Fluid Velocity Research Articles

Modelling the Hall Effect in a Steady Magneto-Convection and Radiative Heat Transfer Past a Porous Plate

Heat transfer features significantly in engineering processes. Blowing of fluids is used in designing thrusters and prevention of corrosion. Suction is used in film cooling and coating of wires in chemical engineering. Numerous research done has focused on thermal reduction in processing streams and neglecting the machine efficiency. The paper investigates the effect of Hall current on a steady magneto-convection and radiative heat transfer over a porous plate with the motive being improving machine efficiency in industries. The transport model is of an incompressible fluid flowing through a porous plate. The magnetic field is imposed perpendicularly to the plate. Equations governing the flow are formulated then converted to higher order ODE’s using the similarity transformation. The resulting ODE’s are solved using the fourth order Runge-Kutta method coupled with a shooting technique. The solution are then executed using MAPLE computer programme and the results displayed graphically and in tabular form. The results are then analysed putting into consideration their industrial and engineering applications. It is observed that Increasing Prandtl number and Grash of number leads to an increase in the fluid velocity and a decrease in skin friction. Increase in magnetic field, and radiation results in increased fluid temperature distribution.

Influence of Magnetic Field and Porous Medium on Taylor–Couette Flows of Second Grade Fluids Due to Time-Dependent Couples on a Circular Cylinder

Axially symmetric Taylor–Couette flows of incompressible second grade fluids induced by time-dependent couples inside an infinite circular cylinder are studied under the action of an external magnetic field. The influence of the medium porosity is taken into account in the mathematical modeling. Analytical expressions for the dimensionless non-trivial shear stress and the corresponding fluid velocity were determined using the finite Hankel and Laplace transforms. The solutions obtained are new in the specialized literature and can be customized for various problems of interest in engineering practice. For illustration, the cases of oscillating and constant couples have been considered, and the steady state components of the shear stresses were presented in equivalent forms. Numerical schemes based on finite differences have been formulated for determining the numerical solutions of the proposed problem. It was shown that the numerical results based on analytical solutions and those obtained with the numerical methods have close values with very good accuracy. It was also proved that the fluid flows more slowly and the steady state is reached earlier in the presence of a magnetic field or porous medium.

Mathematical modeling of interconnected absorber-desorber hollow-fiber membrane contactors for CO2 capture using MEA solution

Abstract In this work, comprehensive three-dimensional models were developed for an interconnected nondispersive absorber–desorber system using hollow fiber membrane contactors (HFMCs) for CO2 capture with monoethanolamine solution. The models were implemented in COMSOL Multiphysics, Matlab/Simulink and Aspen Plus. The models were subsequently validated using laboratory-scale experimental data across a wide range of gas and liquid flow rates, as well as carbon dioxide concentrations, achieving R2 values between 0.922 and 0.987 and root mean square error between 0.1540 and 2.3255. Model predictions provided valuable insights into fluid velocities, concentrations and temperature profiles. Sensitivity studies were performed to determine the optimal CO2 capture parameters under different operating conditions (e.g., flow rates, compositions, and temperature). Simulation results showed that the desorption could reach an efficiency of about 99% by increasing the temperature to 373.15 K. In addition, different geometries of HFMC were studied to enhance the absorption process. The use of shell baffles showed an increase in the absorption efficiency by nearly 5%. Furthermore, the validated models were interconnected using live-link connections with Aspen Plus. The flowsheet simulation results of the entire CO2 capture process using HFMCs demonstrated a capture efficiency higher than 90% with a CO2 purity of about 99 vol%. Graphical abstract

Simulating the Performance of Tesla Turbine Regarding Structural Features

The main topic of this paper is the theoretical investigation of whether the performance and the work of the Tesla turbine are affected by the experimental change of three main variables, namely, the fluid velocity at the input V(m/s), the number of disks A and the disk radius r (m). Then the results are analyzed and commented, with the purpose of enquiring whether or not Tesla turbines can be used for constructing motor-engines, by determining their structural features and properties. The methodology followed comprises computerized simulation, based on a specific mathematical formula of the work produced. The results show that the work produced increases with the increase of the values of each variable, by a different rate accordingly. At the very end, a promising application suggested is the usage of Tesla turbines for energy harvesting in wind-generators.

Thermal and mass transfer performance of non-Newtonian fluids under MHD and chemical reaction effects with thermophoresis and Brownian motion

This study presents a comprehensive investigation into the convective heat and mass transfer characteristics of non-Newtonian fluids, specifically Casson, Maxwell, and Williamson fluids, flowing along a vertical cone under the influence of magnetic fields and chemical reactions. Non-Newtonian fluids are widely utilized in industrial and automotive thermal management systems due to their superior thermal performance characteristics. The mathematical formulation accounts for magnetohydrodynamic effects, homogeneous chemical reactions, and transport phenomena associated with thermophoresis and Brownian motion. The governing equations, derived from the conservation laws of mass, momentum, energy, and species concentration, are reduced to a system of nonlinear ordinary differential equations through the application of similarity transformations. These equations are solved numerically using the BVP4C solver in MATLAB. A detailed parametric study is conducted to analyze the influence of key physical parameters on the velocity, temperature, and concentration distributions. The results indicate that the presence of a magnetic field decreases the fluid velocity due to the Lorentz force, while the thermophoretic and Brownian motion effects enhance the thermal and concentration boundary layers, leading to improved heat and mass transfer rates. Chemical reaction parameters are observed to significantly modify the concentration profiles.The findings contribute to a deeper understanding of non-Newtonian fluid behavior and offer guidance for the design of efficient thermal systems.

Thermal and solutal transportation analysis for nanofluid flow along a stretching sheet with the applications of Soret and Dufour effects and variable fluid properties: Keller Box approach

The significance of Soret and Dufour on convective mass and heat transport of magnetic-driven nanofluid has great importance in the development of geothermal energies, thermal energy storage, reversible technologies and petrochemical reserves. The influence of variable density, Soret and Dufour, entropy optimization, thermophoretic and Brownian movement on electrically conducting nanoparticles through a heated sheet is an important contribution of this work. The Keller box approach with Newton-Raphson technique is an effective computational method for converting the governing formulation into a non-linear differential format to solve computationally. Tables and graphs provide a conspicuous evaluation of the controlling flow variables, including Soret S r , Dufour D f , Eckert parameter E c , density-index parameter n , thermophoresis N t and Brownian motion N b through a stretched sheet. The parametric range of all parameters, such as 0.0 ≤ D f ≤ 2.0 , 0.0 ≤ S r ≤ 3.0 , 0.0 ≤ E c ≤ 1.5 , 0.0 ≤ n ≤ 1.2 , 0.0 ≤ N T ≤ 1.8 and 0.0 ≤ N B ≤ 1.5 , is used for numerical simulation. The lower rate of heat and mass distribution is deduced for a high variable density parameter. It is noticed that the fluid velocity and variation in temperature enhance as the Soret S r , Dufour D f and Eckert parameter E c increase. It is noted that the mass and heat transport significantly improve as thermophoresis and Brownian motion increase. The amplitude sequence in fluid velocity is decreased for every parameter due to temperature-dependent density. The current mechanism is beneficial for ceramic treatment, chemicals, petroleum products, cutting tools and hydrophilic polymers.

Experimental investigation of inertial spheres settling in surface gravity waves

We investigate the motion of weakly negatively buoyant spheres settling in surface gravity waves using laboratory experiments. The trajectories of the settling spheres are tracked over most of the water depth with simultaneous measurements of the background fluid flow. These experiments are conducted in the regime relevant for environmental and geophysical applications where both particle inertia and fluid inertia are important. Using these data, we show that the sphere motion is well described by the kinematic sum of the undisturbed fluid velocity and the particle terminal settling velocity as long as the fluid inertia is not too large. We show how this result can be understood in the context of an ad hoc Maxey–Riley–Gatignol-type equation where the drag on the particle is given by the Schiller–Naumann drag correlation. We also evaluate whether inertial particles experience enhanced settling in waves, finding that measurement uncertainties in the particle terminal settling velocity and the presence of Eulerian-mean flows do not allow the small percentage increase in the settling velocity to be measured. When the fluid inertia becomes large enough, we observe path instabilities caused by particle wake effects in both quiescent and wavy conditions. However, the particle velocity fluctuations associated with the path instabilities are unaffected by the background flow. The minimal influence of the wavy flow on the particle path instabilities is thought to be due to the large-scale separation between the waves and the particle.

Magnetohydrodynamic Casson polymeric flow of nanofluid flow toward Howarth’s wavy circular cylinder with convective Nield’s conditions

The study examined the behavior of Casson nanofluid flow, heat, and mass transfer around a wavy cylinder with convective Nield conditions. We analyzed the effects of several factors, including thermophoresis activation energy, and Brownian motion. We transformed the governing partial nonlinear system into system of ordinary differential equations by applying similarity variables. To derive numerical solutions, we employed the MATLAB bvp4c solver and presented our results using graphical representations. Our graphs illustrated the impact of different parameters, including the thermophoresis (Nt), magnetic parameter (M), Brownian motion parameter (Nb), Casson fluid parameter (β), Lewis number (Le), Saddle/Nodal indicative parameter (c), and Chemical reaction parameter (σ). We also computed Sherwood number and local Nusselt number, and skin friction coefficient along the x and y axes to obtain further understanding of the behavior of these emerging parameters. Increasing the Casson fluid parameter increases fluid velocity concentration while the temperature magnitudes tend to diminish. Improvement in Brownian motion, Biot number, and thermophoresis parameters results in a more effective thermal gradient and concentration.

Influence of slip velocity and heat generation on magneto-nanofluid flow via divergent and convergent plates using perturbation technique

This research investigates the effects of slip velocity and magnetohydrodynamic (MHD) influences on the flow dynamics of non-Newtonian nano-fluids within convergent and divergent channels using the Homotopy Perturbation Method (HPM). The study develops a mathematical framework to model and analyze how slip conditions and magnetic fields impact fluid behavior, velocity profiles, pressure distributions, and heat transfer rates. Analytical solutions to the governing equations are derived using the homotopy perturbation approach, offering valuable insights into fluid dynamics within complex channel geometries. The findings reveal significant changes in velocity profiles and pressure distributions due to slip effects, with increased slip resulting in higher flow velocities in both channel types. Stronger magnetic fields, indicated by higher Hartmann numbers, lead to enhanced fluid velocities and elevated temperatures, highlighting the pronounced impact of MHD effects. Furthermore, the combined presence of slip velocity and MHD effects enhances heat transfer rates, suggesting potential advancements in thermal management systems. Additionally, the study emphasizes that higher magnetic parameters contribute to increased entropy generation, indicating greater energy dissipation and system disorder. These effects underline the potential for optimization in engineering applications such as microfluidic devices and industrial heat exchangers, where an improved understanding of non-Newtonian nano-fluid behavior can enhance performance.

In-cloud characteristics observed in northeastern and midwestern US non-orographic winter storms with implications for ice particle mass growth and residence time

Abstract. The spatial distribution of surface snowfall accumulation is dependent on the 3D trajectories of ice particles and their residence times through regions of ice mass increases and decreases. We analyze 42 non-orographic, non-lake-effect winter storms in the northeastern and midwestern United States from the Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) and Profiling of Winter Storms (PLOWS) field campaigns. In situ aircraft measurements (1 Hz, ∼ 100 m horizontal distance) yield key data on vertical air motions, relative humidity with respect to ice (RHice), and number concentration. When suitable airborne radar data are available, we sort the in situ measurements by distance from cloud radar echo top. In total, 90 % of updrafts (vertical air motion ≥0.5 m s−1) were ≤1.3 km across. Measurements obtained within 3 km of cloud echo top were nearly twice as likely (13 % versus 7 %) to have vertical velocities capable of lofting precipitation-sized ice compared to points sampled at lower levels. Below the near-cloud-top generating cell layer, most of the storm volume has RHice≤95 % consistent with sublimation. Rather than ice precipitation growth within broad areas of vertical air motions, observations indicate that ice growth in these storms primarily occurs episodically within layers of overturning cloud-top generating cells with scales ≤ a few kilometers. Below the generating cell layer, conditions for ice growth are rarer, and the ice particles usually either persist or shrink during most of their descent. The observed distributions of ambient in-cloud conditions provide benchmarks for evaluations of winter storm model output.

Laboratory observation of impact pressure, fluid velocity, and air fraction during dam-break impacts on a square prism

This study experimentally investigates the fluid kinematics and dynamics of dam-break wave impacts on a square prism under a wet-bed condition. The incident of interest was a plunging breaker generated by the wet-bed dam break. Four impact scenarios were established by varying the distance between the wave impingement point and the prism's frontal face. Gate motion, fluid velocity, impact pressure, and air fraction were measured, with ensemble-averaged data obtained from repeated tests. Velocity fields in aerated and non-aerated regions were revealed using bubble image velocimetry and particle image velocimetry, respectively, while local air fractions were measured using fiber-optic reflectometry. Beyond serving as a benchmark for validation purposes, the present datasets support in-depth analysis of flow characteristics, pressure and air fraction distributions, and the correlations among fluid velocity, impact pressure, and aeration level. Maximum horizontal and vertical velocities reached 1.67 C and 2.14 C, respectively, where C is the wave celerity. Peak impact pressures reached to 12.652 ρwC2, with the highest values occurring just above the still water level. The generalized extreme value distribution is recommended for estimating peak impact pressures based on their probability density at specific occurrence frequencies. A dimensionless envelope curve was established to relate peak impact pressure to pressure rise time. Impact coefficients (0.846–7.647) were identified, allowing peak pressure to be estimated from local fluid velocity. A positive correlation between aeration and peak pressure was observed, indicating that existing pressure–aeration models are inadequate for capturing this behavior under wet-bed dam-break conditions.

Asymptotics of liquid velocity to the problem of fluid outflow from a rectangular duct

We have constructed and analyzed the first-order asymptotics of liquid velocity for the two-dimensional steady problem of energy-conserving fluid outflow from a rectangular duct. These asymptotics are constructed using the first-order asymptotics for the liquid depth, which was investigated in [V. V. Ostapenko, “Asymptotics of solutions to the problem of fluid outflow from a rectangular duct,” Phys. Fluids 33, 047106 (2021)] and found to be in good agreement with the Wilkinson laboratory experiment [D. L. Wilkinson, “Motion of air cavities in long horizontal ducts,” J. Fluid Mech. 118, 109 (1982)] on modeling the energy-conserving steady flow predicted by the classical piecewise constant Benjamin solution [T. B. Benjamin, “Gravity currents and related phenomena,” J. Fluid Mech. 31, 209 (1968)]. Two cases are considered: in the first case, it is assumed that in the entire asymptotics constructing region, the Green–Naghdi condition is satisfied; in the second case, this a priori assumption is not used. It is shown that the first-order asymptotics for the liquid depth and the horizontal fluid velocity are the same in both of these cases, wherein the asymptotics of the horizontal velocity is a quadratic function of the vertical coordinate z. At the same time, the first-order asymptotic of the vertical fluid velocity is a cubic function of the vertical coordinate z in the first case, and it is a linear function of the coordinate z in the second general case.

CLIMATE-RESPONSIVE ARCHITECTURE IN SOUTH-WESTERN NIGERIA: A CASE STUDY OF CLIMATE ANALYSIS AND DESIGN ADAPTATION IN A SELECTED TOWN

Climate is a crucial factor in building design worldwide; significantly impacting the physiological comfort of occupants, particularly in indoor spaces. However in Nigeria, the majority of climate-related research has focused primarily on Agriculture and Aviation sectors, overlooking the importance of climate on construction in building design. This paper examined and analyzed the climate pattern of Ede, town in South West Nigeria with a view to suggesting appropriate guidelines for designing Climate-Responsive Buildings. Average climatic data of Ede for a period of five (5) years were examined and analyzed for building design purpose using Mahoney table. The climatic pattern of the town showed that the annual mean temperature values are high for most of the years with 35,534.80C, 34.60C, 33.20C, 33.10C, 32.00C, 31.30C and 30.90C for the years 2018, 2019, 2020, 2021 and 2022 respectively. The average outdoor wind speed is low having 1.51m/s as highest. The annual mean values of solar radiation are high and constant. The climate in Ede is marked by persistently high temperatures, causing resident discomfort. Adequate air movement is essential for relief. To address this, combining passive cooling strategies with air movement can be effective. One approach is using thermal mass with night ventilation to enhance comfort. Southwest Nigeria's climate varies significantly, so it's essential to consider local climatic conditions when designing buildings in the region.

Effect of an Axially Offset Impeller on the Transient Physics of Asymmetric Flow in a Double-suction Centrifugal Fan

The impeller of a double-suction centrifugal fan may be subject to axial offset due to assembly or operational failure. The internal flow is asymmetric about the central disc and deteriorates the fan’s performance. In this work, the characteristics of flow were numerically investigated for the baseline model (Model-BM) and the axially offset impeller model (Model-Offset). The objective and motivation are to provide a detailed assessment and quantification of the effect of offset impeller on the fan’s performance and transient physics of the asymmetric flow. The numerical data reveal that the offset impeller generates highly asymmetric flow. The difference in mean flow rate at the two inlets of Model-Offset is 25.02m³/h, accounting for 6.8% of the total flow rate. The static pressure rise reduces by 2.40% for Model-Offset, and the static pressure efficiency is reduced by 2.11%. The leakage flow gets pronounced in the enlarged clearance with the inward and outward motion of air, while the narrowed clearance blocks it. The reversed flow is significant in the NA-side blade passages, especially close to the impeller end ring, where the leakage flow and the volute tongue confinement dominate. The reversed flow persists throughout the impeller, is still evident as the air first enters the volute, and is significant on the NA-side of the fan outlet.

Microstreaming patterns induced by oscillating non-spherical microbubbles in acoustofluidic systems

This study developed a technology for precise acoustic flow field manipulation using a variety of microbubble shapes (including circular, elliptical, triangular, and square) through an acoustofluidic chip system. By utilizing advanced fabrication techniques, the microcavity structure was optimally designed to achieve stable microbubble trapping. Employing 2 μm diameter polystyrene particle tracking technology, experimental results demonstrate that elliptical microbubbles can induce stable quadruple-vortex patterns. Unlike the dual-vortex limitation of spherical structures, elliptical structures stably generate quadruple-vortices across a broad frequency range (20–120 kHz), with a maximum velocity gradient of 35/s. The velocity gradient variation in this quadruple-vortex field is significantly smaller than that in dual-vortex patterns of other microbubbles, unlike other shapes that typically produced a dual-vortex pattern. Changes in excitation voltage affected the fluid velocity gradient around the microbubbles, with increased voltage resulting in a higher velocity gradient. Additionally, the choice of excitation frequency significantly impacted the flow field patterns of non-circular microbubbles. The key breakthrough lies in demonstrating that elliptical microbubbles can stably generate quadruple-vortex streaming, with significantly superior maximum velocity gradient and shear uniformity compared to conventional spherical microbubbles, offering additional flexibility for microbubble manipulation. These findings confirm the direct influence of microbubble shape on acoustic flow patterns. Moreover, our results reveal the potential of non-circular microbubbles in acoustic manipulation and introduce a new perspective to acoustic fluid engineering, emphasizing the importance of optimizing microbubble shape and frequency selection for future applications, particularly in drug delivery, cell manipulation, and biochemical analysis. Future research will focus on enhancing the practical efficiency of specific microbubble shapes, optimizing designs, and assessing their long-term environmental impact to promote sustainable development of the technology.

Computational modeling of biomechanical response of osteocyte integrin and cytoskeleton based on the piezoelectricity of bone matrix.

Computational modeling of biomechanical response of osteocyte integrin and cytoskeleton based on the piezoelectricity of bone matrix.

Radiation Effects on a General Unified Boundary-Layer Flow of Viscous Fluid with Variable Fluid Properties – A Wavelet Approach

This study considers the modelling of boundary-layer flow of a viscous incompressible fluid due to a stretching sheet or over a wedge. The effect of thermal radiation, temperature-dependent fluid properties such as fluid viscosity and thermal conductivity and an external magnetic field are analysed. The mathematical modelling of the two distinct physical scenarios is unified using a suitable velocity ratio parameter. The posed governing equations are converted to ordinary differential equations using an appropriate generalized similarity transformation. These equations are solved over a semi-infinite domain and analysed using the wavelet-based numerical method. The effect of some vital fluid parameters, such as the Magnetic parameter (M^2), Variable thermal conductivity parameter (δ), Variable viscosity parameter (θ_r), generalized Prandtl number (Pr_v) and Radiation parameter (R) on fluid velocity and temperature profiles are studied. It is found that an increase in the radiation parameter decreases the velocity and temperature profiles. The magnetic parameter is found to retard fluid flow. Error and convergence analysis of obtained solutions using wavelets is performed. The advantages of the wavelet-based numerical method for solving nonlinear coupled equations are also discussed. The findings of this study are expected to contribute to the knowledge of researchers working in this field.

Fluid-structure coupling effect on the setting process of expansive downhole emergency packer

A downhole emergency packer is prepared to seal the drill pipe-casing annulus when the high-pressure overflow and kicks occur during offshore drilling. When there exists fluid in the annulus, the increase in fluid pressure during setting increases the difficulty of working and even results in sealing failure. The primary objective of this research is to investigate the influence mechanism of downhole fluid on the setting efficiency, and provide theoretical support for solving such problems under hydrodynamic conditions. In this work, the hyperelastic constitutive model of the rubber cylinder was established through uniaxial tension and uniaxial compression tests. The fluid-structure coupling model was developed by finite element method, to simulate the setting process of the downhole emergency packer and quantitatively evaluate the impact of downhole fluids on setting efficacy. The results revealed that the fluid velocity and pressure increased throughout the setting process while the annular area shrank, raising the setting difficulty. The existence of fluid flow considerably diminished the setting efficacy of the rubber cylinders. The sealing coefficient, K decreased by 7.15%, 11.06%, and 14.41% when the flow velocities from the inlet were 5 m/s, 6 m/s, and 7 m/s, respectively. Therefore, the setting pressure could be increased according to the actual downhole conditions to achieve the actual setting effect safely.

An Investigation of the Velocity Profile in Poiseuille Flow of an Incompressible Fluid between Concentric Circular Cylinders

This study is to obtain an analytical solution for the Poiseuille flow of an incompressible fluid confined between two fixed concentric circular cylinders with radii R1 ​and R2​, under slip boundary conditions and certain simplifying assumptions. Two distinct cases have been considered: parallel flow with slip boundary conditions on both cylinder surfaces, and combinations of slip and no-slip conditions on the inner and outer surfaces, respectively. For each scenario, the steady-state velocity profile and the volume flow rate have been derived and analyzed under various boundary conditions. The findings demonstrate that both the velocity distribution and flow rate are significantly influenced by the annular gap between the cylinders and the slip length. Additionally, it was observed that as the radius of the gap increases, the fluid velocity distribution decreases, with the maximum velocity shifting towards the centerline of the flow in the vertical motion.

Effects of Ventilation and Forced Air Movement on the Activity Concentration of <sup>222</sup>Rn and <sup>220</sup>Rn

Background: Radon (<sup>222</sup>Rn) and thoron (<sup>220</sup>Rn) are naturally occurring radioactive gases with significant differences in half-life, influencing their indoor behavior. Radon has well-documented health risks and mitigation strategies, but thoron has received less attention. This study explores thoron behavior in relation to air flow dynamics and ventilation conditions used to mitigate radon levels.Materials and Methods: Controlled experiments were conducted from February to June 2021 in an empty basement room and a laboratory simulation. Radon and thoron activity concentrations were measured using Durridge RAD7 radon monitors. Forced air movement was achieved through a fan, and ventilation conditions were simulated in the laboratory using air pumps with inline flow control valves. The exhaust state varied between closed and open air systems.Results and Discussion: The experiments revealed that while radon concentrations were stable or decreased under both forced air movement and increased ventilation rates, thoron concentrations displayed an inverse relationship with forced air movement, irrespective of an open or closed air system. Additionally, thoron required much higher ventilation rates (>50 air changes per hour [ACPH]) to reduce concentration levels that radon achieved with much lower rates (1–10 ACPH). This suggests certain ventilation strategies might inadvertently elevate thoron levels despite reducing radon levels, indicating a nuanced interaction between thoron concentration and air flow dynamics.Conclusion: This study underscores the importance of considering thoron’s unique behavior when implementing ventilation strategies for indoor radioactive gas mitigation. It calls for a nuanced approach to managing air flow dynamics to effectively reduce both radon and thoron levels. Further research is needed to refine models for ventilation strategies in radiation hazard mitigation for radon and thoron.