Fluid Stream Research Articles

Imaging‐Based Lensless Polarization‐Sensitive Fluid Stream Analyzer for Automated, Label‐Free, and Cost‐Effective Microplastic Classification

The presence of microplastics in the environment is of significant concern, yet the exact extent of this pollution remains largely unknown. The ocean is of particular interest as the monitoring of microplastics presents a challenge in that in situ fluid stream solutions are not readily available and traditional sampling methods are labor‐intensive and costly. This study introduces an imaging‐based lensless polarization‐sensitive fluid stream analyzer (FSA) for automated, label‐free, and cost‐effective detection and classification of microplastics. The FSA incorporates digital in‐line holography and birefringence computation, enabling quantitative polarization‐sensitive imaging and machine‐learning‐based activities including sample classification. Birefringent textures of synthetic polymers are investigated owing to their optical anisotropy. A microplastic classifier is developed for the FSA and integrated to form an end‐to‐end workflow capable of sampling fluid streams and determining marine and microplastic particle presence. Cultures of two phytoplankton species form a simplified marine environment for FSA evaluation. The device is tested in a two‐class configuration for marine microorganisms and microplastics, as well as a five‐class configuration for marine microorganisms and four individual microplastic types (polyethylene, polyethylene terephthalate, polypropylene, and polystyrene). The results demonstrate high classification accuracy, supported by experiments in the simulated marine environment that validate the proposed implementation's efficacy.

On Velocity Stopbands in Electrostatic Solitary Wave Propagation in Magnetospheric Plasma in the Presence of an Ion Beam—Application in the Solar Wind

Satellite observations in the Earth’s magnetosphere suggest a coexistence of different types of ion populations, such as protons and heavier helium ions (alpha particles) transported by the solar wind. We have undertaken an investigation, from first principles, of the conditions for the occurrence of electrostatic solitary waves in such a multi-ion plasma environment. Nonlinear analysis has been employed to explore the effect of an ion beam on the occurrence of stopbands in a multicomponent plasma consisting of Boltzmann electrons and two ion species, modeled as cold and warm (adiabatic) ions. A “stopband” is an interval of pulse speed (mach (Mach number) values in which solitary waves cannot propagate. Such stopbands are known to exist in relation to fast ion-acoustic solitary waves (exclusively). Our parametric analysis reveals that the stopband widens over the range of cold ion charge density (values) upon increasing speed of a hot ion beam moving along the direction of wave propagation. However, the stopband becomes narrower in the case of a counterpropagating beam. Similarly, the streaming of a cold ion beam fluid along (or antiparallel) to the wave direction leads to the narrowing (or widening, respectively) of the stopband. The fast soliton existence (velocity) domain is characterized by two critical points (a crossover and a turning point), which are affected by the beam. Our study could be relevant to understanding energy dissipation processes in the fast solar wind associated with relative drifts between the major (protons) and minor (alpha particles) ions which results in the heating of both species.

Rethinking Loss of Available Work and Gouy-Stodola Theorem

Abstract Exergy represents the maximum useful work possible when a system at a specific state reaches equilibrium with the environmental dead state at temperature To. Correspondingly, the exergy difference between two states is the maximum work output when the system changes from one state to the other, assuming that during the processes, the system exchanges heat reversibly with the environment. If the process involves irreversibility, the Guoy-Stodola theorem states that the exergy destruction equals the entropy generated during the process multiplied by To. The exergy concept and the Gouy-Stodola theorem are often used to optimize processes or systems, even when they are not directly connected to the environment. In the past, questions have been raised on if To is the proper temperature to use in calculating the exergy destruction. Here, we start from the first and the second laws of thermodynamics to unambiguously show that the useful energy loss (UEL) of a system or process should equal to the entropy generation multiplied by an equivalent temperature associated with the entropy rejected out of the entire system. For many engineering systems and processes, this entropy rejection temperature can be easily calculated as the ratio of the changes of the enthalpy and entropy of the fluid stream carrying the entropy out, which we call the state-change temperature. The UEL is unambiguous and independent of the environmental dead state, and it should be used for system optimization rather than the exergy destruction.

Design, modeling, and characteristics of ring-shaped robot actuated by functional fluid

The controlled actuation of hydraulic and pneumatic actuators has unveiled fresh and thrilling opportunities for designing mobile robots with adaptable structures. Previously reported rolling robots, which were powered by fluidic systems, often relied on complex principles, cumbersome pump and valve systems, and intricate control strategies, limiting their applicability in other fields. In this investigation, we employed a distinct category of functional fluid identified as Electrohydrodynamic (EHD) fluid, serving as the pivotal element within the ring-shaped actuator. A short stream of functional fluid is placed within a fluidic channel and is then actuated by applying a direct current voltage aiming at shifting the center of mass of the robot and finally pushed the actuator to roll. We designed a ring-shaped fluidic robot, manufactured it using digital machining methods, and evaluated the robot’s characteristics. Furthermore, we developed static and dynamic models to analyze the oscillation and rolling motion of the ring-shaped robots using the Lagrange method. This study is anticipated to contribute to the expansion of current research on EHD flexible actuators, enabling the realization of complex robotic systems.

An experimental acoustofluidic system for analyzing boundary-driven acoustic streaming generated by flat and curved walls

While boundary-driven acoustic streaming in fluids surrounded by flat walls has been extensively studied in the literature, theoretical studies on boundary-driven acoustic streaming generated by curved walls have recently emerged. This paper aims to present a quantitative analysis of acoustic streaming fields driven by forces induced by both flat and curved walls. A semi-circular channel made of stainless steel was designed to serve as a model channel with both flat and curved boundaries. A multi-layered glass-steel-glass device, actuated by a piezoelectric transducer, was assembled for experimental characterization of boundary-driven acoustic streaming in such scenarios. First, the various standing acoustic modes in the semi-circular channel were measured through the acoustophoretic patterning of 20 µm polystyrene particles. Next, the acoustic radiation force fields and boundary-driven acoustic streaming patterns under various resonant acoustic modes were characterized through micro-particle-image-velocimetry measurements of the motion of 20 µm and 1 µm polystyrene particles, respectively. Finally, the experimental results were explained using efficient finite element simulations of acoustofluidics and acoustophoresis in a semi-circular reduced-fluid model, with a focus on analyzing the streaming velocities driven by the flat and curved walls. Both experimental and numerical results demonstrated that the ratio of streaming velocities induced by the flat wall and the curved wall in this semi-circular channel depends on the resonant acoustic modes. This research highlights the diverse boundary-driven acoustic streaming patterns that arise in irregular channels and provides a theoretical foundation for choosing strategies for shape optimization to suppress acoustic streaming in acoustofluidic devices.

Flow past a rotating porous sphere in the existence of a toroidal magnetic field

This model consists of a porous spherical body rotating in an incompressible conducting fluid in the existence of a toroidal magnetic field. The toroidal field is generated by an electric dipole along the axis of symmetry. The model is split into two parts—the clear fluid region and the porous sphere. The clear fluid area is driven by the momentum equation and the permeable sphere region is driven by the Brinkman equation. The study is being done for the scenario where the impact of viscous force is much more than inertia force. The expression is found for fluid velocity and stream function by the superposition method. The results depict the impact of rotational parameters and the Darcy number on separation parameter. It is shown that the separation is low for the highly permeable sphere.

Entropy generation in a chemically reactive magnetohydrodynamic unsteady micropolar nanofluid flow with activation energy over an inclined stretching sheet: A Buongiorno model approach

The goal of this research is to inspect the heat and mass transfer trends and entropy generation in a time-reliant stagnation point stream of a micropolar fluid across an inclined stretched surface. For this objective, a chemically reactive, electrically conducting fluid exposed to an orthogonal magnetic field is studied. The flow governing equations are modelled using Buongiorno model and are reformed to a system of higher order ordinary differential equations by administering appropriate similarity transformations. This system is quantitatively examined by employing the fourth-order Runge-Kutta scheme with shooting approach. The effects of thermal radiation, magnetic field, uniform heat source/sink, Brownian motion, thermophoresis, activation energy, and binary chemical reaction are studied on velocity, microrotation, temperature, and concentration profiles. It is observed that magnetic field and Brownian motion elevate the flow temperature. Increased activation energy spikes the fluid concentration while increase in binary chemical reaction reduces the particle concentration. Later, impact of various parameters on skin friction coefficient and heat and mass transfer rates are tabularised. Increasing values of thermophoretic diffusion parameter, Brownian diffusion parameter, and chemical reaction parameter improve the rate of mass transfer. Unsteadiness parameter triggers the skin friction coefficient 53.2% when the parameter value was increased from 0.7 to 1.0. Viscous dissipation and thermal radiation increase the rate of entropy generation. A comparison of skin friction coefficient with previous studies demonstrates a strong agreement.

Effects of different momentum ratios and Reynolds number in a T-junction with an upstream elbow

This study focuses on analysing thermal mixing in T-junctions with varying momentum and Reynolds number ratios, utilizing computational fluid dynamics (CFD) simulations. The T-junction is a critical component of the primary nuclear thermal–hydraulic circuit within a pressurized water-cooled reactor (PWR). The T-junction connects the pressurizer (PRZ) with the steam generator (SG) and the reactor pressure vessel (RPV). Water from the PRZ and the SG are at different temperatures and incomplete thermal mixing occurs when these two fluid streams meet at the T-junction. This incomplete thermal mixing can induce thermal stratification of the water within the T-junction as well as thermal striping phenomena. Thermal striping phenomena can lead to fluctuations of the temperature at the inner pipe wall of the T-junction. Thermal stratification and thermal striping phenomena can induce thermo-mechanical fatigue and eventual pipe failure which can affect the safety of the reactor. Therefore, a high-fidelity, mechanistic understanding of the turbulent thermo-fluid mixing within T-junctions of PWRs might lead to improvements in component reliability and safety within nuclear power plants (NPPs).The primary aim of the research, presented in this paper, is to understand and quantify the effect of variations in the momentum ratio on the turbulent fluid flow within T-junctions. This is achieved by either varying the branch pipe diameter while keeping the inlet velocity constant (part one) or by adjusting the branch pipe inlet velocity while maintaining a constant diameter (part two). Despite the different variations in momentum ratios, the specific momentum ratios under consideration in both parts of the study remain consistent (namely 98 and 66.4). It is also noteworthy that the momentum ratios considered in the paper can be classified as wall-jet and impinging-jet, according to the definition in (Hosseini, Yuki, & Hashizume, 2008). It should be noted that the momentum ratio is manipulated by adjusting the flow parameters, leading to variations in the Reynolds number ratio between the main pipe inlet and the upstream branch pipe at the T-junction. The turbulent flows in the cases that are considered are simulated using the Improved delayed detached eddy simulation (IDDES-SST) model. The numerical results from these simulations indicate, for the considered momentum ratios, that maintaining the same momentum ratio does not produce similar mean flow behaviour and turbulent quantities of interest (QoI). For instance, the size of the flow recirculation zone is more likely linked to the diameter of the branch pipe. Moreover, the turbulent QoI and temperature fluctuations at the determined locations are likely affected by the changed flow recirculation zone as well as the Reynolds number of the branch pipe flow.

Magnetically Guided Microcatheter for Targeted Injection of Magnetic Particle Swarms.

The initial delivery of small-scale magnetic devices such as microrobots is a key, but often overlooked, aspect for their use in clinical applications. The deployment of these devices within the dynamic environment of the human body presents significant challenges due to their dispersion caused by circulatory flows. Here, a method is introduced to effectively deliver a swarm of magnetic nanoparticles in fluidic flows. This approach integrates a magnetically navigated robotic microcatheter equipped with a reservoir for storing the magnetic nanoparticles. The microfluidic flow within the reservoir facilitates the injection of magnetic nanoparticles into the fluid stream, and a magnetic field gradient guides the swarm through the oscillatory flow to a target site. The microcatheter and reservoir are engineered to enable magnetic steering and injection of the magnetic nanoparticles. To demonstrate this approach, experiments are conducted utilizing a spinal cord phantom simulating intrathecal catheter delivery for applications in the central nervous system. These results demonstrate that the proposed microcatheter successfully concentrates nanoparticles near the desired location through the precise manipulation of magnetic field gradients, offering a promising solution for the controlled deployment of untethered magnetic micro-/nanodevices within the complex physiological circulatory systems of the human body.

Efficient Analysis of Immersion Cooling of Li-Ion Batteries

Immersion cooling, where cooling fluid flows in direct contact with the Li-ion cell, provides superior temperature control compared to other battery thermal management systems (BTMSs). Although the temperature rise during charging/discharging is low for immersion cooling, the inherent complexity of the cooling approach makes it difficult to predict and control performance. In general, numerical approaches are required to design and analyze immersion cooled BTMS configurations. For accurate results, models must fully couple the electrochemical and thermal-fluid physics solvers. However, such a numerical approach is computationally expensive and may not be feasible, in particular, for large BTMS systems. In the present study, we develop a computationally-efficient approach with coupled electrochemical and thermo-fluid physics to study immersion cooling based BTMSs. The core strategy is to use either analytical expressions or combination of analytical and numerical solutions for all the governing physics. Depending on the discharge rate and on the final design objective, different levels of simplification are leveraged to analyze the thermal and electrochemical response of the system.For the present analysis, we consider discharging of a cylindrical nickel manganese cobalt oxide (NCM) 18650 cell that is immersed in a cooling fluid stream. Different combinations of mass flow rates and fluids (deionized water, mineral oil, and air) are considered to evaluate performance. For every configuration, we first analyze the system with a fully-coupled fully numerical model and this data serves as the reference to judge the accuracy of the newly developed models. Note that the parameters used in the electrochemical models (such as electrolyte and electrode properties, as well as the reaction rates) are the same for the fully-numerical and the quasi-analytical models allowing direct comparison of the results. To isolate the impact of using the simplified models for the electrochemical aspects, a second set of comparison data is generated using the analytical electrochemical model in conjunction with the full-scale numerical thermo-fluid model. The analytical models rely on calculating a heat transfer coefficient to include the impact of the fluid flow and the heat transfer coefficient can be estimated from correlations or from the fully-coupled fully-numerical models. In general, for air-cooled configuration, the thermal and electrochemical performance (i.e., trend and magnitude of temperature rise and cell potential) of the quasi-analytical models matches the fully-coupled full-scale numerical model. But for other fluids, the results deviate from the baseline fully-coupled fully-numerical models unless the numerical fluid models are used to estimate the evolution of heat transfer coefficient throughout the discharging process. Specifically, a small number of fully-coupled fully-numerical simulations are leveraged to train the quasi-analytical model (based on a particular geometry) for rapid analysis and optimization of the BTMS. In summary, the newly developed models including the numerical data-driven learning provide an efficient trade-off between computation cost and accuracy.

Newtonian flow with slip and pressure-drop predictions in hyperbolic confined geometries

We study theoretically the steady Newtonian flow in confined and hyperbolic long tubes (symmetric channels and axisymmetric pipes) considering slip along the walls. Using a stream function formulation, and the extended (or high-order) lubrication method in terms of the square of the aspect ratio of the tube, ε, the solution for the stream function is found analytically up to twentieth order in ε. At the classic lubrication limit, i.e. i.e. for a vanishing small aspect ratio, and for perfect slip conditions, the analysis predicts a plug-like velocity profile and a constant strain-rate on the midplane/axis of symmetry of the tube. A constant strain-rate is also predicted for the non-slip case. Furthermore, the high order asymptotic results for the stream function and fluid velocity are post-processed with an acceleration technique to investigate the convergence and accuracy of the solution. The results reveal the existence of a boundary layer at the inlet of the tube, the influence of which diminishes in a very short distance from the entrance. We discuss the effect of the contraction ratio of the tube and the dimensionless slip coefficient on the midplane/centerline and wall (slip) velocities, as well as on the average pressure-drop, required to maintain a constant flow-rate. The acceleration of converge technique on the solution for the pressure-drop revealed a remarkable convergence at a value slightly larger (∼1 %) than the value predicted by the classic lubrication theory. Finally, we comment on the common practice in the literature for approaching the velocity profile with the velocity profile at the classic lubrication limit, and we compare the high-order results for the strain rate at the midplane/centerline with the effective strain rate previously derived in the literature by Housiadas & Beris, J. Rheology, 68(3), 327–339, 2024.

Droplet Microfluidics for High-Throughput Screening and Directed Evolution of Biomolecules.

Directed evolution is a powerful technique for creating biomolecules such as proteins and nucleic acids with tailor-made properties for therapeutic and industrial applications by mimicking the natural evolution processes in the laboratory. Droplet microfluidics improved classical directed evolution by enabling time-consuming and laborious steps in this iterative process to be performed within monodispersed droplets in a highly controlled and automated manner. Droplet microfluidic chips can generate, manipulate, and sort individual droplets at kilohertz rates in a user-defined microchannel geometry, allowing new strategies for high-throughput screening and evolution of biomolecules. In this review, we discuss directed evolution studies in which droplet-based microfluidic systems were used to screen and improve the functional properties of biomolecules. We provide a systematic overview of basic on-chip fluidic operations, including reagent mixing by merging continuous fluid streams and droplet pairs, reagent addition by picoinjection, droplet generation, droplet incubation in delay lines, chambers and hydrodynamic traps, and droplet sorting techniques. Various microfluidic strategies for directed evolution using single and multiple emulsions and biomimetic materials (giant lipid vesicles, microgels, and microcapsules) are highlighted. Completely cell-free microfluidic-assisted in vitro compartmentalization methods that eliminate the need to clone DNA into cells after each round of mutagenesis are also presented.

Kinetic Simulation of Turbulent Multifluid Flows

Despite its visual appeal, the simulation of separated multiphase flows (i.e., streams of fluids separated by interfaces) faces numerous challenges in accurately reproducing complex behaviors such as guggling, wetting, or bubbling. These difficulties are especially pronounced for high Reynolds numbers and large density variations between fluids, most likely explaining why they have received comparatively little attention in Computer Graphics compared to single- or two-phase flows. In this paper, we present a full LBM solver for multifluid simulation. We derive a conservative phase field model with which the spatial presence of each fluid or phase is encoded to allow for the simulation of miscible, immiscible and even partially-miscible fluids, while the temporal evolution of the phases is performed using a D3Q7 lattice-Boltzmann discretization. The velocity field, handled through the recent high-order moment-encoded LBM (HOME-LBM) framework to minimize its memory footprint, is simulated via a velocity-based distribution stored on a D3Q27 or D3Q19 discretization to offer accuracy and stability to large density ratios even in turbulent scenarios, while coupling with the phases through pressure, viscosity, and interfacial forces is achieved by leveraging the diffuse encoding of interfaces. The resulting solver addresses a number of limitations of kinetic methods in both computational fluid dynamics and computer graphics: it offers a fast, accurate, and low-memory fluid solver enabling efficient turbulent multiphase simulations free of the typical oscillatory pressure behavior near boundaries. We present several numerical benchmarks, examples and comparisons of multiphase flows to demonstrate our solver's visual complexity, accuracy, and realism.

Turning Data Center Waste Heat into Energy: A Guide to Organic Rankine Cycle System Design and Performance Evaluation

This study delves into the adoption of the organic Rankine cycle (ORC) for recovering waste heat from data centers (DCs). Through a literature review, it examines energy reuse with a focus on electric power generation, the selection of working fluids, and system design principles. The objective is to develop a thorough framework for system design and analysis, beginning with a quantity and quality investigation of waste heat available. Air cooling systems, chosen often for their simplicity, account for about 70% of used cooling methods. Water cooling demonstrates greater effectiveness, albeit less commonly adopted. This study pays close attention to the selection of potential working fluids, meticulously considering the limitations presented by the available sources of heat and cold for vaporization and condensation, respectively. It reviews an ORC-based system setup, incorporating fluid streams for internal processes. The research includes a conceptual case study where the system is designed and simulations are conducted in the DWSIM environment. The simulation model considers hot air or hot liquid water returning from the data center cooling system for ORC working fluid evaporation. Ambient water serves for condensing, with pentane and isopentane identified as suitable organic fluids. Pentane assures ORC net electric efficiencies ranging between 3.1 and 7.1% when operating pressure ratios increase from 2.8 to 6.4. Isopentane systems, meanwhile, achieve efficiencies of 3.6–7.0% across pressure ratios of 2.7–6.0. Furthermore, the investigation provides key performance indicators for a reference data center in terms of power usage effectiveness (PUE), energy reuse factor (ERF), energy reuse effectiveness (ERE), and greenhouse gas (GHG) savings. This study concludes with guidelines for system analysis, including exergy considerations, and details the sizing process for evaporators and condensers.

Erosion Characterization Of Gas-Solid Jets Impinging Onto Inclined Surfaces

Erosion caused by solid particles is an important phenomenon in many industrial applications. Wear modelling is a complex phenomenon due to the many relevant variables. In any event, the dynamics of the fluid flow and particles need to be characterized so that their interrelations are well understood and models can be advanced. Depending on their sizes, particles immersed in solid-gas flows may deviate from the fluid stream, meaning that any deployed measuring technique must take this into account. The work describes through PIV and PTV the flow and particle dynamics of a round air-jet loaded with carbon silicate particles (SiO2) impinging onto an inclined surface. Flow conditions are set for two different Reynolds numbers and four impinging angles. The experimental results are compared with numerical simulations furnished by a two-way coupling scheme. The results show that erosion wear is highly dependent on the kinetic energy of the particle at impact. The larger the size of the particle or the larger its velocity, the larger is the damage it causes. A correlation between the thickness of removed material with particle size distribution and flow rate is presented. For low flow rates, the distinction between the damage caused by particles of various sizes is small.

Temperature control of sulfonation reaction in a semi-batch reactor

ABSTRACT Due to the basic dynamic nature of a batch or semi-batch reactor, during operation, the control duty may be altogether a set point tracking problem rather than a regulatory task with a fixed set point. In addition to that in a large number of exothermic reactor control, usually the reaction mass has to be raised to a higher temperature for initiation, and after the reaction sets in large amount of heat has to be extracted, so that the control system have the capabilities to heat as well as to cool the reaction mixture (like LAB Sulfonation). This may be done by manipulating the ratio of hot and cold streams of heat transfer fluids to make a mixed stream to be used as the heat transfer medium by using two 2-way control valves, and heating and cooling loads are splitted between them. The choice of this reactor type has been made on the basis of that the target system of our study is Sulfonation of Linear Alkyl Benzene (LAB) to synthesize the product, Linear Alkyl Benzene Sulfonic Acid (LABSA) which is the active species for manufacturing of domestic or industrial detergents. The reaction is essentially carried in semi-batch jacketed reactor.

Nasal Model Experiments Show That a Collimated Fluid Delivers Precise Doses to the Human Olfactory Cavity in the Side-Laying Position

The nasal administration of therapeutic fluids and vaccines is used to treat allergic rhinitis, sinusitis, congestion, coronaviruses and even Alzheimer's disease. In the latter, the drug must reach the olfactory region, so it finds its way into the central nervous system. Effective administration techniques able to reach the olfactory region are challenging due to the tortuous anatomy of the nasal cavity, and are frequently evaluated in vitro using transparent anatomical models. Here, the liquid distribution inside a 3D printed human nasal cavity is quantified for model fluids resulting from the discharge of a 1-mL syringe with either a spray-generating nozzle, and a straight tip emitting a collimated fluid stream. Experiments using two model fluids with different viscosities suggest that a simple, correctly positioned straight tip attached to a syringe is able to efficiently deliver most of a therapeutic fluid in the human olfactory region in the side-laying position, avoiding the adoption of head-back and head-down positions that can be difficult for patients in the age range typical of Alzheimer's disease. Furthermore, we demonstrate by computer simulations that the conclusion is valid within a wide range of parameters.

Investigation of conjugate heat and mass transfer in a sleeve-type hollow fiber membrane for liquid desiccant dehumidification

In adiabatic conditions, the dehumidification capacity of hollow fibre membranes decreases as solution temperature rises. To address this limitation, this study proposed a novel approach based on sleeve-type hollow fibre membranes. The study focused on three distinct fluid streams and the sleeve-type hollow fibre membrane tube. A three-dimensional model of the dehumidifier was created, and the dehumidifier's heat transfer, mass transfer, and fluid flow characteristics were thoroughly analyzed and experimentally validated. The results showed that the average values of the Sherwood number and Nusselt number on the air side are significantly influenced by the Reynolds number. On the solution side of the sleeve-type hollow membrane, the average Nusselt number and Sherwood number are approximately 4.0 and 4.6, respectively. According to the research, 76 % of the resistance is accounted for by the mass transfer resistance on the membrane side. The study's conclusions provide insightful information for improving the design of sleeve-type hollow fibre membrane dehumidifiers.

On the orientation dependence of the pressure and frictional drag experienced by spheroids in creeping flow

The present work deals with the creeping flow past a single oblate or prolate spheroid. On the basis of the investigations by Aoi [J. Phys. Soc. Jpn. 10, 119 (1955)] on the contributions of pressure and frictional drag to the total drag experienced by spheroids when the fluid streams with a speed parallel to the axis of symmetry, we find that the pressure contribution corresponds to half of the dimensionless shape factor γ0 provided by Happel and Brenner, Low Reynolds Number Hydrodynamics (Prentice-Hall Inc. Englewood Cliffs, NJ, 1965). Accordingly, we conjecture the validity of this finding when the fluid streams with a speed perpendicular to the axis of symmetry. Therefore, the formulations of dimensionless shape factors α0/2 and β0/2 are confronted with the numerical results at particle Reynolds number of 0.1. Furthermore, the formulations of the pressure and the frictional drag are deduced and extended to any orientation relative to the flow direction. These results give physical insight into the total drag experienced by spheroids in creeping flow and can be helpful for the validation of simulations of the flow past an obstacle.

Comparison of methanol and ethylene glycol effectiveness as chemical inhibitors in the prevention of gas hydrates in well testing barge DT-05 well Z Mahakam field

Gas hydrate is one of the production problems that are often encountered in the management of natural gas wells. Well Z is a natural gas well in the Mahakam field which routinely be tested periodically to determine the ability of flow rate and the production parameters using well testing barge. However, there are often for the formation of gas hydrate formed in several test components in well testing barge. This study aims to determine the effectiveness use of 2 inhibitor chemicals, which are methanol and glycol in handling gas hydrate in the testing barge. Natural gas flow originating from wellhead / upstream 5 MMScfd and temperature 122 °F and the operating pressure 2187 psia. From the simulation results, gas hydrate will form at 46.33 °F and it is obtained that the gas hydrate formation was predicted at the choke manifold. Fluid stream passing through the choke manifold had decreased the pressure into 254 psi and there is also a decrease in temperature from 122 °F to 41.88 °F. Methanol injection develops free of potential hydrates to form in flowlines. The temperature at which hydrates are formed changes to 33.88 °F. In the other hand, after Ethylene glycol injection in flowline, hydrates formation temperature dropped to 0.48 °F. From these results it can be resumed that the application of Ethylene Glycol injection on the process is more effective lowering the temperature of the formation of hydrates in well testing barge.