Search Results (42)

Intravascular aspiration thrombectomy catheters are widely used to treat stroke, pulmonary embolism, and deep venous thrombosis. However, their performance is frequently compromised by clot material becoming lodged within the catheter tip. To address this, we develop a novel ultrasound-enhanced aspiration catheter approach that generates cavitation within the tip to mechanically degrade clots, with a view to facilitate extraction. The design employs hollow cylindrical transducers that produce inwardly propagating cylindrical waves to generate sufficiently high pressures to perform histotripsy. This study investigates the feasibility of self-sensing cavitation detection by analyzing voltage signals across the transducer during treatment. Experiments were conducted for two transmit pulse lengths at varying driving voltages with water or clot in the lumen. Cavitation clouds within the lumen were assessed using 40 MHz ultrasound imaging. Changes in the signal envelope during the pulse body and ringdown phases occurred above the cavitation threshold, the latter being associated with more rapid wave damping in the presence of bubble clouds within the lumen. In the frequency domain, voltage-dependent cavitation signals—subharmonics, ultra-harmonics, and broadband—emerged alongside transmit pulses. This work demonstrates a highly sensitive, sensor-free method for detecting cavitation within the lumen, enabling feedback control to further improve histotripsy-assisted aspiration. Full article

Histotripsy is a novel, noninvasive, non-thermal technology invented in 2004 for the precise destruction of biologic tissue. It offers a powerful alternative to more conventional thermal or surgical interventions. Using short-pulse, low-duty cycle ultrasonic waves, histotripsy creates cavitation bubble clouds that selectively and precisely destroy targeted tissue in a predefined volume while sparing critical structures like bile ducts, ureters, and blood vessels. Such precision is of value when treating tumors near vital structures. The FDA has cleared histotripsy for the treatment of all liver tumors. Major medical centers are currently spearheading clinical trials, and some institutions have already integrated the technology into patient care. Histotripsy is now being studied for a host of other cancers, including primary kidney and pancreatic tumors. Preclinical murine and porcine models have already revealed promising outcomes. One of histotripsy’s primary advantages is its non-thermal mechanical actuation. This feature allows it to circumvent the limitations of heat-based techniques, including the heat sink effect and unpredictable treatment margins near sensitive tissues. In addition to its non-invasive ablative capacities, it is being preliminarily explored for its potential to induce immunomodulation and promote abscopal inhibition of distant, untreated tumors through CD8+ T cell responses. Thus, it may provide a multilayered therapeutic effect in the treatment of cancer. Histotripsy has the potential to improve precision and outcomes across a multitude of specialties, from oncology to cardiovascular medicine. Continued trials are crucial to further expand its applications and validate its long-term efficacy. Due to the speed of recent developments, the goal of this review is to provide a comprehensive and updated overview of histotripsy. It will explore its physics-based mechanisms, differentiating it from similar technologies, discuss its clinical applications, and examine its advantages, limitations, and future. Full article

The extensibility of dough and its resistance to extension (toughness) are important indicators, since they are directly linked to dough quality. Therefore, this paper used an independently developed device to blow sheeted dough, and then a three-dimensional (3D) camera was used to continuously collect point cloud images of sheeted dough forming bubbles. After data collection, the rotation algorithm, region of interest (ROI) extraction algorithm, and statistical filtering algorithm were used to process the original point cloud images. Lastly, the oriented bounding box (OBB) algorithm was proposed to calculate the deformation height of each data point. And the point cloud image with the largest deformation depth was selected as the data to input into the 3D convolutional neural network (CNN) models. The Convolutional Block Attention Module (CBAM) was introduced into the 3D Visual Geometry Group 11 (Vgg11) model to build the enhanced Vgg11. And we compared it with the other classical 3D CNN models (MobileNet, ResNet18, and Vgg11) by inputting the voxel-point-based data and the voxel-based data separately into these models. The results showed that the enhanced 3D Vgg11 model using voxel-point-based data was superior to the other models. For prediction of dough extensibility and toughness, the R_p was 0.893 and 0.878, respectively. Full article

Owing to the limitations of physical experiments on heavy oil, this study establishes a mathematical model for heavy oil–water two-phase flow based on the theory of multiphase flow, considering factors such as heavy oil viscosity, mixed flow velocity, and inlet water cut. Through transient calculations of 650 groups of heavy oil–water two-phase flows based on this model, six typical heavy oil–water two-phase flow patterns were identified by monitoring flow pattern cloud images, liquid holdup, and the probability density function (PDF) of liquid holdup: water-in-oil bubble flow, transitional flow, water-in-oil slug flow, oil-in-water bubble flow, oil-in-water very fine dispersed flow, and water-in-oil core-annular flow. Five sets of flow pattern maps for a heavy oil–water two-phase flow with different viscosities were established based on the inlet water cut and mixed flow velocity. The results showed that different heavy oil viscosities lead to different oil–water two-phase flow patterns. When the heavy oil viscosity is 100 mPa·s, the flow patterns include water-in-oil bubble flow, transitional flow, water-in-oil slug flow, oil-in-water bubble flow, and oil-in-water very fine dispersed bubble flow. When the heavy oil viscosity reaches 600 mPa·s, a water-in-oil core-annular flow appears, and the oil-in-water very fine dispersed bubble flow disappears. After the heavy oil viscosity exceeds 1100 mPa·s, the oil-in-water bubble flow disappears. Among the different flow patterns, the range of the water-in-oil slug flow is most affected by the viscosity and flow velocity. The greater the heavy oil viscosity, the larger the range. When the viscosity remained constant, a larger flow velocity resulted in a smaller range. The accuracy of the flow pattern predictions in the maps was verified by comparing them with field production data, confirming that the research results can provide a theoretical basis for understanding oil–water two-phase flow patterns in heavy oil wellbores. Full article

Cavitation is a phase-change phenomenon from the liquid to the gas phase due to an increased flow velocity. As it causes severe erosion and noise, it is harmful to hydraulic machinery such as pumps, valves, and screw propellers. However, it can be utilized for water treatment, in chemical reactors, and as a mechanical surface treatment, as radicals and impacts at the point of cavitation bubble collapse can be utilized. Mechanical surface treatment using cavitation impacts is called “cavitation peening”. Cavitation peening causes less pollution because it uses water to treat the mechanical surface. In addition, cavitation peening improves on traditional methods in terms of fatigue strength and the working life of parts in the automobile, aerospace, and medical fields. As cavitation bubbles are utilized in cavitation peening, the study of cavitation bubbles has significant value in improving this new technique. To achieve this, many numerical analyses combined with field experiments have been carried out to measure the stress caused by bubble collapse and rebound, especially when collapse occurs near a solid boundary. Understanding the mechanics of bubble collapse can help to avoid unnecessary surface damage, enabling more accurate surface preparation, and improving the stability of cavitation peening. The present study introduces three cavitation bubble types: single, cloud, and vortex cavitation bubbles. In addition, the critical parameters, governing equations, and high-speed camera images of these three cavitation bubble types are introduced to support a broader understanding of the collapse mechanism and characteristics of cavitation bubbles. Then, the results of the numerical and experimental analyses of non-spherical cavitation bubbles are summarized. Full article

Background: Transcatheter aortic valve replacement (TAVR) was developed for inoperable patients with severe aortic stenosis. However, despite TAVR advancements, some patients remain untreated due to complex comorbidities, necessitating less-invasive approaches. Non-invasive ultrasound therapy (NIUT), a new treatment modality, has the potential to address this treatment gap, delivering short ultrasound pulses that create cavitation bubble clouds, aimed at softening embedded calcification in stiffened valve tissue. Methods: In the prospective Valvosoft^® Serbian first-in-human study, we assessed the safety and efficacy of NIUT and its impact on aortic valve hemodynamics, on the left ventricle, and on systemic inflammation in patients with severe symptomatic aortic stenosis not eligible for TAVR or surgery. Results: Ten patients were included. Significant improvements were observed in hemodynamic parameters from baseline to one month, including a 39% increase in the aortic valve area (from 0.5 cm² to 0.7 cm², p = 0.001) and a 23% decrease in the mean transvalvular gradient (from 54 mmHg to 38 mmHg, p = 0.01). Additionally, left ventricular global longitudinal strain significantly rose, while global wasted work significantly declined at one month. A dose–response relationship was observed between treatment parameters (peak acoustic power, intensity spatial-peak pulse-average, and mean acoustic energy) and hemodynamic outcomes. NIUT was safely applied, with no clinically relevant changes in high-sensitivity troponin T or C-reactive protein and with a numerical, but not statistically significant, reduction in brain natriuretic peptide (from 471 pg/mL at baseline to 251 pg/mL at one month). Conclusions: This first-in-human study demonstrates that NIUT is safe and confers statistically significant hemodynamic benefits both on the valve and ventricle. Full article

Focused on the unsteady property of a cavitating water jet issuing from an orifice nozzle in a submerged condition, this paper presents a fundamental investigation of the periodicity of cloud shedding and the mechanism of cavitation cloud formation and release by combining the use of high-speed camera observation and flow simulation methods. The pattern of cavitation cloud shedding is evaluated by analyzing sequence images from a high-speed camera, and the mechanism of cloud formation and release is further examined by comparing the results of flow visualization and numerical simulation. It is revealed that one pair of ring-like clouds consisting of a leading cloud and a subsequent cloud is successively shed downstream, and this process is periodically repeated. The leading cloud is principally split by a shear vortex flow along the nozzle exit wall, and the subsequent cloud is detached by a re-entrant jet generated while a fully extended cavity breaks off. The subsequent cavitation cloud catches the leading one, and they coalesce over the range of $x/d\approx 1.8~2.5$. Cavitation clouds shed downstream from the nozzle at two dominant frequencies. The Strouhal number of the leading cavitation cloud shedding varies from 0.21 to 0.29, corresponding to the injection pressure. The mass flow rate coefficient fluctuates within the range of $0.59~0.66$ at the same frequency as the leading cloud shedding under the effect of cavitation. Full article

In this work, within finite liquid spaces confined by elastic walls and the free surface, we investigated the influence of wall and liquid on laser bubble-excited vibrational rarefaction waves, via the dynamics of the laser-induced plasma-mediated bubble and its accompanying small secondary bubble clouds. We observed the modulation of the rebound maximum radius (R_max2) relative to the first oscillation period (T_osc1) for the laser bubble and the periodic appearance of secondary bubble clouds, which were caused by extra rarefaction waves. We found an approximate constant modulation period of R_max2 (T_osc1) and increased time intervals between the adjacent secondary bubble clouds with increasing liquid height in the same cuvette, while both of them were remarkably increased with increasing inner size of cuvettes within the same liquid height. This indicated that the cuvette geometry and liquid volume alter the key characteristics of the vibrational rarefaction waves. It was further confirmed that extra rarefaction waves within the liquid are excited by wall vibrations linked to laser bubble expansion and its induced liquid-mass oscillations. Our study provides a better understanding of the interactions of laser-induced cavitation with liquid and elastic walls in confined geometry, which is essential for intraluminal laser surgery. Full article

The artificially submerged cavitation water jet is effectively utilized by ejecting a high-pressure water stream into a low-pressure water stream through concentric nozzles and utilizing the cavitation phenomenon generated by the shear layer formed between the two streams. In this study, we investigated the cavitation characteristics of artificially submerged cavitation water jets by combining numerical simulations and erosion experiments. The results indicate that an appropriate standoff distance can generate more cavitation clouds on the workpiece surface, and the erosion characteristics of the artificially submerged cavitation water jet are most pronounced at a dimensionless standoff distance of S_D = 30. The shear effect formed between the two jets plays a crucial role in generating initial cavitation bubbles within the flow field of the artificially submerged cavitation water jet. Moreover, increasing the convergent angle between the two jets can significantly enhance the cavitation effect between them and lead to a more substantial cavitation effect. Simultaneously, increasing the pressure of the high-pressure inner nozzle also contributes to enhancing the cavitation effect of the artificially submerged cavitation water jet. Full article

Cavitation bubbles near narrow gaps widely exist within microfluidic control devices. In the present paper, a laser-induced cavitation bubble is arranged in a narrow gap composed of two parallel plates. The inception position of the bubble is set to be at the same distance from the two plates so that the dynamic behaviors of the bubble are symmetrical. The collapse and rebound dynamics of the bubble near the boundary of a narrow gap are investigated through high-speed photography. The bubble behaviors (e.g., shape deformation, translational movement, and jet characteristics) are analyzed while considering the influence of the dimensionless distance between the bubble and the boundary and the dimensionless gap width. The principal findings include the following: (1) When the dimensionless distance is small, a violent jet towards the gap is generated during the bubble collapse stage, along with a weak counter-jet towards the boundary appearing during the rebound stage. (2) As the dimensionless distance increases, the translational distance of the bubble during the collapse stage initially decreases, then increases, and finally decreases to zero. (3) Within the parameter range considered in this paper, the dimensionless width mainly affects the expansion degree and movement direction of the bubble cloud during its rebound and subsequent stages. The above research findings can provide experimental support for bubble-driven flow control, pumping, and liquid mixing in microfluidic channels. Full article

Cloud and bubble chambers have historically been used for particle detection, capitalizing on supersaturation and superheating, respectively. Here, we present new results from a prototype snowball chamber, in which an incoming particle triggers the crystallization of a purified, supercooled liquid. We demonstrate, for the first time, simulation agreement with our first results from 5 years ago: the higher temperature of the freezing of water and significantly shorter time spent supercooled compared to the control in the presence of a Cf-252 fission neutron source. This is accomplished by combining Geant4 modeling of neutron interactions with the Seitz nucleation model used in superheated bubble chambers, including those seeking dark matter. We explore the possible implications of using this new technology for GeV-scale WIMP searches, especially in terms of spin-dependent proton coupling, and report the first supercooling of WbLS (water-based liquid scintillator). Full article

In this work, we investigate the effect of dissolved gas concentration on cavitation inception and cavitation development in a transparent sharp-edged orifice, similar to that previously analyzed by Nurick in the context of liquid injectors. The working liquid is water, and carbon dioxide is employed as a non-condensable dissolved gas. Cavitation inception points are determined for different dissolved gas concentration levels by measuring wall-static pressures just downstream of the orifice contraction and visually observing the onset of a localized (vapor) bubble cloud formation and collapse. Cavitation onset correlates with a plateau in wall-static pressure measurements as a function of a cavitation number. An increase in the amount of dissolved carbon dioxide is found to increase the cavitation number at which the onset of cavitation occurs. The transition from cloud cavitation to extended-sheet or full cavitation along the entire orifice length occurs suddenly and is shifted to higher cavitation numbers with increasing dissolved gas content. Volume flow rate measurements are performed to determine the change in the discharge coefficient with the cavitation number and dissolved gas content for the investigated cases. CFD analyses are carried out based on the cavitation model by Zwart et al. and the model by Yang et al. to account for non-condensable gases. Discharge coefficients obtained from the numerical simulations are in good agreement with experimental values, although they are slightly higher in the cavitating case. The earlier onset of fluid cavitation (i.e., cavitation inception at higher cavitation numbers) with increasing dissolved carbon dioxide content is not predicted using the employed numerical model. Full article

Tire defect detection, as an important application of automatic inspection techniques in the industrial field, remains a challenging task because of the diversity and complexity of defect types. Existing research mainly relies on X-ray images for the inspection of defects with clear characteristics. However, in actual production lines, the major threat to tire products comes from defects of low visual quality and ambiguous shape structures. Among them, bubbles, composing a major type of bulge-like defects, commonly exist yet are intrinsically difficult to detect in the manufacturing process. In this paper, we focused on the detection of more challenging defect types with low visibility on tire products. Unlike existing approaches, our method used laser scanning technology to establish a new three-dimensional (3D) dataset containing tire surface scans, which leads to a new detection framework for tire defects based on 3D point cloud analysis. Our method combined a novel 3D rendering strategy with the learning capacity of two-dimensional (2D) detection models. First, we extracted accurate depth distribution from raw point cloud data and converted it into a rendered 2D feature map to capture pixel-wise information about local surface orientation. Then, we applied a transformer-based detection pipeline to the rendered 2D images. Our method marks the first work on tire defect detection using 3D data and can effectively detect challenging defect types in X-ray-based methods. Extensive experimental results demonstrate that our method outperforms state-of-the-art approaches on 3D datasets in terms of detecting tire bubble defects according to six evaluation metrics. Specifically, our method achieved 35.6, 40.9, and 69.1 mAP on three proposed datasets, outperforming others based on bounding boxes or query vectors. Full article

In numerous industries such as drilling, peening, cleaning, etc., a cavitating jet is adopted. However, it is challenging to simulate the cavitating flow field numerically with accuracy. The flow field of the organ pipe cavitation nozzle is simulated in this research using the RNG k−ε, DES, and LES turbulence models. The LES model can more accurately predict the periodic shedding of a cavitating cloud, which is basically consistent with the jet morphology captured with a high−speed camera. The flow pattern, cavitating cloud evolution and shedding period of a cavitating jet are analyzed. The findings demonstrate that the LES model produces a cavitating effect inside the nozzle that is superior to those produced by the RNG k−ε and DES models. The vortex rings in the diffusion section are simulated using the LES model, which accelerates cavitation. The cavitating clouds of the organ pipe nozzle show periodic evolutions, with stages of generation, development, shedding and collapse. The periodic shedding of the cavitating clouds exhibits a similar pattern in the vorticities simulated using the LES model, and the vorticities display the small-scale structures where the cavitating bubbles collapse. This study can provide a reference for the simulation of a cavitating jet and the analysis of the cavitating mechanism. Full article

This study employs the VOF method to conduct the direct numerical simulation of the collapse progress of the near-wall bubble cluster. Factors such as viscosity, compressibility, and surface tension are taken into account, with an emphasis on the flow field energy evolution. Firstly, the collapse of a cubic bubble cluster comprising 64 bubbles is simulated, validating previous research regarding the morphological evolution and energy release mechanisms during cluster collapse. Overall, the cubic bubble cluster collapse exhibits a layer-by-layer phenomenon, where the outer layer bubbles collapse first, converting a portion of bubble potential energy into fluid kinetic energy, which then contributes to the inner layer bubble collapse. The pressure wave energy is primarily released when the whole bubble cluster completely collapses. Secondly, we investigate the collapse process of columnar bubble clusters, which closely resemble realistic cloud cavitation. By comparing the collapse behavior of bubble clusters with different heights, we reveal the non-linear delay effect of the cluster height on the collapse time. Additionally, we consolidate our long-term research on the bubble cluster and conclude that both the scale and shape of the bubble clusters have a limited impact on the conversion rate $\eta$ of bubble potential energy to pressure wave energy $\eta$. For instance, when the stand-off distance $\eta =1.5$ and the inter-bubble distance $D=2.5$, the conversion rate $\eta$ remains consistently 9–15% for various bubble clusters of different scales and shapes. Full article