Fluid Velocity Research Articles

Simulating 2D Fluid Motion with the Smooth Particle Hydrodynamic Approach

Abstract Virtual two-dimensional (2D) fluid simulation is useful for directly simulating fluids in various situations, including geological simulations for landslides and fluid simulations for teaching. This research aims to simulate the behaviour of three different types of fluids (water, coconut oil, and glycerine) in a 2D container and analyse how these three types of fluids behave under various conditions, including interactions with boundaries. The research used Python programming to simulate fluids and the Wondershare Filmora X application to combine images. The Smooth Particle Hydrodynamics method simulated fluid in a 2D container with 10,000 particles by deriving the force density field directly from the Navier-Stokes equations. The Navier-Stokes equations were utilized to find the acceleration and velocity of fluid particles by considering external forces, internal forces, and gravity through this method. Acceleration and velocity were validated due to wall collisions, collisions with boundaries, and collisions between particles, which caused changes in particle position and velocity. During visualization, the fluid velocity decreased over time due to attenuation caused by interactions between neighbour particles, particles with boundaries, and particles with walls. From the simulation, it was observed that the fluid flowed from a higher place to a lower place, with fluid particles taking the shape of the container and the surface of the fluid forming waves. On the other hand, simulations with boundaries indicated that smaller gap sizes and higher viscosities led to increased difficulty in fluid penetration into the gap within the container.

Recent Patents for Optical Component Polishing Technology

Background: Fluid jet polishing, Airbag polishing, Magnetorheological polishing, and Ion beam polishing are all emerging polishing technologies commonly used for processing optical components, which can be used to manufacture various high-precision and high-quality optical components. Their processing mechanisms are to remove materials by high-speed jet impacting the surface of the workpiece; using a spherical flexible airbag as a polishing tool to obtain a super-smooth surface by adding polishing fluid containing fine abrasives; controlling the magnetic field to form a flexible polishing belt of Magnetorheological fluid, which undergoes relative motion to achieve material removal; using a neutral ion beam to bombard the surface of the workpiece to remove workpiece surface atoms and obtain a super-smooth surface through energy and momentum transfer between ions and workpiece atoms. The characteristics and removal mechanisms of various polishing methods are briefly described, and the advantages and key issues that need to be addressed for each polishing technology are pointed out, and suggestions and prospects for future research, application, and development are also given. Objective: In order to meet the growing demand for high-precision optical components and mass-manufactured optical components, this paper aims to study the various polishing technologies that are continuously improved and suggestions are made for future research and development directions. Method: This paper reviews the current patents related to various polishing technologies, such as Fluid jet polishing, Airbag polishing, Magnetorheological polishing and Ion beam polishing and other representative polishing technologies. Results: Various types of polishing technologies have been studied, and the main problem at the current stage is the lack of accuracy. The problem of the polishing device, such as fluid jet polishing, only considers the change of fluid velocity and pressure to construct the removal function model for analysis and summary, and suggestions for the latest research progress of various polishing technologies are given. Conclusion: The improvement and optimization of polishing technology are beneficial to improving the polishing accuracy and quality of optical components and have great help for the future development of related patents.

Turbulence Revealed by Wavelet Transform: Power Spectrum and Intermittency for the Velocity Field of the Cosmic Baryonic Fluid

We use continuous wavelet transform techniques to construct the global and environment-dependent wavelet statistics, such as energy spectrum and kurtosis, to study the fluctuation and intermittency of the turbulent motion in the cosmic fluid velocity field with the IllustrisTNG simulation data. We find that the peak scale of the energy spectrum defines a characteristic scale, which can be regarded as the integral scale of turbulence, and the Nyquist wavenumber can be regarded as the dissipation scale. With these two characteristic scales, the energy spectrum can be divided into the energy-containing range, the inertial range, and the dissipation range of turbulence. The wavelet kurtosis is an increasing function of the wavenumber k, which first grows rapidly then slowly with k, indicating that the cosmic fluid becomes increasingly intermittent with k. In the energy-containing range, the energy spectrum increases significantly from z = 2 to 1, but remains almost unchanged from z = 1 to 0. We find that both the environment-dependent spectrum and kurtosis are similar to the global ones, and the magnitude of the spectrum is smallest in the lowest-density and largest in the highest-density environment, suggesting that the cosmic fluid is more turbulent in a high-density than in a low-density environment. In the inertial range, the energy spectrum’s exponent is steeper than both the Kolmogorov and Burgers exponents, indicating more efficient energy transfer compared to Kolmogorov or Burgers turbulence.

The impact of particle size and concentration on the characteristics of solid–fluid two-phase flow in vertical pipe under pulsating flow

Vertical pipe hydraulic conveying is currently considered the most promising method for deep-sea mining. The conveying velocity at the inlet of the vertical pipe is often close to a pulsating form due to the influence of the flexible pipe and the marine environment. This study employs a combined Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) approach to investigate the impact of various particle sizes and concentrations on the flow behavior of solid–fluid two-phase flow in a vertical pipe under pulsating flow. The study reveals that fluid velocities exhibit periodic fluctuations within the vertical pipe under pulsating inlet flow. Moreover, the periodic phenomenon of local increases in particle velocity and concentration becomes more pronounced as particle size and concentration increase. Larger particle sizes increase particle inertia, reducing the ability to follow the fluid and leading to more localized particle aggregation. Therefore, the flow pattern within the vertical pipe transitions from homogeneous flow to plug flow as particle size increases. Variations in fluid–solid interaction forces and particle collision forces are explored to explain this phenomenon. When the particle size exceeds a critical threshold, the collision force surpasses the fluid–solid interaction force, leading to the transition.

The investigation of micro-crack generation in cementitious mine seals via temperature and strain analysis

Mine seals are employed in underground coal mines to effectively isolate abandoned areas from active workings. The seals are engineered to prevent air movement and endure dynamic pressure events resulting from methane explosions. Mine seals are made from cementitious materials and undergo a curing process that involves an exothermic reaction known as hydration. The presence of moisture (hydration) may result in the mixture contracting, which could subsequently lead to cracking during the early phases of the curing process. Cracks in the seal can influence the performance and structural stability. This study examines the formation of micro-cracks in cementitious mine seals throughout the curing process by evaluating temperature and strain data collected from thermocouples and strain gauges that were installed during the pouring phase. The samples for the mine seal were prepared using two distinct mixtures: traditional concrete and pumpable products sourced from conventional suppliers. Heat evolution curves were produced for each sampling location corresponding to the three samples. The samples of Mixture A and B, prepared according to specifications, exhibited the anticipated heat evolution curves, with the maximum temperature occurring at the center of the samples. In contrast to the other mixtures, the samples of mixture C, which were prepared outside of the specified parameters, exhibited the highest temperature at the bottom of the sample. The strain measurements showed a correlation with temperature readings, indicating that mixtures A and B exhibited the highest strain at the center of the sample, while mixture C demonstrated the greatest strain at the bottom of the sample. The examination of the gathered data reveals a significant likelihood of micro-cracks forming in each of the samples.

Multi-region coupling computational fluid dynamics simulation of the underground compressed air energy storage process

Compressed air energy storage (CAES) in underground spaces is a common method for addressing the instability of renewable energy generation. As the construction and testing of CAES systems are often of high cost, the numerical simulation which offers a more efficient and low-cost research method can provide a better alternative to research the process. In this study, a numerical simulation model has been developed to describe the air movement within the CAES process. Specifically, the study focuses on two different types of motion: air compressible flow within the cavern and air porous flow in the surrounding rock. Using OpenFOAM, a multi-region coupling solver has been developed to address the different governing equations for these two types of motion, and couples pressure, velocity, and temperature at the boundaries. The developed solver is used to simulate a field test of a CAES system. The numerical simulation results closely match the experimental data, verifying the reliability of the solver. Moreover, the solver can achieve multi-region flow simulations that are previously unattainable, resulting in more accurate simulations. Simulations have also been conducted to analyze various working conditions, including different rock permeability, porosity, and air injection mass rates. The results show that different conditions significantly affect air pressure, leakage rate, temperature, and flow field changes within the cavern. These simulation results and the underlying mechanisms have been analyzed to provide reference and technical support for site selection, construction, and operational strategies of CAES systems in underground spaces.

Features of MHD on Secant Curved Annular Circular Plate Lubricant as a Couple-Stress Fluid with Slip Velocity

The purpose of this study is to examine the magneto-hydrodynamic (MHD) and slip velocity effect on secant curved annular circular plates lubricated with couple stress fluid and to derive the modified Reynolds’s equation for non-Newtonian fluid under various operating conditions to obtain the optimum bearing parameters. Based upon the MHD theory and Stokes theory for couple stress fluid, the governing equations relevant to the problem under consideration are derived. This paper analyses the effect of slip velocity on secant curved annular circular plates with an electrically conducting fluid in the presence of a transverse magnetic field. It is found that there is an increase in squeeze film pressure, load carrying capacity and squeeze film time in secant curved annular circular plates due to the presence of magnetic effects with couple stress fluid and slip velocity.

Impacts of slip and activation energy on MHD hybrid nanofluid flow past a stretching radiated surface with heat generation/absorption

The influences of slip and activation energy on the magnetohydrodynamic (MHD) flow of hybrid nanofluid over a permeable stretching radiated surface in attendance of heat source/sink have been studied. Al2O3 and Cu nanoparticles are mixed up in water to produce a hybrid nanofluid which is very important in various industrial sectors as hybrid nanofluid has wider applications in enhancing thermal efficiency to provide efficient and reliable cooling. As no one has yet searched for the collective impacts of radiative heat flux, ‘heat generation/absorption’ and ‘Arrhenius activation energy’ on MHD flow of ‘hybrid nanofluid’ in presence of slip that we are exploring in this article, this identifies the novelty of our work. Using ‘similarity transformations’, the main equations which are partial in nature are transformed to ODEs (ordinary differential equations) which are numerically solved with the assistance of ‘shooting technique and Runge–Kutta method’ using MATHEMATICA software. The outcomes of this investigation have a noteworthy impact on the physical outlook for flow field, transfer of heat and mass. Fluid velocity diminishes due to the rise of magnetic parameter but increasing nature of concentration and temperature are observed. For the rising volume fraction of Al2O3 nanoparticles as well as for rising volume fraction of Cu nanoparticles, the heat transfer coefficient rises. Momentum ‘boundary layer thickness’ diminishes for rising velocity slip. 19.694% decrease in rate of surface heat transfer is observed when volume fraction of Al2O3 nanoparticles changes from 0.01 to 0.12 whereas 24.394% decrease is noted when volume fraction of Cu nanoparticles changes from 0.2 to 0.14. The consequences of this study can be applied to many thermal systems used in engineering and industrial developments that utilize hybrid nanofluid for heating and cooling purposes.

Influential mechanism of operational parameters on internal resonance of drill strings by numerical simulations

Abstract Drill string vibration is highly conductive to drill string fatigue and component failure. In this study, a finite element model of a drill string with bottom hole assembly (BHA) is constructed to investigate the effect of different operational parameters, such as different string length, density, pressure, and velocity of drilling fluid on drill string natural frequencies, and thus internal resonance by considering fluid-structure interaction (FSI) in ANSYS. Numerical simulations demonstrate that the natural frequencies decrease as the length of the drill string increases, which is especially true for the axial mode. The condition of 1:1 internal resonance between the axial and torsional modes only occurs when the length of drill string is sufficiently high. Nevertheless, this resonance fades away in the presence of fluid. The increment of fluid density slightly increases the natural frequency in lateral mode, whereas decreases that in axial mode. On the other hand, this effect of density is negligible in the torsional mode. The natural frequencies for axial, torsional and lateral modes decrease as the fluid velocity increases, and the impact of fluid pressure on natural frequency is almost not observable. The numerical results for the case without drill fluid are in qualitative agreement with analytical solutions. when considing the effect of drill length on natural frequency.

Numerical and Experimental Study of Raceway Pond For Production of Microalgea in Tunisia

The objective of this work is to enhance the production of microalgae under better conditions from microalgae production units. The system studied is a raceway pond constructed in the city of Monastir in Tunisia. Using the commercial CFD software ANSYS Fluent, a series of simulations were developed to validate the hydrodynamic characteristics of the pond. The results were validated by experimental measurements of the fluid velocity in both channels of the system. The standard turbulence model k-ɛ was used to model the turbulence created by the impeller of the fluid flow. The meshing effect was used to reduce the computation time of the simulation. The effect of the velocity inlet and the position of the paddle wheel in the fluid channels on the system behavior was examined .The effect of the inlet velocity and the position of the paddle wheel in the fluid channels on the system behaviour was investigated. The numerical results show good agreement with the experimental measurements. In fact, the error between the numerical and the experimental results is recorded acceptable and is small than 6.38%.

Effect of Atmospheric Mixing on Spectral Reflectivity in Sentinel Images of Baghdad Province

The lowest layer of the atmosphere is called the atmospheric mixed layer, characterized by small-scale, irregular air motions defined by winds that change in speed and direction. Aerosol radiative effects impact the atmospheric boundary layer (ABL), which holds most aerosols in the lower atmosphere. Aerosol absorption and scattering both lower the quantity of solar energy that reaches the ground, which has an impact on the spectral signature of the land coverings. In this study, 51 locations in downtown Baghdad were chosen for four different types of land cover (water bodies, farms, open areas, and residential areas) for Sentinel 2 satellite imagery, and the time the pictures were taken was 8:00 am ( 22 March, 22 June, 20 September, and 22 December) 2021. Their spectral reflectance was calculated at the NIR band using a mathematical equation in the ArcGIS program for Sentinel 2 satellite images that had been processed and analyzed. Also, atmospheric boundary layer height and solar radiation values were downloaded for the same date as the satellite images and compared with the spectral reflectivity values of the land covers(agriculture area, residential area, open area, and river) and knowing the effect of the mixing layer and solar radiation on the spectral reflectance values. The highest value of spectral reflectivity, mixing layer height, and solar radiation was in June at (0.065, 1965.524629, and 897.7088) respectively. The spectral reflectivity of plants at near-infrared (NIR) was higher than the rest of the earth’s features because plants reflect near-infrared radiation and absorb the red and blue parts of the spectrum.

Applications of Optimal Transportation

The mathematical theory of optimal transportation is constantly expanding its range of application, while applications give impulses for new research directions in the field. This workshop was specifically devoted to applications of optimal transportation in the natural sciences, and to the recent developments of the theory that have been motivated by these. The bouquet of current applications includes mathematical models for large-scale air motion, dynamics of plasmas, material design, pattern formation in fluids, collective behaviour in biology, and many more. Related theoretical developments are in the analysis of the Hellinger-Kantorovich metric for modeling reaction–diffusion processes, and in efficient numerical methods for multi-marginal optimal transport, to name two of many examples encountered in this workshop.

Comparative analysis of non‐newtonian fluids over an exponentially stretching sheet with convective boundaries

AbstractThe primary objective of this research is to explore the behavior of several non‐Newtonian fluids, including Casson, Williamson, and Maxwell fluids, over an exponentially stretching sheet considering an inclined magnetic field into account. Non‐Newtonian fluids can be encountered in many industrial and biological applications. They differentiate themselves by their sophisticated viscosity and flow properties. For the purpose of optimizing applications like coating technologies, bioengineering, and polymer processing, it is essential to comprehend their flow dynamics. This work illuminates these fluids' behaviors under convective boundary conditions, which is important for numerous industrial processes. Due to the convective boundary conditions, heat transfer at the sheet is affected by the surrounding fluid. The dominating flow field's nonlinear partial differential equations (PDEs) are synthesized into a system of coupled nonlinear ordinary differential equations (ODEs) using appropriate similarity transformations, and the resulting equations are then numerically solved using the BVP4C solver in MATLAB software. To demonstrate the behaviors of velocity, temperature, and concentration, a parametric research has been attempted. Significant parameter's effect on velocity, temperature, concentration, skin friction coefficient, Nusselt number, and Sherwood number have been investigated, and numerical findings are shown graphically. The numerical data is validated to previously published results on a variety of particular instances and found to be in great agreement. For varying values of the porosity parameter, Darcy‐Forchheimer parameter, and magnetic field, the fluid velocity falls. It is claimed that as the Forchheimer number and the porosity parameter expands, the momentum boundary layer thickness and the velocity profile diminishes. Furthermore, at the maximum levels of Schmidt number, the temperature profile rises synchronously, although the concentration profile reflects the flip pattern.

Analysis of fractionalized Brinkman flow in the presence of diffusion effect

A vertical plate experiences a dynamic flow of fractionalized Brinkman fluid governed by fluctuating magnetic forces. This study considers heat absorption and diffusion-thermo effects. The novelty of model is the fractionalized Fourier’s and Fick’s laws. The problem is solved using the constant proportional Caputo derivative and Laplace transform method. The resulting non-dimensional equations for temperature, mass, and velocity fields are solved and compared visually. We explore the influence of various parameters like the fractional order, heat absorption/generation (Q), chemical reaction rate (R), and magnetic field strength (M) through informative graphs. Additionally, we contrast the velocity fields of fractionalized and regular fluids. The visualizations reveal that diffusion-thermo and mass Grashof number enhance fluid velocity, while chemical reaction and magnetic field tend to suppress it. For the interest of engineering, physical quantities such as Sherwood number, skin friction, and Nusselt number are computed. The present study satisfying all initial and boundary condition can be reduced to to previous published work which shows the validity of present work.

A new evaluation method for sand control performance of slotted screen

Evaluation method of slotted screen performance is a critical concern for sand control. Despite its significance, comprehensive investigations into quantitative study of sand retaining during the complex flow process need further in-depth study, particularly in numerical simulation research model of the slotted screen. This paper adopts the two-way coupling calculation method of computational fluid dynamics (CFD) and discrete element method (DEM) for the particle movement and fluid flow at the slotted screen and establishes a numerical model of the sand particle migration process through the slotted screen. The sand particle deposition and plugging dynamics on the surface of the sand retaining medium and the micro sand plugging mechanism and blockage pattern are studied. The fractal dimension of formation sand is introduced to characterize different distribution of formation sand. The effects of fluid viscosity, width of the slotted screen, sand production concentration, fluid velocity and particle size distribution on sand production, sand passing rate and particle size distribution of formation sand passing through the slot and plugging behavior are studied. The sand plugging process of slotted screen can be divided into three stages: the beginning of blockage, the intensification of blockage, and the balance of blockage. Under simulated conditions, the initial sand plugging rate is 87%, and as the blockage intensifies, the sand plugging rate gradually increases to 96.5%. Based on the analysis of numerical simulation results, the index of total seepage resistance damage amplitude and velocity, general sand retention ratio and passed-sand size were defined to construct the integrated evaluation method of slotted screen media, which involves the performance of sand retention, anti-plugging and flow ability. A brand new set of ideas on quantifying the integrated evaluation method were introduced to calculate the individual and integrated performance indicators of the slotted screen based on simulated data. The quantitative evaluation of the sand control performance of the slotted screen provides guidance and reference for the parameter design of the slotted screen in the target oil region and the accuracy optimization of the sand control medium.

Bubble characterization and bubble population on SiC material surface in subcooled boiling flow

A particularly promising candidate for widespread adopted Accident-Tolerant Fuels(ATF) is Silicon Carbide (SiC), which is deemed significantly advantageous for nuclear energy applications due to its remarkable characteristics. The understanding of bubble behavior on SiC surfaces is critical for the development of improved SiC designs. An experiment study was executed to evaluate the characteristics and population of bubbles on the surface of SiC material in subcooled boiling flow. The experimental setup maintained atmospheric pressure and featured a subcooling range of 0-12 K and a wall superheat from 0K to 30K, and a maximum coolant Reynolds number of 10400. The findings accentuated that the sensitivity of heat to fluid velocity during nucleation boiling is greater on surfaces with small porosity than on those with larger porosity. The Sauter mean diameter displays an upward trend in sync with increasing wall superheat, and the Sauter mean diameter can be represented as a dependence of the maximum and minimum bubble diameters. In terms of bubble distribution properties, it was discovered that bubble size and bubble aspect ratio conform to a lognormal distribution, while bubble orientation adheres to a normal distribution, and bubble circularity validates a Weibull distribution.

The causes of air movement in hidden indoor micro-environments: measurements in historic bookshelves.

The use of ventilation holes in small micro-environments has been proposed by the National Trust as a mechanism to improve the environmental conditions of moisture and temperature within bookshelves. At one National Trust historic property, this mechanism has been used to encourage air movement behind books as a possible strategy to reduce the risk of mould growth. It is believed that including ventilation holes as a passive design solution to promote airflow within micro-environments could prevent decay from occurring in the archives of historic buildings. This paper investigates the mechanisms that cause airflow behind bookshelves using field measurements in three National Trust historic libraries. The measurements indicate that small but measurable velocities, up to 4 cm/s, can be passively generated behind bookshelves. Air movement in such confined micro-environments is probably caused by a combination of natural convection, caused by temperature differences between the walls and the interior and the exterior of the bookshelf, and forced convection due to drafts in the surrounding environment. While in some cases one mechanism prevailed, both mechanisms may be present simultaneously in most cases. Further research is needed to clarify how surface temperature drives air motion behind shelves.

Experimental Study on the Transport Behavior of Micron-Sized Sand Particles in a Wellbore

In the process of natural gas hydrate extraction, especially in offshore hydrate extraction, the multiphase flow inside the wellbore is complex and prone to flow difficulties caused by reservoir sand production, leading to pipeline blockage accidents, posing a threat to the safety of hydrate extraction. This paper presents experimental research on the migration characteristics of micrometer-sized sand particles entering the wellbore, detailing the influence of key parameters such as sand particle size, sand ratio, wellbore deviation angle, fluid velocity, and fluid viscosity on the sand bed height. It establishes a predictive model for the deposition height of micrometer-sized sand particles. The model’s predicted results align well with experimental findings, and under the experimental conditions of this study, the model’s average prediction error for the sand bed height is 12.47%, indicating that the proposed model demonstrates a high level of accuracy in predicting the bed height. The research results can serve as a practical basis and engineering guidance for reducing the risk of natural gas hydrate and sand blockages, determining reasonable extraction procedures, and ensuring the safety of wellbore flow.

The Impact of Wind Movement on Providing Thermal Comfort in Urban Design

The wind movement is a crucial factor in enhancing thermal comfort, forming an essential part towards friendly and sustainable urban environment. Air movement, as a prominent climatic factor, reduces heat stress with improving ventilation quality. Effective natural ventilation and heat stress mitigation can be achieved by orientation, planning and shaping the urban blocks in urban environments. Air movement represents the most important element in improving environmental adaptation, as the rapid airflow reaching buildings can significantly reduce their temperature. Site planning requires precise knowledge of the main wind directions and speeds. The research utilized the ENVI-met Models program for modeling urban environments and predicting thermal effects in the built environment. This program plays a crucial role in understanding and analyzing environmental conditions and their impact on thermal comfort. The research addressed the knowledge gap and lack of local studies in highlighting the role of wind movement in enhancing thermal comfort in urban environments using ENVI-met Models. The research aimed to provide specific knowledge in measuring wind movement and its role in enhancing thermal comfort in urban environments using the program. The research hypothesized that analyzing and modeling wind movement with ENVI-met Models can effectively contribute to understanding and improving thermal comfort in urban environments. One of the key findings is that studying the impact of wind movement with this program is essential for providing scientific and technical foundations to improve urban design and enhance thermal comfort in urban areas, promoting sustainability and environmental quality in cities

Separating Light Impurities from the Combed Heap in the Adapter Case

Introduction. It is possible to increase the separating of loose grain on the lattice bottom of the combine harvester feeder house by removing most of the light impurities from the combed heap using an inertial cleaning system built into the combing adapter body.Aim of the Study. The study is aimed at developing an inertial system for separating light impurities in the combing header body and optimizing its main parameters.Materials and Methods. The object of the study was a large-scale model of a pneumatic cleaning device to simulate the motion of air and components of a combed grain heap inside the combing adapter body. It was a two-factor experiment with three variations of the air flow velocity (4.5; 5.5; 6.5 m/s) and the width of the air channel (0.26; 0.29; 0.32 m). The studies were conducted on a combed heap of Moskovskaya 56 wheat with a moisture content of about 12%. As a parameter for optimization and response function, a portion of the combed heap was selected from the body of the installation with an air flow.Results. According to the results of the experimental studies, it was found that the air flow velocity has a greater effect on separating glumes than the width of the air channel. A simultaneous increase in both factors leads to an improved separation. At the same time, if increasing the air flow velocity ensures a stable increase in the proportion of the combed heap and is limited only by the air velocity at which grain appears in the combed heap along with the glumes, then changing the channel width allows achieving the parameter optimal value.Discussion and Conclusions. The use of an inertial cleaning system makes it possible to remove almost completely light impurities from the combed heap. The optimal parameters of the device are: channel width 0.28...0.3 m, air flow velocity 6...6.5 m/s.