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"Cavitation"
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A novel single-element transducer with curved surface for cavitation detection
Abstract
Acoustic cavitation is increasingly used to apply in industrial and clinical areas. However, with the development of these fields, the precision of devices used to monitor cavitation activity gradually cannot meet the needs of the higher accuracy requirements of practical application. In this paper, we propose several design schemes of a novel passive cavitation detector (PCD) which is hoped to have better measuring performance than traditional plane PCD because of its focusing effect. By conducting FEM simulations, the optimal design plan and the surface curvature of PCD were chosen. It is shown that the measuring ability of the final selected PCD is near 1.7 times of traditional plane PCD.
Journal Article
Synthesis-Analysis of the Use of Cavitation Technologies
An analysis of literature sources in the field of the use of cavitation technologies has shown that the effects of cavitation are used in a wide range of industrial technologies. This paper presents the main results of work on the cavitation treatment of various liquid compositions, multicomponent media in recent decades. The presented review allows us to conclude that the use of cavitation technologies in various fields of engineering and technology is relevant for solving important practical problems and, as a result, the need for their comprehensive study.
Journal Article
Unifying the Modelling of In-Nozzle Flow and Subsequent Spray Formation at High Pressure Injection Systems
The modelling of internal and external flow phenomena of high pressure injection systems has developed significantly in the last few decades. The challenge currently however, is to model these areas of flow together accounting for different multi-phase phenomena that require a wide range of resolutions. More specifically, the highly turbulent nature of internal nozzle cavitation requires a high grid and temporal resolution, whereas the external nozzle atomisation processes exists over a comparatively much larger space with lower time and space resolution needed. The research described in this thesis is focused on coupling the internal nozzle and external processes using a single Eulerian Volume Of Fluid (VOF) multiphase model. First, investigations into the dynamics of internal nozzle cavitation is presented, through simulation of two phase nozzle flows without spray formation demonstrating sensitivities to discretization techniques and boundary conditions. Then, the simulation of internal nozzle cavitation with spray formation using a single model was achieved by the construction of a three phase VOF model with cavitation which is described. A non-condensable gaseous phase is considered alongside the liquid and vapours phases, the liquid interface is sharp with a diffusive interface between gaseous phases. Comparisons were made with both experimental data and previous numerical investigations. Finally, a new solver with the introduction of the Eulerian-Lagrangian Spray Atomization (ELSA) framework with the Interface Capturing Method (ICM) for surface density to the system to describe the liquid structures below the Sub-Grid Scale (SGS) is presented. Thus quantities such as droplet Sauter Mean Diameter (SMD) and droplet spray angle at these scales can be extracted, with comparisons made with experimental data. The coupling of the ELSA-ICM model with the three phase cavitating model allows for processes of the entire spray formation to be resolved. More specifically, for the first time, the evolving surfaces of the entire injection process, from internal nozzle cavitation to spray atomisation, can thus be tracked throughout even at the SGS. This allows for a direct insight into the interaction between the cavitation and atomisation processes.
Dissertation
Cavitation formation and modelling for fluid film bearings: A review
Abstract
Even though the list of references associated with this review is rather extensive, in no way does it exhaust the vast literature dedicated to the study of cavitation. The intent was to summarize (i) advances in analytical and numerical modelling, (ii) draw attention to the thermodynamic aspects of cavitation, and (iii) do so while reflecting on physical or experimental observations.
Journal Article
Experimental and numerical investigation of the propeller thrust reduction in bollard pull condition
Abstract The polar ships are often in bollard pull condition, which is prone to induce propeller cavitation and cause thrust reduction, weakening the ship’s ice-breaking ability. Based on the model tests and numerical simulations, this paper aims to investigate the propeller thrust reduction in the bollard pull condition. Firstly, the test of a self-designed ice class propeller under different cavitation numbers is carried out. The thrust reduction phenomenon is successfully captured and the hydrodynamic characteristics are obtained. Subsequently, the simulation based on Star-CCM+ is performed. It is found that the propeller thrust decreases almost linearly after the cavitation number reaches a certain threshold. When the cavitation number is equal to 0.25, the thrust decreases to 38.1% of that in the open water condition. By analyzing the mechanism of thrust reduction, the main reason is recognized that the average pressure of the blade face decreases greatly due to the influence of the cavitation on the blade back.
Journal Article
Influence of inlet pressure on cavitation characteristics in regulating valve
The cavitation development process in regulating valve under different inlet pressures is investigated experimentally and numerically in our paper. The influence of inlet pressure P
in
on cavitation location, shape, area and intensity is studied in axial and radial directions, and the axial and radial pressure distributions are also analyzed. The cavitation is generally annular in shape radially and irregular polygon in shape axially. Cavitation bubbles occur at the throat entrance when the inlet pressure increases. The bubbles then accumulate, and a bubble ring is formed. The cavitation development process under different inlet pressures is separated into three stages, no-cavitation, initial cavitation and steady-cavitation stages. During the no-cavitation stage, no bubbles exist. During the initial cavitation stage, bubbles occur and the area and intensity of cavitation increase in the radial and axial directions with increasing inlet pressure. During the steady-cavitation stage, the calculation area and intensity of bubble rings reach their maximum values and then remain stable. The cavitation bubbles extend downstream, and the area of cavitation ring and cavitation intensity increase with increasing inlet pressure. A slit exists between the upper and lower parts of bubbles in the cavitation process, both parts touch each other forming a whole.
Journal Article
36063 When the thoracic MRI explains the upper extremity symptoms
Please confirm that an ethics committee approval has been applied for or granted: Not relevant (see information at the bottom of this page)Application for ESRA Abstract Prizes: I don’t wish to apply for the ESRA PrizesSyringomyelia is characterized by the presence of spinal cord cavitation. It has multiple causes and is most commonly seen in association with Chiari I malformation. In these patients, the distribution of symptoms sometimes correlates with the anatomical location of the spinal cavitation. Dysesthesia is found in slightly less than half of the patients and it responds unpredictably and often poorly to currently available treatments. We present a case in which the dysesthesia could have been attributed to cervical syringomyelia, but the cause of this spinal finding remained elusive.Methods36-year-old female with history of Meniere’s disease and carpal tunnel syndrome presenting with numbness and tingling in her right arm and bilateral lower extremities for 1 year. She also reports having pain in her right arm, but not her legs. An MRI of the cervical spine showed central and right paracentral cervical spinal cord edema with small caliber syrinx from the levels of upper C3 through C6/7, moderate sized syrinx with the right hemi cord at C7 and partially visualized large multiseptated syrinx within the upper thoracic spinal cord from T1-T4. Her brain MRI ruled out Chiari’s malformation. A thoracic MRI found continuation of the syrinx and a mass at the level of T9. The patient underwent resection of the mass.Abstract #36063 Figure 1Tumor[Figure omitted. See PDF]Abstract #36063 Figure 2Cervical spine MRI[Figure omitted. See PDF]Abstract #36063 Figure 3Thoracic spine MRI[Figure omitted. See PDF]ConclusionsSpinal cord ependymoma is a rare tumor and surgical resection has been established as first-line treatment and can be curative. This case illustrates that a complete spinal MRI is advisable when symptoms partially match the anatomic location but not the cause.Attachmenttumor.jpg
Journal Article
Limited genetic variability and phenotypic plasticity detected for cavitation resistance in a Mediterranean pine
Resistance to cavitation is a major determinant of plant survival under severe drought and can be used to quantify species adaptive potential. Interspecific variation in this key trait is well defined in woody species, but intraspecific variation (level and structure) resulting from standing genetic variation and phenotypic plasticity has never been determined.
Combining for the first time in situ characterization of natural populations and two reciprocal common gardens in dry and wet sites, we estimated variance components (phenotypic, genetic, environmental, and genetic 9 environmental) of cavitation resistance based on 513 genotypes of a Mediterranean pine, Pinus pinaster.
Despite the selected populations being climatically contrasted, phenotypic plasticity in resistance to cavitation remained low and was essentially attributed to family level. Between-population variation in cavitation resistance for both phenotypic and genetic variation was limited.
These results strongly suggest that cavitation resistance is buffered against genetic and to a lesser extent environmental variation (canalization) in maritime pine. Consequently, in a drier world, the increasing drought tolerance of Pinus species might be severely constrained by the low level of cavitation resistance variation, resulting in a large-scale loss of productivity.
Journal Article
Analysis of the External Conditions Affecting on the Cavitation Resistance of a Steel
The aim of this study is to analyze the effect of cavitation erosion test conditions on the surface resistance of medium carbon steel. The ultrasonic vibratory specimen system was used to perform the experiments under the laboratory conditions. The vibratory frequency and the displacement amplitude were 20 kHz and 20 μm, respectively. In design of experiments, four various cavitation behaviors have been studied based on four cavitation test conditions corresponding to those behaviors. These conditions can be summarized as follows: (1) the usage of water as a testing liquid; (2) replacement the water with 3.5% NaCl solution; (3) applying a certain voltage to cause a combined electrochemical action working simultaneously with the water; and (4) applying the same voltage by using the 3.5% NaCl solution instead of water. The obtained results showed that the mass loss differs by test modes applied.
Journal Article