Liquid Flow Structure Research Articles

Study on the flow structures and distribution law of rotational–perforated coupling flow in tridimensional rotational flow sieve tray

Tridimensional rotational flow sieve trays (TRST) have a variety of gas–liquid flow structures, such as rotational flow, flow through one perforation and flow through two perforations, it is important to have a deep understanding of the coupling and distribution laws of rotational flow and flow through perforations for the selection and regulation of actual working conditions. In this study, the flow structures and proportions for the rotational–perforated coupling flow in a TRST were analyzed and predicted using the measured distribution ratio for the three-blade unit. The results showed that the gas phase mainly flowed in a rotational pattern, and its proportion was approximately 62%–83%. The proportion of flow through perforations in the liquid phase was relatively large, and the proportion of flow through one perforation was approximately 51%–57%. The proportion of flow through two perforations was approximately 27%–29%.

Three-dimensional natural convection of fluid with temperature-dependent viscosity within a porous cube having local heater

A numerical simulation is conducted on the convective heat transfer of liquid having variable viscosity in a closed porous 3D enclosure under an influence of isothermal or heat-generating solid body. Two vertical surfaces of the chamber are considered at fixed low temperature while other surfaces are thermally insulated. The local energy source is placed on the lower surface of the chamber. The control equations are written using non-dimensional variables «vector potential functions – vorticity vector – temperature». The finite difference technique of the second order accuracy is used to work out the differential equations. The effect of control parameters including the Rayleigh number, Ostrogradsky number, Darcy number, viscosity variation parameter and time on the liquid flow structure and heat transfer inside the cavity has been studied. The obtained data show that the porous material and variable viscosity working fluid can be considered as good conditions for the heat removal from the heated element in a closed chamber. A comparison of 2D and 3D models for natural convection of fluid having temperature-dependent viscosity in chambers with local heaters of various types has shown the features of different spatial approaches and boundary conditions for heated elements.

Numerical Analysis of the Influence of the Modification of the Ladle Shroud on Fluid Flow Behavior in a One-strand Tundish during Continuous Steel Casting

A tundish is a device from which liquid steel is pour into a mold. Therefore tundish hydrodynamic conditions have a significant impact on solidification during continuous steel casting (CSC) process. Modification of ladle shroud workspace, allows for the modification of liquid steel movement in the tundish. In the following work, numerical simulations were performed which allowed the impact of the modification of the ladle shroud workspace on the liquid steel flow structure in a one-strand tundish to be determined. In order to assess the impact of the modification of the ladle shroud on the behavior of the liquid steel in the tundish, simulations were performed, on the basis of which the percentage share of stagnant, ideal mixing and plug flow zones were determined. In addition, the mixing parameters were determined, allowing the estimation of casting duration during sequential casting. The flow fields of liquid steel for each modification of the ladle shroud were performed. The average velocity of liquid steel flowing through the tundish, the Reynolds number and turbulent intensity were also described. The obtained results showed, among others, that the application of three cylinders with a diameter of 0.041 m into the ladle shroud with a diameter of 0.11 m increases the share of active flow in the tundish in relation to the tundish with Conventional Ladle Shroud. At the same time, applying a ladle shroud with a diameter of 0.11 m during casting is the most favorable in relation to the hydrodynamics of the tundish.

The study of the physical characteristics and cooling plate thermal control below the lithium battery based on FEA

Four types of cooling plates with serpent channel structures are established to study the cooling effect of rectangular lithium-ion power battery under different cooling plates. Then, the number of serpent bends is analyzed, whether the fillet and pipe wall thickness is set on the cooling performance of the liquid cooling plate. According to the analysis results, a new liquid flow structure form of liquid cooling plate is designed. Numerical simulation results show that the newly designed cooling plate is integrated with the front flow of water and the internal liquid side flow, achieving a cooling effect with the maximum temperature is 309.55K and a pressure drop of 6032.1pa, which has the most effective cooling performance. Under the requirement of controlling reasonable temperature and low-pressure drop, a liquid cooling plate with better performance can be designed by innovatively setting the direction of the water inlet and outlet and the water channel’s internal flow. The above results will provide some ideas for the design of a lithium-ion battery liquid cooling plate.

Dynamic behaviors of anisodiametric bubbles under effects of horizontal attraction and vertical wake

The present study aims to describe the interaction between rising bubbles of different sizes. Coaxial and triangle bubble configurations were investigated. Bubble sizes ranged from 4.0 mm to 10.0 mm. Three-dimensional unsteady numerical simulations were performed and the volume of fluid multiphase model was employed. The numerical scheme was validated through experimental results. Time-dependent bubble geometry, bubble velocity, and near-bubble flow patterns were obtained. The results show that the participation of lateral bubbles causes coalescence delay. The mergence of bubbles is followed by an immediate decrease in bubble velocity. Liquid flow structures tend to be combined accordingly as the bubbles coalesce. For the triangle configuration, the first coalescence of small bubbles takes place between the trailing bubbles. As bubble size increases, the first coalescence arises between the leading bubble and the left trailing bubble.

Cost-based recurrence analysis of conductance time series for gas–liquid two-phase flow system

Gas–liquid two-phase flows are frequently encountered in chemical and nuclear industries. The study of gas–liquid flow structures is of great significance for understanding the mechanisms of the flow pattern transition. In this paper, a direct-image multi-electrode conductance sensor (DMCS) was used to detect the structure information of vertical gas–liquid flows. Recurrence plot (RP) and cost-based recurrence plot (CBRP) are validated using typical nonlinear systems, i.e. Lorenz system and Hénon map, and used to analyze the signals collected by the DMCS. The results indicate that the determinism (DET) derived from the CBRP is sensitive to flow pattern evolution, and can also demonstrate the internal differences in the same flow patterns.

Experimental study on flow and turbulence characteristics of bubbly jet with low void fraction

An experimental study was conducted on the flow characteristics and turbulence suppression in vertically issued bubbly jets with low void fraction (less than 1%, Re = 3,172). The effect of bubble distributions on the flow characteristics of the bubbly jet was investigated using planar Laser-Induced Fluorescence (PLIF) in the same measurement plane as Particle Image Velocimetry (PIV) for the phase separation. To ensure uniform size of the small bubbles, a bubble generator consisting of small needles was designed and manufactured. Due to the low void fraction, the velocity fields of each phase were successfully obtained. The slip velocity was constant in the far-field of the flow as 2.1 times of the inlet velocity in this study. In the early stage of the jet, there is an acceleration region that is attributed to the buoyancy of bubbles. As the potential core of the bubbly jets collapses, the distribution of bubbles seems to have an annular truncated cone shape, which evolves with the liquid flow structure. Most bubbles are populated the region around the velocity radius of the bubbly jet. Reynolds shear stresses and normal stresses of the dilute bubbly jet generally show smaller magnitudes than those of pure jets, buoyant jets, bubbly jets, and bubbly plumes. The case with higher void fraction (1%, Exp.330) shows similar magnitude of Reynolds axial stresses to jets, but magnitudes of other stresses are similar to the case with lower void fraction (0.66, Exp.320). The results are probably attributed to suppression of turbulence in low-void-fraction condition.

Structure of stationary gas slug in an annular channel

Experimental study of liquid flow structure around a stationary gas slug in an annular channel was performed. The channel consisted of two concentric pipes with the diameters of 32 and 10 mm. Slug was produced in a downward liquid flow in an annular channel. Wall shear stress distribution was measured in both walls of the channel using an electrodiffusional technique. It was shown that the shape of the slug in the annular channel differs significantly from that in a circular pipe. The distribution of wall shear stress along the slug was presented for different angular positions in the channel.

Heat transfer features in a PCM-based system under the time-dependent thermal load

Present study is devoted to a numerical analysis of heat transfer processes inside a complex radiator system based on phase change materials (PCM) under the influence of unsteady heat generation local element and external convective cooling. The numerical solution has been implemented by the finite difference method using the enthalpy-based approach to solve the energy equation. As a result of the solution, temperature distributions and liquid flow structures for different time moments, as well as integral characteristics of the melting process as a function of time, have been obtained. The effect of the external Newtonian cooling on the melting intensity and heat transfer patterns has been analyzed.

Turbulent vortex structure of liquid metal flow in pipe subjected to fringing magnetic field

Turbulent vortex structure of liquid metal flow in pipe subjected to fringing magnetic field

Experimental Investigation of Two-Phase Subcooled Liquid Flow Structure under Preburnout Conditions

The article presents the results from experimentally investigating the occurrence conditions and evolution with time of large vapor agglomerates in a rectangular channel during subcooled water boiling. The experiments were carried out at atmospheric pressure with a mass velocity of up to 1200 kg/(m2 s) and subcooling equal to 30–75 K. Agglomerates emerge as a result of coalescence of small vapor bubbles, the merging of which becomes progressively more intense with increasing the heat flux density at the heating wall starting from approximately 0.75–0.80 of the critical flux value. Decreasing the boiling liquid subcooling value facilitates the occurrence of agglomerates. Nucleate boiling may take place, and burnout phenomena (dry spots) leading to wall burnout may emerge in the liquid film between the heating wall and the agglomerate surface. The vapor agglomerates emerging in the flow of subcooled boiling liquid in a channel are burnout onset precursors. When agglomerates emerge in a system of parallel channels with subcooled boiling liquid, the hydraulic stability of its operation is upset.

Effects of sloshing gas–liquid interface on dynamics of meandering bubble plumes and mixing in a shallow vessel: PIV and PLIF measurements

Gas–liquid shallow vessels are widely used in steel-making and refining processes in the steel industry. The efficiency of these processes or the quality of steel depends on the extent of gas–induced liquid–phase mixing achieved through top–blowing of oxygen and bottom–blowing of inert gases. In the present work, the effects of combined top and bottom gas injection and sloshing interface on the dynamics of gas–liquid flow, and their role in the liquid–phase mixing in a shallow vessel, that corresponds 1:6 scaled–down model of a ladle used in steel refining, are investigated. The effects of interface sloshing and top blowing on the motion of multiple meandering bubble plumes on the liquid–phase velocity distribution, recirculatory flow structures and turbulent kinetic energy are analyzed using the time–resolved Particle Image Velocimetry (PIV) measurements. Further, the role of the aforementioned parameters on the liquid–phase mixing is analyzed using the Planar Laser Induced Fluorescence (PLIF) measurements. The effects of coaxial and eccentric top blowing configuration on the liquid flow structures and mixing are also investigated. In the case of combined top and bottom gas injection, in which gas was injected very close to the interface, the liquid–phase mixing was found to be significantly faster than that of the other configurations considered in the present work, due to the formation of strong downward flow regions and higher turbulent kinetic energy provided by the top blowing. The present investigations help to understand and to quantify the effects of the different top gas injection configurations on the meandering motion of bubble plumes, liquid flow structures, turbulence and their contributions to liquid–phase mixing.

Study of the rise of a single/multiple bubbles in quiescent liquids using the VOF method

In this paper, computational fluid dynamics was used to study the dynamics of a single and multiple bubbles in quiescent liquids using the volume of fluid method. The effect of liquid viscosity, bubbles size and initial bubbles configuration on the bubbles dynamics and interactions was investigated. It is found that the bubble rising trajectory changes from rectilinear to zigzag trajectory as liquid viscosity decreases. The different behaviors of bubbles introduce various liquid flow structures. For three bubbles rising side by side, the magnitude of bubble shape oscillations increases compared to the case of a single bubble. This is due to the fluctuations in liquid phase velocity fields which were induced by the liquid flow around the two neighboring bubbles. However, for two in-line bubbles with different sizes, the larger bubble always has a strong effect on the smaller one for each initial configuration.

Experimental and numerical study of convective flow structure above heated horizontal plates of different sizes

Free thermal convection above heated plates formed in circles of different diameters is studied within our paper. Experimental and numerical studies are carried out in a three-dimensional tank filled with water under specified boundary conditions. The initial stage of thermal convection development is mainly considered. The study of liquid flow structure is particularly observed, as well as evolution of temperature field in a plane of the central section of the working sections. Within the study different heating conditions are considered: the diameter of the round source is in the range from 0.010 to 0.024 m, and the Rayleigh number varies in the range from 1.0·102 to 1.30·105. The standard system of Navier-Stokes equations is numerically solved by finite element method to study systematically convection from heat sources of various sizes by the software package COMSOL Multiphysics. Values of the control parameter are estimated in the course of the work. At the control parameter the transition from one flow regime to another one is observed. In addition, an experimental study is carried out to verify the results of numerical simulation. As a result, a qualitative agreement has been obtained between the calculated and observed flow structures during the experiments.

Numerical Analysis of the Structure of Liquid Flow in the Tundish with Physical Model Verification

Numerical Analysis of the Structure of Liquid Flow in the Tundish with Physical Model Verification

Influence of Soluble Surfactants and Deformation on the Dynamics of Centered Bubbles in Cylindrical Microchannels.

In this study, we investigate, using direct numerical simulation, the motion of a small bubble in a horizontal microchannel filled with a liquid containing surfactants. In particular, we study the combined effect of surfactants and bubble deformability on the bubble shape, bubble-liquid relative velocity, velocity field in the liquid, liquid velocity on the gas-liquid interface, and surfactant distribution on the interface. The level-set method is used to capture the gas-liquid interface. The surfactant transport equation on the gas-liquid interface is solved in an Eulerian framework and is coupled to an equation describing the transport of surfactants inside the liquid phase. The Marangoni stress, induced by surfactant concentration gradients, is computed using the continuum surface force model. The simulation results give insights into the complexity of the coupling of the different phenomena controlling the dynamics of the studied system. For instance, the results show that for values of the capillary number much smaller than unity, that is, for spherical bubbles, the bubble velocity decreases as the bubble diameter increases. Moreover, surfactants tend to decrease significantly the bubble velocity, when compared with a bubble with a clean surface. Indeed, they accumulate at a convergent stagnation point/circle on the bubble surface and deplete at a divergent stagnation point/circle. As a consequence, the velocity of the liquid adjacent to the bubble is reduced in between the convergent and divergent stagnation points/circles because of Marangoni stresses. It is shown that regarding the bubble-liquid relative velocity, the bubble behaves as a rigid sphere when the Langmuir number is larger than unity, at least for the range of parameters explored in this study. For values of the capillary number of the order of unity, the bubble can take a "bullet shape". In this case, the bubble velocity increases as the bubble diameter increases. This increase of the bubble-liquid relative velocity is linked to a drastic change in the liquid flow structure near the bubble. Surfactants are swept to the rear of the bubble and have less influence on the bubble dynamics than for spherical bubbles. Finally, it is shown that increasing the amount of surfactants adsorbing to the surface eventually leads to the bursting of the bubble.

Influence of Rotational Wall of Axial Inlet Device on Velocity Distribution at Impeller Inlet

The goal of the article is to identify the influence of geometrical parameters of the axial inlet device, presence of its walls rotation and the pump flow rate on components of the absolute velocity distribution at the impeller inlet.A numerical simulation in the software ANSYS CFX and analysis of liquid flow structure of a double entry centrifugal pump were carried out. The axial inlet device is shaped by cylindrical and diffuser section, which includes fairing in front of the impeller. Four models of the axial inlet casing were researched.In the analyzed variants of geometry of the axial inlet device, structure of absolute velocity distribution component is similar. Rotational speed of 1450 rpm of the rotational walls of the axial inlet device compared to fixed walls affects the change of distribution of an axial component of the absolute velocity more than circumferential. Introduction of sudden expansion at the impeller inlet reduces the average value of the circumferential velocity and improves the axial velocity components distribution. Maximum and average value of the axial component of the absolute velocity and its unevenness in cross-section of the intake reduces while reducing the pump flow rate.

Experimental and numerical analysis of a turbulent spray flame structure

An experimental and numerical study of an academic n-heptane/air lab-scale jet spray burner is presented. The objective is to provide new insight on turbulent spray flame complex structures similar to those encountered in industrial combustors by joint experimental and numerical diagnostics. Experimental measurements include PDA for air velocity and droplet size as well as velocity and OH-PLIF images for the flame analysis. Numerical simulations consist in Large Eddy Simulation (LES) coupled to Discrete Particle Simulation for the dispersed phase. The comparison between experiment and simulation confirms the capability of LES to reproduce the gaseous and liquid flow structure in both non-reacting and reacting cases with good accuracy. The lifted stabilized spray flame exhibits a complex shape due to interactions between turbulence, chemistry and evaporation. A detailed analysis shows that both partially-premixed and diffusion flames are present, depending on the capacity of droplets to evaporate. Furthermore, an attempt is made to identify the processes leading to two-phase flame stabilization.

Two-fluid simulation of liquid drainage in oscillating packed beds for offshore floating applications

Three-dimensional modeling of liquid drainage dynamics in vertical, inclined and oscillating packed bed reactors is virtually inexistent in the literature. An attempt was made in this work where liquid drainage dynamics in vertical, inclined and oscillating packed bed reactors was analyzed via an unsteady-state three-dimensional two-fluid hydrodynamic model. Angular oscillations of the packed bed reactor between two angled symmetrical positions and between vertical and inclined position were considered while bed non-uniformity was described using radial porosity distributions. The simulation results highlighted the fully interpretable trends of the transient liquid flow in packed beds and underlined the differences in the transient behavior of the vertical, inclined and oscillating packed bed reactors. Although the initial period of liquid drainage was dominated by gravity regardless of bed configuration, the packed bed angle with respect to gravity direction had a significant impact on the liquid drainage dynamics. Cross-sections along streamwise direction both for static and oscillating inclined positions of the bed highlighted gas-rich uppermost and liquid-rich lowermost domains. Unlike vertical beds for which drainage occurred according to a quasi-plug flow of the liquid core region, drainage of inclined beds underlined 3D liquid flow structures with liquid-rich lowermost cross-sections which accelerated liquid withdrawal. Compared to the inclined bed case, liquid drainage was delayed under oscillating regimes as a result of reverse secondary flows induced by the column motion. The initial drainage process was controlled by the liquid flow in the bed lowermost part whereas oscillations between two symmetrically angled positions led to almost cross-sectionally uniform liquid drainage distribution. This is valuable and it is plausible that at long time the performance of packed bed reactors onboard offshore floating nonstationary platforms is insignificantly affected by the oscillations between two symmetrically angled positions.

Gas–liquid two-phase flow structure in the multi-scale weighted complexity entropy causality plane

The multi-scale weighted complexity entropy causality plane (MS-WCECP) is proposed for characterizing the physical structure of complex system. Firstly we use the method to investigate typical nonlinear time series. Compared with the multi-scale complexity entropy causality plane (MS-CECP), the MS-WCECP can not only uncover the dynamic information loss of complex system with the increase of scale, but also can characterize the complexity of nonlinear dynamic system. In particular, the algorithm of MS-WCECP performs strong anti-noise ability. Then we calculate the MS-WCECP for the conductance fluctuating signals measured from vertical upward gas–liquid two-phase flow experiments in a small diameter pipe, the results demonstrate that the MS-WCECP is a useful approach for exploring the stability and complexity in gas–liquid two-phase flows.