Axial Velocity Distribution Research Articles

Synergistic influence of gyrotactic microorganisms and bimolecular reaction on bidirectional tangent hyperbolic fluid with Nield boundary conditions: A biomathematical model

In biomedical engineering, the behaviour of gyrotactic microorganisms with non-Newtonian fluids such as tangent hyperbolic fluids improve the design of targeted drug delivery systems. In this system control over microorganism movement is essential. The present study deals with the synergistic influence of gyrotactic microorganisms and bimolecular reactions on the bidirectional flow of tangent hyperbolic fluids under Nield boundary conditions. Further, the flow characteristic of the non-Newtonian fluid is enhanced by incorporating the impact of thermal radiation, heat sources, Brownian motion, and thermophoresis. The presentation of these phenomena is vital for an extensive range of applications, including industrial processes, biomedical engineering, and environmental management. The analysis employs advanced mathematical modelling which needs suitable transformation rules to get the non-dimensional form and further numerical simulation is presented with the assistance of the “shooting-based fourth-order Runge-Kutta technique”. The results are depicted for the several contributing factors via the built-in in-house function bvp4c in “MATLAB”. The authentication of the study with the prior research is a benchmark to precede further research in this direction. However, the outstanding results are; the fluid velocity is controlled by increasing non-Newtonian Weissenberg number whereas the velocity slip shows dual characteristics on the axial velocity distribution. Further, the motile microorganism profile is controlled by the enhanced bioconvection Lewis number.

Flow field analysis of newtonian fluid flow induced by planetary and radial motion of drill string

Abstract At present, in the process of oil drilling, the drill string is an essential downhole drilling tool. It is immersed in the hole filled with drilling fluid for a long time, and it is driven by the rotation of the rotary table to drill down. In this process, the drill string will not only rotate around its axis but also may rotate around the axis of the hole and produce radial motion. It is important to study the flow law of Newtonian fluid flow induced by drill string movement, which can effectively reduce drilling accidents caused by drill string vortex and buckling, thus reducing economic losses. After research and analysis, the finite volume method, which has good applicability and obvious advantages, is used to discretize the established mathematical model, and the mathematical equation after discretization is obtained. By using MATLAB software, the flow field of Newtonian fluid induced by drill string rotation motion is analyzed, the axial velocity distribution diagram and tangential velocity distribution diagram are obtained, and the velocity flow diagram under different eccentricity conditions is drawn. It is found that secondary flow occurs only when the eccentricity reaches a certain distance requirement.

Localization of acoustical sources rotating in the cylindrical duct using a sparse nonuniform microphone array

The Doppler effect caused by the rotation of turbine fans brings significant challenges to the identification of fan noise sources inside the nacelle. Current methods of rotating source localization inside the cylindrical duct are executed with tough requirements for the microphone array mounted on the duct wall, which includes a fair enough number of microphones and equal-space distribution of each microphone in the azimuthal direction. A methodology based on nonuniform measurements and duct spin modes superposition (NMDMS) is proposed to identify rotating sources with high spatial resolution and few side lobes even near cut-on frequencies, which requires much fewer microphones and no uniform distribution of each microphone in the circumference. The sparsity in the azimuthal domain of the duct field generated by multiple rotating sources is verified theoretically, after which the azimuthal mode in each duct cross-section is reconstructed by the inhomogeneous measurements through the orthogonal matching pursuit (OMP) method. Followed by the identification of mode amplitude in the rotation frame, the sound pressure distribution as well as the axial acoustic velocity distribution on the source plane is reconstructed through duct modes summation. Numerical simulations and experiments are implemented to validate the method. Localization results indicate that rotating sources identification using the proposed method could not only save more than half the microphones without requirements of equal-space distribution but obtain good accuracy of localization and remarkably fewer side lobes.

Investigation of computational model for the natural circulation at dual channel facility

The current work investigates a computational model to study the thermal and hydraulic air behavior during the natural circulation at air ingression and accidents. This is done with the RHYS coupling ASYST VER 4 package. The test facility considered for the present study is a dual vertical channel facility comprised of two parallel channels connected to the upper and lower plenum. The flow fields in the heated and cooled channels were comprehensively characterized by analyzing axial temperature and velocity distributions using varied uniform iso-flux (100–1400 W/m2) and different outer surface temperatures (278, 288, 298, and 308 K). Temperature and velocity reversal recorded after maximal spots due to natural convection. The temperature rise from 278 to 308 K gave an average of 25.51 and 25.19° increase in air and inner wall temperatures, respectively, while air velocity increases at high cooling intensity (278 K) within the heated channel, in the cooled channel, low cooling intensity (308 K) resulted in higher velocity. The convective heat transfer is represented in terms of heat transfer coefficients, which are used to compute the Nusselt number. Additionally, the ASYST model was validated with data from literature sources, indicating strong agreement.

Investigation of a Modified Wells Turbine for Wave Energy Extraction

The Oscillating Water Column (OWC) is the most promising self-rectifying device for power generation from ocean waves; over the past decade, its importance has been rekindled. The bidirectional airflow inside the OWC drives the Wells turbine connected to a generator to harness energy. This study evaluated the aerodynamic performance of two hybrid airfoil (NACA0015 and NACA0025) blade designs with variable chord distribution along the span of a Wells turbine. The present work examines the aerodynamic impact of the variable chord turbine and compares it with one with a constant chord. Ideally, Wells rotor blades with variable chords perform better since they have an even axial velocity distribution on their leading edge. The variable chord rotor blade configurations differ from hub to tip with taper ratios (Chord at Tip/Chord at Hub) of 1.58 and 0.63. The computation is performed in ANSYS™ CFX 2023 R2 by solving three-dimensional, steady-state, incompressible Reynolds Averaged Navier–Stokes (RANS) equations coupled with a k-ω Shear Stress Transport (SST) turbulence model in a non-inertial reference frame rotating with the turbine. The accuracy of the numerical results was achieved by performing a grid independence study. A refined mesh showed good agreement with the available experimental and numerical data in terms of efficiency, torque, and pressure drop at different flow coefficients. A variable chord Wells turbine with a taper ratio of 1.58 had a peak efficiency of 59.6%, as opposed to the one with a taper ratio of 0.63, which had a peak efficiency of 58.2%; the constant chord Wells turbine only had a peak efficiency of 58.5%. Furthermore, the variable chord rotor with the higher taper ratio had a larger operating range than others. There are significant improvements in the aerodynamic performance of the modified Wells turbine, compared to the conventional Wells turbine, which makes it suitable for wave energy harvesting. The flow field investigation around the turbine blades was conducted and analyzed.

Numerical investigation of non-uniform inflow effects on internal and external characteristics of an axial-flow pump

This paper investigates the effects of non-uniform inflow on the internal and external characteristics of an axial-flow pump. Numerical simulation is employed to study two different configurations: one with an intake sump (referred to as the intake system) and another without an intake sump (referred to as the pump system), where the intake sump introduces non-uniform inflow conditions. First, under low flow conditions, typical unstable flow phenomena are observed in the impeller, including leading edge spillage and tip leakage vortex, which are consistent with previous research findings. Second, the analysis reveals that the non-uniform inflow causes the pump system to enter the hump zone earlier, as indicated by the external characteristic curves. Energy loss analysis identifies the increased energy loss at the bell mouth due to backflow from the impeller as the main contributor to the head drop. Finally, it is observed that submerged vortices exist at the bottom of the intake sump; however, their swirling strength is insufficient to significantly affect the hump characteristics of the intake system under low flow conditions. The distinguishing factor between the two systems is the distribution of axial velocity along the radial direction in the bell mouth. The higher axial velocity near the casing of the bell mouth in the pump system supplements the energy of the liquid near the shroud side of the impeller, thus delaying the occurrence of backflow.

Flow-field characteristics of the thermal plume above an elliptical high-temperature heat source surface

The thermal plume formed by the high-temperature elliptical heat source surface during the smelting process is often captured and removed by the local exhaust system. Accurately mastering the flow-field characteristics of such high-temperature elliptical heat plumes is helpful for efficient design of local exhaust systems. In this paper, the effects of the ratio of long and short axes (5/4 ≤ ξ ≤ 5/1) and the intensity of heat source (80 ≤ F ≤ 160 W) on the axial and radial velocity distribution of thermal plume in an elliptical heat source are investigated by numerical simulation combined with experimental validation. The results show that in the range of ξ ≤ 5/1, the axial dimensionless velocity distribution of the elliptical plume field and the spreading range of the plume field are mainly affected by ξ instead of F. For 5/4 ≤ ξ ≤ 5/1, the maximum axial velocity Um appears at 1.7 to 2.7 times Z/L (plume height to heat source long axis ratio). For ξ ≤ 5/2, the height at which the cross-sectional velocity field transitions to a circular distribution aligns with the height of Um. It is found that the plume velocity field is characterized by applying the point source model for ξ ≤ 5/3, and vice versa for the linear source model. The plume flow rate formulation obtained by modifying the linear source model for ξ > 5/3 has a better predictive ability in the Z/L ≤ 5 region. This study provides a reference for the design of ventilation systems for elliptical surface heat sources.

Anisotropic turbulence modeling for natural channel flow: A numerical approach with finite element method

In this study, we propose a numerical model aimed at improving the understanding and prediction of flow velocities in natural channels. This model specifically focuses on the challenges presented by anisotropic turbulence and bottom roughness. By incorporating the mixing length concept into an algebraic turbulence model and employing the finite element method with Streamline-Upwind/Petrov–Galerkin (SUPG) stabilization, our model seeks to refine the simulation of axial velocity distribution and secondary motions. Validation was achieved through Acoustic Doppler Current Profiler (ADCP) measurements in three sections of the Canal do Rodeador, showing our model’s predictions of discharge and average velocity to have a deviation of approximately 9.34% from experimental data. The results underline the significance of secondary currents and turbulence anisotropy in shaping channel flow behaviors, offering new insights into the interactions between flow characteristics and channel bed features. This model stands out as a robust tool for hydraulic structure design and hydrokinetic potential evaluation, providing a non-intrusive, cost-effective alternative to traditional methods.

Influence of different turbulence models on tip vortex prediction

Abstract Tip vortex cavitation usually occurs in marine propellers and axial-flow turbines, the cavitation in the tip vortex could potentially result in blade erosion, at the same time, it will cause the pump vibration and noise emission. The tip vortex mainly occurs in rotating machinery with complex three-dimensional flow, but the prediction of the hydrofoil tip vortex can provide a basis for the study of the blade tip vortex in rotating machinery by simplifying the blade model. Hence, in this paper, we use the commercial software CFX to investigate the impact of distinct turbulence models on the configuration of tip vortex distribution in the NACA 16-020 hydrofoil, including SST (Shear Stress Transport), DES (Detached Eddy Simulation), LES (Large Eddy Simulation) turbulence models which are widely used in the field of rotating machinery. At the same time, the axial and radial velocity distributions at different locations downstream of the tip of the hydrofoil are compared to analyse the effects on the velocity distribution near the vortex core line stemming from various turbulence models. By comparing with the experimental data, the most accurate turbulence model for tip vortex prediction is obtained, which will provide guidance for the next step tip vortex prediction and the control of tip vortex flow.

Microscopic spray characteristics of diethyl ether–diesel blends under single and split injection strategies

The phase doppler interferometry technique was used to thoroughly investigate microscopic spray characteristics of single and split injection strategies. The diethyl ether blending with diesel resulted in smaller and uniform droplet formation. Diethyl ether–diesel blend spray exhibited a lower droplet axial velocity distribution than baseline diesel, which can be improved by split injection strategies. At atmospheric pressure, the maximum axial velocity for diesel and diethyl ether–diesel blends was almost identical under single and split injection strategies. However, split injection improved the spray droplet's axial velocity at higher ambient pressures compared to single injection. The chances of coalescence and having coarse droplets were higher at elevated ambient pressure, especially for lower fuel injection pressures. Therefore, increasing the fuel injection pressure is more suitable to avoid droplet coalescence. Unlike the split ratio, dwell time strongly influenced fuel spray atomization. The droplet diameter distribution exhibited a higher probability of finer droplets for a longer dwell time of 0.45 ms than a shorter dwell time of 0.15 ms. A major finding of this study is that diethyl ether–diesel blend spray with a longer dwell time exhibited superior spray characteristics.

Tightly Trapped Atom Interferometer inside a Hollow-Core Fiber

We demonstrate a fiber-guided atom interferometer in a far-off-resonant trap (FORT) of 100 μK. The differential light shift (DLS) introduced by the FORT leads to the inhomogeneous dephasing of the tightly trapped atoms inside a hollow-core fiber. The DLS-induced dephasing is greatly suppressed in π/2-π-π/2 Doppler-insensitive interferometry. The spin coherence time is extended to 13.4 ms by optimizing the coupling of the trapping laser beam into a quasi-single-mode hollow-core anti-resonant fiber. The Doppler-sensitive interferometry shows a much shorter coherence time, indicating that the main limits to our fiber-guided atom interferometer are the wide axial velocity distribution and the irregular modes of the Raman laser beams inside the fiber. This work paves the way for portable and miniaturized quantum devices, which have advantages for inertial sensing at arbitrary orientations and in dynamic environments.

The impact study of variable diameter stabilizer on drilling fluid and cuttings transport

Through numerical simulation, this study investigates the flow field characteristics of the variable diameter stabilizer in drilling tools under various conditions. It analyzes the influence of different flow rates and speeds on axial velocity and pressure distribution. The results indicate that more significant flow rates correspond to higher average axial velocities across sections, facilitating the transport of drilling fluid and cuttings. Increasing rotational speed leads to greater pressure differences between adjacent sections, consequently elevating the overall pressure drop of the tool, which, to some extent, aids in transporting drilling fluid with cuttings. During rotation, the vortex zone on the backside of the stabilizer creates a hovering and accumulation of cuttings, causing mud agglomeration, thereby affecting tool performance. During structural optimization of the tool, priority should be given to a transitional design of the outlet area in the functional core zone, aiming to alleviate the impact of abrupt structural expansions on cuttings transport.

Orifice section velocity fitting method and its application in flash spray research

Although spray technology is widely used, research on spray flow is limited by the complexity of its flow field. To simplify the spray simulation, this work proposed an orifice section velocity fitting method, which can simplify the calculation of the flow field inside the nozzle by using a set of special velocity fitting equations as boundary conditions. For the application and verification of the method, the characteristics of methyl nonafluorobutyl ether (HFE7100) flash spray under temperature influence were experimentally studied in this paper using phase Doppler particle analyzer equipment and compared the results of simulation and experiment. The comparison results show that the simulation and experimental results of the spray axial velocity distribution have good consistency at different temperatures. The simulation results show that the swirling flow in the orifice is stronger when the temperature is lower than the boiling point and the spray velocity isosurface is conical. The swirling flow in the nozzle is attenuated by flash evaporation when the temperature increases above the boiling point, while the spray velocity isosurface changes to a bell shape. The experimental results show that the spray velocity increases with increasing evaporation caused by increasing temperature and that the spray axial velocity distribution also changes from a saddle shape to a single peak shape. The spray droplet size increased significantly under the influence of flash evaporation, but the spatial distribution maintained a saddle shape. This study can provide a reference for spray simulation analysis and the study of flash spray characteristics.

Experimental analysis of lifelines in a 15,000 L bioreactor by means of Lagrangian Sensor Particles

This study employs Lagrangian Sensor Particles (LSPs) with a diameter of 40 mm equipped with a pressure sensor to investigate cell lifelines in a 15,000L stirred tank reactor (STR) with three Elephant Ear impellers. The Stokes number of the LSPs is approx. 0.004 on a macro-scale. The vertical probability of presence, axial velocity profiles, circulation time distributions, and residence time distributions are quantified to analyze single-phase mixing heterogeneities, detect hydrodynamic compartments and conduct a Lagrangian regime analysis. Results reveal a similarly distributed probability of presence in the vertical reactor center but emphasize the LSP’s sensitivity to fluctuating densities. Axial velocity distributions illustrate characteristic impeller-induced flow patterns, and circulation time distributions identify three compartments with comparatively shorter times in the axial center. Residence time distributions exhibit a similar compartmentalized profile. Moreover, the study estimates a potential oxygen deprivation zone for CHO cells in the upper compartment and demonstrates the LSP’s efficacy in characterizing impeller systems. Contrary to literature, the ratio of examined global mixing times to circulation times is 1.0, highlighting macro-scale mixing. The research underscores that LSPs offer crucial insights into industrial-scale STRs, specifically for determining hydrodynamic compartments without having optical access.

Fluidized bed hydrodynamics under variable air inlet configurations to enhance gasification reactor efficiency: Computational study

This study employs diverse strategies to enhance motion dynamics within the reactor, with a specific focus on the critical geometric parameter of air nozzle configuration. Methodical analysis of various air nozzle angles, 0°, 45o, and 90° relative to the horizontal bottom line is undertaken to discern their influence on these key parameters throughout multiple stages during the recorded flow duration. A CFD model of the physical model is constructed and solved using ANSYS software. Parameters scrutinized include the longitudinal and lateral distribution of particle volume fraction, alongside radial and axial velocities of particles. The results emphasize the significant impact of air-feeding orientation on both radial and axial particle velocities. Notably, 45° air nozzle angle is the best orientation for the fluidized bed reactor displaying maximal values in particle volume fraction fluctuations and bed height. Furthermore, peak values for radial and axial velocity persist consistently throughout the entire flow duration.

Numerical investigation of the aerodynamic performance and loss mechanism in a low bypass ratio variable cycle engine fan

The aerodynamic performance of the variable cycle engine fan changes sharply during mode transition. Investigating the variations of flow structure and understanding the loss mechanism are helpful in providing guidance for the fan design. Three-dimensional models of single bypass and double bypass compression systems are established, and static pressure is applied at the bypass stream outlet to simulate the opening of the mode selection valve. The characteristic band of variable cycle engine fan is obtained by gradually increasing the bypass stream pressure while maintaining specific values for the core stream pressure. Results show that the overall performance of the double bypass configuration, without bypass recirculation, is almost identical to that of the conventional single bypass configuration during the throttling process. With the increase in bypass pressure, the shock wave and the trajectory of tip leakage vortex gradually move forward, thereby increasing the blockage region induced by the interaction between the shock and tip leakage vortex. In addition, the performance of fan with reverse flow is also calculated. The recirculation causes the operating point to move closer to the stability limit, reducing the isentropic efficiency. Additionally, the recirculation changes the radial distribution of axial velocity and total pressure, leading to inlet distortion in the core driven fan stage. Furthermore, the loss mechanism is clarified by modeling the splitter and conducting entropy generation analysis. The sharp expansion of bypass stream could cause severe flow separation, and reducing the curvature of casing can effectively suppress the viscous shear loss.

Nominal wake field of a ship with moonpool

ABSTRACT To investigate the influence of a moonpool on the nominal wake field of a ship during calm water navigation, computational fluid dynamics calculations are performed using the STAR-CCM + software. The analysis found that the influence of boundary layer separation in the moonpool causes the hull boundary layer thicker, which reduces the average axial velocity of the propeller behind the moonpool and enhances the wake. The uniformity of the axial velocity distribution at the propeller disc is also reduced, worsening the uniformity of the wake field. In addition, the wake field characteristics of rear propellers change periodically with the fluctuation of moonpool. As a result the propeller bearing force and vibration characteristics change periodically with not only blade frequency and multiple blade frequency, but also the fluctuation of moonpool. These phenomena make the performance of propellers on ships with moonpool different from that of normal ships.

Flow analysis for lateral synthetic jets to remove contaminants from the outer surface of an automobile camera module

A test facility was constructed to investigate the flow characteristics of lateral synthetic jets generated by an actuator composed of a cavity, an orifice and a vibrating piezoelectric disc. Subsequently, 3D unsteady numerical simulations were conducted to analyze the formation of the synthetic jets and their dependence on the height of the orifice exit from the outer surface of the cavity. The time-averaged axial velocity was measured and used to validate the numerical results, and the maximum velocity reached approximately 8 m/s. In this work, it was found that the interaction of the vortex tube generated at the edge of the orifice exit and the outer surface of the cavity has a significant impact on the axial velocity distribution and characteristics of the lateral synthetic jets. Based on the experimental data and the numerical results, an attempt has been made to understand the formation of the synthetic jets and their interaction with the outer surface.

Propeller–hull interaction simulation for self-propulsion with sinkage and trim

This paper presents numerical simulations of propeller–hull interaction of a ship model for the dynamic condition, demonstrating the ability of the developed self-propulsion module in OpenFOAM. A dynamic motion class has been developed based on the sliding mesh method to simulate a rotating propeller with ship motions. A body-force method is also implemented to simulate propeller–hull interaction to reduce the computational cost of propeller modeling. Validation studies were carried out for the Japan Bulk Carrier (JBC) ship model. The bare-hull resistance, sinkage, and trim are verified against the experimental data. The propeller open-water hydrodynamic characteristics are then computed and validated using sliding mesh and body-force methods. Finally, the self-propulsion simulations are carried out for the JBC model in calm water with sinkage and trim at the design speed. Numerical predictions of the self-propulsion parameters and axial flow velocity distributions at different transverse locations are presented.

Electrohydrodynamic peristaltic microfluidic flow with thermal and molecular analysis featuring sloped configurations

This study examines the simultaneous impacts of thermal and molecular transfer of non-Newtonian fluid propelled by the collective impact of electroosmosis and peristaltic pumping via inclined channel. Internal frictional heating and heat generation are also taken into consideration. The electrohydrodynamic phenomenon is described by the nonlinear Poisson–Boltzmann equation. The problem is modulated mathematically through a system of coupled non-linear differential equations in wave frame of reference. Using the regular perturbation method around a small wave number δ, we obtain sequential solutions for stream function ψ, electric potential ϕ, velocity u, pressure gradient dpdx, temperature θ and concentration Ω distributions. The influences of newly arising parameters such as the electroosmotic parameter me, relaxation time parameter λ1, retardation time parameter λ2, wave number δ, Reynold’s number Re, heat generation parameter β, Prandtl number Pr, Schmidt number Sc, Froude number Fr and Soret number Sr on physical characteristics are analyzed graphically. There is an inverse correlation between the parameters of relaxation time and retardation time and their effects on axial velocity, concentration, and temperature distributions. In particular, the temperature of the fluid increases as the EDL parameter, relaxation time parameter, viscous dissipation parameter, and Reynolds number increase, but decreases as the retardation time parameter increases. Moreover, the axial pressure gradient increases as Reynolds number and inclination angle increase, while it decreases as Froude number increases. The current model has applicability in the chemical industry, reservoir engineering, micro-fabrication, and biomedical applications, where electroosmotic effects on heat and mass movement are crucial.