Deformation Of Liquid Surface Research Articles

Liquid sloshing in a tank vehicle: A numerical and experimental investigation with baffle configurations

A three-dimensional numerical model based on VOF (Volume of Fluid) method is established to investigate anti-sloshing effects of various baffle configurations, proposed in this paper, on liquid sloshing in a partially filled tank vehicle. A series of experiments were conducted in a scaled clean-bore or baffled tank. The liquid surface deformations obtained from the numerical model exhibit good agreement with the experimental results at each moment, demonstrating the validity of the numerical model. The validated numerical model was further used to investigate the anti-sloshing effect of different baffle configurations in full-size tank vehicles. The results imply that the addition of baffles can decrease longitudinal force and pitch moment to some extent, in terms of peak value or mean value. Moreover, the addition of baffles may elevate the fundamental sloshing frequency by 50% to 200%, mitigating the risk of resonance phenomena in tank vehicles.

Effect of liquid surface depression size on discharge characteristics and chemical distribution in the plasma-liquid anode system

Abstract Atmospheric pressure plasma-liquid interactions exist in a variety of applications, including wastewater treatment, wound sterilization, and disinfection. In practice, the phenomenon of liquid surface depression will inevitably appear. The applied gas will cause a depression on the liquid surface, which will undoubtedly affect the plasma generation and further affect the application performance. However, the effect of liquid surface deformation on the plasma is still unclear. In this study, numerical models are developed to reveal the mechanism of liquid surface depressions affecting plasma discharge characteristics and the consequential distribution of plasma species, and further study the influence of liquid surface depressions of different sizes generated by different helium flow rates on the plasma. Results show that the liquid surface deformation changes the initial spatial electric field, resulting in the rearrangement of electrons on the liquid surface. The charges deposited on the liquid surface further increase the degree of distortion of the electric field. Moreover, the electric field and electron distribution affected by the liquid surface depression significantly influence the generation and distribution of active species, which determines the practical effectiveness of the relevant applications. This work explores the phenomenon of liquid surface depression, which has been neglected in previous related work, and contributes to further understanding of plasma-liquid interactions, providing better theoretical guidance for related applications and technologies.

A comprehensive investigation on liquid sloshing of rectangular water tank with vertical baffles

Although numerical method is used to analyze the liquid sloshing-induced wave height and control force, it is worth noting that the effects of vertical baffle on liquid sloshing of rectangular water tanks have not been thoroughly explored. Further research in this domain would be invaluable for gaining a more profound understanding of liquid sloshing in such tanks. Therefore, the CFD method and finite volume model are employed in this paper, and the effects of vertical baffle on the liquid sloshing behaviors are comprehensively investigated, including wave height of free surface, horizontal control force, damping ratio of liquid sloshing, natural frequency, and free surface deformation. Then, the influences of excitation amplitude, water depth, number of baffles, baffle position, and baffle height are extensively explored. The accuracy of the modeling is confirmed through rigorous comparisons with existing experimental results. The number of baffles has a considerable influence on the behaviors of liquid sloshing. The effectiveness of the baffle in reducing liquid sloshing is closely tied to its position. Exceeding the baffle height beyond the water depth causes a transformation of the working mechanism and inherent properties of the rectangular water tank. The natural frequency is generally overestimated by linear potential flow theory.

A comparison study of the behaviors of single-phase turbulent flow at low to moderate Reynolds numbers through a vertical pipe: 3D counters analysis

The study presented three-dimensional (3D) analysis of water's upward flowing through the vertical pipe under turbulent characteristic considerations. Both numerical constructed and improved the model of 3D for cylindrical coordinates of governing equations for incompressible turbulent flow with the Reynolds Average Navier-Stokes (RANS) model using the improved constants of the (k–ε) type. The present model is then compared with a previous study to give the feasibility of the present single-phase turbulent flow parameters. The pipe length is tested to measure how much it affected the turbulent parameters though one of the expected factors is the turbulent time scale. On the other hand, the model is numerically examined to determine the velocity profile, shear rate, and surface deformation of the water domain. While the pressure distribution, turbulent kinetic energy, and turbulent dissipation rate, these parameters are classified as the mechanic's system factors. The simulation is done with wide software used to simulate industrial is COMSOL 5.4 Multiphysics software. The results obtained increased the velocity of three inlet water velocities used ranging from (0.087, 0.105, and 0.123 m/sec) of upward flow. High fluctuation in the water flow moves along the entire pipe length and it can notice the sensitivity to any change in water properties or mechanical properties. The liquid upward flow in turbulent conditions is suffered from many characteristics such them related to liquid properties and others related to the mechanics of the application through the systems. The interaction between the fluid film (fluid boarded the pipe inner diameter) has been observed by the shear rate and liquid surface deformation

Surface instability of static liquid metal in magnetized fusion plasma

Understanding surface instability in magnetized fusion plasma supports the appropriate implementation and handling of liquid metal as plasma facing components (PFCs) in future fusion reactors. A Lagrange equation describing a viscous liquid surface deformation in a magnetized plasma is derived using Rayleigh’s method. Its solution justifies the general instability criterion and helps in characterizing the key interactions driving such instability under fusion conditions. Surface tension and gravity, especially with the poloidal angles of the lower part of a plasma chamber, mainly stabilize the liquid surface at small and large disturbance wavelengths, respectively. The sheath electric field and the external tangential magnetic field cause the liquid surface to disintegrate at an intermediate wavelength. Practically, a magnetic confinement fusion (MCF) device requires a strong magnetic field for confinement. The study suggests that such a strong field dominates the rest and governs instability. In addition, this implies that the configuration of a static planar free liquid surface is difficult to adopt as a candidate for handling the liquid metal as PFCs in next step MCF devices.

Analysis of liquid surface deformation and breakups using three-dimensional high-speed data recorded with a single camera

Analyzing the deformation of liquid surfaces to better understand, for example, wave generation in oceanology or the formation of industrial spray systems, requires a series of three-dimensional snapshots that temporally resolve such events. This requirement is challenging, especially when applied to transient liquid surfaces that deform rapidly. A technique called Fringe Projection-Laser Induced Fluorescence (FP-LIF), developed by the authors, generates three-dimensional surface reconstructions of irregular liquid structures using snapshots recorded via a single camera only. In this article, FP-LIF is associated, for the first time, with a high-speed detection system, allowing the three-dimensional visualization of liquid surface deformation and breakups at a kHz frame rate. The technique is applied here at 20 kHz for imaging the complete development of a wide hollow-cone water spray and analyzing, in detail, the transition from early injection to stabilization. The three-dimensional image series covered a total time window of 300 ms (6000 frames). It is observed during the first 100 ms that the initial liquid jet deforms into a stable tulip shaped sheet. Then, between 100 and 180 ms, the tulip shape gradually grows until its stabilization corresponds to the final conical shaped sheet. Once the stabilization is reached, the fluctuation of the final spray-angle—ranging from 40° to 50°—is extracted by post-processing 1000 consecutive three-dimensional images, providing a detailed analysis of the radial symmetry of the spray over time and three-dimensional space. The results provided in this article are relevant for the validation of Computational Fluid Dynamics spray models.

Laser light-induced deformation of free surface of oil due to thermocapillary Marangoni phenomenon: Experiment and computational fluid dynamics simulations

Remote light-induced free liquid surface deformation has been studied in various systems for decades. One of the mechanisms able to do this task is driven by the thermocapillary Marangoni effect. The strength of the light–matter interaction, which is usually weak, here is amplified by the light absorption and heat production that changes surface tension. Here, we report on an experimental study aimed at dynamical aspects of the deformation induced under conditions of chopped laser excitation light. The light-induced deformations are usually in the range of several micrometers. Therefore, we applied the interferometric technique to measure deformation profiles in real time. Experiments were performed in the shallow bath of the rapeseed oil with an azo-dye and excited with 514.5 nm and probed with 650 nm coherent laser beams, respectively. The mechanism of deformation driven by Marangoni effect was carefully modeled in 3D by computational fluid dynamic numerical simulations within the COMSOL Multiphysics package. The adaptive mesh technique used in the simulation together with solving the time-dependent coupled Navier–Stokes and heat transport differential equations allowed us to replicate the experimental findings. A satisfactory agreement between the results of the simulations and those of the experiment in terms of the dynamics, shape, and depth of the deformation has been obtained. The toroidal-like whirls accompanying the thermocapillary Marangoni effect were identified by the simulation results. We then experimentally proved that these toroidal-like vortices, which accompany laser heating in dyed oil, formed a kind of novel hydrodynamic trap, in the center of their quiet zone, in which microcrystals can be trapped.

A versatile interferometric technique for probing the thermophysical properties of complex fluids

Laser-induced thermocapillary deformation of liquid surfaces has emerged as a promising tool to precisely characterize the thermophysical properties of pure fluids. However, challenges arise for nanofluid (NF) and soft bio-fluid systems where the direct interaction of the laser generates an intriguing interplay between heating, momentum, and scattering forces which can even damage soft biofluids. Here, we report a versatile, pump-probe-based, rapid, and non-contact interferometric technique that resolves interface dynamics of complex fluids with the precision of ~1 nm in thick-film and 150 pm in thin-film regimes below the thermal limit without the use of lock-in or modulated beams. We characterize the thermophysical properties of complex NF in three exclusively different types of configurations. First, when the NF is heated from the bottom through an opaque substrate, we demonstrate that our methodology permits the measurement of thermophysical properties (viscosity, surface tension, and diffusivity) of complex NF and biofluids. Second, in a top illumination configuration, we show a precise characterization of NF by quantitively isolating the competing forces, taking advantage of the different time scales of these forces. Third, we show the measurement of NF confined in a metal cavity, in which the transient thermoelastic deformation of the metal surface provides the properties of the NF as well as thermo-mechanical properties of the metal. Our results reveal how the dissipative nature of the heatwave allows us to investigate thick-film dynamics in the thin-film regime, thereby suggesting a general approach for precision measurements of complex NFs, biofluids, and optofluidic devices.

Dynamics of liquid film rupture under local heating

Rupture dynamics of a horizontal liquid film non-uniformly heated from below was experimentally studied in a wide range of liquid viscosity. To visualize the liquid surface deformations and disruption of the film, an optical schlieren system was used. The instantaneous local film thickness was measured using a chromatic confocal sensor. In order to measure the thickness of thin liquid films, the substrate was covered with a black coating eliminating reflection of the incident light. Angular and frequency characteristics of the confocal sensor were studied in detail. The process of film rupture can be divided into three stages: 1) film thinning down to a residual film on the heater; 2) existence of a stable residual film for some time; 3) rupture and dry out of the residual film. The thickness of the residual film was found to strongly depend on the liquid viscosity: for water it is about 10 µm, whereas for silicone oil PMS-200 it is about 275 µm. The data obtained for various working liquids were generalized by a dimensionless correlation.

Use of the reflective background oriented schlieren technique to measure free surface deformations in a thin liquid layer non-uniformly heated from below

To measure liquid film surface deformations, we use the Background Oriented Schlieren (BOS) technique with a reflective optical scheme, which includes a random dot pattern located above the liquid surface, and a camera that captures its reflection from the liquid interface. The substrate was covered with a special black coating to minimize stray light reflection, which allowed to provide clear visualization of the dot pattern reflected from the free surface even for very thin liquid films. Local slopes of the film surface cause the dot displacement on the pattern image relative to the pattern image captured in the absence of any free-surface deformations. Hence, the topography of the liquid film surface is encoded by the apparent displacement of the dot pattern. Using the cross correlation image processing, the displacement vector field was determined, which was then substituted in Poisson equation to reconstruct the free-surface profile of the liquid film. The main advantages of this technique are: applicability for liquids with surface temperature inhomogeneities, experimental simplicity, sensitivity and applicability for both transparent and opaque liquids. Using the reflective BOS technique and using substrate with black coating we measure the free-surface deformation field of a thin layer of silicone oil non-uniformly heated from below. Despite the fact that thermocapillary shear stresses tend to decrease the thickness of the liquid layer in hotter regions, in the experiment, a convex deformation of the liquid film surface was observed above the heater for a few seconds immediately after the start of heating. This phenomenon is explained by the expansion of the liquid induced by the heating, due to the dependence of the liquid density on temperature. The measurement results are compared with those obtained in a single point using the confocal sensor. A good agreement is achieved.

Bubble dynamics and deformation of free liquid surface in aerated liquid storage tanks

OpenFOAM was utilized for analyzing bubble behavior and deformation of free liquid surface due to bubble formation and bursting in a rectangular container. Influence of three system parameters, orifice diameter, number of orifices and spacing between orifices, on various bubble dynamics and deformation of gas-liquid interface is presented. The study also incorporates information on bubble formation, bubbling frequency, and orientation of bubbles. Considering different orifice spacing, bubbling synchronicity is also reported. Details regarding interaction of wakes during bubble coalescence for single, double and triple inlet orifices are presented. The deformation of free liquid surface due to bubble formation and bursting is quantified using a new parameter called deformation index (D L * ). The analyses indicate that the frequency of bubble detachment is augmented with increase in orifice diameter and number of orifices. However, bubble detachment frequency is reduced when orifice spacing increased. Orientation of detached bubbles keeps on changing for larger orifice spacing. Results show that variations of these geometric parameters have substantial influence on free liquid surface deformation due to bubble bursting and other bubble behavior. Using results of these studies, one can develop a bubble-generating device for optimal performance.

An entropic Young’s equation approach for magneto-wetting modeling

Although Young’s equation is widely applied in surface science and engineering, its application in magneto-wetting has not been reported. The nuclear spin processes that dominate liquid surface deformation in magnetic fields remain unclear. Here, we derived an entropic Young’s equation where the entropy of a sessile droplet is a function of its cosine contact angle. Subsequently, an equation to calculate changes of contact angle activated by magnetic fields was established using Maxwell’s relationship. We (1) further model the Moses and Inverse Moses magneto-wetting processes, (2) reproduce experimental liquid contact-angles in the range of 0 to 8 T with one or maximum two Moses parameters, and (3) replicate the phenomena of water-cluster fragmentation and hydrogen-bond creation reported by molecular dynamic simulation from 0 to 10 T. These results enable a quantitative study of the magneto-wetting process while offering exciting possibilities in electromagnetic-device development, ferrofluids navigation, and invention of portable MRIs.

Inhibiting bulging deformation of liquid metal free surface by magnetic pressure

A new method was presented to inhibit bulging deformation and fluctuation of free surface by magnetic pressure. A research combined with numerical and experimental methods was conducted to investigate the feasibility and inhibition efficiency. The parameters including magnetic flux density, frequency and action area of magnetic pressure were analyzed. The results show that the method is feasible, and the bulged free surface is fully inhibited by the proper magnetic pressure. The inhibition efficiency increases as the increase in magnetic flux density and frequency, which shows a linear relationship with the magnetic flux density. The frequency has a great influence on the inhibition efficiency when the frequency is changed from 0.15 to 5.00 kHz. However, the frequency more than 5.00 kHz has little influence on the inhibition efficiency and is recommended in application process. When the ratio of the action area to the area of bulged free surface is 0.8, the best inhibition is achieved. However, when the ratio is more than 1.2, a distinct W-shaped free surface is observed. The surficial and internal flow is strengthened with proper magnetic pressure imposed. Moreover, under the action of magnetic pressure, the fluctuation amplitude of free surface decreases from 4.0 to 1.2 mm and the main fluctuation with frequency of 2.34 Hz is dispersed into several minor fluctuations with frequency of 0.4–4.3 Hz.

Multi-scale dynamics of atmospheric-pressure discharges ignited over liquid electrodes

A multiphase computational model of atmospheric-pressure gas discharges ignited over liquid electrodes is developed. The model takes into account both the liquid electrode motion under applied electric fields and plasma generation in the gas phase. The influence of the applied voltage and liquid properties (density, viscosity, and surface tension) on the liquid surface deformation is analyzed. It is shown that the shape of dynamic cones formed on the liquid surface differs from the static Taylor's cones. The influence of the liquid surface protrusions on gas breakdown dynamics is demonstrated. It is shown that the breakdown develops in two stages: first, a fast ionization wave propagates from the cathode to the anode, and then the cathode sheath collapses due to secondary electron emission from the liquid surface. It is shown that dynamics of the multiphase system containing gas, plasma, and liquid states is characterized by three disparate time scales: the fast electron time scale, the intermediate ion time scale, and the slow liquid dynamics time scale.

The effect of viscosity on rupture dynamics in the non-uniformly heated horizontal liquid film

In the present work, we study the rupture dynamics of a horizontal liquid film non-uniformly heated from below in a wide range of liquid viscosity. To visualize the liquid surface deformations and disruption of the film, we use a Nikon digital camera (shot at 60 fps) coupled with an optical schlieren system. In order to measure the instantaneous film thickness, we use the confocal Micro-Epsilon chromatic sensor. It was found that the process of film rupture can be divided into three stages: 1) film thinning down to a residual film on the heater; 2) existence of a stable residual film for some time; 3) rupture and dryout of the residual film. The thickness of the residual film was found to strongly depend on the liquid viscosity: for water, it is about 10 µm, whereas for PMS-200 it is about 275 µm.

Application of free surface synthetic schlieren method in determining surface tension from a light floating object

Free surface synthetic schlieren (FS-SS) is a liquid surface topography visualization technique relying on apparent dot pattern displacement due to liquid surface deformation. It has gained attention in the fluid visualization field due to its relatively simple and inexpensive setup. One of the most powerful features of the FS-SS technique is the 3D topography of deformed liquid surface, in which submillimeter scale changes can be readily observed in great detail. The visualization of liquid meniscus at the solid interface is proposed in this study to calculate surface tension by equating the surface tension force with weight of light, floating object with circular geometry. It was found that surface tensions of liquids are much greater than anticipated, suggesting that the effect of buoyant force of displaced liquid due to deformed interface cannot be neglected. When the buoyant force is included, the calculated surface tension of liquids are within 10% of the reference values.

Numerical simulation study on flow field distribution and load characteristics of trans-media aerial underwater vehicle during its water-exit process

The oblique water-exit process of a trans-media aerial underwater vehicle is a highly non-linear, unsteady and dramatic process of flow field change. Based on the underwater configuration of a variable trans-media aerial underwater vehicle, the water-exit process of this configuration under typical operating conditions was simulated by CFD fluid simulation software, and the flow field characteristics and load distribution of the vehicle at different stages of the water-exit process were analyzed. The simulation results show that when the vehicle crosses the water-air interface obliquely, the phenomenon of liquid surface deformation and uplift, liquid surface attachment wrapping up the water-exit and wake dragging fracture will occur sequentially, which will lead to sudden change and continuous drastic change of the flow field around the vehicle, forming a backflow zone with different radius and direction on both sides. High-frequency positive and negative alternative oscillation of the body load of the vehicle wrapped by water produces pitching moment.

High sensitivity liquid surface deformation sensor based on cascaded Bowknot Type Tapers

ABSTRACTA liquid surface deformation sensor with high sensitivity based on a Mach–Zehnder interferometer (MZI) was demonstrated. The MZI was constructed by cascading two Bowknot Type Tapers (BTTs) with an interval of 1.0 cm. As the liquid surface changes gradually from the position higher than the optical fibre to a position lower than the optical fibre, the external environment of the optical fibre changes gradually from the liquid to air, this will result in a change of the interference of the MZI. By measuring the intensity variations of the resonant wavelength, the liquid surface deformation in the range from 0 to 5.22 mm can be determined with a high sensitivity of 0.99 dB/mm.

Nonlinear analysis of magnetic liquid free surface deformation in a 3D space

Abstract The nonlinear analysis of magnetic liquid free surface deformation under the influence of a static vertically oriented magnetic field produced by a pair of Helmholtz coils in a 3D space is presented in the article. The hexagonal pattern of peaks resulting from the Rosensweig or normal instability, occurs when the magnetization of the magnetic liquid exceeds the critical value. To predict the amplitudes and distance between peaks in the pattern, nonlinear analysis should be performed with employed higher order terms in the mean curvature expression of the free surface. The computational strategy presented in the article is divided into two stages. At the first stage, the magnetic field in the 3D space is calculated by the FEM based software Opera Field, while the second stage is devoted to determining the surface profile by minimizing the energy functional using a Differential Evolution algorithm in Matlab. The amplitudes of the central spike and wave number have been computed for the various values of the excitation magnetic field.

3P4-8 Liquid Surface Deformation Caused by Acoustic Radiation Force of Focused Ultrasound

3P4-8 Liquid Surface Deformation Caused by Acoustic Radiation Force of Focused Ultrasound