Hydrodynamic Device Research Articles

Mathematical Modeling of the Transport of H2O–CH4 Steam–Gas Mixtures in Hydrodynamic Devices: The Role of Helical Screws

Mathematical Modeling of the Transport of H2O–CH4 Steam–Gas Mixtures in Hydrodynamic Devices: The Role of Helical Screws

Cavitating flow through a Venturi using CFD: effects of inlet and outlet pressures

Hydrodynamic cavitation is a complex physical phenomenon that appeared in hydraulic systems (pumps, turbines, valves, Venturi tubes …etc.) when the fluid pressure decreases below the saturated vapor pressure. The works carried out in this study aimed to get a better understanding of the cavitating flow phenomenon. For this, we have numerically studied a cavitating bubbly flow through a venturi nozzle. The cavitation model is selected and solved using commercial code computational fluid dynamics (CFD). The numerical results are compared to the previous experimental and numerical data.The obtained results showed that the effect of the inlet pressure (10, 7, 5 and 2 bars) and outlet pressures (6.5, 6, 5, 4, 3.5, 1.5, and 1 bars) of the Venturi on pressure, velocity of the fluid flow and the vapor fraction formation. We found that the inlet and outlet pressures of the venturi are strongly affected on the evolution of the pressure, velocity and vapor fraction formation in the cavitating flow. The results presented in this study provide insight and useful guidance to the designer of hydrodynamic cavitation devices, identifying key geometrical and physical parameters of cavitation onset and intensification that can be manipulated to achieve the desired level of cavitation flow.

Comparison of devices used for continuous production of emulsions: Droplet diameter, energy efficiency and capacity

Liquid-liquid emulsions are used in various sectors, including food, health care, personal care, home care and nutrition. There is an increasing need for developing equipment and devices for producing emulsions with desired drop size distribution (DSD) in a continuous mode of operation to fulfil market demands. In this work, we experimentally investigated droplet size distributions of emulsions made using selected cavitation-based emulsion producing devices operated in a continuous mode. Emulsion production devices considered in this work are wet mill, Soldo cavitator, Dynaflow cavitator and different scales of vortex based hydrodynamic cavitation devices. The continuous emulsion production experiments were performed for generating 5 % rapeseed oil-in-water emulsions using different devices. Performance of different emulsion production devices based on energy efficiency of emulsification (η), energy consumption per kilogram of emulsion (E), interfacial area created per unit energy consumption (Anet)P, Sauter mean diameter (d32), other characteristic diameters (D10,D50,D90), and drop size distribution (DSD) was compared. Among all the devices, vortex based hydrodynamic cavitation (HC) devices showed excellent performance in terms of lower d32 and DSD with low E and high η. The smallest scale of vortex-based HC device exhibited the highest efficiency (∼0.16 % at E = 2.6 kJ/kg) over the entire range of E compared to the other devices considered in this study. The presented data and analysis will be useful for selection of emulsion producing devices for desired emulsion characteristics and production capacity.

Estimating droplet size distribution of emulsions using turbidity measurements: A soft sensor based on artificial neural network

Ability to characterise droplet size distribution (DSD) of emulsions in real-time is essential for on-demand production of customised emulsions. In this work, for the first time, we demonstrate a possibility of estimating full DSD of oil in water emulsions from turbidity measurements using a single wavelength light source. We used recently published data of DSD and turbidity measurements of rapeseed oil in water emulsions (oil volume fractions of 0.15, 0.3 and 0.45) produced with vortex based hydrodynamic cavitation device. Measured DSDs are represented by weighted sum of three log-normal distributions. We developed an approach and a methodology based on artificial neural network (ANN) to estimate DSD from a single measurement of turbidity. A mathematical model is developed to simulate measured turbidity profiles using the known DSDs. The validated model was then used to generate simulated data of turbidity and oil volume fraction pairs (105 pairs). This synthetic data was used to train ANN which used turbidity and volume fraction as input and eight parameters of DSD as output. The developed ANN was able to capture the experimentally measured characteristic diameters and DSDs very well for three oil volume fractions and four different number of passes. The presented methodology and results will be useful for developing an in-line soft sensor based on turbidity measurements for real time estimation of full DSDs of emulsions.

Preparation of water-soluble cadmium sulfide quantum dots with narrow small-size distribution by controlling hydrodynamic cavitation device parameters

With the increasingly broad application of quantum dots in many fields, how to further improve the performance of quantum dots in various aspects has become an urgent problem to be solved. In this study, hydrodynamic cavitation (HC) technology was applied for the first time in the preparation of quantum dots. Specifically, cadmium sulfide quantum dots (CdS QDs) with small particle size, narrow distribution, high concentration and large Stokes shift are prepared. Firstly, CdS precipitation was obtained in an aqueous solvent, using cadmium nitrate tetrahydrate (Cd(NO3)2·4H2O) and sodium sulfide nonahydrate (Na2S·9H2O) as Cd and S sources, respectively. Subsequently, CdS QDs were formed from top to bottom through hydrodynamic cavitation reactor, which generates high temperature, high pressure, high-speed jets, shear forces, and shock waves. In summary, the intrinsic advantages of HC technology offer a new opportunity for manufacturing large-scale quantum dots with superb performance.

One-Step Microfluidic Fabrication of Bioinspired Microfibers with a Spindle-Knot Structure for Fog Harvest.

Many biomimetic microfibers have been designed from spider silk to collect water efficiently from humid air as a result of its periodic spindle-knot structure, which enhances the direct movement and convergence of captured fog droplets. Here, a hydrodynamic flow-focusing microfluidic device with a theta-shaped tube is designed for the one-step fabrication of bioinspired microfibers with a spindle-knot structure for fog harvest. The morphology of the structured microfibers, including height, width, and spacing of spindle knots, can be adjusted readily by regulating the flow rate of specific phases. The production rate of these structured microfibers can reach 1100 cm/min. Moreover, the capture, transportation, and collection performance of fog droplets on various microfibers are investigated in a fog collection platform. It is demonstrated that our one-step microfluidic device presents a ready method for the fabrication of structured microfibers with spindle knots, which provide a significant facilitation on efficient fog capture and water collection.

Study on the Hydrodynamic Performance of Swing-Type Flapping Hydrofoil Bionic Pumps Affected by Foil Camber

The flapping hydrofoil bionic pump is an innovative hydrodynamic device that utilizes flapping hydrofoil technology. Flapping hydrofoil bionic pumps are crucial in addressing issues like inadequate river hydropower and limited water purification capabilities in flat river network regions. Optimizing the foil characteristics is essential for enhancing the hydrodynamic efficiency of the flapping hydrofoil bionic pump. This study investigates the impact of foil camber parameters on the hydrodynamic performance of swing-type asymmetric flapping bionic pumps. The NACA series standard foils with varying cambers are analyzed using the overlapping grid technology and finite volume method. The thrust coefficient, flow rate, pumping efficiency, and flow field structure of the flapping hydrofoil bionic pump are examined under pressure inlet conditions with the foil camber. The findings indicate that increasing the foil’s curvature within a specific range can greatly enhance the maximum values of thrust coefficient, propulsive efficiency, and pumping efficiency of the flapping hydrofoil bionic pump. Specifically, when the foil curvature is 6%c, the maximum value of the instantaneous thrust coefficient of the flapping hydrofoil bionic pump is significantly improved by 31.25% compared to the symmetric foil type under the condition of an oscillating frequency of f = 1 HZ. The flapping hydrofoil bionic pump achieves its maximum pumping efficiency when the oscillation frequency is within the range of f ≤ 2.5 Hz. This efficiency is 11.7% greater than that of the symmetric foil, and it occurs when the foil curvature is 8%c. Within the frequency range of f > 2.5 Hz, the flapping hydrofoil bionic pump that has a foil curvature of 6%c exhibits the highest enhancement in pumping efficiency. It achieves a maximum increase of 12.8% compared to the symmetric foil type. Nevertheless, the average head was less than 0.4 m, making it suitable for ultra-low-head applications.

Analysis for Levitation of EHD and Electrostatic Propulsion Device in Direction of Gravity using Optical Flow Method

Electro hydro dynamic (EHD) and electrostatic propulsion devices have no moving parts and, in the air, operate on electrical energy. Thus, electric propulsion systems without moving parts such as propellers are expected to be developed in the future. EHD devices levitate in the direction opposite the direction of gravity when a high voltage is applied. In this study, detailed properties of the accurate propulsion direction, speed, and acceleration were clarified by imaging analysis. The analysis clarified that even if the orientation of the device was initially tilted from a horizontal line, the device was made to levitate vertically upward in the same direction as the direction of gravity, and a restoring force acts to return the orientation to a horizontal line during the levitation. These phenomena are very strange and different from those of drones with propellers. When the device levitates, the acceleration does not become constant immediately after the voltage is applied, but after passing through 0, it increases linearly in temporal duration of sub 0.1 s and saturates. The saturation of the acceleration changed with the input voltage. In this study, we used optical flow analysis, which is a well-known and proven imaging analysis, to analyze the trajectory of an object using image analysis. Detailed levitation properties have not been analyzed until now. First, as a result of analyzing the free flight characteristics of a single plate electrode, a single unit that has been very well researched in many papers, it was revealed that the direction of propulsion changes from the lateral direction to the direction of gravity midway through. Analysis on the levitation property of a EHD device, which has a special structure with a large area on the ground at a triangular center, and a propulsion device revealed that the EHD device can only levitate in almost the same direction as gravity. The maximum acceleration of the EHD device in these experiments was estimated to be 7 m/s2 .

Realizing the multifunctional microfluidic flow manipulation based on hydrodynamic metamaterials

From their initial application to the fields of chemistry and biology, microfluidic chips used as micro total analysis systems have developed into new technologies to satisfy the requirements of various societal industries. Microchannels are essential components of microfluidic chips; they play a vital role in connecting the inlet and outlet as well as determining the flow distribution and reagent mixing. Microfluidic research has always been devoted to minimizing energy dissipation, fluid resistance, and pressure drop to realize energy-efficient microfluidic chips. This study proposes a new theory for manipulating the flow in microchannels based on hydrodynamic metamaterials according to the spatial transformation theory. In particular, hydrodynamic metamaterials are specifically designed to construct flow shifters, flow splitters, and flow combiners, and theoretical and numerical simulations are performed to assess their hydrodynamic performance. The systematic design of hydrodynamic metamaterial devices proposed in this work establishes a theoretical framework to achieve a steady flow state without inducing unstable flow disturbances in complex-shape microchannels.

Evaluating performance of vortex-diode based hydrodynamic cavitation device scale and pressure drop using coumarin dosimetry

The present work investigates the hydrodynamic cavitation (HC) performance of vortex-diode based devices, which show early inception and superior cavitational performance compared to conventional devices. The study provides novel data on the cavitational efficiency at different operating pressures for two sizes of cavitation devices, addressing a gap in the literature. Using coumarin as a chemical dosimeter in acidic conditions, the study tracked the formation of 7-hydroxycoumarin (7OHC), a hydroxylation product of coumarin, to evaluate cavitational performance. Optimization of solution pH and initial concentration led to selecting pH 3 and a 15 ppm concentration for subsequent experiments with two vortex-diode devices of 12 mm (D12) and 6 mm (D6) diameters. These devices were tested under various pressure conditions. The formation of 7OHC was analyzed in relation to process time, number of passes, and a characteristic number of passes (n*) – which correlates device dimensions with operating velocity. The results indicated that the D6 device outperformed the D12 in terms of efficiency at inlet pressures ranging from 100 to 400 kPag. Analysis of 7OHC formation trends with respect to n* revealed that while there were variations within different pressures for a given device, the performance was comparable across different scales. By keeping a constant n* across varying pressures (P1 = 100 to 400 kPag and P2 = 0 to 300 kPag), the study observed comparable 7OHC formation across different operating conditions and scales. This data is vital for selecting suitable scales and conditions for HC devices and for validating multi-scale models in this field.

Calculation of a cavitation device for industrial water treatment

Relevance. Currently, the issue of preventing pollution of the hydrosphere by industrial wastewater, the use of new effective technologies for industrial water purification and its reuse in production is extremely acute. In this regard, the urgent tasks are the search and implementation of new methods of water treatment: innovative technologies, disinfection and desalination of water, methods of its reuse.Methods. The article proposes a new technology for water treatment – the cavitation effect on the flow is enhanced by the shock effect of a pressure surge, which makes it possible to suppress the vital activity of microorganisms in the water. On the basis of the developed workflow, its mathematical model and the author’s methodology, calculations were made for three hydrodynamic cavitation devices with a pressure jump in order to disintegrate sulfate-reducing bacteria in industrial waters.Results. In accordance with the terms of reference (nominal fluid flow Q, nominal absolute pressure before installation P1, allowable pressure drop on the device ΔP, nominal fluid temperature t, physical properties of the medium) based on the proposed working process of a hydrodynamic cavitation device that forms a supersonic flow with a transition to subsonic through a pressure jump, an appropriate mathematical model and an adequate technique, the regime and geometric parameters of three pilot samples of hydrodynamic cavitation devices designed to destructurize sulfate-reducing bacteria in industrial waters were calculated. In order to form a supersonic flow in the installation under sufficiently strict conditions for ensuring permissible pressure drops, a nozzle was profiled with a minimum drag coefficient along the Vitashinsky curve. Industrial testing of cavitation devices showed good convergence of theoretical and experimental data: the suppression of bacteria was carried out by 80–100%.

Design of vortex-based cavitation devices/reactors: Influence of aspect ratio, number of inlets and shape

Vortex-based hydrodynamic cavitation devices are being used in a wide range of applications. However, adequate information on the design of such devices is not available. In this work, we have computationally investigated the influence of key design parameters such as the aspect ratio of the vortex chamber, the number of tangential inlets and the shape of the device on resulting flow characteristics and cavitation. Experiments were carried out to validate key findings from the computational studies. These investigations revealed that the aspect ratio of the vortex chamber as six may be considered as optimum. The performance of single and multiple inlet devices was found to be comparable at the same pressure drop (that is at same energy consumption per m3). Scale-up with a geometric similarity led to a reduction in the extent of cavitation for same energy consumption per m3. For facilitating scale-out option, an attempt was made to simplify the configuration of the vortex-based cavitation device. Computational results indicated that the cavitation performance of simplified configuration was not significantly inferior. A case of the formation of liquid–liquid emulsion was taken as a test case for evaluation of a modified cavitation device based on the present investigations. The droplet size distributions of emulsions generated by both the devices indicate that the proposed simplified configuration, which may facilitate fabrication and offer integrated scale-out options, performs almost at par with a complex configuration. The presented results will be useful for optimising designs of vortex-based hydrodynamic cavitation devices/ reactors.

Transport of Steam-Gas Mixture in Hydrodynamic Devices: A Numerical Study of Steam Reforming of Methane

The paper introduces a mathematical model that describes the cavitation process occurring during the passage of a water steam flow in various geometric configurations of a hydrodynamic device. The flow experiences a localized constriction (convergent nozzle) followed by expansion (divergent nozzle), exemplified by a Venturi tube or a Laval nozzle. A narrow flow channel connecting the convergent and divergent sections is equipped with a narrow-section nozzle for injecting methane molecules into the high-speed steam flow. As the steam-gas mixture passes through this zone, it is irradiated with an electron beam and sprayed into a cylindrical chamber at atmospheric pressure, where the distribution of methane molecules in water vapor forms an aerosol. Key geometric parameters of the constriction and expansion zones of the hydraulic system (cavitation-jet chamber) are determined to ensure the uniform distribution of dispersed-phase particles (methane) in the dispersion medium (water vapor). Velocity and pressure distributions of the mixed steam-gas flow are calculated using a turbulent mathematical model, specifically the k-ω model, while the motion of methane particles is simulated using a particle tracing method. The uniformity of methane molecule distribution in water vapor is assessed using Ripley’s K-function. The best performance of the hydrogen-producing chamber was observed when the cavitation-inducing nozzle’s convergence angle exceeded 50 degrees. The divergence angle of the nozzle within the range of 30–40 degrees provided the best distribution in terms of uniformity of the methane particles in the chamber.

Macro- and micromechanical properties of flawed sandstone and their degradation mechanisms under hydrodynamic scouring

To reveal the degradation mechanisms of the mechanical properties of a rock mass in a reservoir bank slope under hydrodynamic scouring, a hydrodynamic scour test device was developed in this study. Sandstone specimens containing prefabricated flaws were used as the research objects. Three conditions, namely, natural conditions, hydrostatic immersion, and hydrodynamic scouring, were considered. By considering the results of laboratory testing, digital image correlation (DIC), scanning electron microscopy (SEM), and thermodynamic analysis and fractal theory, the effects of different flow states on the mechanical properties of the flawed rock mass were systematically investigated in terms of the macromechanical parameters, strain field, strain energy, and microstructure. A crack initiation stress identification method based on the differentiation rate of the effective variance of strain fields was proposed. The energy conversion in the rock loading process was quantitatively characterized using three strain energy characteristic indicators. The internal microstructure of the rock was quantitatively characterized using a combination of SEM image characteristics and the fractal dimension. It was found that the uniaxial compressive strength, elastic modulus, crack initiation stress, energy storage limit, elastic strain energy conversion rate, and dissipated strain energy conversion rate of the hydrodynamically scoured specimen were the smallest, while the fractal dimension was the largest. There was a strong correlation among the mechanical parameters, energy characteristic indicators, and fractal dimensions of differently treated sandstone specimens because the macromechanical response and energy conversion characteristics of a rock mass are closely correlated with changes in its internal structure.

Real-time control of ship's roll motion with gyrostabilisers

The safety of ship manoeuvring operations is greatly affected by large roll motions under severe wave conditions. While existing studies have focused on optimizing hydrodynamic performance devices, these approaches may not be effective under realistic sea conditions where wave frequency and direction are irregular. Thus, predicting ship motion tendencies and implementing a reasonable control approach is crucial for improving ship safety. This study proposes a novel and practical control strategy that can effectively suppress roll motion of ships under realistic random wave conditions. The approach utilizes a real-time controller based on model predictive control (MPC) that is actuated by a dual gyrostabilizer. The ship's roll motion response in beam waves is calculated using one degree-of-freedom hydrodynamic modeling, and the wave memory effect is taken into consideration by employing system identification. A synthetic mathematical model of MPC and the dual gyrostabilizer method is introduced in state-space representation to compensate for wave excitation moment in real-time. The proposed method's efficacy is validated by comparing with a roll stabilization scenario of a particular ship in the literature, and control performance of a standard ship under regular and irregular wave conditions is separately discussed. Results indicate that the proposed method can significantly reduce roll motion amplitude and is feasible for nonlinear ship motion control problems. This study sheds light on the multi-degree-of-freedom motion control of ships under beam wave conditions.

Evaluation of the controlled hydrodynamic cavitation as gas mass transfer system for ex-situ biological hydrogen methanation

The present work represents the first study focused on controlled hydrodynamic cavitation applied as gas transfer system to supply the methanogenic archaea with exogenous H2 and CO2. Starting from a generic mixed inoculum sampled from a thermophilic full-scale anaerobic digester, a bubble column bioreactor was coupled with a rotating hydrodynamic cavitator and fed with different H2/CO2 loading rates. Process efficiency and long-term effects on process stability and microbial population were evaluated. Gas sparging through the controlled hydrodynamic cavitation device is feasible under the operating conditions tested, resulting in almost 100% efficiency in H2 utilization and recording a CH4 volumetric content more than 99% in the gas leaving the reactor, without any gas recirculation from the headspace. The experimental trials lasted about 160 days and the behavior of the bioreactor showed a substantial stability over the time. Metagenomic and FISH analyses were carried out at the end of the experimental trials, revealing a remarkable increase of hydrogenotrophic methanogens species, related to the selection-effect of H2 on community composition. The findings provide previously unidentified insights into long-term effect on process stability and microbial community diversity in the biological hydrogenotrophic methanation process coupled with a gas–liquid mass transfer system based on controlled hydrodynamic cavitation technology.

Liquid‐Liquid Emulsion Produced by 3D‐Printed Vortex‐Based Hydrodynamic Cavitation Device

Abstract3D‐printed vortex‐based devices have shown excellent performance in realizing hydrodynamic cavitation (HC) and have opened up new ways of effectively producing oil‐in‐water emulsions via cavitation. In this work, the performance of machined and 3D‐printed vortex‐based HC devices for producing liquid‐liquid emulsions was compared in terms of droplet breakage efficiency and energy consumption per kilogram of emulsion. The Euler numbers of 3D‐printed and VMC‐machined HC devices were 42 and 48, respectively. The differences in droplet size distribution and other characteristic diameters were insignificant after 50 passes. The present work confirms the potential of harnessing 3D printing technology for fabricating HC devices and can facilitate development of new device designs to improve overall emulsification performance.

Management of Thrombosed Dialysis Access Circuits.

Thrombotic occlusion of autologous arteriovenous fistulas or synthetic arteriovenous grafts is a serious adverse event in hemodialysis patients and declotting should be performed before next hemodialysis session, in order to avoid a central venous catheter. Various techniques exist to declot a thrombosed vascular access, including open surgical thrombectomy, catheter-directed thrombolysis and use of different types of percutaneous thrombo-aspiration catheters and mechanical thrombectomy devices. These devices can be categorized as devices with direct wall contact and hydrodynamic devices without direct wall contact. Technical and early clinical outcome results of percutaneous hemodialysis declotting are high and ranging between 70 and 100%; late clinical patency results are much lower related to restenosis or re-thrombosis; these patency results are higher for autologous arteriovenous fistulas compared to synthetic arteriovenous grafts and mainly depend on the combined efficacy of successful thrombectomy and durable treatment of the underlying stenoses, associated with the acute thrombosis.

A bi-level control framework with temperature rise inference and intelligent decision-making longitudinal control on downgrade hydrodynamic braking process

Temperature rise is a salient characteristic of the braking device of heavy-duty vehicles (HDVs) during long downhill braking. The temperature-independent effect on braking performance is an inevitable challenge for the longitudinal controller, which also causes the overheating of mechanical or hydrodynamic braking devices and may bring about brake failures for heavy-duty vehicles. To this end, a universal Bi-level control framework combining a temperature hierarchy system performance prediction method and a deep reinforcement learning (DRL)-based controller is proposed for long downhill braking of heavy-duty vehicles. Firstly, the temperature-independent characteristic is clustered to predict the braking performance under various rotating speeds. Secondly, a data-driven model for temperature rising is built for the long-time braking thermal prediction and estimates the safety remaining braking time using the auxiliary braking. Thirdly, a temperature-hierarchy environmental perceptive control framework with Double Deep Q Network (DDQN) algorithm is exploited to achieve the target speed tracking accuracy. Thermal safety is ensured with the application of fast calculating for the thermal rising, along with the effective estimation of remaining braking performance on endurance braking. The proposed Bi-level longitudinal controller is compared with the average-temperature strategy and the classic PID strategy to validate its superiority in terms of speed-tracking accuracy on robust conditions. The simulation results show that the proposed strategy improves the speed tracking accuracy by 37.31% on constant slope conditions and 68.11% on varying slope conditions compared with the classic PID strategy. Furthermore, a processor-in-the-loop test experiment verifies its real-time application.

Open flow cytometer with the combination of 3D hydrodynamic single cell focusing and confocal laser-induced fluorescence detection

Flow cytometry is among the most powerful tools for single-cell analysis, while the high cost and mechanical complexity of the commercial instrumentation limit the applications in personalized single-cell analysis. For this issue, we hereby construct an open and low-cost flow cytometer. It is highly compact to integrate the functions of (1) single cell aligning by a lab-made modularized 3D hydrodynamic focusing device, and (2) fluorescence detection of the single cells by a confocal laser-induced fluorescence (LIF) detector. The ceiling cost of the entire hardware for the LIF detection unit and 3D focusing device is $ 3200 and $ 400 respectively. A sheath flow velocity of 150 μL/min produces a focused sample stream of 17.6 μm × 14.6 μm at sample flow of 2 μL/min, based on the LIF response frequency and the laser beam spot diameter. The assay performance of the flow cytometer was evaluated by characterizing fluorescent microparticles and acridine orange (AO) stained HepG2 cells, producing throughputs of 40.5/s and 6.2/s respectively. Favorable assay precision and accuracy were demonstrated by the agreement of frequency histogram with imaging analysis, and good Gaussian-like distributions of fluorescent microparticles and AO-stained HepG2 cells. Practically, the flow cytometer was successfully applied for the evaluation of ROS generation in single HepG2 cells.