Search Results (2,366)

To explore the influence of inter-formation variables on swimming performance during fish schooling, this paper adopts the sharp interface immersed boundary method based on virtual cells to conduct numerical research on the swimming of three-fish and four-fish swarms with different formations and spacings. The study finds that both streamwise spacing and lateral spacing have significant impacts on the swimming performance of fish schools. In the three-fish formation, when the tandem arrangement has a streamwise spacing of 1.3 times the body length (L), the trailing fish achieve the highest swimming efficiency; when the parallel arrangement has a lateral spacing of 0.25L, the fish in the middle position exhibits the optimal swimming performance. In the four-fish formation model, fish in symmetric positions within the same swarm have similar hydrodynamic performance. For the diamond formation, under the configuration of streamwise spacing 1.2L and lateral spacing 0.5L, the propulsive efficiency of the trailing fish is markedly diminished; however, for the rectangular formation, all trailing fish obtain lower swimming efficiency, and a stable 2S-type vortex structure appears in the wake under the configuration of streamwise spacing 1.5L and lateral spacing 0.5L, which is conducive to thrust generation. The conclusions of this paper can provide certain hydrodynamic advantages and support the development of bionic underwater vehicles and robot technology. Full article

In-line cavitation is relevant to many continuous processes; however, its intensity depends on flow rate, available pressure, temperature, fluid properties, and plant conditions, complicating the maintenance of a repeatable regime within a prescribed band. This paper presents the DVRA, an actuated Venturi module with a Reuleaux triangular cross-section for in-operation regulation of hydrodynamic cavitation through device configuration. The novelty lies in combining two degrees of freedom—an in-operation adjustable hydraulic throat and boundary-imposed swirl forcing—within a compact in-line device: all rotation is confined to the module, and no rotation of the process line is required. The hydraulic throat is tuned via an actuated elastomeric liner, while swirl is generated by external end collars. Reproducible operational conventions are introduced together with a normalized input set and a configuration-space formalism that distinguishes admissible from achievable configurations. Regulation is cast as a control-oriented inverse mapping given a target band for an in-line estimated cavitation indicator and standard industrial measurements of flow rate, pressure, and temperature; configuration commands are selected to keep the indicator within bounds. The contribution is methodological and provides an implementable basis; comprehensive validation and performance benchmarking are outside the scope of this paper and will be reported separately. Full article

Humic substances (HSs) pose a significant challenge to safe drinking-water production due to their ubiquity, limited removal by conventional methods, and their role in forming toxic disinfection by-products, reinforcing the need for more efficient, energy-favorable, and scalable treatment technologies. This study developed and evaluated a compact hydrodynamic cavitation (HC) system that simultaneously induces coagulation and generates microbubbles for flotation-based HS removal. For the first time, HC is explored as a multifunctional unit capable of integrating rapid mixing, coagulant destabilization, and flotation within a single device. Optimal coagulation conditions were established at pH 5.0 and 9.5 mg L⁻¹ of ferric chloride. Process optimization using a Rotated Central Composite Design demonstrated that inlet pressure, flotation time, and initial HS concentration were the dominant operational factors, enabling the HC system to achieve a maximum removal efficiency of 81.9%. Five Venturi geometries with divergent angles of 4°, 8°, 11°, 14°, and 90° were investigated, with the 8° Venturi exhibiting superior performance due to stable microbubble formation and effective coagulant dispersion, as confirmed by CFD analyses. Comparative tests with a conventional Flotest unit showed that achieving similar efficiencies required at least 30% saturated water. In contrast, the HC system delivered equivalent removal in continuous flow without external air saturation. These findings demonstrate the potential of HC as an integrated coagulation–flotation core and highlight its promise as a compact, energy-efficient, and scalable technology for natural organic matter removal in water treatment. Full article

Seabed response and local scouring around pile groups under combined wave–current loading pose critical threats to the stability and long-term performance of offshore structures, particularly those supporting offshore renewable energy infrastructures. In this study, we present a systematic experimental investigation on the pore-water pressure and local scour around pile groups subjected to regular waves, combined regular wave–current conditions, and irregular waves generated using the JONSWAP spectrum under wave-only conditions. Pore-water pressures and seabed morphology were analyzed for different hydrodynamic conditions, pile spacings, and pile arrangements. The experimental results demonstrate that the presence and magnitude of current are the dominant factors controlling scour development. Increasing the current velocity from 0 to 0.25 m/s leads to a three (3) to five (5) times increase in maximum scour depth, whereas comparable variations in wave height and wave period produce relatively small effects. The direction of a current affects the location of maximum scour, with the wave–forward current condition promoting the development of an interconnected scour area within the pile array and wave–opposing current condition, shifting local scour toward downstream piles. Small-spaced piles ($G/D$ = 1) intensify hydrodynamic interactions and increase scour depth by approximately 30–40% compared with wider spacing. Irregular waves generate more spatially distributed but shallower scour than regular waves of comparable wave characteristics. These findings provide insights into the mechanisms governing seabed instability around pile group foundations and contribute to more sustainable design and operation of offshore infrastructure, such as offshore wind turbine foundations. Full article

Using computational fluid dynamics (CFD) coupled with the volume of fluid (VOF) method, we developed an analytical framework to quantify free-surface suction around ship hulls. The DTMB 5415 benchmark hull was employed to investigate the mechanisms by which underwater tail fins influence surface wake dynamics. We systematically evaluated the effects of tail-fin span on hydrodynamic drag and free-surface suction across the investigated speed range. Within the Froude number range of 0.05–0.45, underwater tail fins reduced air entrainment by optimizing hull attitude and attenuating stern waves. Free-surface suction capacity exhibited a positive correlation with vessel speed and a negative correlation with tail-fin span length. At Fr = 0.45, the free-surface suction capacity of the bare hull was 13.78 times greater than that at Fr = 0.15. At this speed, the L₄ tail-fin configuration achieved a 13.292% reduction in free-surface suction. In contrast, the L₂ tail-fin configuration provided a suction reduction of only 9.98%. The optimal tail-fin span represents a trade-off between drag reduction and wake suppression, as longer spans do not necessarily yield superior performance. Under cruise conditions (Fr = 0.25–0.35), the L₂ tail-fin configuration exhibited optimal performance, achieving a 5.292% reduction in drag and a 13.492% reduction in free-surface suction. Across the tested Froude number range of 0.05–0.45, underwater tail fins simultaneously improved hydrodynamic performance and reduced free-surface suction, thereby effectively suppressing bubble wake formation. Full article

Floods pose significant risks to human lives, infrastructure, and the environment. Timely and accurate flood forecasting plays a pivotal role in mitigating these risks. This study proposes a Digital Twin proof-of-concept framework aimed at improving flood forecasting and validated its effectiveness through a pilot study of the 2021 flood event in Luxembourg. The baseline forecasting method combines GloFAS ensemble streamflow forecasts with a high-resolution flood hazard datacube generated using a LISFLOOD-FP hydrodynamic model and then averaging among the member forecasts. To dynamically update the flood forecasts and improve their accuracy, the framework integrates satellite-based Earth observations (EOs)—specifically Sentinel-1-derived flood probability maps from the Global Flood Monitoring service—via a particle filter-based data assimilation (DA) process. As such, the simulations with more coherence with the observed Sentinel-1-derived flood probability maps are prioritized. This results in a Digital Twin capable of delivering daily flood depth forecasts, at detailed spatial resolution, up to 30 days ahead, with reduced prediction uncertainty. Using the 2021 flood event, we evaluate the performance of the Digital Twin in assimilating EO data to refine hydraulic model simulations and issue accurate flood forecasts. Although certain challenges persist—particularly the difficulty in quantifying the error structure of GloFAS discharge forecasts—the proposed approach demonstrates clear improvements in forecast accuracy compared to open-loop simulations. As a result, the approach reduces water level prediction errors by an average of 15–33% and increases the Nash–Sutcliffe Efficiency of discharge predictions by approximately 15–36%. Future work will aim to refine the flood hazard datacube and advance the characterization and modeling of uncertainties associated with both GloFAS streamflow forecasts and Sentinel-1-derived flood maps, thereby further enhancing the system’s predictive capability. Full article

Background and Objectives: Pelvic ring injuries with symphyseal disruption are classically associated with high-energy mechanisms such as motor vehicle collisions. Recently, waterslides have emerged as an underrecognized but distinct source of severe pelvic trauma. Waterslide-related pelvic trauma represents a distinct biomechanical entity characterized by a supine or semi-supine body position at splashdown, extreme forced hip abduction, asymmetric lower-limb positioning, and abrupt hydrodynamic deceleration. The high descent velocity, abrupt hydrodynamic deceleration, and forced hip abduction at water entry may combine to generate open-book-type pelvic injuries. Evidence guiding diagnosis and surgical management in this setting remains scarce. Materials and Methods: We retrospectively analyzed a consecutive series of adult patients sustaining waterslide-related anterior–posterior compression type II (APC2) pelvic ring injuries. Demographic data and the body mass index (BMI), fracture classification, surgical strategy, complications, and functional outcomes were reviewed. Only patients with complete imaging, operative records, and follow-up were included. Results: Four patients (38–72 years) met the inclusion criteria. All sustained rotationally unstable open-book pelvic injuries and were classified as APC2; three were AO/OTA 61B2.3 and one 61B3.3. All patients were overweight or obese (BMI 27.2–31.2). Pelvic binders provided an effective acute reduction in symphyseal diastasis; however, in one bilateral injury, CT imaging obtained with the binder in situ masked posterior ligamentous instability. Definitive surgical fixation was performed in all cases. Early mechanical failure occurred in two patients treated with short anterior symphyseal plate constructs. In the bilateral injury, isolated anterior fixation failed repeatedly until posterior sacroiliac stabilization was added. No deep infections or thromboembolic events occurred. Although two patients required short observational ICU stays, none were admitted for hemodynamic instability or pelvic bleeding. Conclusions: At 12-month follow-up, three patients achieved pain-free ambulation without assistive devices, while one patient required intermittent use of a single crutch; all patients regained independence in daily activities. Waterslide accidents represent a high-energy injury mechanism capable of producing severe APC2 pelvic disruptions, particularly in patients with an elevated BMI. Awareness of this mechanism and meticulous assessment of posterior stability are essential to avoid under-treatment and mechanical failure. Full article

Tuned liquid dampers (TLDs) are widely used in structural vibration mitigation, but they are limited by their damping frequency to use as passive damping equipment. To enhance the damping performance of the conventional TLD, a unique layered tuned liquid damper (LTLD) filled with water and diesel is proposed. The interfacial wave coupling mechanism for broadband energy dissipation has not been previously explored in sloshing-type dampers. A series of frequency-sweeping tests were carried out in the laboratory to compare the vibration suppression performance of the proposed LTLD against conventional TLD. The dampers were installed on an elastic supporting structural platform (SSP) with a height of one meter, and the bottom was horizontally excited with different amplitudes and frequencies using a hexapod motion simulator. The results indicate that the LTLD showed a better damping performance than the TLD under small-amplitude excitation and achieved optimization at two peaks. The separation surface movement dissipated the liquid motion’s energy and enhanced the hydrodynamic force in the horizontal direction. However, the damping effect of the LTLD weakened when the two liquids were no longer immiscible under large-amplitude excitation. Therefore, we recommend utilizing the LTLD to improve structural damping performance when $d_{max}/L$< 0.04984. In addition, the LTLD reduced the maximum wall pressure by about 25% in the transient state under large-amplitude excitation. This study presents experimental evidence that a water–diesel LTLD achieves broadband damping through interfacial wave coupling. The stable interfacial waves enhance energy dissipation and excite new vibration mitigation frequencies, offering a novel approach to overcoming the narrow-band limitation of conventional TLD. Full article

Hydrodynamic Energy-Saving Devices (ESDs) have become effective solutions to improve vessel operational efficiency in maritime applications. A novel toroidal boosted appendage which is installed behind the KP505 propeller, featuring an integrated self-driving turbine and closed-loop blade structure, is proposed to simultaneously enhance propulsion efficiency, rectify wake non-uniformity, and mitigate vortex-induced energy losses. High-fidelity Computational Fluid Dynamics (CFD) simulations are conducted to evaluate the hydrodynamic performance of the device, aiming to minimize side effects such as the generated tip vortices and pressure pulses. Based on the STAR-CCM+ software, the Realizable k − ε turbulence model is adopted to simulate the flow fields of the propeller with and without the novel appendage. This paper focuses on investigating the influence of the new appendage on the propeller’s propulsion performance and conducts open-water performance prediction and wake field comparative analysis under different advance coefficients. The results show that the new appendage significantly improves the wake situation behind the propeller disk, changing from diffusion-flow to constriction-flow and achieving a uniform distribution of the wake field. The propulsion efficiency is increased by up to 7.453% at the design advance coefficient, and the novel toroidal boosted appendage is confirmed to have the potential to enhance the hydrodynamic performance of the propeller. Full article

Inspired by observations of manta ray gliding, this study designed and evaluated a more biologically accurate pectoral fin bending model. We assessed its hydrodynamic performance using six-degrees-of-freedom (6-DoF) Computational Fluid Dynamics (CFD) simulations, which were validated by tethered water tunnel experiments. Key findings reveal that symmetric bending significantly impacts longitudinal stability, increasing the pitch angle to nearly twice that of the flat-wing model (80° model) but compromising gliding efficiency. During this symmetric motion, the lift-to-drag ratio (K) minimum point is significantly delayed as the bending angle increases, following a negative quadratic trend. Conversely, asymmetric bending triggers a sharp 3.5-fold increase in the roll angle (80° vs. 30° model) and produces significant lateral displacement. Importantly, “roll-induced yaw” was confirmed as the dominant mechanism for lateral control, contributing up to 88.5% of the lateral force in the 80° model, despite minimal changes in the yaw angle. These findings reveal the intrinsic trade-offs between fin deformation, gliding efficiency, and attitude control, providing a theoretical basis for active configuration optimization and control strategies for bionic gliders. Full article

Resonant Wave Energy Converter 1 (REWEC1) is a submerged caisson breakwater integrating a device designed to absorb incoming wave energy. Although the wave energy-extraction performance of this system and its hydraulic characteristics have been extensively investigated, its potential role in reducing coastal inundation, as an alternative to traditional rubble-mound breakwaters, has not yet been examined. In this context, the present study analyzes the mitigation effects on coastal flooding induced by the installation of REWEC1 barriers. The analysis focuses on the coast of Cetraro, located along the Tyrrhenian Sea in the province of Cosenza (Calabria, Southern Italy). The effectiveness of REWEC1 farms in reducing coastal flooding was assessed by considering fixed-air and no-air operation modes, as well as different spatial configurations. The input wave conditions were propagated in the nearshore using the SWAN model to simulate wave–structure interactions, while the XBeach model was employed to investigate coastal inundation processes based on the wave field behind the caissons, also accounting for Sea Level Rise (SLR). The results were evaluated in terms of maximum flooded areas and water penetration lengths along the emerged coast, as well as wave run-up and set-up along selected transects. To assess the robustness of the results, a sensitivity analysis was carried out by varying the transmission coefficients of the REWEC1 units within a plausible uncertainty range, and the corresponding variability in flooding indicators was quantified. The numerical results indicate a progressive reduction in these hydrodynamic response indicators as the spacing between adjacent REWEC1 devices decreases, and show that the relative mitigation performance of REWEC1 remains consistent when accounting for uncertainties in wave–structure interaction parameters. Further analyses were conducted to compare the effectiveness of REWEC1 farms with that of conventional rubble-mound breakwaters in reducing coastal flooding. Full article

The demand for effective downstream processing of adeno-associated virus (AAV) is increasing as gene therapies advance toward broader clinical applications. Robust, efficient, and scalable ultrafiltration and diafiltration (UF|DF) operations are essential for generating high-quality AAV preparations, with tangential flow filtration (TFF) serving as a critical unit operation for vector concentration, impurity reduction, and buffer exchange while maintaining viral functionality. Development of TFF processes requires careful consideration of membrane characteristics—including chemistry, pore size or channel architecture—as these parameters directly influence vector retention, fouling behavior, and overall process efficiency. Equally important is the optimization of critical process parameters such as recirculation rate, transmembrane pressure (TMP), and total processing time, all of which govern hydrodynamic performance and product quality. This study assessed two Sartocon^® Hydrosart^® TFF cassette architectures—ECO-Screen and E-Screen—for the ultrafiltration and diafiltration of AAV8 clarified lysate. Through flux characterization and controlled small-scale evaluations, cassette-specific operating regions were defined. Both configurations supported high viral genome retention; however, the E-Screen geometry achieved faster processing and superior removal of host–cell protein and DNA contaminants, whereas the ECO-Screen format allowed for efficient operation under reduced pump rates and, therefore, lower shear conditions. Reproducibility assessments demonstrated minimal run-to-run variability, confirming the robustness of the optimized operating parameters. A 10-fold scale-up further validated the linearity and predictability of the UF|DF process, with consistent impurity-reduction profiles and only modest deviations in viral recovery. Collectively, these findings provide a quantitative basis for rational cassette selection in AAV purification workflows and establish a scalable, scientifically grounded UF|DF framework applicable across development and manufacturing scales. Full article

To investigate the heat-generation mechanisms of journal bearings under different whirl motion and to clarify the corresponding temperature distribution characteristics, a computational fluid dynamics-based method was developed. The model incorporates temperature-dependent lubricant viscosity and employs an unsteady dynamic-mesh updating approach based on structured grids, enabling the automatic iterative tracking of the journal center during whirl motion. A thermal-effect analysis model that accounts for journal whirl trajectories was thereby established. The whirl orbit shape is characterized using elliptical eccentricity, and the effects of whirl direction, elliptical eccentricity, and whirl frequency on the circumferential temperature and pressure distributions of the journal are examined. Results show that under forward whirl, increasing whirl frequency and elliptical eccentricity initially enhances and then weakens local hydrodynamic pressure and viscous shear dissipation in the oil-film convergent region, producing pronounced first-order circumferential temperature nonuniformity and a high risk of thermal bending at intermediate frequencies. Under backward whirl, hydrodynamic effects are reduced and heat generation shifts from localized concentration to global shear dissipation, forming a relatively uniform second-order circumferential temperature field. Increasing elliptical eccentricity causes the whirl orbit to become more linear, improving load-carrying capacity and heat-transfer performance and thereby mitigating thermally induced vibration and oil-film whirl instability. Full article

Heterogeneous ion-exchange membranes (IEMs) are cost-effective but suffer from low electrochemical efficiency due to surface inhomogeneities. While surface coating with homogeneous ionomers is a known modification strategy, its direct impact on electro-hydrodynamic behavior and desalination performance has rarely been visually verified. In this study, we employed a microfluidic platform to visualize and quantify the performance enhancement of Nafion-coated heterogeneous cation exchange membranes (CEMs). Contrary to conventional theories linking electro-convection (EC) to surface hydrophobicity, our results show that the hydrophilic Nafion coating significantly amplifies EC vortices. Direct visualization revealed that the coating layer acts as an electrical nozzle, inducing intense electric field focusing that triggers macroscopic vortex growth. Furthermore, we visually confirmed that the coating layer physically seals catalytic sites, effectively suppressing parasitic water-splitting reactions. In continuous desalination experiments, this hydrodynamic synergy led to a 32% increase in current efficiency (CE: 1.23) and an 18% increase in salt removal ratio (SRR: 79.4%) compared to bare membranes in the over-limiting regime. These findings demonstrate that inducing controlled hydrodynamic instability via surface modification is a dominant factor for high-efficiency desalination. Full article

Nucleation remains one of the least understood steps during protein crystallization, although it strongly impacts product quality attributes, including total crystal numbers, final crystal size distributions, and thus downstream processing. In this work, the nucleation behavior of Lactobacillus brevis alcohol dehydrogenase (LbADH) wild type (WT) and five mutants (Q207D, Q126H, K32A, D54F, and T102E) is investigated in a stirred 7 mL crystallizer monitored by in situ multi-angle dynamic light scattering (MADLS). Nucleation was studied with highly pure homotetrameric LbADHs by establishing a crystallization, lyophilization, and re-solubilization protocol combined with size exclusion chromatography (SEC) and size exclusion high-performance liquid chromatography (SE-HPLC), yielding tetramer purities above 94% and removing low molecular weight impurities. During stirred batch crystallizations initiated by the addition of polyethyleneglycol 550 monomethyl ether (PEG 550 MME), SEC and SE-HPLC revealed decreasing tetramer peak areas but essentially constant peak apex positions, indicating that no long-lasting oligomeric intermediates accumulate at detectable levels. Time-resolved MADLS measurements using a custom-made flow-through cuvette in a bypass to the stirred crystallizer uncovered transient cluster populations. All protein variants exhibited an initial tetramer peak, followed by the formation of larger aggregates and a rapid rise in signal above a hydrodynamic diameter of 1000 nm, coinciding with the onset of macroscopic turbidity. A simple mesoscale nucleation model was formulated, yielding end-of-nucleation times, crystallized fractions, critical soluble concentrations, and apparent nucleation rate constants. The crystal contact mutations modulate both the timing and magnitude of the nucleation burst (rapid build-up of nuclei/cluster populations). The mutant Q207D showed strongly attenuated nucleation compared to the WT, whereas the other mutants (K32A, D54F, and particularly T102E) display markedly accelerated nucleation at nearly invariant critical concentrations. The combined workflow demonstrates how in situ MADLS, together with a tailored kinetic description, can provide mechanistic insight into protein nucleation in stirred batch crystallizers. Full article