Fluid Flow Research Articles

Advances in Numerical Heat Transfer and Fluid Flow

Scientists continuously are looking for new methods that allow them to better understand the flow and heat transfer phenomena [...]

Analysis of non-Darcy fluid flow in and around porous medium by the effects of its properties on body wake parameters

Analysis of non-Darcy fluid flow in and around porous medium by the effects of its properties on body wake parameters

Evolution of reservoir quality related to clay coating overgrowths in tight sandstone in the fluvial facies of the southeastern Sichuan Basin

As a result of silicate overgrowth, clay coatings influence the evolution of reservoir quality during diagenesis. Most studies indicate coatings can resist compaction and inhibit cementation, thus preserving primary porosity and serving as one of the primary controlling factors for improving reservoir quality. However, some research suggests clay coatings have insufficient hardness to resist compaction and could potentially block pore throats and prevent fluid flow within the sandstone, negatively affects reservoir quality. Therefore, to address whether coatings are positive to reservoir evolution, this study employs polarized light microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and porosity-permeability testing to investigate the characteristics of clay coatings within the fluvial facies sandstone of the Xiashaximiao Formation. The microscopy reveals abundant clay coatings were found, mainly in lithic-arenite with 30%–45% feldspar and rock fragments. The underlying Lianggaoshan Formation locally exhibits interbedded siltstones with volcanic rock fragments, providing material sources for the clay coatings formation. SEM and EDX analyses indicate two predominant forms of clay coatings: single-layer (primarily chlorite) and double-layer (inner smectite/illite, outer ferroan chlorite). Single-layer overgrowths primarily consist of thin layers of chlorite (5–15 μm), whereas double-layer overgrowths consist of a thin inner zone (1–5 μm) covering the grain surface and a thicker outer zone (10–20 μm) covering the inner zone, demonstrating characteristics indicative of multi-stage growth. Porosity-permeability testing results the sandstone samples have <10% porosity, which are typically tight sandstones, but those with clay coatings have higher porosity. Nevertheless, sandstones with double-layer overgrowths exhibit lower permeability relative to those with single-layer overgrowths or without overgrowths. Therefore, based on the integration of morphological and physical properties of silicate overgrowths, it is proposed the efficiency of clay coatings in resisting compaction, inhibiting cementation, and preserving primary porosity increases with the number of growth stages, layers, and thickness, which in turn depends on the abundance of source materials. Single-layer coatings facilitate fluid migration, whereas thicker double-layer overgrowths are prone to occluding narrow pore throats, thereby restricting fluid mobility. Consequently, this study establishes a model for the multi-stage evolution of clay coatings overgrowths, elucidating the varying fluid migration behaviors across different stages and providing a more detailed investigation of the implication of clay coatings on reservoir quality, thus offering new theoretical insights into diagenesis and the evolution of tight sandstone reservoirs.

Influences of directional aperture heterogeneity on the performances of two-phase enhanced geothermal system considering the CO2 buoyant force

The technology of Enhanced Geothermal System (EGS) using CO2 as working fluid is believed to be a promising method for harnessing geothermal energy, contributing to the reduction of atmospheric greenhouse gas emissions and decreasing the dependency on traditional fossil fuels. Due to the buoyant force of CO2 in water-saturated EGS, the effects of aperture heterogeneity on fluid flow and heat transfer may be directional and differ in the two-phase flow system from the traditional single-phase EGS. In this case, we employed a thermal-hydraulic coupled model, considering a structured fracture geometry to comprehensively investigate the effect of directional distributed aperture combined with buoyant force on the EGS energy performances. The Monte Carlo method is applied to ensure that the simulation results reach statistical equilibrium. Results show that the vertical aperture heterogeneity leads to poorer energy output and carbon sequestration in a two-phase EGS, compared to the horizontal aperture heterogeneity. On the other hand, the negative effects of directional aperture heterogeneity on the total EGS energy output become more significant with the decreasing fracture density. Finally, compared to the EGS using water as the working fluid, those employing CO2 exhibits greater sensitivity to directional aperture heterogeneity for both high and low fracture-density networks due to the buoyant force of CO2.

Classification of numerical, experimental, and analytical approaches for gearbox oil flow and no-load gear power loss

The interaction of rotating machine elements with fluid in gearboxes results in fluid flow and no-load power loss. A targeted design of the gearbox lubrication system enables a reliable operation under economical and sustainable use of lubricant. This study focuses on the influence of various parameters on the oil flow and no-load gear power loss of a dip-lubricated single-stage gearbox. Numerical, experimental, and analytical results are presented and compared. A single numerical simulation setup without parameter-specific tuning is applied for a wide range of parameters. The evaluated wetted gear surface strongly depends on the circumferential speed and shows a strong correlation with the resulting no-load gear loss torque. At lower circumferential speed, the wetted gear surface decreases before increasing at higher circumferential speed. Numerical and experimental results show good agreement in terms of magnitude and trend. The analytical approaches underestimate the numerical and experimental results. Nevertheless, they do provide a good representation of the trends in terms of the influence of immersion depth and rotation direction.

Perivascular space diffusivity and brain microstructural measures are associated with circadian time and sleep quality.

The glymphatic system is centred around brain cerebrospinal fluid flow and is enhanced during sleep, and the synaptic homeostasis hypothesis proposes that sleep acts on brain microstructure by selective synaptic downscaling. While so far primarily studied in animals, we here examine in humans if brain diffusivity and microstructure is related to time of day, sleep quality and cognitive performance. We use diffusion weighted images from 916 young healthy individuals, aged between 22 and 37 years, collected as part of the Human Connectome Project to assess diffusion tensor image analysis along the perivascular space index, white matter fractional anisotropy, intra-neurite volume fraction and extra-neurite mean diffusivity. Next, we examine if these measures are associated with circadian time of acquisition, the Pittsburgh Sleep Quality Index (high scores correspond to low sleep quality) and age-adjusted cognitive function total composite score. Consistent with expectations, we find that diffusion tensor image analysis along the perivascular space index and orbitofrontal grey matter extra-neurite mean diffusivity are negatively and white matter fractional anisotropy positively correlated with circadian time. Further, we find that grey matter intra-neurite volume fraction correlates positively with Pittsburgh Sleep Quality Index, and that this correlation is driven by sleep duration. Finally, we find positive correlations between grey matter intra-neurite volume fraction and cognitive function total composite score, as well as negative interaction effects between cognitive function total composite score and Pittsburgh Sleep Quality Index on grey matter intra-neurite volume fraction. Our findings propose that perivascular flow is under circadian control and that sleep downregulates the intra-neurite volume in healthy adults with positive impact on cognitive function.

Dynamic Simulation of the Stability of Annular Flows in Gas Wells

This paper provides a holistic view of the development and progression of multiphase gas-liquid annular flow in gas wells. With the help of a momentum balance, the stability of a fully developed annular flow is defined. The Euler-Euler model was used to model the multiphase flow system, while the Reynolds-Averaged Navier–Stokes (RANS) model was used to depict a time-dependent solution for a vertical fluid flow system, considering acceleration due to gravity and fluid compressibility. The resultant flow regime was tested for stability by gradually reducing the field velocity of flow and observing the effects using a computational fluid dynamics (CFD) software. The principal parameters considered are the superficial gas velocity and liquid film flow rate. The properties of the region where the flow becomes unstable are documented and related to the incidence of liquid loading in a typical gas well. The effect are critically observed and compared to flow regimes at lower superficial gas velocity. The resultant flow regime configurations are analyzed and compared to the annular flow system. This study will help researchers understand the behaviour of gas wells that have potential in developing liquid loading problems and the movement of liquid film on the wall of the tubing when in annular flow regime.

Fluid Flow to Electricity: Capturing Flow-Induced Vibrations with Micro-Electromechanical-System-Based Piezoelectric Energy Harvester

We introduce a micro-electromechanical system (MEMS) energy harvester, designed for capturing flow energy. Moving beyond traditional vibration-based energy harvesting, our approach incorporates a cylindrical oscillator mounted on an MEMS chip, effectively harnessing wind energy through flow-induced vibration (FIV). A highlight of our research is the development of a comprehensive fabrication process, utilizing a 5.00 µm thick cantilever beam and piezoelectric film, optimized through advanced micromachining techniques. This process ensures the harvester’s alignment with theoretical predictions and enhances its operational efficiency. Our wind tunnel experiments confirmed the harvester’s capability to generate a notable electrical output, with a peak voltage of 2.56 mV at an 8.00 m/s wind speed. Furthermore, we observed a strong correlation between the experimentally measured voltage frequencies and the lift force frequency observed by CFD analysis, with dominant frequencies identified in the range of 830 Hz to 867 Hz, demonstrating the potential application in actual flow environments. By demonstrating the feasibility of efficient energy conversion from ambient wind, our research contributes to the development of sustainable energy solutions and low-power wireless electron devices.

Numerical Coupling between a FEM Code and the FVM Code OpenFOAM Using the MED Library

This paper investigates a numerical code-coupling technique to tackle multiphysics and multiscale simulations using state-of-the-art software packages that typically address some specific modeling domain. The coupling considers the in-house FEM code FEMuS and the FVM code OpenFOAM by exploiting the MED library from the SALOME platform. The present approach is tested on a buoyancy-driven fluid flow within a square cavity, where the buoyancy force constitutes the coupling term. In uncoupled scenarios, momentum and temperature equations are solved in both FEM and FVM codes without data exchange. In the coupled setting, only the OpenFOAM velocity and the FEMuS temperature fields are solved separately and shared at each time step (or vice versa). The MED library handles the coupling with ad hoc data structures that perform the field transfer between codes. Different Rayleigh numbers are investigated, comparing the outcomes of coupled and uncoupled cases with the reference literature results. Additionally, a boundary data transfer application is presented to extend the capabilities of the coupling algorithm to coupled applications with separate domains. In this problem, the two domains share interfaces and boundary values on specific fields as fluxes are exchanged between the two numerical codes.

Experimental study of heat transfer performance in rectangular microchannels enhanced by ultrasound

Ultrasound is recognized as an effective technology to enhance heat transfer, which is widely used in industrial fields such as microelectronics and heat storage. However, the heat transfer characteristics in rectangular microchannels assisted with ultrasound has little revealed in present research. In this work, the external ultrasonic was added in a rectangular microchannel to reveal the influence of ultrasound on the heat transfer characteristics of micro-channels. Hence, the comparative experiments were completed to explore the heat transfer performance with and without ultrasonic. Moreover, a large number of experiments were carried out within rectangular microchannels by varying the velocity of the working fluid and the heat flux at the bottom of the microchannels. The results indicate that the heat transfer performance of rectangular microchannels can be enhanced by ultrasound. But the enhanced heat transfer effect could be limited with the increase of the flow velocity and heat flux in microchannel correspondingly. For rectangular microchannels with adding ultrasound, the lower the flow rate and heat flow density are, the better the enhancement effect will be. During the measurement, when the fluid flow velocity is 0.2 m/s and the heat flux is 408.2 kW/m2, the heat transfer performance of the ultrasound-enhanced microchannel can be improved by a maximum of 12.9 %. Additionally, the tests indicate that the pressure drop mainly comes from the viscous loss along rectangular channel, yet the ultrasound has no negative impact on pressure drop in microchannel. This work could be beneficial to the further application of ultrasonic enhancement technology.

Transportation of melting heat in stratified Jeffrey fluid flow with heat generation and magnetic field

In current years, storage of energy is a challenging task for the scientists and researchers. So, they are interested to develop some extra ordinary techniques of energy storage. Thus, our main theme here is to focus on the latent heat energy (melting heat) which is more economical and sustainable. Transportation of melting heat in quadratic stratified Jeffrey fluid flow in the vicinity of stagnation point is scrutinized. The flow is deformed by linear stretchable sheet. Characteristics of heat transportation are scrutinized through viscous dissipation and heat generation or absorption. Constant magnetic field is implemented to electrically conducting fluid in vertical direction. The arising governing equations are converted in the non-dimensional state through suitable transformations. Homotopic technique is utilized for simulation of solutions. Graphical behavior of velocity and temperature fields is investigated corresponding to relevant parameters. As a conclusion, higher amount of energy can be achieved as melting phenomenon enhances, and also results in low temperature. Further, dominant stratification decays the temperature field. Current study will play key role in industrial liquids like polymer solutions to make high quality fiberglass, paints, silicone heat valves etc. This study will also deliberate efficiently for the storage of energy through phase change procedure i.e., melting phenomenon.

Chemical Approach to Control Hydrate in Offshore Gas Production Facilities

- Hydrate formation presents a significant operational challenge in offshore oil and gas production, primarily due to the potential formation of hydrate plugs which obstruct fluid flow, thereby posing serious flow assurance risks. Additionally, these solid, crystalline, icelike structures, composed of low molecular weight gases (such as methane, ethane, and propane) encapsulated in hydrogen-bonded water cages, can aggregate into larger masses capable of damaging or rupturing pipelines. Such formations typically occur under the high-pressure and low-temperature conditions prevalent in subsea flowlines and cold-weather operations. This study employs the Prosper simulation software to model these complex thermodynamic and hydrodynamic conditions and to predict the effective dosages of chemical inhibitors required to prevent hydrate formation. Specifically, our simulations suggest optimal dosages of 35% wt. methanol (MeOH) and 45% wt. monoethylene glycol (MEG) for gas stream 1, and 22% wt. MeOH and 33% wt. MEG for gas stream 2. Based on these findings, we advocate the use of Prosper simulation software as a predictive tool for the strategic administration of hydrate inhibitors in offshore gas production facilities. This research contributes to the ongoing development of chemical strategies for hydrate management, providing a basis for improved safety and efficiency in hydrocarbon extraction processes.

A GPU based accelerated solver for simulation of heat transfer during metal casting process

Abstract The metal casting process, which is one of the key drivers of the manufacturing industry, involves several physical phenomena occurring simultaneously like fluid flow, phase change, and heat transfer which affect the casting yield and quality. Casting process modeling involves numerical modeling of these phenomena on a computer. In recent decades, this has become an inevitable tool for foundry engineers to make defect-free castings. To expedite computational time Graphics Processing Units (GPUs) are being increasingly used in the numerical modeling of heat transfer and fluid flow. Initially, in this work a CPU based implicit solver code is developed for solving the 3D unsteady energy equation including phase change numerically using Finite Volume Method (FVM) which predicts the thermal profile during solidification in the metal casting process in a completely filled mold. To address the computational bottleneck, which is identified as the linear algebraic solver based on the Bi-Conjugate Gradient Stabilized (BiCGSTAB) method, a GPU-based code is developed using CUDA toolkit and was implemented on the GPU. The CPU and GPU based codes are then validated against a commercial casting simulation code FLOW-3D CAST® for a simple casting part and against in-house experimental results for gravity die casting of a simple geometry. Parallel performance is analyzed for grid sizes ranging from 10x10x10 to 210x210x210 and for three time-step sizes. The performance of the GPU code based on occupancy and throughput is also investigated. The GPU code exhibits a maximum speedup of 308x compared to the CPU code for a grid size of 210x210x210 and a time-step size of 2s.

The freedom law

This article explains (strong) emergence in reductionist terms. Two laws predict the structure of reality from the smallest particles to consciousness. The freedom law predicts (in a reducible way) how and when new systems, life and even new matter will emerge and where reducibility ends. The law of life, that is Bejan's “constructal law,” predicts how this life will evolve or die. If this being or system persists then it is either alive in the sense that it persists and evolves in its “design” while being a process, or it is dead in the sense of being “bricked” after having been alive. But ‘to predict’ is not ‘to understand.’ This article is about understanding. As an illustration and elaboration the laws are applied to heat and fluid flow examples, and to the emergence of consciousness.

Reconstruction of the Subsurface of Al-Hassa Oasis Using Gravity Geophysical Data

Al-Hassa city, located in Eastern Saudi Arabia, boasts the world’s largest oasis and the most expansive naturally irrigated lands. Historically, a total of 280 natural springs facilitated significant groundwater discharge and irrigation of agricultural land. Furthermore, the water in certain springs formerly had a high temperature. The spatial variability of the water quality was evident. At the same time, Al-Hassa Oasis is situated on the northeastern side of the Ghawar field, which is the largest conventional onshore oil field in the world in terms of both reserves and daily output (approximately 3.8 mmb/d). The aforementioned traits suggest an intricate subsurface that has not yet been publicly and thoroughly characterized. Due to the presence of significant cultural noise caused by agricultural and nearby industrial activities, a robust, easy-to-use, and accurate geophysical method (gravity) was used to cover an area of 350 km2, producing the 3D subsurface model of the study area. A total of 571 gravity stations were collected, covering the whole Al-Hassa Oasis and parts of the nearby semi-urban areas. The gravity data were corrected and processed, and a 3D inversion was applied. The resulting 3D geophysical subsurface modeling unveiled an intricate subterranean configuration and revealed lateral variations in density, indicating the presence of a potential salt dome structure, as well as fracture zones that serve as conduits or obstacles to the flow of the subsurface fluids. This comprehensive modeling approach offers valuable insights into the subsurface dynamics of the broader study area, enhancing our understanding of its qualitative tectonic and hydraulic features and their impacts on the area’s natural resources, such as groundwater and hydrocarbons.

CSF pulsations measured in Parkinson’s disease patients using EPI-based fMRI data

IntroductionCerebrospinal fluid (CSF) flow is involved in brain waste clearance and may be impaired in neurodegenerative diseases such as Parkinson’s disease. This study aims to investigate the relationship between the CSF pulsation and the development of dementia in Parkinson’s disease (PD) patients using EPI-based fMRI.MethodsWe measured CSF pulsation in the 4th ventricle of 17 healthy controls and 35 PD patients using a novel CSF pulsation index termed “CSFpulse” based on echo-planar imaging (EPI)-based fMRI. The PD patients were classified into a PD with dementia high-risk group (PDD-H, n = 19) and a low risk group (PDD-L, n = 16), depending on their development of dementia within 5 years after initial brain imaging. The size of the 4th ventricle was measured using intensity-based thresholding.ResultsWe found that CSF pulsation was significantly higher in PD patients than in healthy controls, and that PD patients with high risk of dementia (PDD-H) had the highest CSF pulsation. We also observed an enlargement of the 4th ventricle in PD patients compared to healthy controls.ConclusionOur results suggest that CSF pulsation may be a potential biomarker for PD progression and cognitive decline, and that EPI-based fMRI can be a useful tool for studying CSF flow and brain function in PD.

Design, analysis, and testing of a prototype-scale latent heat thermal energy storage (LTES) system

A parametric analysis was performed to design a prototype-scale latent heat thermal energy storage (LTES) system using commercial grade hexahydrate calcium chloride as phase change material (PCM) in a staggered tube array configuration, placed horizontally. The study involved numerical analysis of melting and solidification processes of the PCM within the tube array, considering transient two-dimensional Navier-Stokes equations and a Realizable k-ɛ turbulence model to predict fluid flow and heat transfer. The enthalpy-porosity technique was used to model PCM melting and solidification. The study included a comparison between numerically predicted and experimentally obtained air temperatures at the tube array outlet, as well as PCM temperatures. This comparison revealed an excellent level of agreement. Additionally, the study compared the pressure drop within the array and the average peripheral heat transfer coefficient calculated from the numerical results to the well-established Zukauskas correlation. The resulting design successfully met the predefined performance criteria: achieving a cooling effect of 4 °C for a four-hour duration while maintaining a pressure drop of <100 Pa. The proposed prototype-scale tube array design can be efficiently cooled down and PCM frozen overnight. The energy storage density of the system falls within the range of 22 to 27 kWh/m3.

Environmental Impact of Enhanced Geothermal Systems with Supercritical Carbon Dioxide: A Comparative Life Cycle Analysis of Polish and Norwegian Cases

Low-carbon electricity and heat production is essential for keeping the decarbonization targets and climate mitigation goals. Thus, an accurate understanding of the potential environmental impacts constitutes a key aspect not only for the reduction in greenhouse gas emissions but also for other environmental categories. Life cycle assessment allows us to conduct an overall evaluation of a given process or system through its whole lifetime across various environmental indicators. This study focused on construction, operation and maintenance, and end-of-life phases, which were analyzed based on the ReCiPe 2016 method. Within this work, authors assessed the environmental performance of one of the renewable energy sources—Enhanced Geothermal Systems, which utilize supercritical carbon dioxide as a working fluid to produce electricity and heat. Heat for the process is extracted from hot, dry rocks, typically located at depths of approximately 4–5 km, and requires appropriate stimulation to enable fluid flow. Consequently, drilling and site preparation entail significant energy and material inputs. This stage, based on conducted calculations, exhibits the highest global warming potential, with values between 5.2 and 30.1 kgCO2eq/MWhel, corresponding to approximately 65%, 86%, and 94% in terms of overall impacts for ecosystems, human health, and resources categories, respectively. Moreover, the study authors compared the EGS impacts for the Polish and Norwegian conditions. Obtained results indicated that due to much higher electricity output from the Norwegian plant, which is sited offshore, the environmental influence remains the lowest, at a level of 11.9 kgCO2eq/MWhel. Polish cases range between 38.7 and 54.1 kgCO2eq/MWhel of global warming potential in terms of electricity production. Regarding power generation only, the impacts in the case of the Norwegian facility are two to five times lower than for the installation in the Polish conditions.

Numerical Scheme by Legendre-Galerkin for Characterization of Micropolar-Maxwell Unsteady Fluid Model

In this dissertation, Micropolar-Maxwell unsteady fluid flow prior an expanding sheet is asymptotically investigated using an efficient Legendre-Galerkin technique in the existence of magnetic field. By employing fitting similarity mapping to the controlling partial differential equations, a system of nonlinear ordinary differential equations is obtained. In comparison to the prior studies, the suggested asymptotic outcomes are guaranteed. The impacts of elasticity/material parameters on velocity/micro-rotation profiles are shown and explored with the help of tables and figures to enhance the mechanical properties of the sheet.

Rigorous benchmarking of an iterative IBM solver by comparison to body-fitted mesh results

This study addresses the validation challenges of Immersed Boundary Method (IBM) solvers by proposing a consistent benchmarking approach. A temporally second-order Arbitrary Lagrangian–Eulerian (ALE) solver implemented in OpenFOAM is verified against lid-driven cavity flow and flow past static and oscillating cylinders. It then serves as the underlying fluid flow solver for a fully implicit diffusive direct forcing IBM solver that achieves temporal second-order accuracy, verified by the static and oscillating cylinder cases. Leveraging the shared numerical framework, the IBM solver is rigorously validated against ALE using identical settings, parameters, and nearly identical grids across twenty test cases, including stationary cylinder flow (Re = 40, 100, 185), oscillating cylinder in quiescent flow (Re = 100, KC = 5), and transversely oscillating cylinders with varying amplitudes and frequencies (16 cases in total). The IBM solver demonstrates robustness (CFL up to 8) and accuracy over a wide Reynolds number range, with relative drag coefficient errors below 7% for all considered cases. Incorporating body force correction, which reduces slip errors at negligible added computational cost, drastically improves accuracy. Proper Rhie–Chow momentum interpolation, including body forces, is critical in the adopted collocated finite volume method. For unsteady problems, the computational cost is greatly reduced without compromising accuracy by using CFL≈1.5−2 with only two outer iterations. The proposed benchmarking framework can be easily used for validation of other IBM approaches and thus potentially help to advance the state of IBM.