Fluctuations Of Liquid Surface Research Articles

Multiscale dynamic distribution characteristics of dust collectors in wet scrubber based on image fields

ABSTRACT In order to reveal multiscale dynamic distribution characteristics of dust collectors in a wet scrubber, a method for scale decomposition of dust collectors based on Wigner–Ville distribution (WVD), empirical mode decomposition (EMD) and Hurst analysis of grayscale signals is reported. The WVD features of grayscale signals were used to observe the energy distribution details of dust collectors at different frequency bands and time periods. Then, the scale decomposition of dust collectors based on EMD and Hurst analysis of the grayscale signals was carried out. These analysis results showed that the motion behaviors of micro-, meso- and macro-scale subsets of dust collectors were determined: specifically, the single fractal features of micro-scale subsets conform to the motion characteristics of individual dust collectors. The dual fractal characteristics of meso-scale subsets denote the interactions among dust collector aggregations. Additionally, the fractal features of the macro-scale subsets reflect persistent liquid surface fluctuation behavior in wet scrubbers. Finally, the relative contribution of dust collectors at different scales to the effectiveness of dust removal was represented. This is not only an important innovation in the study of micro mechanism of wet dust removal but provides powerful theoretical support for technological innovations in wet scrubbers. Implications: The multiscale dynamic distribution characteristics of dust collectors in wet dust scrubber were explored, using a method for scale decomposition of dust collectors based on Wigner–Ville distribution, empirical mode decomposition and Hurst analysis of grayscale signals. The fractal characteristics of different scales of dust collectors are determined. Besides, the contribution of different scales of dust collectors to the effect of dust removal is quantized. Therefore, this research is very meaningful, which not only has important innovation in the study of micro mechanism of wet dust collectors but provides a powerful theoretical support for technological innovation of wet dust scrubbers.

Sloshing in liquid tank with the density function method

The Great East Japan Earthquake of March 2011 was the huge earthquake with a magnitude of 9.0 exceeding the imagination, ranging from the offshore to Iwate Prefecture to the offshore of Ibaraki Prefecture became the focal region. It is easy to imagine that damage increases to long-period earthquake ground motion as the magnitude increases. Damage to dangerous facilities due to long-period earthquake ground motion is caused by liquid surface fluctuation (sloshing) of oil, LNG and liquid storage tanks. In this paper, the interface capturing method deals with complex water surface large deformation problems. We use the density function method which is one of the effective methods of interface capturing method for numerical analysis of two phase fluid fields of gas and liquid. As a result, the proposed method shows a good agreement with the experimental result of the Martin and Moyce dam break problem, and this method improved the suppression of effortless motion. Also, under the calculation condition of the sloshing phenomenon, this method does not generate numerical diffusion. Therefore, this model is more robust than the conventional model.

Water wave energy harvesting and self-powered liquid-surface fluctuation sensing based on bionic-jellyfish triboelectric nanogenerator

Due to the natural working mechanism of triboelectric nanogenerators (TENGs), potential energy stored by elastic materials may not be effectively converted into electric power, post mechanical triggering. Here, we report a practical bionic-jellyfish triboelectric nanogenerator (bjTENG) with polymeric thin film as the triboelectric material, which is shape-adaptive, with a hermetic package and a unique elastic resilience structure, similar to the behavior of a jellyfish. The charge separation in the elastic resilience of this bionic-structure is based on the liquid pressure-induced contact-separation of the triboelectric layers. On the basis of the conjunction of the triboelectrification and the electrostatic induction, a sustainable and enhanced output performance of 143 V, 11.8 mA/m2 and 22.1 μC/m2 under a low frequency of 0.75 Hz and at a water depth of 60 cm is produced, which can be used to supply power for dozens of green LEDs or a temperature sensor directly. More significantly, bjTENG is believed to be a priority technology which is attributable to its highly sensitivity, portability, and suitability for continuous detection of water level and fluctuation. Furthermore, a wireless self-powered fluctuation sensor early-warning system, which provides exact and wireless monitoring of fluctuation of a liquid surface, is also successfully developed.

Measurements of liquid surface fluctuations using a self-mixing solid-state laser

We propose a highly sensitive method for measurements of liquid surface fluctuations with nanometer-order displacement using a self-mixing laser Doppler velocimeter (LDV) comprising a laser-diode-pumped thin-slice solid-state laser and a simple photodiode. In this measurement system, the scattered light from the liquid surface is reinjected into the solid-state laser, and then the laser output from the solid-state laser is modulated by this reinjected laser light. The time dependence of the displacement of liquid surface fluctuations can be obtained from the analysis of the modulated laser output. We describe various measuring methods and the optical system of the self-mixing LDV for real-time measurements of liquid surface fluctuations. Real-time measurement of liquid surface fluctuations can be performed with high amplitude and frequency resolutions by the analysis of the modulated laser output.

Effect of dispersion forces on the capillary-wave fluctuations of liquid surfaces.

We present molecular dynamics evidence for the nonanalytic effects of the long-range dispersion forces on the capillary waves fluctuations of a Lennard-Jones liquid surface. The results of the intrinsic sampling method, for the analysis of the instantaneous interfacial shape, are obtained in large systems for several cut-off distances of the potential tail, and they show good agreement with the theoretical prediction by Napiórkowski and Dietrich, based on a density functional analysis. The enhancement of the capillary waves is quantified to be within 1% for a simple liquid near its triple point.

Measurements of liquid surface fluctuations at sub-shot-noise levels with Michelson interferometry

Surface fluctuation spectra of liquids are measured to unprecedented precision, down to 3 orders of magnitude below the shot-noise level using averaged correlations of interferometry measurements. This allows us to investigate the limits in our current theoretical understanding of these phenomena. The spectrum derived from hydrodynamical considerations agrees well with the observed results for water. However, for oil, deviations are seen at high frequencies (>/~1 MHz), perhaps indicating its more complex underlying physics. The measurements are made possible by dualizing the Michelson interferometry measurements and employing the averaged correlation of signals, in which the shot noise is statistically reduced. The method works in the presence of the quantum noise of a coherent state of light. The optical part of the experimental setup is essentially the same as that of Michelson interferometry so that the method can be applied when Michelson interferometry can be used. Furthermore, the measurement method requires a relatively low light power and a short time so that it has a wide range of applicability.

Numerical simulation of droplet impacting liquid surface by SPH

Droplet impacting liquid surface is not only the extremely prevalent phenomenon in the nature and industrial production but also the extremely complicated problem of strong non-linear transient impact and free-surface flow. On the basis of the two-dimensional viscous incompressible N-S equations, this paper conducts a study of numerical simulation on the problem of droplet impacting liquid surface (water beads) of water container in certain initial velocity by the method of SPH (smoothed particle hydrodynamics). The effect of surface tension is considered between surface particles by searching the free surface particles in the course of study; the effect of initial impact has been solved by use of artificial viscosity; at the same time, the side-wall virtual particles and image virtual particles are both introduced to deal with the boundary condition, which has solved the boundary defects quite well and eliminated the instability of real particles dropped to the corner of container. The calculated results form the distribution chart of particles, flow field chart, pressure chart and the displacement and velocity variation curve of different particles. The comparison between simulated results and experimental photos shows that the simulation is effective. This paper compares the variational curves for fluctuations of liquid surface qualitatively through adopting the methods of level-set, BEM and SPH, respectively at last. The simulated results show that it will produce strong non-linear phenomena, such as the splash of liquid, discrete liquid surface, and strong wave of free liquid surface, when the droplet impacts liquid surface; in the course of impacting, the movement of liquid particles exhibits the characteristic of oscillation; the method of SPH has certain advantages of dealing with the large deformation problem of free surface.

CFD simulation of free liquid surface motion in a pilot plant stirred tank

AbstractThe Volume of Fluid method together with the Large Eddy Simulation technique for turbulence flow was used for CFD prediction of liquid flow and free liquid surface motion in a pilot plant cylindrical flat‐bottomed stirred tank with an inner diameter of 1 m filled with tap water at room temperature. A pitched‐blade (45°) down pumping impeller (diameter of 0.33 m) with six blades was used for stirring. The impeller speed was 180 rpm. For simulation of the impeller motion, the sliding mesh method was adopted. The CFD simulations of the flow field predicted a highly complex, multi‐dimensional dynamic system exhibiting unstable, pseudo‐stationary behaviour. The main advantage of this CFD simulation is the prediction of the velocity flow patterns and the free surface elevation/depression in the whole system at one time. The results for the location and dimensions of the free liquid surface fluctuation correspond well with an experimental investigation by a conductivity method.

High frequency capillary waves: A light scattering spectrometer

Modifications to a light scattering apparatus to permit study of liquid surface fluctuations of significantly higher wave number than hitherto are described. Various problems associated with the modified system are discussed. Typical results are presented for capillary wave propagation on the surface of two different fluids, demonstrating the satisfactory functioning of the spectrometer despite these problems.

Thermal fluctuations of thin wetting films on disordered solids

We consider thin liquid layers which completely wet nonideal (either rough or heterogeneous in composition) solid surfaces. Two different sources of fluctuations of the liquid surface are identified, and the competition between them is investigated. For thick enough films (but still in the submicrometer range), the liquid surface fluctuations are dominated by thermally induced capillary waves. For thin films, capillary waves are strongly damped and the liquid surface fluctuations are correlated with the disorder of the underlying solid surface. The fluctuation spectrum is explicitly calculated for a van der Waals liquid and for several different types of solid disorder. Our findings are in agreement with recent X-ray specular reflection and diffuse scattering experiments. 25 refs., 3 figs.

Surface fluctuation spectroscopy: some further considerations

Instrumental effects which have previously been shown to cause systematic errors in laser light scattering studies of liquid surface fluctuations are reexamined. The resulting conclusions about experimental design, while different from those previously published, are entirely compatible with established experimental data. The theory of these instrumental effects is extended to include variation of scattered intensity with surface wave vector. This extension is shown to alter the systematic errors causing them to be much less than previously quoted for the recommended optical system.