Search Results (242)

Understanding the dynamics of gas bubbles in viscoelastic media is crucial for applications involving stable cavitation under ultrasound, such as drug delivery, materials processing, and biomedical imaging. The Rayleigh-Plesset equation formulated in terms of bubble volume variation, incorporating viscoelastic effects via the linear Kelvin–Voigt model, is extended here to a fourth-order approximation. This formulation allows a more accurate description of nonlinear bubble dynamics at finite acoustic amplitudes. The resulting equation is solved numerically under various acoustic conditions, with particular emphasis on driving frequencies near the bubble’s resonance and differences between Newtonian and viscoelastic media. To identify the physical conditions under which higher-order nonlinearities become necessary, a decision-tree classification analysis is performed. The results show that the proximity to resonance and the excitation amplitude are the primary determinants of higher-order nonlinear effects, while rheological properties act as modulators, with viscosity exerting a stronger influence than elasticity within the explored ranges. This work provides a physically interpretable criterion for selecting the appropriate model order, improving the prediction and control of nonlinear bubble oscillations under ultrasound excitation in viscoelastic media. Full article

Geothermal energy extraction, hydrocarbon recovery, and CO₂ geological sequestration are frequently hindered by interfacial barriers and slow mass transfer. While high-power ultrasound offers a sustainable, purely physical method for reservoir stimulation, its field effectiveness remains debated because traditional macroscopic experiments fail to isolate mechanisms like acoustic streaming and cavitation. This review systematically examines acoustic mechanisms in porous media via microfluidic visualization, focusing on pore-scale fluid dynamics during enhanced oil recovery, hydrate dissociation, and CO₂ sequestration. Microscopic evidence reveals that fluid transport mechanisms depend heavily on pore geometry and local acoustic intensity. In wider channels, nonlinear acoustic flow provides sustained, directed convection to strip away concentration boundary layers; in narrow throats, microjets and pulsed stresses generated by transient cavitation are responsible for physically breaking capillary barriers. The spatiotemporal synergy of these mechanisms is critical for multiphase fluid transport in tight porous networks. Pore geometry serves not only as the application context but also as a core physical variable. To translate microfluidic results into reservoir-scale applications, future research must address two-dimensional simplifications, thermodynamic discrepancies under high-temperature and high-pressure conditions, and bubble cluster interactions, alongside the development of adaptive frequency-modulated control and multiscale computational models. Full article

The exponential growth of the fruit-processing industry generates significant quantities of organic by-products, such as peels, seeds, and pomace, which represent a rich but underutilized source of bioactive polyphenols. Valorizing these residues is critical for the transition toward a circular bioeconomy, yet conventional extraction methods remain solvent-intensive and kinetically inefficient. This review provides a comprehensive analysis of emerging green extraction technologies, specifically Ultrasound-Assisted (UAE), Microwave-Assisted (MAE), Enzyme-Assisted (EAE), Pressurized Liquid (PLE), and Supercritical Fluid Extraction (SFE), and Pulsed Electric Field (PEF), applied to key industrial matrices including apple, citrus, grape, olive, and coffee. Comparative data demonstrate that intensification technologies significantly outperform conventional maceration, with UAE and MAE reducing processing times by up to 90% while enhancing polyphenol yields by 20–55% through mechanisms such as acoustic cavitation and dipole rotation. Furthermore, high-pressure methods exhibit tunable selectivity, enabling the specific recovery of heat-sensitive anthocyanins and bound phenolics without the use of toxic organic solvents. The study concludes that the future of industrial valorization lies in the adoption of hybrid technologies and sequential biorefinery strategies to achieve high-purity isolates with minimal environmental impact. Full article

Electric discharge cavitation is an effective method for water treatment that combines physical and chemical effects within a single process. It enables water disinfection, extraction acceleration, dispersion of solid particles, and enhancement of porous material permeability. Compared to conventional chemical treatment, it reduces the demand for reagents and minimizes secondary pollution. This new and developing technology significantly contributes to the preservation of natural aquatic ecosystems by providing a sustainable alternative to traditional decontamination methods, thereby reducing the overall anthropogenic pressure on the environment. This study focuses on developing a reliable method for assessing electric discharge cavitation intensity and controlling water purification processes. The proposed approach is based on the oxidation of iodide ions to molecular iodine by reactive species generated during electric discharge cavitation. The adapted iodometric method is sensitive, reproducible, and does not require complex optical or acoustic equipment. Experimental results confirmed that iodometry provides an accurate evaluation of cavitation intensity, allowing control of specific energy consumption and optimization of treatment parameters. Optimal operating conditions were established to control the water processing by electric discharge cavitation: stainless-steel electrodes, specific input energy not exceeding 280 kJ·L⁻¹, the presence of a free liquid surface in the working chamber, and a discharge pulse frequency below 10 Hz. The proposed method supports the development of energy-efficient, low-waste technologies for wastewater and natural water treatment and facilitates the integration of electric discharge systems into existing water treatment infrastructure, particularly under resource-limited conditions. Full article

Ultrasonic cavitation is a key mechanism in the dispersion and erosion of solid materials in liquids; however, the influence of processing conditions and medium properties on its efficiency in ultrasonic baths remains poorly systematized. Despite the widespread use of ultrasonic baths in materials processing, general optimization principles are lacking, and operating parameters are typically determined empirically for each system. In this work, cavitation activity was quantitatively assessed using an aluminum foil erosion test, with the foil clamped in a plastic frame to evaluate the mechanical effects of cavitation. The effects of ultrasonic power, frequency, treatment time, temperature, solvent nature, and vessel material on the foil mass loss were systematically investigated. The results demonstrate that both the instrumental parameters and physicochemical properties of the dispersion medium, including viscosity and surface tension, significantly affect the cavitation activity. Solvents with lower cavitation thresholds and favorable acoustic properties promote more intense erosion, while the vessel material and geometry also influence energy transmission to the liquid. This study provides a systematic framework for assessing the cavitation dose in ultrasonic baths and offers practical guidelines for optimizing ultrasonic dispersion processes and improving their reproducibility. Full article

Underwater radiated noise (URN) has attracted increasing attention due to its environmental impact, with cavitation recognized as the dominant source. This study investigates cavitation-generation mechanisms and associated noise radiation for open-type and gap-type wings using high-fidelity numerical simulations. Cavitation noise was predicted using the Ffowcs Williams–Hawkings (FW–H) equation. The Fitzpatrick–Strasberg bubble noise model was independently employed for analysis to relate cavitation dynamics and cavity-volume variation to the resulting acoustic emissions. The results show that the gap-type configuration produces significantly stronger low-frequency noise, with the Tip Leakage Vortex Cavitation (TLVC) contributing up to 15 dB/Hz higher noise levels than the Tip Separation Vortex Cavitation (TSVC). This enhancement is attributed to the strong interaction between TLVC and TSVC, which amplifies cavitation dynamics and acoustic emissions. Analysis of three gap sizes reveals that, for small gaps, this interaction induces periodic cavitation behavior, generating a distinct harmonic component at St ≈ 2. As the gap size increases, the TLVC-TSVC interaction weakens, and the cavitation behavior transitions toward that of the open-type configuration, leading to the disappearance of the tonal component. These findings highlight the critical role of gap-induced vortex interaction in determining URN characteristics. Full article

Rain erosion is a critical issue for the development of wind power generation because it limits the lifetime of wind turbine blades. To clarify the erosion initiation mechanism in wind turbine blades of metallic material, pit formation and erosion initiation on a smooth wet wall of aluminum materials A3003 and annealed A5052 were investigated; water droplets were impinged on the wall using a pulsed-jet tester; and combined theoretical and numerical studies were performed by considering the influence of the water film on the wall. Although the theoretical and numerical impact pressures were much lower than the offset yield strength of the materials, random pit formation and erosion initiation were observed on the target material. To clarify the reason for this, the occurrence of cavitation erosion was investigated based on the numerical pressure distribution of a droplet impacting a wet wall. The numerical results showed that the pressures in the droplet center and water film became lower than the saturated vapor pressure, suggesting the occurrence of cavitation erosion. Furthermore, a similar pit formation and erosion initiation were observed on the wall material in the acoustic cavitation test under the cavitation erosion condition. These results indicate that the pit formation could have been caused by the high impact pressure caused by the micro-jet mechanism that occurs when a droplet impacts the wet wall. This could potentially explain the mechanism of the more severe erosion in the actual wind turbine blade than was expected. Full article

Chelating agents can extend the operational pH range of iron-based advanced oxidation processes, yet comprehensive studies on chelated Fe-activated persulfate systems for textile dye degradation remain scarce. This study establishes an integrated framework for optimizing Fe(II)/persulfate (PS) systems using chelating ligands and hybrid energy inputs under near-neutral conditions. Among the tested systems, Fe(II)/PS complexed with citric acid (CA) exhibited superior performance, achieving ~91% dye removal within 20 min at pH 6.5 under optimized conditions (1.25 mM Fe(II), 10 mM PS, 0.1 mM CA). Chelation stabilized Fe redox cycling and prevented precipitation, enabling effective catalysis across pH 3–10. Optimal CA/Fe and Fe/PS ratios (0.1:1.25 and 1.25:10) yielded ~96% decolorization and 67.65% TOC removal in 60 min, while excessive chelation reduced activity. Transition metal screening (Mn(II), Zn(II), Cu(II), Co(II), and Ni(II) confirmed Fe(II) as the most effective activator, providing removal efficiencies up to 3.2-fold higher than competing metals. Mixed-dye experiments showed competitive degradation, with >37% color removal after 60 min for ternary dye mixtures. Mineralization reached ~92% TOC reduction after 120 min, indicating deep oxidation beyond chromophore cleavage. Reactive species quenching revealed a mixed oxidation mechanism involving ^•OH radicals and high-valent Fe(IV) species. Hybrid assistance improved mineralization, with UVC increasing TOC removal by 15.6%, while solar irradiation provided moderate enhancement under low-energy input. In contrast, low-power ultrasound (40 kHz, 60 W) delivered only 17.6 W acoustic power to the solution and did not improve performance due to limited cavitation and mixing. This work thus contributes a robust platform for advancing chelated iron-persulfate oxidation systems toward practical, effective treatment of recalcitrant dye-contaminated wastewaters under near-neutral conditions. Full article

Metal additive manufacturing (AM) offers unprecedented opportunities to fabricate complex, lightweight metallic components, yet its practical deployment remains fundamentally constrained by defects arising from rapid melting and solidification. Cyclic thermal transients generate cracks, pores, residual stresses, and lack-of-fusion regions, undermining mechanical performance and reliability. Ultrasonic field-assisted laser-based additive manufacturing (UF-LBAM) has emerged as a powerful approach to manipulate melt pool dynamics and suppress defect formation. Nevertheless, the governing physical mechanisms remain poorly understood, particularly under highly non-equilibrium ultrasonic excitation, where acoustic pressure oscillations, melt convection, cavitation, and solidification are intricately coupled across multiple temporal and spatial scales. Here, we provide a systematic review of X-ray based fundamental studies in UF-LBAM and the diverse applications of machine learning (ML), detailing the literature selection criteria and methodology. We highlight advances spanning synchrotron X-ray revealed physical phenomena, ML-driven real-time monitoring and defect prediction, and pathways toward industrial implementation. Critical challenges persist, including fundamental physics gaps, transferability of ML models across alloy systems, and real-time control limitations. We further identify promising directions for the field, such as physics-informed models, multimodal diagnostics, and closed-loop control, which together promise to unlock the full potential of UF-LBAM for high-performance metal component fabrication. Full article

This study investigates the acoustic pressure field in a 20 kHz sonoreactor filled with water. A modular sonoreactor and ultrasonic stack were developed at the Łukasiewicz-ITR laboratory. Modal, harmonic response, and harmonic acoustic analyses were performed using the ANSYS Workbench, considering two reactor heights (800 mm and 550 mm). Experimental tests using aluminium foils were conducted, and the results were compared with FEM simulations. The bulk viscosity of the liquid was found to have a significant impact on the numerical results. The novelty of this work lies in estimating an effective bulk viscosity that enables accurate representation of the pressure field distribution within the tank. This parameter is theoretical and, as defined in this study, accounts for the overall energy losses associated with cavitation rather than representing an intrinsic material property. The proposed simulation approach reduces computational time and cost while maintaining agreement between predicted and experimental pressure fields. Good consistency was achieved when the effective bulk viscosity was set to 1300 Pa·s. The presented methodology may support further development and optimization of sonoreactors. It enables rapid evaluation of various geometries, providing a foundation for prototype development or subsequent detailed analyses. Full article

Ultrasound has emerged as a versatile and promising tool to enhance and speed up traditional processing operations used by the food industry or to be used as an alternative food-processing method. This review provides an overview of the fundamental principles of sonication and its diverse applications in food processing. The core concepts of acoustic cavitation and the influence of power on processing outcomes are discussed in detail. The design and operation of different ultrasound systems, including direct-contact probe and indirect-contact bath systems, and their respective advantages were reviewed. Furthermore, a wide array of applications were explored, namely extraction, homogenization, degassing and deodorizing, pasteurization and vegetable blanching, drying and dehydration, freezing and thawing, brining and hydration, and cutting, highlighting how ultrasound waves can enhance process efficiency and improve product quality. The review also provides a critical analysis of the challenges and limitations associated with scaling up the technology for industrial use, including potential impacts on food quality, safety considerations, and economic viability. Finally, future perspectives and potential areas for further research are outlined to encourage the broader adoption of this technology in the food sector. Full article

The dynamic evolution of microbubbles under ultrasonic excitation is fundamental to applications ranging from targeted drug delivery to acoustic cleaning. This study employs a synchronous high-speed microscopic imaging system to systematically investigate the size-dependent stability and fragmentation of air microbubbles (R₀ = 25–82.5 μm) in a free field at a driving frequency of 16.6 kHz. Our results demonstrate a clear mechanistic transition from stable radial oscillations to complex surface instabilities and, eventually, deterministic fragmentation. Smaller bubbles (R₀ < 55 μm) exhibit long-term stability, transitioning through higher-order surface modes (n = 3 to n = 4) as surface energy accumulates. In contrast, larger bubbles (R₀ > 60 μm) undergo violent non-spherical deformations characterized by centripetal necking and high-speed micro-jetting. Notably, we identify an inverse relationship between initial radius and fragmentation onset time, with larger bubbles reaching instability thresholds significantly earlier. Furthermore, a transition from stochastic breakup to bimodal, volume-symmetric splitting was observed as R₀ increased, where daughter bubbles reached comparable volumes. These findings provide a theoretical and empirical basis for the controlled generation of monodisperse microbubble clouds, offering significant potential for enhancing the efficacy of ultrasonic contrast agents and therapeutic cavitation. Full article

Background/Objectives: Solid tumors are characterized by a dense stromal structure and heterogeneous microenvironments that limit intratumoral drug penetration and contribute to immune exclusion. We developed perfluoropentane (PFP)-based phase-change nanodroplets (IMP700) and aimed to identify focused ultrasound (FUS) parameters that enhance cavitation and sonoporation to improve drug delivery and immune engagement in tumor models. Methods: IMP700 was prepared as lipid-shelled PFP nanodroplets and physicochemically characterized. Acoustic droplet vaporization (ADV), echogenicity, and cavitation were evaluated in vitro and in vivo using ultrasound imaging and cavitation analysis under varying FUS parameters, including acoustic intensity, duty cycle, and pulse repetition frequency (PRF), in PANC-1 xenograft tumors. Sonoporation was assessed by co-administering an ultrasound-responsive doxorubicin liposome (IMP301), and intratumoral drug distribution was analyzed by confocal imaging. Immune responses were evaluated in a syngeneic 4T1 tumor model by quantifying CD8⁺ T-cell infiltration after repeated treatments. Results: IMP700 exhibited nanoscale size and high PFP encapsulation efficiency and underwent ADV with increased echogenicity and intensity-dependent cavitation. In vivo, a 2% duty cycle and 10 Hz PRF produced strong and reproducible cavitation. Under these conditions, IMP700 markedly increased inertial cavitation and enhanced intratumoral drug penetration compared to FUS alone. Combined IMP700 and FUS treatment also increased intratumoral CD8⁺ T-cell infiltration. Conclusions: IMP700 amplifies FUS-induced cavitation, improves sonoporation-mediated drug delivery, and promotes CD8⁺ T-cell infiltration, which supports the use of FUS-activated nanodroplets as a strategy to overcome stromal and immunological barriers in solid tumors. Full article

Phthalates (PAEs), commonly incorporated into materials such as polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC), are easily to migrate readily into the surrounding environment, which have become a matter of increasing concern. Traditional PAEs extraction methods have been prevented by long extraction times and high costs, requiring substitute to accelerate the extraction speed while reducing extraction costs. Ultrasonic-assisted extraction facilitates the release and dissolution of target compounds through the combined effects of acoustic cavitation and molecular vibration acceleration, which could be an effective means to overcome the limitations of traditional extraction methods. Herein, we have developed a four-frequency composite ultrasonic extraction technology for PAEs, with a recovery of 95.2%, approximately 38.2% higher than mode MU 20 kHz. Besides, an in-depth study on the mechanism of ultrasound-assisted extraction with sequential multi-frequency was conducted and we confirm that stepped-frequency ultrasound could achieve precise control of cavitation effects by dynamically adjusting frequency distribution, ensuring high extraction efficiency while maximally protecting the PVC matrix structure, providing a new technical path for efficient and green recovery of plasticizers. Full article

Pancreatic ductal adenocarcinoma (PDAC) remains a highly lethal malignancy due to late presentation, limited resectability, therapeutic resistance, and a dense desmoplastic immunosuppressive tumor microenvironment that impairs drug penetration and antitumor immunity. Focused ultrasound (FUS) is an emerging non-invasive, image-guided therapeutic platform capable of delivering spatially confined acoustic energy to induce tumor ablation, disrupt stromal barriers, and enhance delivery of drugs, nanoparticles, and nucleic acids. Depending on acoustic parameters, FUS can produce thermal effects resulting in coagulative necrosis or non-thermal mechanical effects, including cavitation, sonoporation, and histotripsy which remodel extracellular matrix architecture, increase vascular and cellular permeability, and facilitate tumor debulking. In addition, FUS-induced cell injury can promote immunogenic cell death and release tumor-associated antigens and danger signals, providing a rationale for combination strategies with chemotherapy, radiation, and immunotherapy. This review synthesizes the mechanistic foundations, preclinical modeling advances, and emerging clinical applications of FUS in PDAC, with emphasis on treatment integration, patient selection, real-time monitoring, and acoustic parameter optimization, while acknowledging current safety considerations and limited clinical toxicity data. Key limitations, translational challenges, and priority knowledge gaps are also discussed to define the role of FUS in multimodal PDAC care. Full article