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Abstract We investigate the demise and expansion of a cavitation bubble in a porous medium deformable. We develop a continuum-scale model that blends compressible fluid movement in the pore network with elastic response of a solid skeleton. The extended Rayleighu2013Plesset equation shows that finite-size fluctuations contribute to the reduction of the universal scaling relationship between bubble radius and time that does not exist in the infinite scale model.
Source link: https://doi.org/10.1093/pnasnexus/pgac150
Through two approaches, this effort investigates the latest advances in cavitation model analysis important to computational fluid dynamics. With respect to the Rayleighu2013Plesset equation, the first portion of the paper revisits cavitation model formulations with respect to the Rayleighu2013Plesset equation. The new strategy rewrites the cavitation model by using analytic solutions to the RPE. In addition, the model scheme is extended beyond conventional homogeneous models to a two-fluid modeling framework that explicitly simulates the slippage between cavitation bubbles and the liquid. The results reveal a significant effect of slip on the predicted cavitation model, indicating that the inclusion of such modeling could potentially increase CFD cavitation models.
Source link: https://doi.org/10.1115/1.4042421
Abstract Extreme environmental changes resulting from the cavitation bubble explosion, such as high pressure, high temperature, and the microjet, could result in pyrolysis reaction at the gas and liquid interface inside the bubble. The self-excited pulsed cavitation jet has an immediate and high pulse pressure, resulting in local hot spots around the cavitation bubbles. The synthesis of strong oxidizing free radicals contributes to rapid ozone conversion into oxygen. To measure and analyze the ozone degradation reaction, three groups of different collision angles were applied.
Source link: https://doi.org/10.1515/phys-2022-0005
The fidelity of an axial-flow pump under various VVVF conditions was investigated by variable voltage and variable frequency control on the cavitation results of the axial-flow pump's cavitation results. The change of flow field inside the impeller was stable, the expansion rate of cavitation was slow, and the cavitation rate was slowest, with steady acceleration. It was found that the three acceleration plans all have large pressure fluctuations, despite being able to test the effect of cavitation on pressure distribution under VVVF. With higher acceleration, the pressure fluctuation amplitude increased in the late stage of acceleration, and the pressure decline rate slowed.
Source link: https://doi.org/10.3390/w14172757
Pressure fluctuations inside the draft tube of a Francis turbine that may fail the turbine due to resonance and erosion, which may lead to cavitation inception at part load. The present research investigates the effect of fin shapes and locations on the Francis turbine's internal flow characteristics, as well as its potential effect on the pressure surge. Three cases are investigated in which internal flow physics are compared among DTs with longer fins, shorter fins, and no fins in which internal flow physics are compared among DTs with longer fins, shorter fins, and no fins. The vortex rope occurrence is minimized when using fins on the DT periphery and longer fins that are extending up to the elbow have the lowest load of the vortex rope. Using longer fins, maximum pressure recovery inside the DT is achieved. Using longer fins, the pressure peak of low frequency is reduced by about 60%.
Source link: https://doi.org/10.1063/5.0097685
Stepped spillways are one of the oldest spillway designs dating back to 500 B. C. Various crest pier styles were introduced for flow aeration in order to increase the discharge capacity on stepped spillways, thereby minimizing the risk of cavitation damage. Both with a standard ogee crest profile that transits to a stepped spillway chute, two physical models were investigated on two physical models, both with a 1:15 and 1:50 scale. The results of the 1:15 scale model revealed that the introduction of a short bullnose pier increased the safe unit discharge capacity to 30 rm/s. Based on the latest research's experimental findings, the safe unit discharge capacity was up to 50 m2/s with an X-shape Flare Gate Pier on the spillway crest.
Source link: https://doi.org/10.17159/2309-8775/2019/v61n2a3
This paper, Aiming at the difficult vortex issue that affects diesel engine nozzle flow stability, this paper examines the effect of ventilation on the string cavitation patterns in the nozzle hole with a self-built scale-up test bench. The position of hole-to-hole string cavitation in the SAC volume, according to Relatively speaking, is highly variable as a result of bubble contents. Only if there are many bubbles, the cavitation pattern shifts to hole-to-hole string cavitation or string cavitation emanating from the upper wall of the hole inlet's upper wall.
Source link: https://doi.org/10.1177/09544070221117016
The ultrasonic radio frequency signal will provide more detailed information about the acoustic scattering phenomenon in comparison to the traditional commercial ultrasonic gray value signal. The dynamic range of the RF signals is extended by data standardization processing, and the entropy image is reconstructed based on the sliding window information entropy analysis to reveal the spatiotemporal evolution status of the HIFU-induced cavitation behanviors. The experimental findings show that the acoustic cavitation imaging algorithm based on radio signal entropy measurements should be more accurate and accurate than the B-model gray scale imaging scheme for determining the onset time and geographic location of cavitation procedures, which is helpful in ensuring the safety and efficacy of HIFU clinical therapy's safe and effective use of HIFU clinical therapy.
Source link: https://doi.org/10.7498/aps.71.20220558
Bubbles display translational instability, the well-known erratic dancing motion caused by shape oscillations of the bubbles that are excited by their volume oscillations, in a high-intensity acoustic field. Bubble dynamics in the HIFU literature is mainly based on experiments, lacking a systematic approach to determine the threshold for shape oscillations and translational movement. We extend the existing multiphysics mathematical modeling platform on bubble dynamics for including the effects of nonlinearity, shape modes, and absorption of HIFU, as well as the effects of nonlinearity, timmation, and absorption of HIFU to include the acoustic nonlinearity due to wave kinematics or medium u2014all in one model.
Source link: https://doi.org/10.3390/acoustics1010003
We report a rare occurrence of a woman in her 60s with rheumatoid arthritis who exhibited fever of unknown origins, cutaneous leucocytoclastic vasculitis, and progressive pulmonary infiltrates with cavitation. The patient was diagnosed with cryoglobulinaemic vasculitis with pulmonary involvement, and it was administered with high-dose prednisolone and rituximab, resulting in complete lung closure and marked clinical improvement.
Source link: https://doi.org/10.1136/bcr-2022-251705
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