Fluid-fluid interaction during miscible and immiscible displacement under ultrasonic waves

This paper aims at identifying and analyzing the influence of high-frequency, high-intensity ultrasonic radiation at the interface between immiscible (different types of oils and aqueous solutions) and miscible (different types of oil and solvent) fluids. An extensive set of Hele-Shaw type experiments were performed for several viscosity ratios, and interfacial tension. Fractal analysis techniques were applied to quantify the degree of fingering and branching. This provided a rough assessment of the degree of perturbation generated at the interface when the capillary forces along with the viscous forces are effective. Miscible Hele-Shaw experiments were also presented to isolate the effect of viscous forces. We found that ultrasound acts to stabilize the interfacial front, and that such effect is most pronounced at low viscosity ratios. An erratum to this article is available at .     

Mechanistic modeling of destratification in cryogenic storage tanks using ultrasonics

Stratification is one of the main causes for vaporization of cryogens and increase of tank pressure during cryogenic storage. This leads subsequent problems such as cavitation in cryo-pumps, reduced length of storage time. Hence, it is vital to prevent stratification to improve the cost efficiency of storage systems. If stratified layers exist inside the tank, they have to be removed by suitable methods without venting the vapor. Sonication is one such method capable of keeping fluid layers mixed. In the present work, a mechanistic model for ultrasonic destratification is proposed and validated with destratification experiments done in water. Then, the same model is used to predict the destratification characteristics of cryogenic liquids such as liquid nitrogen (LN₂), liquid hydrogen (LH₂) and liquid ammonia (LNH₃). The destratification parameters are analysed for different frequencies of ultrasound and storage pressures by considering continuous and pulsed modes of ultrasonic operation. From the results, it is determined that use of high frequency ultrasound (low-power/continuous; high-power/pulsing) or low frequency ultrasound (continuous operation with moderate power) can both be effective in removing stratification.     

Shear horizontal (SH) ultrasound wave propagation around smooth corners

Shear horizontal (SH) ultrasound guided waves are being used in an increasing number of non-destructive testing (NDT) applications. One advantage SH waves have over some wave types, is their ability to propagate around curved surfaces with little energy loss; to understand the geometries around which they could propagate, the wave reflection must be quantified. A 0.83 mm thick aluminium sheet was placed in a bending machine, and a shallow bend was introduced. Periodically-poled magnet (PPM) electromagnetic acoustic transducers (EMATs), for emission and reception of SH waves, were placed on the same side of the bend, so that reflected waves were received. Additional bending of the sheet demonstrated a clear relationship between bend angles and the reflected signal. Models suggest that the reflection is a linear superposition of the reflections from each bend segment, such that sharp turns lead to a larger peak-to-peak amplitude, in part due to increased phase coherence.     

In-depth analysis of ultrasonic-induced geological pore re-structures

Understanding and manipulating geological pore structures is of paramount importance for geo-energy productions and underground energy storages in porous media. Nevertheless, research emphases for long time have been focused on understanding the pore configurations, while few work conducted to modify and restructure the porous media. This study deploys ultrasonic treatments on typical geological in-situ core samples, with follow-up processes of high-pressure mercury injections and nitrogen adsorptions and interpretations from nuclear magnetic resonance and x-ray diffraction. The core permeability and porosity are found to increase by 8.3 mD, from 4.1 to 12.4 mD, and by 0.95%, from 14.03% to 14.98%, respectively. Meanwhile, the number and size of the micro- and mesopore are increased with progressing of ultrasonic treatment, while those of the macropore decrease, which finally increase the permeability and porosity. The increase of micro- and mesopore number, from x-ray diffraction results, is attributed to the migration and precipitation of clay minerals caused through ultrasonic wave. The relocation of clay minerals also helps to improve the pore-throat connectivity and modify the micro-scale heterogeneity. Basically, this study reveals the characterizations of geological pore reconfigurations post-ultrasonic treatments and interprets the associated mechanisms, which provides guidance to manipulate the geological pores and be of benefit for further porous media use in science and engineering.     

Mechanical spectrum and interstitial oxygen in YBaCuFeO5+δ

Double perovskite YBaCuFeO_5+δ samples were prepared by two different sintering procedures. The interstitial oxygen contents of two samples are different which were estimated from thermogravimetric analysis (TGA). The mechanical spectrum below room temperature was measured using the vibrating reed method at kilohertz frequencies. Two internal friction peaks can be discerned in two samples above 200 K whose intensities show a correlation with the interstitial oxygen concentration. The lower temperature peak is attributed to the freezing transition of the interstitial oxygen. Another internal friction peak observed around 150 K can be explained by the stress induced hopping of electrons in the Fe ion sites.     

横观各向同性材料中激光超声谱有限元数值模拟

研究了横观各向同性材料中激光超声波的传播特征．基于谱有限元方法,建立了横观各向同性材料中激光超声的数值模型．利用谱有限元方法模拟脉冲激光作用于材料上产生超声波及其传播的过程．讨论了横观各向同性薄板的各向异性及各向同性平面内超声波的传播特征,并分析了材料厚度的变化对产生超声波模态的影响．     

多分量超声波换能器及其应用

为提高超声无损检测的精度的可靠性，本文研究了几种多分量超声波换能器，即二分量换能器和三分量换能器，分析和探讨了它们在声发射检测以及超声法应力测试中的应用。     

Study of the structural properties of organic mixed solvents by ultrasonic methods

Ultrasonic absorptions and velocities in mixtures of acetic acid-chloroform and trifluoroacetic acid-chloroform have been measured at 25°C. The excess absorptions are interpreted in terms of the reaction kinetics associated with the breakage and formation of hydrogen bonds using a linear free-energy relation. Unusual ultrasonic relaxation properties have been attributed to the free-energy difference between the open dimer and cyclic dimer of the acid. The NMR chemical shifts have also been measured for the mixtures in order to ascertain the interaction between the acid and chloroform. The results are compared with those obtained from the ultrasonic absorption data.     

The changing anisotropy character of weathered low-density polyethylene films recognized by quasi-static and ultrasonic mechanical testing

Unstabilised polyethylene films used for greenhouse covering have been exposed outdoors under the severe weathering conditions in the Sahara.The chemical and the morphological changes followed by infrared spectroscopy and by differential scanning calorimetry (DSC) show that the damages caused by oxidation to the tie molecules increase crystallinity and lead to a severe deterioration of the mechanical properties.The mechanical aspect of aging was studied by using standard quasi-static (QS) tensile testing measurements and by a non-destructive method based on ultrasound (US). This latter technique consists of measuring velocities and attenuations of ultrasonic waves propagating in several directions in the film plane.Both methods show the changing anisotropic character of the films with aging. The transverse direction has been found to be the principal axis of anisotropy consequently to a little more significant chain orientation in this direction acquired during processing.The connection between the chemical aspect of aging and the mechanical one (i.e. the viscoelastic properties and the anisotropic character) is discussed.     

A Possible Explanation as to Why Ions in Aqueous Solutions Do Not Extract

Abstract

Evidence is obtained to show that the ion-dipole bond between an ion and the water molecule adducts surrounding it is stronger than the bond between the ion and the organic phase molecules. The water adducts cannot be displaced and the system remains hydrophilic and resists extraction.