Hydrodynamic Studies Research Articles

Residence Time Distribution as a Tool for Hydrodynamic Study of Electrocoagulation Reactors Design and Scaling up

An electrocoagulation reactor operating continuously is designed for the treatment of industrial effluents in Senegal. One of the main challenges for electrocoagulation reactors design is each reactor is specific for its domain. In this paper, a methodology using residence time distribution curve (RTD) is presented and can be used for any other examples. The optimization of the operating parameters such as the flow rate, the residence time, the conductivity and so on for the treatment of these effluents requires an understanding of the reactor hydrodynamics. Thus, this hydrodynamic study based on the residence time distribution curve (RTD) showed the presence of dead zone in the reactor with a theoretical residence time of 607.76 s for an average residence time obtained from the residence time distribution curve of 554.85 s. A comparison of the curve obtained experimentally with the curves for an ideal reactor of the piston type or of a perfectly stirred type, has shown that the electrocoagulation reactor behavior is like a cascade of two perfectly stirred reactors with a difference between them of 0.15%. The numerical simulation with COMSOL allowed to illustrate the velocity fields and to highlight the preferential zones during the flow in the reactor and thus to confirm the results obtained with the hydrodynamics with a relatively low absolute error of 4.6% obtained with the least squares method.

Conditions for Effective Application of the Decline Curve Analysis Method

Determining the reliable values of the filtration parameters of productive reservoirs is the most important task in monitoring the processes of reserve production. Hydrodynamic studies of wells by the pressure build-up method, as well as a modern method based on production curve analysis (Decline Curve Analysis (DCA)), are some of the effective methods for solving this problem. This paper is devoted to assessing the reliability of these two methods in determining the filtration parameters of terrigenous and carbonaceous productive deposits of oil fields in the Perm Krai. The materials of 150 conditioned and highly informative (obtained using high-precision depth instruments) studies of wells were used to solve this problem, including 100 studies conducted in terrigenous reservoirs (C1v) and 50 carried out in carbonate reservoirs (C2b). To solve the problem, an effective tool was used—multivariate regression analysis. This approach is new and has not been previously used to assess the reliability of determining the filtration parameters of reservoir systems by different research methods. With its use, a series of statistical models with varying degrees of detail was built. A series of multivariate mathematical models of well flow rates using the filtration parameters determined for each of the methods is constructed. The inclusion or non-inclusion of these filtration parameters in the resulting flow rate models allows us to give a reasonable assessment of the possibility of using the pressure build-up method and the DCA method. All the constructed models are characterized by high statistical estimates: in all cases, a high value of the determination coefficient was obtained, and the probability of an error in all cases was significantly less than 5%. As applied to the fields under consideration, it was found that both methods demonstrate stable results in terrigenous reservoirs. The permeability determined by the DCA method and the pressure build-up curve does not control the flow of the fluid in carbonate reservoirs, which proves the complexity of the filtration processes occurring in them. The DCA method is recommended for use to determine the permeability and skin factor in the conditions of terrigenous reservoirs.

Modern approaches to the intensification of heat and mass exchange in multi-temperature condensation filters

The article considers the problems and features of heat and mass exchange on developed surfaces in the conditions of both single-phase and vapour-liquid flow during its condensation. We give a brief analytical review of studies of hydrodynamics and heat exchange in such systems. We analyzed the efficiency of the working channel of the condensation filter and identified problematic points. We offer possible methods for intensifying heat and mass transfer on working surfaces.

Hydrodynamics study of the flow past a cylinder with fine suspensions and evaluation of micropolar parameters

The fluid in nature or engineering application usually contains fine suspensions, which differs the hydrodynamic properties from those of the pure fluid. To investigate the effect of the suspensions and evaluate micropolar parameters, micropolar fluids model and classical fluid-particle coupling model are adopted in the simulation of the flow past a cylinder. In this study, the program for the micropolar fluids was implemented based on OpenFOAM, and its correctness was validated comparing to the analytical solution of the micropolar Poiseuille flow. Then, flow behaviors involving the variation of the vorticity, microrotation and drag force were analyzed under different micropolar parameter N/Ls and Reynolds numbers. Last, coupling results of the classical fluid with discrete particles were presented to establish the relationship between the suspensions volume fraction and the micropolar parameter N/L. The results show that the drag force on a cylinder decreases with the increase of the micropolar parameter N/L (when N/L equals to zero, it represents the classical fluid.) and the increase of the Reynolds number augments the value of the microrotation. In addition, a quadratic function relationship between the suspensions volume fraction and the micropolar parameter N/L is established under certain conditions.

CFD model for transient flow fields around teabag during tea infusion

A three-dimensional transient CFD study was performed to investigate the hydrodynamic characteristics of the teabag motion in a cup during tea infusion. The hydrodynamic study helps to estimate the fluid flow through each surface of the teabag, which can be used to predict the tea infusion kinetics through teabag. The transient motion of the teabag and the flow through a swollen tea bed were modeled with a frame of reference and porous media approach, respectively. The predicted instantaneous velocity from CFD simulation is in good agreement with the experimental measurement by Ultrasonic Velocity Profiler. The tea infusion experiments were performed and infusion through respective sides of the teabag was quantified to support the CFD simulation. The estimated flow through teabag for a cycle from CFD model was found to be in good agreement with the previously published 1-D mathematical model.

Use of X-Band Radars to Monitor Small Garbage Islands

The aim of this work is to verify and demonstrate the possibility of using X-band radars to identify, discriminate, characterize and follow small floating aggregations of marine litter (Small Garbage Islands—SGIs) made up mainly of plastic debris. To this end, a radar measurement campaign was carried out on a series of controlled releases into the sea of SGI modules assembled in the lab using the waste collected along a beach near the port of Livorno, in Tuscany, where the X-band radar of the Institute of Bioeconomy (IBE) of the National Research Council (CNR) is installed. The results of this first measurement campaign, which are illustrated in this preliminary work, are of interest to the entire scientific community that operates in the field of macroplastics analysis and monitoring, opening a new experimental avenue for the use of X-band radars also to monitor plastic waste at sea. Furthermore, the results obtained suggest good prospects for the use of X-band radars also for the study of coastal hydrodynamics on a local scale as well as in areas where it would be difficult to carry out measurements employing other technologies.

Prediction of reservoir pressure and study of its behavior in the development of oil fields based on the construction of multilevel multidimensional probabilistic-statistical models

Determination of the current reservoir pressure in oil production wells selection zones is an urgent task of field development monitoring. The main method for its determination is hydrodynamic studies under unsteady conditions. At the same time, the process of restoring bottomhole pressure to the value of reservoir pressure often lasts a significant period of time, which leads to long downtime of the fund and significant shortfalls in oil production. In addition, it seems rather difficult to compare reservoir pressures with each other in the wells due to the different timing of the studies, since it is impossible to simultaneously stop the entire fund for measuring the reservoir pressure in the field. The article proposes a new method for determining the current reservoir pressure in the extraction zones, based on the construction of multidimensional mathematical models based on the data of geological and technological development indicators. As the initial data, the values of reservoir pressure, determined during processing of the materials of hydrodynamic studies of wells, as well as a set of geological and technological indicators, probably affecting its value, were used (initial reservoir pressure for each well, the duration of its operation at the time of study, liquid rate, bottomhole pressure, the initial permeability and the current collector in the drainage area, GOR accumulated values oil, and liquid water, and skin factor). In the course of the research, several variants of statistical modeling were used, in the process of which the regularities of the reservoir pressure behavior during the development of reserves were established, individual for the object of development. The obtained models are characterized by a high degree of reliability and make it possible to determine the desired value with an error of no more than 1.0 MPa.

A novel rotating wide gap annular bioreactor (Taylor-Couette type flow) for polyhydroxybutyrate production by Ralstonia eutropha using carob pod extract

An annular bioreactor (ABR) with wide gap was used for PHB production from Ralstonia eutropha. Hydrodynamic studies demonstrated the uniform distribution of fluid in the ABR due to the Taylor-Couette flow. Thereafter, the ABR was operated at different agitation and sparging rates to study its effect on R. eutropha growth and PHB production. The ABR operated at 500 rpm with air sparge rate of 0.8 vvm yielded a maximum PHB concentration of 14.89 g/L, which was nearly 1.4 times that obtained using a conventional stirred-tank bioreactor (STBR). Furthermore, performances of the bioreactors were compared by operating the reactors under fed-batch mode. At the end of 90 h of operation, the ABR resulted in a very high PHB production of 70.8 g/L. But STBR resulted in a low PHB concentration of 44.2 g/L. The superior performance was due to enhanced oxygen and nutrient mass transfer in the ABR.

Comparative energy, exergy and CO2 emission evaluations of a LS-2 parabolic trough solar collector using Al2O3/SiO2-Syltherm 800 hybrid nanofluid

The use of hybrid nanofluids in parabolic trough solar collectors (PTCs) is a promising way to improve their performance. There have been some studies on utilization of hybrid nanofluids in PTCs, however there has been no study on utilization of Al2O3/SiO2-Syltherm 800 hybrid nanofluid. In the present study, after showing the superiority of utilization of this hybrid nanofluid in a LS-2 PTC over four previously studied hybrid nanofluids, thermal and hydrodynamic performance evaluation studies together with exergy and environmental analyses have been performed. Also for the sake of comparison Syltherm 800 as the base fluid and the corresponding mono nanofluids of Al2O3 and SiO2 have been considered and for all of the cases the flow regime has been considered turbulent. In some previous studies related to hybrid nanofluids the acceptable range for Reynolds and Prandtl numbers have not been observed, thus the results such as energy and exergy efficiencies and other output parameters stated before are not trustworthy. In this study, proper ranges of 10000–22000 for Reynolds number and 550–600 K for inlet temperature have been considered. The results showed that the energy and exergy efficiencies of the Al2O3/SiO2-Syltherm 800 hybrid nanofluid are always the highest, such that the maximum enhancements compared to those of the base fluid are 5.22 % and 5.49 %, respectively; whereas for mono nanofluid of SiO2 they are 1.71 % and 1.75 % and for mono nanofluid of Al2O3 they are 1.19 % and 1.36 %, respectively. Moreover, the results showed that the hybrid nanofluid is the most suitable with the highest PEC of 1.76. Environmental analysis based on exergoenvironmental method showed that if the hybrid nanofluid is utilized the maximum carbon dioxide emission in the life cycle of PTC is 1.657 kg/day; whereas for Syltherm 800 and mono nanofluids of SiO2 and Al2O3, it is 2.089, 1.925 and 1.961 kg/day, respectively. Energy, exergy and environmental analyses showed that the best performance of PTC is attained when hybrid nanofluid is utilized and Tin and Re are 600 K and 104, respectively.

Wave forces on box-girder-type bridge deck located behind trench or breakwater

Wave forces severely damage low-lying coastal bridges during hurricanes. In this study, a model for analyzing hydrodynamic wave forces acting on a bridge superstructure with a box girder behind a trench or breakwater was developed. First, the boundary value problem was defined based on necessary assumptions and simplifications. Next, an analytical solution of wave forces on the bridge superstructure was obtained using the potential flow theory and the eigenfunction-matching method. The validity and convergence of the analytical model were verified against the results of an experimental hydrodynamic study and a limiting case. With the proposed method, the effects of the trench and breakwater on the wave loads were investigated. Finally, a parametric analysis was conducted to reveal the hydrodynamic characteristics that influenced the wave–bridge interaction. The parametric study shows that both the trench and breakwater are useful in mitigating wave forces. A specialized design of the wave–structure system configuration is required to reduce the wave forces acting on bridge decks effectively.

Hydrodynamics study of dolphin's self-yaw motion realized by spanwise flexibility of caudal fin

The hydrodynamic performance of the virtual underwater vehicle under self-yaw is investigated numerically in this paper, we aim to explore the fluid laws behind this plane motion achieved by the bionic flexibility, especially the spanwise flexibility of the caudal fin. The kinematics of the chordwise flexible body and the spanwise flexible caudal fin are explored through dynamic mesh technology and user-defined functions (UDF). The 3-D Navier-Stokes equations are applied to simulate the viscid fluid surrounding the bionic dolphin. The study focuses on quantitative problems about the fluid dynamics behind the specific motion law, including speed of movement, energy loss and working efficiency. The current results show that the self-yaw can be composed of two motions, autonomous propulsion and active steering. In addition, the degree of the flexible caudal fin can produce different yaw effects. The chordwise phase difference Ф is dominant in the propulsion function, while the spanwise phase difference δ has a more noticeable effect on the steering function. The pressure distribution on the surface of the dolphin and the wake vortex generated in the flow field reasonably reveal the evolution of self-yaw. It properly turns out that the dolphin can combine the spanwise flexible caudal fin and the chordwise flexible body to achieve self-yaw motion.

Hydrodynamics Study of Riser with Helical Strakes Oscillating in Flow

Hydrodynamics Study of Riser with Helical Strakes Oscillating in Flow

Comparative hydrodynamic study of granitic and sedimentary catchments in Western Niger

ABSTRACT This study aims to compare hydrological processes in the Liptako-Gourma crystalline basement and the Iullemeden sedimentary zone in Western Niger. These two sites were equipped to quantify water infiltration, runoff and water retention within the beds of the ravines. We found that for the same surface type, while hydraulic conductivity was similar in both sites, surface runoff was 15–50% higher in the crystalline site compared to the sedimentary site. Within the sedimentary basin, we assume that runoff mainly originated from the tiger bush (typical vegetation and bare soil stripes found on plateaus). We suggest that the main reason for differences in stream flow was the stream storage capacity, which was four-fold higher in the sedimentary area compared to the crystalline domain. We thus conclude that the crystalline area functions as a water production and draining zone whereas the sedimentary basin is an accumulator of this resource.

Hydrodynamic characterisation of flotation impeller designs using Positron Emission Particle Tracking (PEPT)

Impellers play a key role in flotation cells, as the turbulence generated through agitation aids particle suspension, air dispersion and particle–bubble collision. Therefore, it is important to understand the effect that different impeller designs have on flotation hydrodynamics, as small variations could enhance flotation performance. The study of flotation hydrodynamics is, however, a complex task due to the nature of flotation systems, which are opaque, multiphase, and polydisperse. In this paper, the impact of impeller design modifications on the hydrodynamics of a flotation cell was quantified for the first time in a three-phase system. Two different impeller designs, with and without a stator, were assessed using positron emission particle tracking (PEPT), a technique that allows the position and velocity of radioactive particle tracers within an opaque vessel to be determined. A novel PEPT data analysis strategy, as well as a statistical analysis on the basis of the Jensen–Shannon distance, were used. This statistical analysis, applied for the first time to PEPT data, facilitated the comparison of the different designs, by generating a robust quantification of their hydrodynamic differences. The experimental results showed that the stator significantly modified the hydrodynamics within the flotation cell, distorting the lower mixing loop that is characteristic of radial impellers. The use of a stator also resulted in the reduction of particle velocity and swirling outside of the impeller–stator region, both at the level of the impeller and, notably, at the pulp–froth interface. These findings have important implications for impeller–stator design, evidencing that the impeller has a direct effect on the hydrodynamics of the pulp and froth.

Nature-based solutions for improving navigation reliability on the Madeira River, Brazil.

The Madeira River Navigation and Improvement Project provides a unique opportunity to incorporate nature-based solutions (NbS) into the built environment to promote sustainable communities and water resources infrastructure. The Madeira River has no major physical interventions (river training structures, navigation locks and dams, etc.) to improve navigation, and so is one of the world's last remaining undeveloped megarivers that exhibits natural morphological processes. The objective of this study is to create a safe, reliable, and sustainable navigation channel in the Madeira River. This is being accomplished by designing navigation improvement measures that leverage natural geomorphic processes of the river while minimizing conventional engineering practices that alter the river's morphology. To meet this objective, fluvial geomorphology analysis and hydrodynamic modeling studies have been performed to improve understanding of the morphological behavior of the system. Measures that incorporate beneficial reuse of dredged sediment within the system are being prioritized and incorporated into the study's design. Natural processes are being leveraged through the implementation of an adaptive management process to shape the navigation channel by incorporating the use of dynamic structures using natural local materials (e.g., large woody debris already in the system), a direct application of NbS in practice. This process includes extensive stakeholder collaboration and utilizing nature's energy to balance navigation, ecological, and social benefits along the Madeira River. This project demonstrates that nature-based approaches not only provide navigation benefits but can also provide ecological and social benefits in ways that are sustainable in the long term, consistent with United Nations Sustainable Development Goals (SDGs) and the International Union for the Conservation of Nature's global standard for NbS. Integr Environ Assess Manag 2022;18:115-122. © 2021 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Hydrodynamic study of the flow developed around a bare hull ship in static drift motion

The present study gives a Computational Fluid Dynamics (CFD) based insight into the three-dimensional incident flow developed around a very large crude carrier ship during static drift motion. The research proposes a set of virtual Planar Motion Mechanism (PMM) tests of “static drift” type conducted for a number of seven drift angles in the range of -9o to +9o. The emergence and development of vortical structures along the 1:58 KRISO Very Large Crude Carrier 2 (KVLCC2) tanker model are examined and explained, the influence of the considered drift angles being highlighted.

Hydrodynamic study of the oil flow in a protective relay coupled to a power transformer: CFD simulation and experimental validation

The present study aimed at performing a hydrodynamic analysis of the safety device's behavior in a gas relay, using computational fluid dynamics techniques and experimental data validation obtained in a protective relay pilot unit (PRP) using different safety flaps geometries for fault detection within high-power transformers. The proposed methodology was carried out in four stages: (i) development of computational meshes from the three-dimensional geometry of the protective relay and safety flaps; (ii) specification of the physical properties of fluids, boundary conditions, and fluid dynamic models; (iii) obtaining speed profiles, flap angle, oil flow and system pressure difference; and (iv) comparison of simulated and experimental data. The devices installed in the relay showed satisfactory performance for failures caused by the oil volumetric expansion. It was observed that from the flap 10° tilt, the orifice ceases to be the preferred path oil, reducing detection sensitivity of the flow. Using the CFD (computational fluid dynamics) computational tool, it was possible to understand the flow behavior within the relay, allowing to detect quickly and efficiently cases of failure with oil expansion.

Hydrodynamics study of a fast liquid–liquid oxidation process with in situ gas production in microreactors

AbstractHydrodynamics characteristics of a fast and highly exothermic liquid–liquid oxidation process with in situ gas production in microreactors were studied using a newly developed experimental method. In the adipic acid synthesis through the K/A oil (the mixture of cyclohexanol and cyclohexanone) oxidation with nitric acid, bubble generation modes were divided into four categories. The gas production became more intensive, unstable, even explosive with increasing the oil phase feed rate and the temperature. A novel automatic image processing method was developed to monitor the instantaneous velocity online by tracking the gas–liquid interface. The axial velocity at the same location was unstable due to the changing gas production rate. Furthermore, the actual residence time was obtained easily with being only 36% of the space–time minimally, beneficial for establishing accurate kinetics and mass transfer models with time participation. Finally, an empirical correlation was developed to predict the actual residence time under different conditions.

Eulerian CFD analysis of clustering gas-solid flows in fluidized bed pyrolysis reactors

Presence of meso-scale structures such as particle clusters and gas bubbles is ubiquitous in fluidized beds frequently used in pyrolysis of coal and biomass. In recent years, bubbling and circulating fluidized beds have become popular for highly efficient conversion of carbonaceous feedstock into pyrolysis products. The characterization and study of hydrodynamics inside these reactors can provide an insight into the mechanisms controlling the performance of these reactors. Among others, cluster size distribution and mean cluster size are the key parameters defining the hydrodynamics of these reactors. In the current work, Digital Image Analysis (DIA) was applied to computationally obtained instantaneous snapshots during the CFD simulations of gas-solid flows. Transient two fluid modeling (TFM) was applied to three different gas-solid systems in periodic domains with different particulate systems keeping same grid size. The dimensionless axial cluster size was defined in line with literature. The cluster sizes and their distributions are obtained and compared with the available empirical correlations present in the literature based on experimental observations having similar range of operating conditions as well as system characteristics. It is found that the results of current approach agree well with the available data. The methodology followed in current work presents an alternative to expensive experimentation for development of a universal cluster size correlation.

Constraints and funs of global hydrodynamic studies

Constraints and funs of global hydrodynamic studies