified flow in a Hele-Shaw cell is constructed. Numerical modelling of jet flow and development of viscous fingers with the influence of inertia and friction is carried out. One-dimensional multi-layer flows are studied. In the framework of three-layer flow the interpretation of the Saffman–Taylor instability is given. A kinematic-wave model of viscous fingering taking into account friction between the fluid layers is proposed. Comparison with calculations on the basis of two-dimensional equations shows that this model allows to determine the propagation velocity of the viscous fingers.     

On the stability of distorted laminar flow(III)—The nonlinear stability analysis of distorted parallel shear flow

Based on the hydrodynamic stability theory of distorted laminar flow and the kind of distortion profiles on the mean velocity in parallel shear flow given in paper [1], this paper investigates the nonlinear stability behaviour of parallel shear flow, carries on stability calculation taking account of the perturbations of background turbulence noise under certain assumption, and obtains some results in accordance qualitatively with those of experiment for plane Poiseuille flow and pipe Poiseuille flow.The author thanks Prof. Zhou Heng sincerely for his kind offer of his computer program of the artificial neutrality method on the stability in subcritical range of plane Poiseuille flow.     

“Ion wind”, a gas-dynamic flow in the corona discharge,and its interaction with the external flow

The “ion wind”, a gas-dynamic flow in the corona discharge that arises owing to transfer of the ion component momentum to the neutral particles of an initially stationary gas, and its interaction with the external flow perpendicular to it are studied. A physico-mathematical model of the flows considered is proposed and the corresponding equations are analyzed numerically. The boundary conditions used for the electric quantities approximately model the conditions in the negative corona discharge between a thin corona-forming electrode and a plane grid electrode transparent to the gas.     

Magnetohydrodynamics hemodynamics hybrid nanofluid flow through inclined stenotic artery

The present study aims to perform computational simulations of twodimensional(2D) hemodynamics of unsteady blood flow via an inclined overlapping stenosed artery employing the Casson fluid model to discuss the hemorheological properties in the arterial region. A uniform magnetic field is applied to the blood flow in the radial direction as the magneto-hemodynamics effect is considered. The entropy generation is discussed using the second law of thermodynamics. The influence of different shape pa...