Fluid Flow Research Articles

Predicting the physics of turbulent fluid flow passing through nature-inspired dolphin turbulator by artificial neural network

Predicting the physics of turbulent fluid flow passing through nature-inspired dolphin turbulator by artificial neural network

Intravenous arachnoid granulation hypertrophy in patients with Parkinson disease

Intravenous arachnoid granulations (AGs) are protrusions of the arachnoid membrane into the venous lumen and function as contributors to the cerebrospinal fluid (CSF) flow circuit. Patients with Parkinson disease (PD) often present with accumulation of alpha synuclein. Previous works have provided evidence for neurofluid circulation dysfunction in neurodegenerative diseases associated with changes in CSF egress, which may have implications regarding AG morphology. The present study aims to investigate group differences in AG volumetrics between healthy and PD participants, as well as relationships between AG characteristics and clinical assessments. Generalized linear models revealed significant increases in AG volumetrics and number in PD compared to healthy controls. Partial Spearman-rank correlation analyses demonstrated significant relationships between AG metrics and motor and cognitive assessments. Finally, AG volumetrics were positively correlated with objective actigraphy measures of sleep dysfunction, but not self-report sleep symptoms.

Fluid Flow Behavior in Nanometer-Scale Pores and Its Impact on Shale Oil Recovery Efficiency

Fluid Flow Behavior in Nanometer-Scale Pores and Its Impact on Shale Oil Recovery Efficiency

Heat transfer assessment of magnetized tangent hyperbolic fluid flow through porous disk using LWCM: Application in solar thermal power plant

Heat transfer assessment of magnetized tangent hyperbolic fluid flow through porous disk using LWCM: Application in solar thermal power plant

Obstructed Branching Networks: A Constructal Approach in Fluid Flow Investigation

Tree flow networks are common in both natural and manufactured systems. The organization of the flow hierarchy passes through the dimensional evolution of the form that is linked to the function. Thus, the objective of comparing bifurcated tube networks obtained by the constructal design method, where part of the structure is obstructed, aims to understand the effects on fluid flow and the prediction of evolutionary deviations in its function. This study compares designs of 3D tree networks with various homothety reduction factors for sizes, having tubes obstructed in some locals of the network. In this computational fluid dynamics study, the geometric constraint applied to these networks is the equal total volume of tubes at each branch level. The evaluation is based on the flow resistance of the networks. This study shows, among other things, that the performance of tree designs is highly dependent on geometric characteristics and the branching level where the obstructions are applied. The effect of the number and position of tubes obstructed in the network, as well as the alignment of the tubes across the network branching levels, on the asymmetry of fluid flow through the network is also studied. It is recommended that the results presented be considered when designing networks for engineering systems.

Evaluation of cavitation phenomena in three-way globe valve through computational analysis and visualization test

A three-way valve has a multi-port structure with three openings, which allows control of the fluid direction. However, owing to the complicated trim shape of the internal flow, an irregular fluid flow occurs, which hinders precise fluid flow control. In severe cases, cavitation induces mechanical damage owing to abrupt changes in the fluid direction. In this study conducted a computational fluid dynamics (CFD) analysis was performed to estimate the localized cavitation around the bottom plug of the three-way valve. To quantify localized cavitation, the percentage of cavitation (POC) was derived using the vapor volume fraction (VVF). The POC, defined by the cavitation occurrence zone with VVF > 0.5 divided by the volume of the cavitation danger zone, was 34.90%. Cavitation at this POC level could cause mechanical damage; therefore, a size optimization was performed. The lengths of the optimized waist and tail regions of the bottom plug were obtained wherein the POC level decreased by 19.06%. In addition, experiments were conducted using a flow visualization test setup. The experimental results were quantified into the POC employing the image gradients method, and the results were in good agreement with the CFD analysis.

Implicit hydromechanical representation of fractures using a continuum approach

Fractures control fluid flow, solute transport, and mechanical deformation in crystalline media. They can be modeled numerically either explicitly or implicitly via an equivalent continuum. The implicit framework implies lower computational cost and complexity. However, upscaling heterogeneous fracture properties for its implicit representation as an equivalent fracture layer remains an open question. In this study, we propose an approach, the Equivalent Fracture Layer (EFL), for the implicit representation of fractures surrounded by low-permeability rock matrix to accurately simulate hydromechanical coupled processes. The approach assimilates fractures as equivalent continua with a manageable scale (≫1 μm) that facilitates spatial discretization, even for large-scale models including multiple fractures. Simulation results demonstrate that a relatively thick equivalent continuum layer (in the order of cm) can represent a fracture (with aperture in the order of μm) and accurately reproduce the hydromechanical behavior (i.e., fluid flow and deformation/stress behavior). There is an upper bound restriction due to the Young's modulus because the equivalent fracture layer should have a lower Young's modulus than that of the surrounding matrix. To validate the approach, we model a hydraulic stimulation carried out at the Bedretto Underground Laboratory for Geosciences and Geoenergies in Switzerland by comparing numerical results against measured data. The method further improves the ability and simplicity of continuum methods to represent fractures in fractured media.

Regression modeling of Bödewadt slip flow dynamics involving Reiner-Rivlin nanofluid based on a modified Buongiorno approach

Regression models are useful in analyzing rotational flows as they enable accurate predictions of wall shear and heat transfer coefficient. In addition, Bödewadt flow is of paramount importance in fluid dynamics of rotating systems such as turbomachinery and geophysical flows. Moreover, nanofluid’s enhanced heat transfer properties can improve cooling efficiency in applications involving turbines and electronic systems. This study delves into the Bödewadt boundary layer flow of a Reiner-Rivlin fluid containing nanoparticles over a stationary porous disk under slip conditions. The two-phase Buongiorno model is employed, incorporating temperature-dependent diffusion coefficients for enhanced accuracy. To facilitate numerical simulations, the transport equations are converted into an ordinary differential system comprising four unknowns. In the present work, a highly reliable Keller-Box methodology is adopted which agrees very well with the MATLAB built-in program ‘bvp4c’. The computed 2-D and 3-D streamlines vividly capture the Bödewadt flow scenario with Reiner-Rivlin nanofluid. The principle aim to investigate the impact of non-Newtonian behaviour and slip on the flow pattern, while also examining the behavior of temperature/concentration field for nanoparticle working fluids. As thermophoretic diffusion increases, the thermal boundary layer thickens considerably, leading to a notable decrease in the cooling rate of the disk. In contrast, Brownian diffusion has only a minimal impact on the heat transport. In addition, wall suction effect is observed to significantly boost the disk’s cooling rate, though at the expanse of increasing skin friction coefficients. This study introduces linear and quadratic regression models designed to precisely predict both the surface drag and disk cooling rate, which are crucial factors in engineering processes.

Analyzing Foam Injection Dynamics in Porous Media: A Combined Computational and Experimental Approach

The study of foam injection dynamics into porous media holds numerous applications, with its primary use being the optimization of the oil extraction process. Additionally, it finds utility in various other domains, including soil decontamination techniques. This study focuses on evaluating foam injection through low-cost experiments and computational models. The model integrates a classic two-phase immiscible fluid flow in a porous media framework, augmented by a mobility reduction factor to simulate foam’s impact on gas phase mobility. Simple experiments were conducted to assess water displacement using both gas and gas-foam injection methods. Results revealed that while gas injection tends to form preferential paths rapidly, leading to gas disruption, foam injection generates a more compact front, enhancing sweep efficiency by mitigating preferential path formation. The computational model successfully reproduced the experimental findings qualitatively. This research introduces a cost-effective experiment suitable for didactic purposes, illustrating complex concepts and underscoring the complementary nature of experimental and computational methodologies in advancing engineering techniques.

Atmospheric Bubbling Fluidized Bed Risers: Effect of Cone Angle on Fluid Dynamics and Heat Transfer

Abstract In this paper, a comparative study of fluid flow behavior and thermal characteristics of sand particles has been carried out numerically and experimentally in bubbling fluidized beds for five-cone angles of the riser wall having 0 deg, 5 deg, 10 deg, 15 deg, and 20 deg. An Eulerian model with a k–ε turbulence model is used to explore the numerical analysis, and the findings are compared to those of the experiments. For the study, the inlet air velocity is fixed at 1.5 m/s with sand particles filled up to 30 cm to maintain bubbling conditions in the risers. The results indicate that increasing the cone angle up to 10 deg while maintaining the amount of bed materials constant leads to a reduction in pressure drop. The expansion of particles along the riser is observed to decrease with the increase in the cone angle up to 10 deg. The radial solid volume fraction profile transforms to a U shape from the W-type profile as the cone angle increases up to 10 deg. Correspondingly, the solid velocity is found to have an inverted U-type and W-shaped profile for the risers. The granular temperature is also found to increase with a decrease in the solid percentage at any location. The average bed temperature, interphase, and bed-to-wall heat transfer coefficient at a location of 10 cm axial height also increase with the cone angle increase up to 10 deg. As a result, the conical riser, when designed with a greater cone angle up to 10 deg, exhibits more efficiency in terms of heat transfer characteristics. The 3D simulation results are in strong concurrence with the experimental results in all investigations.

A Thermal Model for a Hybrid Gas Bearing System in Oil-Free Turbochargers

Abstract With little drag friction, gas bearings operate at high rotor speed and high temperature and thus enable long operating life along with material damping for mechanical energy dissipation. However, most computational tools for modeling gas bearings are not accessible to bearing manufacturers or potential end-users, and the models are restricted to specific geometries and operating conditions or are missing important features, thus limiting their utility. This paper presents the thermal energy transport in a hybrid gas bearing for oil-free turbochargers with integrated heat and fluid flow models to produce a comprehensive thermo-hydrodynamic analysis predictive tool, and to design and evaluate air-lubricated gas bearings by predictions and experiments. An efficient algorithm couples the solution of the Reynolds equations and the thermal energy transport equations in the film between the rotor and a pad of the hybrid gas bearing, and updates the temperature-dependent viscosity and film thicknesses during the iterative process. The test repeats and averaged for each rotor speed from 2 krpm to 22 krpm at intervals of 2 krpm, for supply pressure varying along 25 psi to 100 psi and predicted film temperature matches well with the measured one. The parameters of interest in this analysis include the gas supply condition, bearing configuration, and the gas properties at high altitudes and high rotation speeds. The parametric study results show the density and kinematic viscosity are the most dominant properties of the gas lubrication for the film temperature.

Enhancing geothermal efficiency: Experimental evaluation of a high-temperature preformed particle gel for controlling preferential fluid flow

Enhanced Geothermal System (EGS) reservoirs represent a vital frontier in clean energy production. However, short-circulation flow within these reservoirs can significantly affect their immediate efficiency and long-term viability. Injected cold fluids moving through wide fractures or direct channels between injection and production wells reduce thermal production temperatures, disrupting energy output. Preformed Particle Gels (PPGs) have proven effective in controlling preferential fluid flow in oil and gas reservoirs, effectively regulating fluid movement. This work explores the potential of a novel High-Temperature Preformed Particle Gel (HT-PPG), designed for geothermal applications, to plug fractures in a simulated geothermal reservoir. Core flooding experiments in coated and uncoated sandstone models were conducted under varying HT-PPG sizes, swelling ratios, and fracture widths to determine gel plugging efficiency. Variations in the HT-PPG injection pressure, breakthrough pressure, and residual resistance factor (Frr) were evaluated. Water breakthrough pressures can reach 464.10 psi/ft. While the stable injection pressure of HT-PPG decreased with increasing swelling ratio and fracture width, it was higher in uncoated cores. The HT-PPG significantly sealed the fractures, drastically reducing conductivities to millidarcy levels. This work validates HT-PPG a robust solution to mitigate fluid diversion challenges in sandstone EGS reservoirs, enhancing performance and advancing sustainable geothermal energy production.

Numerical Study of High-g Combustion Characteristics in a Channel with Backward-Facing Steps

High gravity (high-g) combustion can significantly increase flame propagation speed, thereby potentially shortening the axial length of aero-engines and increasing their thrust-to-weight ratio. In this study, we utilized the large eddy simulation model to investigate the combustion characteristics and flame morphology evolution of premixed propane–air flames in a channel with a backward-facing step. The study reveals that both the increase in centrifugal force and flow velocity can enhance pressure fluctuations during combustion and increase the turbulence intensity. The presence of centrifugal force promotes the occurrence of Rayleigh–Taylor instability (RTI) between hot and cold fluids. The combined effects of RTI and Kelvin–Helmholtz instability (KHI) enhance the disturbance between hot and cold fluids, shorten the fuel combustion time, and intensify the dissipation of large-scale vortices. The increase in fluid flow velocity can raise the flame front’s hydrodynamic stretch rate, thereby enhancing the turbulence level during combustion to a certain extent and increasing the fuel consumption rate. When a strong centrifugal force is applied, the global flame propagation speed can be more than doubled. Within a certain range, the increase in high-g field strength can enhance the intensity of RTI and accelerate the transition of RTI to the nonlinear stage.

Oil Distribution around Ball–Raceway Local Contact Region in Under-Race Lubrication of Ball Bearing

The distribution of oil and gas phases around ball–raceway local regions is an important basis and foundation for determining whether a bearing is sufficiently lubricated. To obtain the oil phase distribution law in the inner raceway–ball contact local region (IBCR) and outer raceway–ball contact local region (OBCR) of the ball bearing with under-race lubrication, the numerical simulation method is used. The effects of bearing rotation speed, oil flow rate, oil viscosity, and oil density on these two regions are studied. The results indicate that the oil phase exhibited significant periodic changes in both time and space. Compared with that in the IBCR, the oil phase distribution in the OBCR is more uniform. Increasing the bearing rotation speed and reducing the oil flow rate made the IBCR and OBCR more uniform. Changing the oil viscosity only alters the distribution pattern of the OBCR. The oil density may not affect the fluid flow state or the oil phase distribution in the bearing.

Anatomy of a fumarole field: drone remote-sensing and petrological approaches reveal the degassing and alteration structure at La Fossa cone, Vulcano, Italy

Abstract. Hydrothermal alteration and mineralization processes can affect the physical and chemical properties of volcanic rocks. Aggressive acidic degassing and fluid flow often also lead to changes in the appearance of a rock, such as changes in surface coloration or intense bleaching. Although hydrothermal alteration can have far-reaching consequences for rock stability and permeability, limited knowledge exists on the detailed structures, extent, and dynamic changes that take place near the surface of hydrothermal venting systems. By integrating drone-based photogrammetry with mineralogical and chemical analyses of rock samples and surface gas flux, we investigate the structure of the evolving volcanic degassing and alteration system at the La Fossa cone on the island of Vulcano, Italy. Our image analysis combines principal component analysis (PCA) with image classification and thermal analysis through which we identify an area of approximately 70 000 m2 that outlines the maximum extent of hydrothermal alteration effects at the surface, represented by a shift in rock color from reddish to gray. Within this area, we identify distinct gradients of surface coloration and temperature that indicate a local variability in the degassing and alteration intensity and define several structural units within the fumarole field. At least seven such larger units of increased activity could be constrained. Through mineralogical and geochemical analysis of samples from the different alteration units, we define a relationship between surface appearance in drone imagery and the mineralogical and chemical composition. Gradients in surface color from reddish to gray correlate with a reduction in Fe2O3 from up to 3.2 % in the unaltered regime to 0.3 % in the altered regime, and the latter coincides with the area of increased diffuse acid gas flux. As the pixel brightness increases towards higher alteration gradients, we note a loss of the initial (igneous) mineral fraction and a change in the bulk chemical composition with a concomitant increase in sulfur content from close to 0 % in the unaltered samples to up to 60 % in samples from the altered domains. Using this approach of combined remote-sensing and in situ analyses, we define and spatially constrain several alteration units and compare them to the present-day thermally active surface and degassing pattern over the main crater area. The combined results permit us to present a detailed anatomy of the La Fossa fumarole field, including high-temperature fumaroles and seven larger units of increased alteration intensity, surface temperature, and variably intense surface degassing. Importantly, we also identify apparently sealed surface domains that prevent degassing, likely as a consequence of mineral precipitation from degassing and alteration processes. By assessing the thermal energy release of the identified spatial units quantitatively, we show that thermal radiation of high-temperature fumaroles accounts for < 50 % of the total thermal energy release only and that the larger part is emitted by diffuse degassing units. The integrated use of methods presented here has proven to be a useful combination for a detailed characterization of alteration and activity patterns of volcanic degassing sites and has the potential for application in alteration research and for the monitoring of volcanic degassing systems.

Influence of radiation on the stability of MHD micropolar fluid in a vertical channel

The objective of the present article is to explore the stability of micropolar fluid flow in a vertical channel in the presence of thermal radiation and a transverse magnetic field. The generalized eigenvalue problem is numerically solved by utilizing the Chebyshev spectral collocation method, which is obtained from the perturbed state using the normal mode technique. The numerical data were compared with previously published results for particular cases. The critical modified Grashof number (Grc′) and the associated wave numbers (αc) are calculated and displayed graphically for different values of the parameters. It is noticed that the boundaries of instability may be increased or decreased with the flow governing parameters because of the presence of a magnetic field and thermal radiation.

An immersed multi-material arbitrary Lagrangian–Eulerian finite element method for fluid–structure-interaction problems

Fluid–structure-interaction (FSI) phenomena are widely concerned in engineering practice and challenge current numerical methods. In this article, the finite element method is strongly coupled with the multi-material arbitrary Lagrangian–Eulerian (MMALE) method to develop a monolithic FSI method named the immersed multi-material arbitrary Lagrangian–Eulerian finite element method (IALEFEM). By immersing the finite elements in the MMALE computational grid, the fluid–solid interface is directly tracked by the element boundary with accurate normal directions. The fluid–structure-interaction is implicitly implemented by assembling the nodal variables and updating the Lagrangian momentum equation on the MMALE grid. Combining the advantages of both MMALE and FEM with the immersed boundary method, the IALEFEM is effective for solving complicated FSI problems with multi-material fluid flow. A slip fluid–structure-interaction method is also proposed to enhance the computational accuracy in simulating FSI problems with significantly different velocity fields. The accuracy and effectiveness of the IALEFEM are verified and validated by several benchmark numerical examples including the shock-cylinder obstacle interaction, flexible panel deformation induced by shock wave, dam break problem with large structural deformation, water entry of a wedge, fragmentation of a cylinder shell induced by blast, response of elastic plate subjected to spherical near-field explosion and structural damage of open-frame building under blast loading.

Experimental Study on Nonlinear Fluid Flow Characteristics of Fractured Granite Rocks Treated by Chemical Corrosion Under Confining Pressure Conditions

Experimental Study on Nonlinear Fluid Flow Characteristics of Fractured Granite Rocks Treated by Chemical Corrosion Under Confining Pressure Conditions

Experimental Characterization of the Mechanical Properties of Filter Media in Solid–Liquid Filtration Processes

Nonwoven filter media are used in many industrial applications due to their high filtration efficiency and great variety of compositions and structures which can be produced by different processes. During filter operation in the separation process, the fluid flow exerts forces on the filter medium which leads to its deformation, and in extreme cases damage. In order to design or select a reliable filter medium for a given application, it is essential to have a comprehensive understanding of the mechanical properties of the nonwoven material. In general, the properties of the filter material are influenced by temperature and can be changed during loading due to irreversible deformation, fatigue, and aging processes. In order to gain a deeper comprehension, the presented study examines the influence of temperature and repeated tensile stress on the filter medium properties. The focus is on fuel and oil filters employed in automotive applications. The characteristic properties of the samples, including thickness, porosity, and permeability as well as Young’s modulus and Poisson’s number, are measured. Young’s modulus is determined for both new and aged samples. In addition, the viscoelastic behavior is investigated via a dynamic mechanical thermal analysis. The results demonstrate a significant dependence of mechanical properties on the material composition and the aging effects.

Thermohaline convection in MHD Casson fluid over an exponentially stretching sheet

Abstract This study investigates the thermohaline convection in MHD Casson fluid over an exponentially stretching sheet. This study has practical significance in industrial processes, materials processing, energy systems, and environmental applications. The governing equations describing the conservation for an electrically conducting fluid flow, thermal and concentration transports are considered based on the principles of mass, momentum, energy and concentration equations. Our first step involves transforming the governing nonlinear partial differential equations into a coupled nonlinear ordinary differential equations with the help of suitable similarity transformations. Second step, infinite domain [0, ∞) of the problem to a finite domain [0, 1] through a coordinate transformations. This specific choice is motivated by the wavelet's significance in the finite domain of [0, 1]. Third step, we effectively solve the resulting coupled nonlinear ordinary differential equations using the numerical Hermite wavelet method (HWM). This approach proves to be a valuable technique for obtaining significant results and insights in our study. Finally, the effect of known physical parameters on velocity, temperature and concentration are analysed through tables and graphs.