Fluid Velocity Research Articles

Numerical modeling of the fracturing mechanisms of unconsolidated sand reservoirs under water injection

Produced Water Re-Injection is a standard practice in oil and gas operations. When performed at sufficiently high pressures, it can trigger the fracturing of the reservoir, which should be controlled to stimulate the formation without compromising its safety. While the mechanisms of the hydraulic fracturing of brittle rocks are well-understood, this understanding is more challenging in the case of unconsolidated sand reservoirs. Recent experimental studies indicate that pseudofractures in such formations primarily result from shear banding and flow channelization. There is a need for further interpretation of the experimental findings through numerical models that account for the proper physical phenomena. For that, a coupled finite element model of water percolation, particle transport and strain localization is developed to replicate the experiments of radial injection of water in mixtures of sand and fines by Nguyen et al., 2022: An experimental setup with radial injection cell for investigation of fracturing in unconsolidated sand reservoirs under fluid injection. Journal of Petroleum Science and Engineering 213:11036. To simulate shear banding, the model accounts for strain-softening behavior and introduces material imperfections in a few weak elements. Particle mobilization starts once a critical fluid velocity is reached and permeability is assumed to be a function of particle concentration. The numerical models can replicate the geometry of the observed radial pseudofractures, as well as the measured fracturing pressures. They also qualitatively capture the effects of the initial stress state on the fracturing pressure, the fracture length and on the permeability increases during the fracturing regime as observed in the laboratory tests. Notably, the numerical results gave hints on the role of the coupling between strain localization and particle transport on the formation of the pseudofractures. These findings are used to propose an updated conceptual model for the hydraulic fracturing of sand packs.

Hygrothermal response to air movements in wall junctions: Comparison between two numerical approaches and experiments

Airflow in wall-to-wall junctions is known to have a major hygrothermal impact on building performance. However, current and validated modeling options to simulate such phenomena are limited. This paper develops and compares two numerical models to study the heat and moisture transfer due to air infiltrations through a prefabricated wall-to-wall junction. The first model explicitly accounts for the airflow with a pipe flow approach. The second model is a modification to a typical approach to simulate ventilated cavities in building envelope simulation tools and mimics the effect of the airflow through source terms. Both approaches were introduced in a heat and moisture transfer 2D finite element model. Additionally, laboratory measurements were conducted in a climatic chamber to validate the simulation results. Six scenarios were tested experimentally under steady-state conditions. These datasets were used to calibrate different parameters of the models, such as material properties, the junction air gap thickness, and the magnitude of the heat and moisture source terms. Both sets of numerical results provided reasonable agreement with the measurements. The first approach outputs more accurate temperature and relative humidity values than the second one. However, considering uncertainties, no method predicted a perfect fit with the relative humidity profiles. Close to the junction, the first method estimates better the relative humidity than the second one. This work provides guidelines to better model and account for wall junctions in building envelope simulators.

Mesosphere/Lower Thermosphere 3‐Dimensional Spatially Resolved Winds Observed by Chinese Multistatic Meteor Radar Network Using the Newly Developed VVP Method

AbstractWe present the first continuous observations of three‐dimensional spatially resolved wind fields and atmospheric motions in the mesosphere and lower thermosphere in the mid‐latitudes of the Northern Hemisphere. Our observations were performed during a 19‐month campaign from January 2022 to July 2023 and exploited the composite data from the first multistatic meteor radar system in China and an adjacent monostatic meteor radar. To retrieve the atmospheric kinetic properties, we introduce an improved volume velocity processing method including coordinate transformations and non‐linear constraints to minimize errors. The vertical winds are estimated separately from the iteration of the horizontal divergence to avoid potential biases or contamination from the horizontal winds. The winds and air motions show annual/semiannual variation characteristics within certain altitudes, usually more variable around the equinoxes. The vertical winds are basically within the magnitude of 1 m/s and are upward as expected at the mesopause during the summer, which corresponds to the adiabatic cooling.

Heat and mass transfer analysis of Casson-based hybrid nanofluid flow in the presence of an aligned magnetic field: An application toward mechanical engineering

This examination explores the flow of a hybridized nanofluid (HyNf) containing silica and tin oxide nanoparticles mixed with engine oil (EO/SnO2-SiO2). The flowing occurs via a permeable material constrained by a semi-infinite flat plate. The study takes into account various factors such as convective heat and mass transference, chemical reactions, the Dufour effect, the Lorentz force, thermal radiative fluxing, and radiative absorbing. The research involves converting the managing formulas of the flowing model into a dimensionless form and applying the regular perturbation procedure to find solutions for the rate of fluid flow, temperature, and species diffusion. The surface frictional factor, Nusselt quantity, and Sherwood quantity reflect the shearing stress, rates of heat transference, and rates of mass transport at the plate, respectively. An analysis is conducted on the impact of several factors, including the suction variable, magnetic variable, radiation-absorbing factor, Casson parameter, and Dufour number, on the flow and related quantities. This analysis is based on an examination of graphs and tables. The findings suggest that the heat transference rate in the Casson hybridized nanofluid is better than that in the mono nanofluid. It is exposed that the temperature reduces at the plate having improved frequency of oscillation and also fluid velocity declines for improving values of aligned magnetized field [Formula: see text], but it shows the reverse phenomenon with Gr1 and Gc1.

Finite difference simulation of natural convection of two-phase hybrid nanofluid along a vertical heated wavy surface

This study employs finite difference modelling to investigate the natural convection of a two-phase hybrid nanofluid consisting of Al 2 O 3 and Cu nanoparticles dispersed in water along a vertically heated wavy surface. The hybrid nanofluid has unique features that influence convective heat transfer. Numerical solutions analyze fluid flow patterns and temperature distributions, providing insights into heat exchange and thermal management. The research highlights the importance of hybrid nanofluids, notably those containing Al 2 O 3 and Cu in a water base, in improving overall heat transfer efficiency. The mathematical model accounts for laminar and incompressible fluid flow with a Prandtl number of Pr = 6.2, Lewis number Le = 10, and maximum 10 % concentration of hybrid nanoparticles. After transforming the governing equations into a non-dimensional form, the implicit finite difference method is used to solve them. The solution employs the in-house FORTRAN 90 code and compares its outcomes with the benchmark results. Various parameters, such as the Schmidt number (Sc = 1 to 10), volume fraction of nanoparticles ( ϕ = 0.0 to 0.1), wavy amplitude (A = 0.0 to 0.3), and N BT = (0.05 to 0.2), are investigated regarding temperature, velocity, local skin friction coefficient ( C f ) , local Nusselt number (Nu), streamlines, and isotherms. Elevated volume fraction generally decreases skin friction, increases temperature, and may reduce velocity. Meanwhile, higher skin friction, temperature, velocity, and local Nusselt numbers often correlate with elevated Schmidt numbers. Changes in amplitude and N BT affect skin friction, temperature, velocity, and local Nusselt numbers, providing information on the dynamics of fluid systems. For example, when the volume fraction (ϕ) increases from 0 to 0.1 at Y = 2, the temperature rises by 75 % , while the velocity gradually decreases by 11.11 % . This is in contrast to findings according to when the N BT rises from 0.05 to 0.2 at Y = 1. In this case, the temperature drops by 18.75 % , followed by a 9.68 % fall in fluid velocity. Understanding these interactions enhances comprehension of heat transfer and fluid dynamics. By investigating these interactions, we not only improve our understanding of heat transfer and fluid dynamics, but also open the door to new strategies for improving thermal systems and manufacturing procedures.

DROPLET MOTION ON HYDROPHOBIC AND HYDROPHILIC SURFACES USING LATTICE BOLTZMANN METHOD WITH BLOOD TEST MICROPAD APPLICATION

Laboratory sciences and disease diagnostics need accelerated medical tests, ease of testing for patients, and lower diagnostic costs. In this respect, one of the most innovative methods is paper-based microfluidic analysis tools, called micro-PAD. Since the chemical-based micro-PADs need sufficient blood to show an accurate blood test, the shape of the micro-PADs, the blood quantity, and the droplet flow to reach the end of the microchannels are important. Therefore, this research showed the liquid droplet motion on a heterogeneous (hydrophobic and hydrophilic) surface using the lattice Boltzmann method, and two star-shaped micro-PADs were modeled to investigate the effect of the droplet size and the droplet deflection from the center of the micro-PAD on liquid flow in microchannels. Based on the obtained results, fluid behavior was similar in two patterns (ten-pointed pattern and four-pointed pattern). This study compared the effects of parallel, convergent, and divergent channels in a four-pointed pattern on fluid velocity. The off-center error of the droplet was considered at the initial moment. The obtained results confirmed the direct relationship between the increased deviation of the center and the lack of uniformity in the fluid penetration. The present simulation results were validated against the laboratory data.

Fractional Second-Grade Fluid Flow over a Semi-Infinite Plate by Constructing the Absorbing Boundary Condition

The modified second-grade fluid flow across a plate of semi-infinite extent, which is initiated by the plate’s movement, is considered herein. The relaxation parameters and fractional parameters are introduced to express the generalized constitutive relation. A convolution-based absorbing boundary condition (ABC) is developed based on the artificial boundary method (ABM), addressing issues related to the semi-infinite boundary. We adopt the finite difference method (FDM) for deriving the numerical solution by employing the L1 scheme to approximate the fractional derivative. To confirm the precision of this method, a source term is added to establish an exact solution for verification purposes. A comparative evaluation of the ABC versus the direct truncated boundary condition (DTBC) is conducted, with their effectiveness and soundness being visually scrutinized and assessed. This study investigates the impact of the motion of plates at different fluid flow velocities, focusing on the effects of dynamic elements influencing flow mechanisms and velocity. This research’s primary conclusion is that a higher fractional parameter correlates with the fluid flow. As relaxation parameters decrease, the delay effect intensifies and the fluid velocity decreases.

An overview of conjugate heat transfer augmentation methods for thermal management and recent advancements in microchannel heat sink overall performance

Recent technological advancement creates high-dense circuits development which creates colossal cooling demand requirements. In the future, advanced technology and scientific applications need to balance heat fluxes beyond limitation that catalyse the research opportunities further to achieve cooling requirements. Conventional cooling equipment is inappropriate for extracting heat from microchips within the minimal surface area. Microchannel technology appeared as a next-generation heat exchanger for the given heat duty. In the classical case of accounting, micro-heat exchangers both axial and transverse wall conduction effects is usually neglected. However, from the year 2005 onwards, researchers identified conduction dominance at fluid velocity is zero zones at the interface, which created balance between conduction–convection currents, finally included axial wall/heat conduction effects to a general model. This present study made a comparative evaluation fluid flow, heat transfer characteristics, thermal performance (TP) based on geometrical parameters, substrate materials and discusses previous issues, and current issues-based future research directions. Till today, based on applications of microchannels in thermal management, several experimental and numerical investigations have been reported for further improvement in TP. However, many researchers are still trying to accomplish things over a long period. Therefore, an overview of previous studies is furnished in the present study to assist researchers in this area much useful for further improvement.

Magnetohydrodynamic Marangoni fluid flow, heat, and mass transfer over a radially stretching disk in the presence of heat generation and chemical reaction

The analysis of magnetohydrodynamic (MHD) Marangoni fluid flow, heat, and mass transport over a disk is considered in this article. The fluid is assumed to pass radially over a stretching disk. Suction/blowing at the boundary, internal heat generation/absorption, and a first-order chemical reaction are also considered. By using appropriate similarity transformations, the governing nonlinear partial differential equations (PDEs) are transformed into ordinary differential equations (ODEs). These ODEs along with the appropriate boundary conditions for the model are solved numerically by a shooting technique using MATHEMATICA software. The obtained results are compared with the available results in the literature for some special cases. The effects of the magnetic parameter, the Marangoni number, Marangoni ratio parameter along with the other pertinent parameters on fluid flow, heat and mass transport are analyzed and discussed in detail. It is noted that higher magnetic field depresses the fluid velocity whereas the fluid temperature and fluid concentration are uplifted with an increase in the magnetic field parameter. A quite opposite behavior is observed for Marangoni number. Marangoni ratio parameter boosted the fluid velocity as well as the fluid concentration and the temperature. Also externally applied suction significantly affects the fluid behavior. Increasing chemical reaction parameter reduces the fluid concentration. It is observed that a maximum increase in the Nusselt number occurs for Marangoni parameter Ma, which is 34.75595% when the suction/injection parameter s = 0.5. Also, for Marangoni ratio parameter Ra, a maximum increase in Nusselt number occurs, which is 6.7884% when suction/injection parameter s = 0.5.

Magnetohydrodynamic bioconvective flow past an elongated surface with convective heat transport, and velocity slip in a non‐Darcian porous regime

AbstractIn recent times, bioconvection has numerous uses, like, biological and biotechnological problems. The present study describes the magnetic bioconvective Buongiorno's flow model with microorganisms in a stretchable area with convective heat transfer and second‐order velocity slip in a non‐Darcian porous regime. Here, the influence of variable viscosity, viscous dissipation, Joule heating, and heat source/sink are considered in the occurrence of higher‐order chemical reactions. Employing proper similarity transformations leading equations are transformed to dimension‐free form. The transformed equations are solved via MATLAB bvp4c problem solver. This study's main objective is to graphically analyze the effects of different pertinent factors on the density of motile microorganisms, velocity, concentration, temperature, number of motile microorganisms' density, skin friction, mass transport rate, and heat transport rate. The main findings drawn from this study are viscosity and magnetic parameter lowers the fluid velocity. Biot number increases fluid temperature, but reduces heat transport rates and skin friction. Schmidt and Eckert numbers reduce the fluid concentration. A rise of 0.3 in bioconvective Rayleigh number and 0.2 in buoyancy ratio number causes a percentage drop in velocities of 8.79% and 3.91% (approximately), respectively, in the neighborhood of the sheet. Furthermore, the increase in Peclet number by 0.2 lowers the density number of microorganisms by 28%. Additionally, the profile of motile microorganisms is improved by thermophoresis impact, while it is diminished by chemical reaction.

Linear and nonlinear stretching sheet for enhanced heat and mass transfer in Casson nanofluid with activation energy

In this study, we delve into the magnetohydrodynamic heat and mass transfer flow of a Casson nanofluid over specifically chosen linear and nonlinear stretching surfaces embedded in a porous medium to understand their distinct effects on fluid behavior. By focusing on the influences of Brownian motion, thermophoresis, thermal radiation, and chemical reactions, we transformed nonlinear partial differential equations into ordinary differential equations, leveraging the Runge-Kutta method and Shooting Techniques for numerical solutions of momentum, temperature, and concentration profiles under predetermined boundary conditions. Our results, depicted in both graphical and tabular forms, shed light on how various parameters, including the Casson fluid characteristics, magnetic fields, buoyancy ratio, and mixed convection effects, influence fluid dynamics. A notable finding is that an increase in the Brownian motion parameter intensifies the fluid velocity and temperature profiles, but reduces its concentration profile, unveiling complex interactions within the nanofluid dynamics. This investigation underscores the importance of linear and nonlinear stretching surfaces in mimicking practical industrial scenarios, thereby providing insights that are crucial for optimizing processes such as coating, cooling of electronic devices, and in the manufacturing of thin plastic films, where precise control over heat and mass transfer is essential.

Computational fluid dynamics modeling of coronary artery blood flow using OpenFOAM: Validation with the food and drug administration benchmark nozzle model.

Cardiovascular disease (CVD), a global health concern, particularly coronary artery disease (CAD), poses a significant threat to well-being. Seeking safer and cost-effective diagnostic alternatives to invasive coronary angiography, noninvasive coronary computed tomography angiography (CCTA) gains prominence. This study employed OpenFOAM, an open-source Computational Fluid Dynamics (CFD) software, to analyze hemodynamic parameters in coronary arteries with serial stenoses. Patient-specific three-dimensional (3D) models from CCTA images offer insights into hemodynamic changes. OpenFOAM breaks away from traditional commercial software, validated against the FDA benchmark nozzle model for reliability. Applying this refined methodology to seventeen coronary arteries across nine patients, the study evaluates parameters like fractional flow reserve computed tomography simulation (FFRCTS), fluid velocity, and wall shear stress (WSS) over time. Findings include FFRCTS values exceeding 0.8 for grade 0 stenosis and falling below 0.5 for grade 5 stenosis. Central velocity remains nearly constant for grade 1 stenosis but increases 3.4-fold for grade 5 stenosis. This research innovates by utilizing OpenFOAM, departing from previous reliance on commercial software. Combining qualitative stenosis grading with quantitative FFRCTS and velocity measurements offers a more comprehensive assessment of coronary artery conditions. The study introduces 3D renderings of wall shear stress distribution across stenosis grades, providing an intuitive visualization of hemodynamic changes for valuable insights into coronary stenosis diagnosis.

Fluid dynamics and leukocyte transit in the lymphatic system

Abstract The lymphatic system plays a vital role in maintaining fluid balance in living tissue and serves as a pathway for the transport of antigen, immune cells and metastatic cancer cells. Here, we investigate how the movement of cells through a contracting lymphatic vessel differs from steady flow using a lattice Boltzmann-based computational model. Our model consists of cells carried by flow in a 2D vessel with regularly spaced, bi-leaflet valves that ensure net downstream flow as the vessel walls contract autonomously in response to calcium and nitric oxide levels regulated by stretch and shear stress levels. The orientation of the vessel with respect to gravity, which may oppose or assist fluid flow, significantly modulates cellular motion due to its effect on the contraction dynamics of the vessel, even when the cells themselves are neutrally buoyant. Additionally, our model shows that cells are carried along with the flow, but when the vessel is actively contracting, they move faster than the average fluid velocity. We also find that the fluid forces cause significant deformation of the compliant cells, especially in the vicinity of the valves. Our study highlights the importance of considering the complex, transient flows near the valves in understanding cellular motion in lymphatic vessels.

Analysis of Heat Transfer for the Copper–Water Nanofluid Flow through a Uniform Porous Medium Generated by a Rotating Rigid Disk

This study theoretically investigates the temperature and velocity spatial distributions in the flow of a copper–water nanofluid induced by a rotating rigid disk in a porous medium. Unlike previous work on similar systems, we assume that the disk surface is well polished (coated); therefore, there are velocity and temperature slips between the nanofluid and the disk surface. The importance of considering slip conditions in modeling nanofluids comes from practical applications where rotating parts of machines may be coated. Additionally, this study examines the influence of heat generation on the temperature distribution within the flow. By transforming the original Navier–Stokes partial differential equations (PDEs) into a system of ordinary differential equations (ODEs), numerical solutions are obtained. The boundary conditions for velocity and temperature slips are formulated using the effective viscosity and thermal conductivity of the copper–water nanofluid. The dependence of the velocity and temperature fields in the nanofluid flow on key parameters is investigated. The major findings of the study are that the nanoparticle volume fraction significantly impacts the temperature distribution, particularly in the presence of a heat source. Furthermore, polishing the disk surface enhances velocity slips, reducing stresses at the disk surface, while a pronounced velocity slip leads to distinct changes in the radial, azimuthal, and axial velocity components. The study highlights the influence of slip conditions on fluid velocity as compared to previously considered non-slip conditions. This suggests that accounting for slip conditions for coated rotating disks would yield more accurate predictions in assessing heat transfer, which would be potentially important for the practical design of various devices using nanofluids.

Thermal radiation and Soret/Dufour effects on amplitude and oscillating frequency of Darcian mixed convective heat and mass rate of nanofluid along porous plate

The influence of thermal radiations and Soret/Dufour significantly increases the mass and heat transport in material science, geothermal process, chemical rectors and heat exchangers due to temperature and concentration variation of nanoparticles. Main objective is to enhance the amplitude, oscillation and frequency of heat transfer using the Soret and Dufour characteristics in Darcian radiating flow of thermophoretic nanoparticles along vertical porous surface. The dimensionless analysis is performed to develop the convenient form of governing thermodynamic Darcian nanofluid formulation. To develop the programming algorithm in FORTRAN language, the primitive variable formulation is used for both time-dependent and steady models. The numerical and graphical outcomes of primitive type equations under boundary conditions are explored by using implicit finite difference approach with Gaussian elimination scheme. Various pertinent parameters are used to elaborate the steady fluid velocity, surface temperature and steady concentrated nanoparticle volume fraction. Valuable novelty of current research is to use steady results for fluctuating shear stress, fluctuation heating rate and fluctuating mass rate. It is found that the influence of Soret and Dufour parameter enhances the fluid velocity and temperature distribution with maximum variations. It is noticed that the temperature distribution enhances as thermal radiation parameter increases. The oscillation and transient stability of heating rate enhances with prominent variations as thermal radiation and Soret/Dufour parameter increases. It is depicted that amplitude in shear stress and mass rate enhances as Soret and Dufour parameter enhances.

Radiative nanofluid flow over a slender stretching Riga plate under the impact of exponential heat source/sink

Abstract Recognizing the flow behaviours across a Riga plate can reveal information about the aerodynamic efficiency of aircraft, heat propagation, vehicles, and other structures. These data are critical for optimizing design and lowering drag. Therefore, the purpose of the current analysis is to examine the energy and mass transfer across the mixed convective nanofluid flows over an extending Riga plate. The fluid flow is deliberated under the influences of viscous dissipation, exponential heat source/sink, activation energy, and thermal radiation. The Buongiorno’s concept is utilized for the thermophoretic effect and Brownian motion along with the convective conditions. The modelled are simplified into the lowest order by using similarity transformation. The obtained set of non-dimensional ordinary differential equations is then numerically solved through the parametric continuation method. For accuracy and validation of the outcomes, the results are compared to the existing studies. From the graphical analysis, it can be observed that the fluid velocity boosts with the rising values of the divider thickness parameter. The fluid temperature also improves with the effect of Biot number, Eckert number, and heat source factor. Furthermore, the effect of heat source sink factor drops the fluid temperature.

Sodium alginate-based MHD ternary nanofluid flow across a cone and wedge with exothermic/endothermic chemical reactions: A numerical study

The use of magnetohydrodynamic ternary nanofluid flow for heat transfer is essential in various industrial and commercial applications. This work examines heat transfer over cone and wedge shapes with Sodium Alginate-based ternary nanofluid flow, considering the effects of activation energy and exothermic/endothermic processes. Using similarity transformations, the controlling set of partial differential equations is converted into a network of interconnected nonlinear ordinary differential equations. Numerical solutions using the Runge-Kutta Fehlberg 4th 5th order method and shooting approach offer insights into the effects of several dimensionless factors. The outcomes show that the magnetic field parameter is crucial in lowering fluid velocity within a cone more efficiently than a wedge. Due to activation energy considerations, the cone shape notably impacts heat transmission in exothermic reactions, but the wedge geometry is more effective in endothermic reactions. Concentration profiles rise with activation energy and fall with increasing chemical reaction rates. The rate of thermal distribution is 48.68% more in wedge than cone geometry for the exothermic case and 35.57% in the endothermic case while the rate of mass transfer is higher in cone geometry than wedge geometry, about 7.83% in the exothermic case and 19.27% in the endothermic case. The present study has many applications, including optimizing heat transfer processes in sectors such as thermal systems, energy generation, and electronics. Additionally, it may be used to guide the design of magnetically affected systems and provide assistance for uses in chemical engineering.

Modeling the Unsteady Wake of an Impulsively Started Circular Cylinder Using Refined Potential Flow Theory

Abstract Cylindrical structures find usage in many engineering applications including tethered oil drums and engine canisters slung beneath helicopters in flight. The motion of air around such circular cylindrical structures and the helicopter presents interesting phenomena including flow separation, wakes and turbulence. The physics of these are enshrined in the continuity equation and the Navier-Stokes equations. Therefore, their studies are not only important in mathematics and physics, but they are also required for efficient helicopter operations. In practice, reduced-order models of these operations that take in aerodynamics models of the tethered loads are utilized for stability analysis, flight certification and pilot training because of the prohibitive cost of experimentation and computational analyses of these configurations. However, there is a dearth of realistic analytical models of finite cylinder flows because of the Navier-Stokes problem. Classical potential flow theory provides an avenue to develop such models, but the extant gaps in its predictions significantly preclude its usage for engineering applications. Attempting to bridge these gaps, this article introduces refined potential flow theory in which the governing equations and boundary conditions are satisfied. Viscous effects, fluctuations of the mean flow and three-dimensional effects are also incorporated. For characterization, refined potential flow theory is employed on an incompressible flow over an impulsively started circular cylinder for Reynolds numbers and non-dimensional times in the range 30 < Re < 10^4 and 0.2 ≤ T≤ 77, 047 respectively. There is an excellent prediction of 0.209 for the Strouhal number at Re = 3, 900. At this transitional Reynolds number, the harmonics of the Strouhal frequency are also captured, and the characteristic irregular fluctuations at sub-Strouhal frequencies are discernible in the velocity spectra. As the flow becomes more turbulent, these become more pronounced at Re = 9, 500 when the predicted Strouhal number is within 10% of experimental result. In the fully developed stage, spectra analyses of the wake velocity components at some downstream locations also display Kolmogorov’s Five-Thirds law of homogeneous isotropic turbulence. The present model can thus aid the development of reduced-order models of helicopter operations that feature tethered cylindrical loads.

Entropy generation analysis of kerosene oil flow with ternary hybrid nanoparticles on the stretchable exponential surface

ABSTRACT In this research, the flow of kerosene oil with ternary hybrid nanoparticles on a stretchable exponential surface has been investigated. There is also a discussion about the entropy analysis of the flow of hydromagnetic radiation by the surface. The ternary hybrid nanofluid (THyNF) contains graphene oxide (GO), magnesium oxide (MgO), and zinc oxide (ZnO) as nanoparticles and kerosene oil as a base fluid. Using useful transformations, differential equations with partial derivatives (PDEs) were transformed into ordinary differential equations (ODEs). Then, the ODEs were solved using the RK5th method. Furthermore, the impacts of parameters like radiation parameter ( Rd ), porosity parameter ( λ ), and volume fraction ( φ ) of THyNF were investigated. Magnetic field (M) and shape factor (SF) on the temperature ( θ ( η )) and velocity ( f ′ η ) profiles have been investigated. Increasing the magnetic field parameter (M) raises the Lorentz force, which produces resistance to fluid flow and reduces fluid velocity ( f ′ η ). The temperature profile ( θ ( η )) rises with increasing magnetic field because the reduced flow rate due to increasing magnetic parameter allows the nanoparticles to transfer more heat. As the nanoparticle volume fraction increases, both the velocity and temperature profiles increase. The effects of M, Rd, SF (shape factor), and λ on entropy generation ( S G ) and Bejan number (Be) have been discussed. Also, the results show that at a fixed value of the magnetic field or the porosity parameter, with the increase in the volume fraction of nanoparticles, the − C fx R e x 12 rises. At a constant value of the φ value of N u x R e x − 12 rises with the increase of the radiation parameter.

Analytical and numerical study of water-based silver nanofluid (Ag) across a Riga plate with nonlinear radiation and viscous dissipation: A three-dimensional study

The primary endeavor of this investigation is to determine the Darcy–Forchheimer flow of water-based silver nanofluid (Ag) across a bidirectional Riga plate with viscous dissipation and nonlinear radiation. By manipulating the pertinent variables, the governing equations undergo a transformation into nonlinear ordinary differential equations. The remodeled flow problems are investigated numerically and analytically using the MATLAB (bvp4c built-in function) algorithm and the homotopy analysis method scheme. The repercussions of the appropriate factors on the x− and y− direction velocity profiles, temperature profile, skin friction coefficient of the x− and y− directions, and local Nusselt number are examined via tables and graphs. It is found that both directional fluid velocities decline in the presence of the suction/injection parameter. Increasing the radiation parameter and the Eckert number exalts the fluid temperature. The surface shear stress decays as the suction/injection parameter and the Forchheimer number grow larger. In addition, a greater heat transfer rate appears on the Riga plate compared to the stationary plate.