The effects of gravity and surface tension on the circular hydraulic jump for low- and high-viscosity liquids: A numerical investigation

2021 ◽  
Vol 33 (1) ◽  
pp. 012105
Author(s):  
Yunpeng Wang ◽  
Roger E. Khayat
Keyword(s):  
Surface Tension ◽  
Numerical Investigation ◽  
Hydraulic Jump ◽  
High Viscosity

Experimental and numerical investigation of electrostatic spray liquid-liquid extraction with ionic liquids

2012 ◽  
Vol 33 (1) ◽  
pp. 167-183 ◽  
Author(s):  
Marek Krawczyk ◽  
Kamil Kamiński ◽  
Jerzy Petera
Keyword(s):  
Ionic Liquids ◽  
Numerical Investigation ◽  
High Viscosity ◽  
Liquid Extraction ◽  
Separation Processes ◽  
Organic Mixture ◽  
Liquid Liquid Extraction ◽  
Key Factor ◽  
A New Technique ◽  
Electrostatic Spray

Experimental and numerical investigation of electrostatic spray liquid-liquid extraction with ionic liquids A new concept of an electrostatic spray column for liquid-liquid extraction was investigated. An important problem for separation processes is the presence of azeotropic or close-boiling mixtures in their production, for example heptane with ethanol, since the separation is impossible by ordinary distillation. The use of ionic liquids (IL) as a dispersed solvent specially engineered for any specific organic mixture in terms of selectivity is a key factor to successful separation. As IL present particularly attractive combination of favorable characteristics for the separation of heptane and ethanol, in this work we use 1-butyl-3-methylimidazolium methyl sulfate [BMIM][MeSO4]. Because of high viscosity and relatively high cost of IL a new technique was introduced, consisting in the electrostatically spray generation to enhance the mass transport between the phases. In order to optimally design the geometry of the contactor a series of numerical simulation was performed. Especially multi-nozzle variants for better exploitation of contactor volume were investigated. Experiments showed excellent possibility of control of the dispersion characteristics by applied voltage and thus control of the rate of extraction. The preliminary simulations based on our mathematical model for a three nozzle variant exhibited visual agreement with the theory of electrostatics.

Experiments on the breakup of drop-impact crowns by Marangoni holes

2018 ◽  
Vol 844 ◽  
pp. 162-186 ◽  
Author(s):  
Abdulrahman B. Aljedaani ◽  
Chunliang Wang ◽  
Aditya Jetly ◽  
S. T. Thoroddsen
Keyword(s):  
Surface Tension ◽  
Lower Surface ◽  
High Viscosity ◽  
Solid Substrate ◽  
Immiscible Liquid ◽  
Hole Formation ◽  
Low Viscosity ◽  
Stress Changes ◽  
Lower Surface Tension ◽  
The Impact

We investigate experimentally the breakup of the Edgerton crown due to Marangoni instability when a highly viscous drop impacts on a thin film of lower-viscosity liquid, which also has different surface tension than the drop liquid. The presence of this low-viscosity film modifies the boundary condition, giving effective slip to the drop along the solid substrate. This allows the high-viscosity drop to form a regular bowl-shaped crown, which rises vertically away from the solid and subsequently breaks up through the formation of a multitude of Marangoni holes. Previous experiments have proposed that the breakup of the crown results from a spray of fine droplets ejected from the thin low-viscosity film on the solid, e.g. Thoroddsen et al. (J. Fluid Mech., vol. 557, 2006, pp. 63–72). These droplets can hit the inner side of the crown forming spots with lower surface tension, which drives a thinning patch leading to the hole formation. We test the validity of this assumption with close-up imaging to identify individual spray droplets, to show how they hit the crown and their lower surface tension drive the hole formation. The experiments indicate that every Marangoni-driven patch/hole is promoted by the impact of such a microdroplet. Surprisingly, in experiments with pools of higher surface tension, we also see hole formation. Here the Marangoni stress changes direction and the hole formation looks qualitatively different, with holes and ruptures forming in a repeatable fashion at the centre of each spray droplet impact. Impacts onto films of the same liquid, or onto an immiscible liquid, do not in general form holes. We furthermore characterize the effects of drop viscosity and substrate-film thickness on the overall evolution of the crown. We also measure the three characteristic velocities associated with the hole formation: i.e. the Marangoni-driven growth of the thinning patches, the rupture speed of the resulting thin films inside these patches and finally the growth rate of the fully formed holes in the crown wall.

The standing hydraulic jump: theory, computations and comparisons with experiments

1992 ◽  
Vol 242 ◽  
pp. 145-168 ◽  
Author(s):  
R. I. Bowles ◽  
F. T. Smith
Keyword(s):  
Surface Tension ◽  
Liquid Layer ◽  
Hydraulic Jump ◽  
Computational Study ◽  
Boundary Layer Separation ◽  
Quantitative Agreement ◽  
Primary Role ◽  
Viscous Effects ◽  
Free Interaction ◽  
Everyday Context

In this theoretical and computational study of the flow of a liquid layer, under the influence of surface tension and gravity most notably, the nonlinear equations governing an interaction between viscous effects and the effects of surface tension, gravity and streamline curvature for the limit of large Reynolds numbers are derived. The aim is to make a comparison between the predictions of this theory and the experiments of Craiket al.on the axisymmetric hydraulic jump. Such a jump is commonly encountered in the everyday context of the initial filling of a kitchen sink, for example, and it is found in the present work that initially all the effects listed above can play a primary role in practice in the local jump phenomenon. As a first step here, the flow of the layer over a small obstacle is considered. It is seen that as surface tension becomes increasingly significant the upstream influence becomes more wave-like. Second, calculations and analysis of the nonlinear free interaction are presented and show wave-like behaviour upstream, followed downstream by a depth profile not unlike that in the typical hydraulic jump. The effects of gravity dominate those of surface tension downstream. Finally, comparisons are made with the experiments and show fair quantitative agreement, supporting the present proposition that these hydraulic jumps are caused by boundary-layer separation due to a viscous–inviscid interaction forced by downstream boundary conditions on, in this case, a fully developed, high-Froude-number liquid layer.

Interactions Between High-Viscosity Droplets Deposited on a Surface: Experiments and Simulations

2012 ◽  
Author(s):  
J. Esmaeelpanah ◽  
A. Dalili ◽  
S. Chandra ◽  
J. Mostaghimi ◽  
H. C. Fan ◽  
...  
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Piecewise Linear ◽  
Three Dimensional ◽  
Surface Force ◽  
Line Length ◽  
High Viscosity ◽  
Droplet Shape ◽  
Viscous Liquids ◽  
Straight Lines

A combined numerical and experimental investigation of coalescence of droplets of highly viscous liquids dropped on a surface has been carried out. Droplets of 87 wt% glycerin-in-water solutions with viscosity 110 centistokes were deposited sequentially in straight lines onto a flat, solid steel plate and droplet impact photographed. Impacting droplets spread on the surface until liquid surface tension and viscosity overcame inertial forces and the droplets recoiled, eventually reaching equilibrium. Droplet center-to-center distance was varied and droplet line length was measured from photographs. As droplet spacing was increased there was less interaction between the droplets. A three dimensional parallel code has been developed to simulate fluid flow and free surface interaction by solving the continuity, momentum and volume-of-fluid (VOF) equations. The two-step projection method was employed to solve the governing equations for the whole domain including both liquid and air phases. The continuum-surface-force (CSF) scheme was applied to model surface tension and the piecewise-linear-interface-construction (PLIC) technique used to reconstruct the free surface. Computer generated images of impacting droplets modeled droplet shape evolution correctly and compared well with photographs taken during experiments. Accurate predictions were obtained for droplet line length during spreading and at equilibrium.

Numerical Calculation of Spray and Combustion with Heating Fuel in a Medium Speed Diesel Engine

2013 ◽  
Vol 316-317 ◽  
pp. 1162-1165
Author(s):  
Xiao Yi Lai ◽  
Cheng Cheng Zhang ◽  
Zhou Rong Zhang ◽  
Jian Zhi Li ◽  
Qian Wang
Keyword(s):  
Surface Tension ◽  
Diesel Engine ◽  
Combustion Process ◽  
High Viscosity ◽  
Calculation Model ◽  
Low Temperature Combustion ◽  
Fuel Temperature ◽  
Marine Diesel ◽  
Set Up ◽  
Cfd Method

The fuel usually has high viscosity and low quality for marine diesel engines. Especially for its shallow combustion chamber structures, the preparation of in-cylinder mixture gas is mainly rely on spray and atomization, which is vulnerable influenced by fuel viscosity and surface tension seriously. Based on the case, this paper introduced a CFD method to heat the diesel fuel to reduce fuel viscosity and surface tension, expecting to explore the in-cylinder combustion process and emissions generation, so that the atomization effect of fuel spray and combustion in diesel could be improved. The calculation model was set up according to the L23/30H diesel engine. Temperature field and pressure field in cylinder were calculated and the emission of NO were studied under conditions of different fuel temperatures. The results show that the increasing of fuel temperature is helpful to realize low-temperature combustion and reduce NO emission to some extent.

A photographic investigation into the disintegration of liquid sheets

1954 ◽  
Vol 247 (924) ◽  
pp. 101-130 ◽  
Keyword(s):  
Surface Tension ◽  
High Surface ◽  
Free Edge ◽  
High Viscosity ◽  
Liquid Sheet ◽  
Flow Rates ◽  
High Surface Tension ◽  
Liquid Sheets ◽  
Low Viscosity ◽  
Spinning Disk

The types of apparatus used to produce liquid sheets are classified according to the manner in which the energy is imparted to the liquid. The factors influencing the development, stability and manner of disintegration of a liquid sheet are examined more particularly with flat sheets produced from the single-hole fan-spray nozzle and the spinning disk. The development of the liquid sheet is influenced by the liquid properties. As the working pressure is raised the width of the sheet increases, but this development is hindered by high surface tension. It is shown that the effect of a surface-active agent on the development is only influential where the surface is not expanding or changing rapidly. Consequently its effect is more pronounced as the liquid moves farther away from the orifice. Increase of viscosity at the same pressure causes the region of disintegration to move away from the orifice, and high viscosity maintains the sheet undisturbed by air friction. Density has little effect on the area of the sheet. The effect of turbulence in the orifice is shown to be responsible for at least two types of disturbance in the sheet which results in holes being formed near the orifice. The depth of the disturbance in the sheet has to be equal to the thickness before disruption occurs. Similar disruption through the formation of holes can be caused by suspensions of unwettable particles. Wettable particles in low concentration, irrespective of their size, have no effect on the manner of disintegration. The most placid, stable and resistant sheet is obtained with a liquid of high surface tension, high viscosity, low density, giving low turbulence in the nozzle. Such a sheet will disintegrate when the velocity is raised and disintegration can occur through air friction. The easiest sheet to disintegrate is obtained with a liquid of low surface tension, low viscosity, low density and with low turbulence in the nozzle. Disintegration will occur near the nozzle at low velocities through waves caused by air friction. Disintegration through the formation of holes in the sheet can occur at low velocity with liquids of high surface-tension, low viscosity and high density where turbulence obtains in the nozzle. The formation of ligaments or threads is a necessary stage before the production of drops. Threads can be formed directly from any free edge or in the boundary. A free edge is formed when equilibrium exists between surface tension and inertia forces. In the spinning disk, at low flow rates, where the sheet is in contact with the surface of the disk, drops are formed at the ends of threads which break down into a limited number of sizes. At high flow rates a free edge of liquid exists outside the periphery of the disk with the formation of more irregular threads and a wider spectrum of drop sizes results. Where perforations occur in the sheet, expansion of the hole by surface tension occurs very regularly so that the holes remain nearly circular until they coalesce forming long threads. These long threads quickly become unstable and break down into drops. Threads being approximately uniform in diameter produce uniform drops, but the irregular areas of liquid which occur when a number of holes expand towards each other produce a wide variety of drop sizes. When the velocity of the sheet in the atmosphere is high, air friction causes slight variations in the sheet to develop rapidly into major wave disturbances, and these can result in holes being blown through the sheet so that disruption starts before the formation of a leading edge. With liquids having visco-elastic properties the sheet disintegrates through the formation of waves, but the rapid increase of viscosity, as the rate of shear is reduced, prevents further break-up of the threads into drops and a web of fine threads only is produced.

A stationary circular hydraulic jump, the limits of its existence and its gasdynamic analogue

2008 ◽  
Vol 601 ◽  
pp. 189-198 ◽  
Author(s):  
ASLAN R. KASIMOV
Keyword(s):  
Surface Tension ◽  
Hydraulic Jump ◽  
Stokes Equations ◽  
Critical Value ◽  
Water Model ◽  
Navier Stokes ◽  
Jump Conditions ◽  
Shallow Water Model ◽  
Finite Radius ◽  
Navier Stokes Equations

We propose a theory of a steady circular hydraulic jump based on the shallow-water model obtained from the depth-averaged Navier–Stokes equations. The flow structure both upstream and downstream of the jump is determined by considering the flow over a plate of finite radius. The radius of the jump is found using the far-field conditions together with the jump conditions that include the effects of surface tension. We show that a steady circular hydraulic jump does not exist if the surface tension is above a certain critical value. The solution of the problem provides a basis for the hydrodynamic stability analysis of the hydraulic jump. An analogy between the hydraulic jump and a detonation wave is pointed out.

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