Hydrodynamic Characterization Research Articles

Numerical Simulation Analysis of the Correlation between Hydrodynamic Noise of Hydraulic Turbines and Defects in Runner Blades

To investigate the hydrodynamic noise characterization of hydraulic turbines with runner blade defects, this article establishes the intact machine model and three kinds of models with runner blade defects. Using the Computational Fluid Dynamic (CFD) and Computational Acoustic (CA) hybrid simulation computational methods, the hydrodynamic noise field of the hydraulic turbine is numerically simulated, and the results of the acoustic near field and acoustic far field are shown. 1. The double-row leaf grille and the runner are the primary sound source areas of the hydraulic turbine, and the intensity of sound radiation from these areas is positively correlated with the degree of runner blade defects. 2. As the runner blade defects develop, the sound power level (SWL) increases more significantly in the guide vanes near the nose of the spiral case in the double-row leaf grille. The most pronounced increase in the SWL is observed at the defective craters on the runner blades. 3. The frequency of the defective noise signal is primarily concentrated in the low-frequency band. The dominant frequency amplitude associated with runner blade defects increases and rises after the occurrence of defects. Secondary frequency changes are also observed, and the location of these changes varies at different receiving points.

Hydrodynamic characterization of bubble column using Dynamical High Order Decomposition approach

Bubble columns play a crucial role in a wide range of industries, including chemical and biochemical processes, petrochemicals, and environmental engineering. Understanding the dynamics of bubble columns is essential for optimizing their performance in various applications. This study proposes a data-driven approach for analyzing the dynamics of a two-dimensional bubble column system. We conducted simulations with varying superficial velocities and generated a comprehensive training dataset encompassing the entire velocity and pressure fields to achieve this. We then compared the performance of two approaches, the Fast Fourier Transformation (FFT) and the High-Order Dynamic Mode Decomposition (HODMD), in representing the system’s dynamics. Our findings demonstrate that the conventional FFT approach fails to adequately capture the complex dynamics of the dispersed multiphase flow system. This limitation arises due to the distribution of frequencies along the domain. Conversely, our work highlights the success of the HODMD method in accurately representing the system’s dynamics using only a few arbitrary sampling points within the domain. The implications of this study are significant, as it sheds light on the potential benefits of employing HODMD for analyzing bubble column dynamics. By utilizing this approach, industrial processes can be optimized more effectively across various applications.

Hydrodynamic Characterization of Carbonate Aquifers Using Atypical Pumping Tests without the Interruption of the Drinking Water Supply

The Gran Sasso carbonate aquifer is the largest and most productive in the Apennines. Its hydrogeological structure has been studied since the middle of the last century for the springs’ characterization for drinking purposes and for a motorway tunnel. Meanwhile, its hydrodynamic parametrization is less developed and has been limited to monitoring the discharge and chemical and isotopic parameters. Secondary porosity characterizes the aquifer, and an underlying impermeable marly complex represents the basal aquiclude. It might appear inappropriate to characterize the hydraulic properties via pumping tests, as their reliability has been proven in homogeneous and isotropic media. However, the high extent of the aquifer, the wells’ location, the scarcity of information available and the lack of alternatives has forced the estimation of hydrodynamic parameters as in porous aquifers and the experimental testing of the aquifer, especially in maximum pumping conditions, for a possible exploitation increase. Since aquifer testing was performed during the normal well field’s activities, it was not possible to perform typical tests. Therefore, the step-drawdown test was conducted by turning on an increasing number of wells over time and keeping the observation points fixed. As results, a mean hydraulic conductivity of 5 × 10−3 m/s and a mean transmissivity of 0.3 m2/s were established without interrupting the water supply; meanwhile, the influence radius and flow directions were also estimated.

An in-silico analysis of hydrodynamics and gas mass transfer characteristics in scale-down models for mammalian cell cultures

Bioprocess scale-up and technology transfer can be challenging due to multiple variables that need to be optimized during process development from laboratory scale to commercial manufacturing. Cell cultures are highly sensitive to key factors during process transfer across scales, including geometric variability in bioreactors, shear stress from impeller and sparging activity, and nutrient gradients that occur due to increasing blend times. To improve the scale-up and scale-down of these processes, it is important to fully characterize bioreactors to better understand the differences that will occur within the culture environment, especially the hydrodynamic profiles that will vary in vessel designs across scales. In this study, a comprehensive hydrodynamic characterization of the Ambr® 250 mammalian single-use bioreactor was performed using time-accurate computational fluid dynamics simulations conducted with M-Star computational fluid dynamics software, which employs lattice-Boltzmann techniques to solve the Navier-Stokes transport equations at a mesoscopic scale. The single-phase and two-phase fluid properties within this small-scale vessel were analyzed in the context of agitation hydrodynamics and mass transfer (both within the bulk fluid and the free surface) to effectively characterize and understand the differences that scale-down models possess when compared to their large-scale counterparts. The model results validate the use of computational fluid dynamics as an in-silico tool to characterize bioreactor hydrodynamics and additionally identify important free-surface transfer mechanics that need to be considered during the qualification of a scale-down model in the development of mammalian bioprocesses.

Cartography of liquid-liquid flow in corrugated millichannels

If the interest of heat exchanger/reactors have been demonstrated for homogeneous liquid phase applications, many chemical syntheses take place in multiphase media (gas-liquid, liquid-liquid, gas-liquid-solid…). Thus, in order to evaluate the versatility of a plate-type heat exchanger/reactor with a 2D-meandering millichannel, this work is focused on the characterization of hydrodynamics of liquid-liquid flow in the reaction channel. Therefore, several prototypes are built with millichannels of increasing dimensions to address the scale-up issue. Flow visualizations are performed with a high-speed camera; four flow regimes with octanol/water fluid system are observed: annular/plug, annular, annular/dispersed, and dispersed. The study shows that interfacial tension and dispersed phase inertia are the main forces driving the interface. A dimensionless map based on the dispersed phase Weber number as a function of the continuous phase internal Dean number is built up. This map turns out to be valid in the range (2–4 mm) of the tested corrugated millichannel size.

Physical modelling and hydrodynamic characterization of an internally circulating fluidized bed for biomass fast pyrolysis

This study investigates the hydrodynamics of the cold flow model (CFM) of an internally circulating fluidized bed (ICFB) finalized to biomass fast pyrolysis. The ICFB, basically consisting of a bubbling fluidized bed interconnected with a moving bed, is designed aiming at high fuel particles heating rates, efficient solids mixing and low gas residence times. Experimental techniques such as basket collection, solids and gas tracing are adopted to determine solids circulation rates, gas bypassing and particles residence times, consequently a compartment model of the CFM is proposed. The influence of operating conditions such as bed inventory and superficial gas velocity is investigated together with the effect of the opening ratio between the two interconnected beds. Results highlight that different operation regimes can occur and an optimization of operating and design parameters allows high solids circulation rates, low gas bypass and residence times lower than 1 s, as pursued in fast pyrolysis.

Groundwater apparent ages and isotopic composition in Crystalline, Diabase and Tubarão aquifers contact area in Campinas, Southeastern Brazil

This study refines the hydrogeological conceptual model of an area with three interconnected aquifers, namely the Crystalline Aquifer System (CAS - igneous and metamorphic rocks), which is in contact with the Tubarão Aquifer System (TAS - sedimentary rocks) and the Diabase Aquifer System (DAS – diabase rocks). The detailed investigation involved geophysical logging and hydraulic and hydrodynamic characterization with straddle packers in a local tubular well, in which groundwater presents high uranium concentrations. Hydrogeochemical and isotope (δ2H, δ18O, 3H, δ13C, 14C) analysis in this well and in other three neighboring wells, with lower U concentrations, showed that ancient and modern waters (3H from <0.8 to 1.12 TU, 14C from 69.43 to 78.72 pMC) mix within the aquifer. During groundwater pumping, vertical fractures in the diabase aquifer possibly induce water mixing and recharge of the deeper levels of the aquifers from shallow layers. The high [U] are related to ancient waters from a confined aquifer hosted in CAS that reaches the wells through hydraulically active fractures located deeper than 159 m depth. Groundwater apparent ages do not increase systematically with depth, revealing a complex circulation model for CAS. The results obtained from the other wells, which are all located on drainage lineaments, reveal that one extracts modern water from DAS and TAS, another one extracts modern and ancient water from DAS and CAS, and the third extracts only ancient water from CAS, confirming the complexity of the local hydrogeology. Regarding regional groundwater management, the study revealed the need to characterize the sources of groundwater in each well, in order to protect modern waters from anthropogenic contamination and to protect ancient groundwater from overexploitation, as CAS hosts groundwaters recharged thousands of years ago or more.

Coupling catalytic bed fluidization with impeller rotation for improved hydrodynamic characterization of Berty reactors

We studied the hydrodynamics in a Berty reactor, integrating several computational fluid dynamic methods. Our results demonstrate that the hydrodynamics are predominantly influenced by impeller rotation, irrespective of the bed.

Numerical validations and investigation of a semi-submersible floating offshore wind turbine platform interacting with ocean waves using an SPH framework

In this work, we propose numerical validations of the DeepCwind semi-submersible floating platform configuration for a single horizontal axis wind turbine using data from two experimental testing investigations. A Smoothed Particle Hydrodynamics solver is employed to estimate fluid induced loads, whereas the mooring connections are handled via an external library. The first validation setup is based on the DeepCwind offshore wind semi-submersible concept moored with a system of taut-lines and tested for free-decay surge and heave motion (OC6-Phase Ia). The damping evaluation yields a fair estimation of the heave damping behavior, whereas much more dissipation is experienced for the surge. The second validation features a full hydrodynamic characterization of the frequency-related load patterns induced by three different sea-state representations (mono-, bi-chromatic, and irregular waves) (OC6-Phase Ib). The model accurately matches the hydrodynamic load estimation for the whole spectrum of investigated wave components, perfectly capturing the non-linear behavior shown by the considered wave patterns. This work concludes with a systematic study on the motion response, mooring tension, pressure and vorticity, suggesting that: the wave steepness criterion alone cannot identify the most restrictive load case; waves with spectral characteristics close to the heave resonance period lead to higher tensions in the mooring systems, whereas the maximum fluid-induced loads on the hull are decoupled from displacement peaks, showing an average reduction of 30% with respect to the maxima; very steep waves maximize the likelihood of wave overtopping and slamming loads, resulting in locally induced overpressure on the free-board of up to 100% higher than expected for similar wave heights with milder profiles. The input data for these last tests is released for the sake of reproduction.

Fine-scale geographic risk assessment of oxybenzone sunscreen pollution within Hanauma Bay using hydrodynamic characterization and modeling

Hanauma Bay's coral reef system is threatened by sunscreen pollution. Understanding the hydrodynamic nature of the bay is crucial for understanding the transport and fate of pollutants within the bay. This study conducted a comprehensive hydrodynamic analysis, revealing significant aspects of current patterns and their influence on sunscreen pollutant behavior. The analysis demonstrated the formation of flows that drive currents parallel to the shoreline, resulting in increased pollutant retention time over sensitive reef areas. Direct flushing currents were identified as playing a role in reducing pollution buildup. Particle dynamics analysis highlighted the importance of considering temporal dynamics and their implications for pollutant pathways, particularly through the swash zone during high tide phases. The study identified primary current patterns near the reef area and emphasized the circular behavior within the water body, affecting corals' susceptibility to bleaching in the southwestern part of Hanauma bay. To understand where oxybenzone concentrations were a threat to wildlife, we created a geographic model that integrated ecological risk assessment with hydrodynamic behavior in a given system, which we designate the Risk Quotient Plume – the geographic area where the concentration is above the threat level for a chemical. The study found high oxybenzone concentrations throughout the bay, threatening coral, fish, and algae populations. Oxybenzone's distribution indicated a serious threat to the entire back reef habitat and a hinderance to coral restoration efforts. The study also emphasizes the need to consider the hydrodynamic behavior of pollutants and their interaction with microplastics in the bay. Overall, the findings provide insights into hydrodynamics and pollutant dispersion in Hanauma Bay, supporting effective pollution management and conservation strategies.

Global characterization of hydrodynamics and gas-liquid mass transfer in a thin-gap bubble column in presence of Newtonian or non-Newtonian liquid phase

Bubble columns are commonly used as photobioreactors (PBRs) due to their good mixing and mass transfer capabilities. Modification in design and operating parameters are nevertheless needed to intensify volumetric productivity. Thin-gap bubble column can be used in this context to operate with high biomass concentration, up to conditions where the culture becomes non-Newtonian. In the present study, the global hydrodynamics and gas–liquid mass transfer inside a 4 mm thickness thin-gap bubble column are characterized in presence of low viscosity Newtonian fluid (water) and two aqueous solutions of Carboxymethyl Cellulose and Xanthan Gum. These shear-thinning solutions are used to mimic high concentration cultures of Chlorella Vulgaris at 42 g.L−1. A range of superficial gas velocities and different capillary diameters are explored to investigate the effect of sparging on hydrodynamics and gas–liquid mass transfer. Studied parameters are flow regimes, mixing, and gas–liquid mass transfer. Results are compared with literature results in classical bubble columns to put into evidence the original effects of both confinement and liquid rheology. Among others, these results show that compared to Newtonian media, non-Newtonian media result in higher gas holdup and mixing times and a lower gas–liquid mass transfer coefficient. The findings suggest that the presence of smaller bubbles would improve mass transfer due to the increased interfacial area, while the presence of larger bubbles would improve mixing performance due to increased vorticity in their wake and relatively greater species transport.

Development of a test setup for hydrodynamic characterization of hydrocephalus shunts

Abstract Implantation of a shunt system is the most common neurosurgical procedure for the treatment of hydrocephalus. Hydrodynamic parameters of hydrocephalus shunt systems are valuable variables to address patients' needs. In this report, we present a test setup to evaluate hydrodynamic parameters of hydrocephalus shunt systems. The test setup was validated using a stainless steel capillary and compared with the analytical solution according to Bernoulli's equation. It was demonstrated that the experimental setup is able to model the pressure in a physiologically relevant range. The measured and averaged flow resistance was 2.96 mmHg/(ml min-1). According to the analytical solution of Bernoulli's equation, the flow resistance is 2.86 mmHg/(ml min-1). Therefore, the measured flow resistance is 3.5% higher than the analytical solution. Moreover, the nonlinear characteristic of the pressure drop at the inlet and outlet of the capillary plays a minor role compared to the friction of the tube flow. As a result, the increase in flow rate with increasing pressure load can be well approximated by a linear function for the low flow rates measured here. The experimental setup presented will be used in the future to characterize commercially available shunt systems under various hydrodynamic conditions.

In-Line Detection of Bed Fluidity in Gas-Solid Fluidized Beds Using Near-Infrared Spectroscopy.

A novel approach was developed to detect bed fluidity in gas-solid fluidized beds using diffuse reflectance near-infrared (NIR) spectroscopy. Because the flow dynamics of gas and solid phases are closely associated with the fluidization state, the fluidization quality can be evaluated through hydrodynamic characterization. In this study, the baseline level of NIR spectra was used to quantify the voidage of the fluidized bed. Two indicators derived from the NIR baseline fluctuation profiles were investigated to characterize bed fluidity, named bubble proportion and skewness. To establish a robust fluidity evaluation method, the relationships between the indicators and bed fluidity were investigated under different conditions firstly, including static bed height and average particle size. Then, a generalized threshold was identified to distinguish poor and good bed fluidity, ensuring that the probability of the α- and β-errors was less than 15% regardless of material conditions. The results show that both indicators were sensitive to changes in bed fluidity under the investigated conditions. The indicator of skewness was qualified to detect bed fluidity under varied conditions with a robust threshold of 1.20. Furthermore, the developed NIR method was successfully applied to monitor bed fluidity and for early warning of defluidization in a laboratory-scale fluidized bed granulation process.

Solvent-Free Enzymatic Synthesis of Dietary Triacylglycerols from Cottonseed Oil in a Fluidized Bed Reactor.

The synthesis of structured lipids with nutraceutical applications, such as medium-long-medium (MLM) triacylglycerols, via modification of oils and fats represents a challenge for the food industry. This study aimed to synthesize MLM-type dietary triacylglycerols by enzymatic acidolysis of cottonseed oil and capric acid (C10) catalyzed by Lipozyme RM IM (lipase from Rhizomucor miehei) in a fluidized bed reactor (FBR). After chemical characterization of the feedstock and hydrodynamic characterization of the reactor, a 22 central composite rotatable design was used to optimize capric acid incorporation. The independent variables were cycle number (20-70) and cottonseed oil/capric acid molar ratio (1:2-1:4). The temperature was set at 45 °C. The best conditions, namely a 1:4 oil/acid molar ratio and 80 cycles (17.34 h), provided a degree of incorporation of about 40 mol%, as shown by compositional analysis of the modified oil. Lipozyme RM IM showed good operational stability (kd = 2.72 × 10-4 h-1, t1/2 = 2545.78 h), confirming the good reuse capacity of the enzyme in the acidolysis of cottonseed oil with capric acid. It is concluded that an FBR configuration is a promising alternative for the enzymatic synthesis of MLM triacylglycerols.

Development and Hydrodynamic Characterization of a Modular Mini-Plant Photoreactor

Development and Hydrodynamic Characterization of a Modular Mini-Plant Photoreactor

Fluid dynamics characterization of stirred-tank reactors via approximate Bayesian computational (ABC) for parameter estimation and model selection

The Approximate Bayesian Computing (ABC) was used in this work to perform the selection and calibration of models in reactor dynamics. Five phenomenologically based hydrodynamic models on dead volume, flow deviation and retro-mix anomalies were evaluated and classified into two groups. The inverse problems were solved from experimental data obtained by the technique of residence time distribution (RTD) in positive step, using the methylene blue tracer in a stirred-tank reactor. The experiments evaluated the influence of volumetric flow, effluent outlet position, agitation position and rotation on the hydrodynamic characterization of the reactor. The results revealed that the most influential parameter in the first group was the dead volume, while in the second group, the retro-mix anomaly was highly sensitive to rotation. The ABC algorithm applied in this work used the Morozov discrepancy principle to select the tolerance in the final population. Tolerances for other intermediate populations were obtained from the median distance of each particle accepted in the previous population. HIGHLIGHTS The application of the Bayesian approach in RTD problems was excellent for the hydrodynamic characterization of reactors. The ABC SMC algorithm proved to be efficient for the calibration and selection of hydrodynamic models of reactors. The most influential anomaly in the flow was the dead volume.

Hydrodynamic and experimental characterization of pumps as turbines

To estimate the performance, efficacy, modes of operation, hydrodynamic instabilities, and methodologies for harnessing energy from the pump as turbine (PAT), it is necessary to characterize these hydraulic turbomachines in all their modes of operation using an experimental test rig that simulates actual operating conditions. In this process, the characteristic curve of four quadrants of a turbomachine is constructed, especially its five modes: pump mode, brake pump mode, turbine mode, brake turbine mode, and reverse pump mode. In addition, with dynamic sensors installed in the pump volute, it is possible to know the hydrodynamic phenomena within PAT, finding its average behavior and frequency response, which is a tool for diagnosing the machine’s condition.

Aerobic bioreactors: A Bayesian point of view applied to hydrodynamic characterization and experimental evaluation of tracers

This work describes the hydrodynamic diagnosis of an aerobic fixed-bed reactor, obtained by estimating parameters via the Markov chain Monte Carlo (MCMC) method. Five hydrodynamic models are evaluated. Of these models, four were classical (large dispersion, small dispersion, N-CSTR in series and plug flow with mass exchange), while the fifth is a proposal for the characterization of the short-circuit anomaly, the N-CSTR in parallel model. Due to the three-phase peculiarities of the reactor involving adsorption and dispersion phenomena, three tracers were evaluated through the stimulus–response test: eosin Y, bromophenol blue and bromocresol green. Green bromocresol is the most appropriate tracer for this type of analysis, with the hydrodynamic characterization showing that the reactor is mainly influenced by short-circuit anomaly. Parameter estimation obtained via MCMC, together with the model selection carried out by Bayesian criteria, pointed at the proposed model, n-CSTR in Parallel, as the best fit to the experimental data.

Hydrodynamic characterization of a vesicular stomatitis virus-based oncolytic virus using analytical ultracentrifugation.

Determination of the size, density, and mass of viral particles can provide valuable information to support process and formulation studies in clinical development. Analytical ultracentrifugation (AUC), as a first principal method, has been shown to be a beneficial tool for the characterization of the non-enveloped adeno associated virus (AAV). Here, we demonstrate the suitability of AUC for the challenging characterization of a representative for enveloped viruses, which usually are expected to exhibit higher dispersity than non-enveloped viruses. Specifically, the vesicular stomatitis virus (VSV)-based oncolytic virus VSV-GP was used to evaluate potential occurrence of non-ideal sedimentation by testing different rotor speeds and loading concentrations. The partial specific volume was determined via density gradients and density contrast experiments. Additionally, nanoparticle tracking analysis (NTA) was used to determine the hydrodynamic diameter of VSV-GP particles to calculate their molecular weight via the Svedberg equation. Overall, this study demonstrates the applicability of AUC and NTA for the characterization of size, density, and molar mass of an enveloped virus, namely VSV-GP.

Modeling a Metamorphic Aquifer through a Hydro-Geophysical Approach: The Gap between Field Data and System Complexity

The productivity of metamorphic aquifers is generally lower than that of the more common alluvial and carbonates ones. However, in some Mediterranean areas, such as the Calabria region (Italy), water scarcity combined with the presence of extensive metamorphic water bodies requires the development of further studies to characterize the hydrodynamic properties of these groundwater systems in order to achieve their sustainable exploitation. The interest in this goal becomes even greater if climate change effects are considered. The purpose of this study was to provide the geological-structural and hydrogeological numerical modeling of a metamorphic aquifer, using direct and indirect data measurement, in a large area of the Sila Piccola in Calabria. The hydrodynamic characterization of the crystalline-metamorphic aquifer, constituted by granite and metamorphic rocks, is extremely complex. The MODFLOW-2005 groundwater model was used to simulate flow phenomena in the aquifer, obtaining hydraulic conductivity values of 2.7 × 10−6 m/s, which turned out to be two orders of magnitude higher than those obtained from the interpretation of the slug-tests performed in the study area. The mathematical model was also able to estimate the presence of a lateral recharge from a neighboring deep aquifer providing a significant water supply to the system under investigation.