Search Results (1,624)

This study utilizes a novel self-excited oscillatory hydrodynamic cavitation (HC) device for tetracycline degradation. The effects of key parameters, including cavity length, inlet-to-outlet diameter ratio, and operational conditions (inlet pressure of 0.3–0.8 MPa), as well as the initial tetracycline concentration (5.0–20.0 mg/L) and the addition of common inorganic anions, on tetracycline degradation are systematically explored. The results show that the self-excited oscillating hydrodynamic cavitator, with a cavity length of 23.0 mm and an inlet-to-outlet diameter ratio of 0.75 (inlet diameter: 3.0 mm; outlet diameter: 4.0 mm), generates a strong HC effect. Under an inlet pressure of 0.5 MPa and an initial tetracycline concentration of 10.0 mg/L, the degradation rate reaches 51.32 ± 0.56%. The three common inorganic anions, CO₃²⁻, NO₃⁻, and SO₄²⁻, all inhibit tetracycline degradation. The addition of Fenton’s reagent further enhances the degradation efficiency of tetracycline via hydrodynamic cavitation. The optimal molar ratio of Fenton’s reagent (TC:Fe²⁺:H₂O₂ = 1:1:10) is determined, resulting in a tetracycline degradation rate of 85.91 ± 0.29% after 120 min of reaction. The self-excited oscillatory hydrodynamic cavitator proposed in this study offers a simple structure, high reliability, and improved degradation efficiency, providing a novel approach to antibiotic treatment. Full article

The cavitation phenomenon significantly impacts the performance of pump turbines, necessitating in-depth research on their cavitation characteristics. This study investigates the performance characteristics of a pump turbine through experimental and numerical simulation methods, with consistent results verifying the accuracy of the numerical simulations. The cavitation flow field is numerically analyzed to compare the cavitation distribution and velocity streamlines at different stages of cavitation development. The Q criterion and entropy production method are employed to identify vortex structures and energy loss regions, respectively, exploring the correlation between vortices and energy losses in the cavitation flow field under low-flow pump conditions. The results demonstrate that intensified cavitation generates more multi-scale vortices in the flow field, leading to increased entropy production and reduced energy efficiency. Proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) methods were subsequently applied to extract vorticity characteristics from transient cavitation flow fields, revealing primary energy loss regions and elucidating the evolution and distribution patterns of vortices. The POD analysis shows that low-order modes represent dominant vortex structures, while intensified cavitation increases both the quantity of vortices and their complexity in scale, distribution, and evolutionary frequency. The DMD results further indicate distinct evolutionary patterns for vortices of different scales. This research provides insights into the instability characteristics of cavitation flow fields in pump turbines under low-flow pump conditions and offers theoretical support for optimizing the design of pump turbines to expand their high-efficiency operational range. Full article

The enzymatic hydrolysis of lignocellulosic biomass is often hindered by lignin, which acts as a physical barrier and promotes non-productive enzyme adsorption. This study evaluated the potential of soybean protein in powdered and cavitated forms, along with lactonic sophorolipid biosurfactant (LSLB), to enhance sugar yields from cellulignin derived from sugarcane bagasse, a residue with a high lignin content. A Box–Behnken design was used to investigate the effects of enzyme loading (10–20 FPU/g cellulignin), soybean protein powder (10–30% w/w of dried cellulignin), and LSLB concentration (25–250 mg/L) on glucose and xylose yields. Hydrodynamic cavitation was employed to produce soluble soybean protein, achieving a solubility yield of 44.4% w/w in 10 min. The cavitated protein was compared with powdered protein to assess its impact on enzymatic hydrolysis efficiency. The results showed that hydrodynamic cavitation reduced the required SBP dosage while maintaining sugar yields, allowing 10% w/w of dried cellulignin cavitated SBP to achieve glucose and xylose yields comparable to 25% w/w of dried cellulignin non-cavitated SBP. Specifically, glucose yield increased by 24.92% (from 34.1% ± 1.01 to 42.6% ± 1.4), and xylose yield by 30.86% (from 32.4% ± 0.53 to 42.4% ± 2.21) compared to the no-additive condition. These improvements were linked to enhanced solubility, increased surface area, and reduced particle size in the cavitated protein. This study highlights hydrodynamic cavitation as a novel approach for modifying soybean protein structure to optimize enzymatic hydrolysis in lignocellulosic bioconversion. Full article

As internal combustion engines (ICEs) develop towards higher explosion pressures and lower weights, their structures need to be more compact; thus, the wall thickness of their cylinder liners is reducing. However, intense vibrations in the cylinder liner can lead to coolant cavitation and, in severe cases, penetration of the liner, posing a significant reliability issue for ICEs. Therefore, research on cylinder liner cavitation has attracted increasing interest. Gray cast iron is widely used in cylinder liners for its hardness and wear resistance; however, additional surface plating is necessary to improve cavitation resistance. This study developed a novel surface-modification technology using electroless Ni-P plating combined with high-temperature heat treatment to create cylinder liners with refined grains, low weight loss rate, and high hardness. The heat-treatment temperature ranged from 100 to 600 °C. An ultrasonic cavitation tester was used to simulate severe cavitation conditions, and we analyzed and compared Ni-P-plated and heat-treated Ni-P-plated surfaces. The findings showed that the combination of Ni-P plating with high-temperature heat treatment led to smoother, more refined surface grains and the formation of cellular granular structures. After heat treatment, the plating structure converted from amorphous to crystalline. From 100 to 600 °C, the weight loss of specimens was within the range of 0.162% to 0.573%, and the weight loss (80.2% lower than the plated surface) and weight loss rate at 600 °C were the smallest. Additionally, cavitation resistance improved by 80.1%. The microhardness of the heat-treated plated surface reached 895 HV at 600 °C, constituting a 306 HV (65.8%) increase compared with that of the unplated surface, and a 560 HV increase compared with that of the maximum hardness of the plated surface without heat treatment of 335 HV, with an enhancement rate of 62.6%. Full article

Bubbles in pipes are widely present in marine engineering, transmission, and fluid systems with complex environments. This paper divides tubes into short, longer, and long tubes due to different lengths. In short tubes, the formation, development, and stability of spark bubbles are deeply analyzed through numerical simulation and experimental measurement, and the morphology and period of vortex rings generated in the surrounding fluid are studied. The results show that bubbles in tubes are significantly elongated compared with those in free fields. Changing the parameters of tubes can affect the size and oscillation speed of vortex rings. Secondary cavitation is found in asymmetric positions in longer tubes. The conditions, positions, and periods of multiple secondary cavitations are summarized in a series of experiments on long tubes. It is found that bubbles in tubes are related to the ${\gamma }_t$ and ${\gamma }_L$ tube parameters. More secondary cavitation is easily generated in thinner and longer tubes. In addition, the pumping effect brought about by the movement of bubbles in tubes is studied. By designing reasonable tube parameters, the life cycle of bubbles can be changed, and the pumping efficiency can be improved. This study provides important theoretical support for the reliability of the movement of bubbles and surrounding fluid in tubes and lays a foundation for the optimization and promotion of this technology in practical applications. Full article

This study investigates the onset and decay mechanisms of sheet cavitation within a chamfered orifice under turbulent conditions, using high-speed backlight imaging for detailed frame-by-frame analysis. A distinctive metastable sheet cavitation regime was identified, distinguished by its unique hysteresis behavior during onset conditions, with the ability to control periodicity through variations in cavitation numbers. This new sheet cavitation regime appears at high cavitation numbers, contrary to typical expectations of cavitation inception, highlighting a new potential risk within the range of safe operation for hydraulic systems equipped with control valves. Furthermore, linear growth and rapid collapse of the bubble sheet were observed, which differs from the conventional periodic behavior of sheet cavitation on hydrofoils. The new mechanism to intentionally initiate and control this sheet cavitation regime by manipulating the pressure drop across the orifice could potentially be adopted for industrial applications, particularly in the generation of controlled and dispersed bubbles. Future research should include quantifying bubble dynamics within this regime and assessing the effects of fluid properties and orifice geometries on cavitation characteristics. In summary, this study introduces a new perspective on metastable sheet cavitation, emphasizing its potential applications and importance in the design and operation of fluid systems. Full article

High-speed mixed-flow and axial-flow pumps often exhibit hump or double-hump patterns in flow–head curves. Operating in the hump region can cause flow disturbances, increased vibration, and noise in pumps and systems. Variable-speed ship navigation requires waterjet propulsion pumps to adjust speeds. Speed transitions can lead pumps into the hump region, impacting efficient and quiet operation. This paper focuses on mixed-flow waterjet propulsion pumps with guide vanes. Energy, entropy production, and flow characteristic analyses investigate hump formation and internal flow properties. High-speed photography in cavitation experiments focuses on increased vibration and noise in the hump region. This study shows that in hump formation, impeller work capacity decreases less than internal fluid loss in the pump. These factors lead to an abnormal increase in the energy curve. The impeller blades show higher pressure at peak conditions than in valley conditions. Valley conditions show more pressure and velocity distribution variance in impeller flow passages, with notable low-pressure areas. This research aids in understanding pump hump phenomena, addressing flow disturbances, vibration, noise, and supporting design optimization. Full article

The goal of this study is to investigate the surface morphology changes induced by the cavitation erosion of a coating based on cordierite with an epoxy matrix for an aluminum substrate. The literature review shows a certain lack of knowledge regarding the coating’s resistance to wearing induced by water flow, which is a highly important property of the material immersed in or in contact with water streams. The main idea behind the investigation is that such a protective coating will also improve the cavitation erosion resistance of metal substrates. The protective coatings were based on cordierite filler (88 wt.%) and epoxy resin (7 wt.%). The filler, made of a mixture of kaolin, alumina, and talc, is obtained by a sintering procedure that took place at 1350 °C. X-ray diffraction analysis and scanning electron microscopy were employed in the characterization of the produced filler. The adherence of the obtained epoxy-based protective coating and resistance to water flow were tested by the ultrasonic vibration method (i.e., cavitation erosion testing). Scanning electron microscopy was used for analysis of the coating’s morphology upon cavitation erosion. Based on the value of the cavitation erosion rate and the analyzed final surface damage, it was assessed that the investigated protective coating is resistant to cavitation erosion. Full article

This study presents an innovative approach to processing refractory zinc-bearing clinker through the synergistic application of microwave thermal treatment and ultrasonic-assisted leaching. Microwave irradiation induces phase transformations in the clinker, improving its reactivity and facilitating subsequent zinc dissolution, while ultrasonic cavitation enhances mass transfer by disrupting passivation layers. Key process parameters, including acid concentration, temperature, pulp density, and leaching time, were systematically investigated using response surface methodology (RSM) and central composite design (CCD). The results demonstrate that the optimized process conditions led to a significant increase in zinc recovery from refractory materials. Full article

Acid leaching is an effective method for dephosphorization; however, it is time-consuming and requires a high amount of acid consumption, resulting in increased production costs and environmental risks. This work aims to remove silicon, aluminum, and phosphorus from high-phosphorus oolitic magnetite concentrate through high-pressure alkaline leaching and ultrasonic acid leaching. Compared with traditional acid leaching processes, the sulfuric acid dosage can be significantly reduced from 200 kg/t to 100 kg/t, and the pickling time is shortened from 60 min to 10 min. Thermodynamic and kinetic studies have demonstrated that acid leaching facilitates apatite dissolution at low temperatures, whereas the dephosphorization reaction is controlled mainly by diffusion. The application of ultrasonic waves leads to finer particle sizes and greatly increased specific surface areas, thereby accelerating the diffusion rate of the leaching agent. Furthermore, microscopic analysis revealed that under the influence of ultrasonic waves, numerous micro-fragments and pores form on particle surfaces due to cavitation effects and mechanical forces generated by ultrasonic waves. These factors promote both the reaction rates and diffusion processes of the leaching agent while enhancing the overall leaching efficiency. Full article

This study addresses the issue of biofouling on marine aquaculture cages, where organisms like algae and purple mussels negatively impact both the safety of the aquaculture environment and the integrity of the cages. To solve this problem, the paper introduces a cage cleaning device based on the cavitation jet principle. Using finite volume simulation software, the cavitation process of the device’s nozzle was modeled, with the gas-phase volume fraction used as the evaluation metric. Key experimental factors, such as the second section throat contraction angle, second section throat radius, and end diffusion angle, were analyzed through single-factor and quadratic regression orthogonal experiments to assess their effect on the cavitation performance. The optimal combination of nozzle parameters was determined to be a second section throat contraction angle of 41.047°, a second section throat radius of 0.834 mm, and an end diffusion angle of 35.495°. Under these conditions, the gas-phase volume fraction reached 0.941, indicating optimal cavitation performance. To validate these findings and further optimize the nozzle’s operational parameters, a nozzle cavitation test bench was constructed. Test results demonstrated that when the target distance was set at 15 mm and the angle at 20°, the surface roughness and maximum surface depth of the target were 6.215 μm and 22.030 μm, respectively, with the nozzle exhibiting the best cavitation effect at these settings. This nozzle design meets the requirements for efficient mesh cleaning, and the research provides valuable insights for future development and optimization of cleaning devices for aquaculture net cages. Full article

A balanced flowmeter not only inherits the advantages of orifice plate flowmeters but also stabilizes the flow field, reduces permanent pressure loss, and effectively increases the cavitation threshold. To perform an in-depth analysis of flow characteristics through the perforated plate and achieve performance optimization for the liquid hydrogen (LH₂) measurement, a numerical calculation framework is established based on the mixture model, realizable turbulence closure, and Schnerr–Sauer cavitation model. The model is first evaluated through comparison with the liquid nitrogen (LN₂) experimental results of a self-developed balanced flowmeter as well as the measuring setup. The flow coefficient and pressure loss coefficient are especially considered, and a comparison is made with the orifice plane considering cavitation and non-cavitation conditions. The cavitation cloud and temperature contours are also presented to illustrate the difference in the upper limit of the Re between water, LN₂, and LH₂ flow. The results show that compared to LN₂ and water, LH₂ has a larger cavitation threshold, indicating a wider range of Re number measurements. Full article

Antibiotics in aquaculture pose significant environmental risks due to their widespread distribution in water, impacting ecosystem health. To address this hot issue, an ozone-assisted hydrodynamic cavitation (OAHC) system was developed for the efficient treatment of aquaculture seawater contaminated with antibiotics. The system demonstrated remarkable efficiency, achieving complete degradation of eight antibiotics within a reaction time of 20 s. At the same time, water quality parameters, such as dissolved oxygen (increased from 9.79 mg/L to 13.19 mg/L) and nitrite nitrogen (reduced from 0.14 mg/L to 0.01 mg/L), significantly improved post-treatment. The OAHC-based system minimized harmful by-products, ensuring compliance with Chinese water quality standards. As a supplementary study, a laboratory-based simulated experiment was conducted with FLO as the target antibiotic. The investigation of kinetics and mechanisms indicated that •OH plays a predominant role in the OAHC-based aquaculture seawater treatment system. As global regulations tighten on antibiotic discharge, OAHC-based technology is poised to become a cornerstone of next-generation water treatment solutions. Future research should prioritize field-scale validation and real-time monitoring to accelerate industrial adoption. Full article

As global shipping accelerates toward a green and low-carbon transformation, submerged water jet propulsion has emerged as a promising alternative to traditional propellers due to its high speed efficiency, noise reduction, and adaptability. This study establishes a high-fidelity CFD (computational fluid dynamics) model incorporating vehicle body wake characteristics, validated through open-water experiments. A comparative analysis reveals that the vehicle body wake improves propulsion efficiency by 4.66% for conventional propellers and 2.32% for submerged water jet systems in near-surface operations while exacerbating cavitation-induced efficiency losses by 1.7% and 1.0%, respectively. Notably, submerged water jet propulsion demonstrates superior performance under high-velocity conditions, achieving 5–12.27% higher efficiency than conventional propellers across both open-water and vehicle body wake-affected scenarios. These findings substantiate submerged water jet propulsion’s advantages in complex flow fields, offering critical insights for marine propulsion system optimization. Full article

This paper presents experimental results regarding the development of new alloys from the binary ZnCu and ternary ZnCuMg systems. The alloys had controlled chemical compositions and were annealed at 300 °C and 400 °C, with holding times of 5 h and 10 h, followed by air cooling. Mechanical properties (tensile strength, yield strength, elongation, and elastic modulus) were determined. Structural analysis conducted after different heat treatments revealed that homogenization transforms the dendritic structure into a granular structure with intergranular eutectic presence. Biodegradation behavior showed that the ternary alloy exhibits higher degradation rates than the binary alloy. Applying the homogenization heat treatment has a good influence on the binary alloy only, not on the ternary alloy. Our research shows that that the complex alloying of zinc with copper and magnesium may improve cavitation behavior, doubling both the MDE_max parameter and cavitation resistance expressed by R_cav. Full article