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A new axisymmetric CFD model capable of describing pumping loss is proposed for free piston Stirling engine (FPSE). Inclusion of clearance seals, bounce space, heater, cooler and regenerator in a single model is the unique strength of this work. For transient simulation of engine, dynamic mesh was utilized for catering needs of moving boundaries. The model was validated with 12.5 kW component test power converter (CTPC) and successfully predicted indicated power, efficiency, pressure amplitude, pressure drop, and gas temperature in expansion and compression space at different piston amplitudes with 6% maximum deviation. The results showed that the heat exchange at heater and cooler was minimized at each flow reversal and was strongly influenced by oscillating gas flow rate. The results also present optimum displacer and piston seal clearance at different charge pressure and operating frequencies. The displacer seal clearance could be increased up to 125μm without compromising power: however, engine output was severely affected with increasing piston seal gap.

This work studies the flow characteristics in a Berty reactor, a gradientless reactor for kinetic studies, using three-dimensional (3D) computational fluid dynamics (CFD), and a non-ideal continuous stirred tank reactor (CSTR) model. The state-of-the-art method could describe the flow characteristics including the dead volume, bypassing, and back-mixing inside the Berty reactor to effectively determine the suitable operating conditions with perfect mixing. The limitations of such behaviors are usually observed in most reactors and possibly in the Berty reactor. According to the CFD results, the dead volume could contribute up to 7.42% at atmospheric pressure, while it was observed to be slightly below 1% at a pressure above 6 atm due to improved recirculation inside the Berty reactor. The increment of pressure and impeller speed potentially improves the mixing characteristics of the Berty reactor with an abatement of dead volume. In contrast, the reduction of flow rate significantly leads to limited back-mixing. Bypassing in the Berty reactor could be observed especially in the temperature range of 350–450 °C due to excessively high velocity. This method can be used as a tool for characterizing non-ideal flows and enables researchers to reliably determine the suitable operating windows of perfect mixing for designing intrinsic kinetic experiments in the Berty reactor.

In order to improve the energy utilization rate, this paper analyzes the flow around the cylinder in the tube-row channel heat exchanger through numerical simulation. Effects of micro-rib structure types (vertical rib and ring rib), number of ribs (N = 0, 4, 6, 8), height of ribs (H = 2, 3, 4 mm), pitch diameter ratio (ST/D = 1.5, 2, 2.5), mass fractions (ω = 0–0.5%) and Reynolds numbers (Re = 514–1205) on the flow and heat transfer characteristics of tube-row channel heat exchangers are analyzed. Results showed that TiO2-H2O nanofluids can improve the comprehensive performance of heat exchanger, and when the mass fraction is 0.4%, the tube-row channel heat exchanger has the best performance. For heat exchangers with different types and structural parameters, the adjustment of the number of ribs, the height of ribs, the ratio of transverse pitch diameter and the use of nanofluids can increase Nusselt numbers by 53.63%, 57.25%, 52.38% and 12.93% at maximum, respectively.

As one of the major functions of drilling mud is to maintain pressure inside a wellbore to avoid any invasion of unwanted high-pressure, this makes the determination of this pressure loss a very complicated task in the petroleum drilling industry. The aim of this paper is to predict the behaviour of drilling fluid flowing inside rotating pipe then in a concentric annulus at various values of inlet velocity and rotation speed. The governing equations (continuity and momentum) are solved numerically using CFD simulation with FLUENT commercial code. The flow is laminar in three-dimensional steady-state with non-Newtonian fluid. The results are visualized as: contours, pressure drop and velocity. The results show that pressure drop is decreased when pipe rotational speed increase. At the conditions of rotation speed of 300 rpm and inlet velocity of 1.2 m/s, the pressure loss present a significant decrease compared to the other conditions, furthermore, an uniform distribution of velocity in the pipe and annulus, is indicated. Therefore we can considerate this conditions of rotation speed and inlet velocity as optimal conditions.

The hydrogen Knudsen compressor has great potential to transport hydrogen and provide the required pressure in MEMS and microfluidic systems. The microchannel composed of cold and hot serrated surfaces is beneficial to the temperature control of the multistage Knudsen compressor. In the present study, a serrated hydrogen Knudsen compressor model is established initially, and the non-equilibrium evolution is numerically studied by using the method of N–S equations with the slip boundary. The key factors affecting the non-equilibrium evolution are comprehensively analyzed. The flow behaviors and performance of the serrated hydrogen Knudsen compressor in different times are studied. It is found that the main factors affecting the non-equilibrium evolution are the thermal expansion flow, thermal transpiration flow, and Poiseuille flow. Meanwhile, the serrated structure affects the local flow in the serrated microchannel at different times. Under the interaction of the thermal transpiration flow and the Poiseuille flow, the pressure difference between the two containers first increases rapidly and then decreases slowly, and finally approaches 1886 Pa. The research reveals the flow mechanisms of the hydrogen Knudsen compressor in the non-equilibrium evolution, which provides theoretical support for the safety and reliability of the hydrogen Knudsen compressor.

Filtration by the fibrous medias is recognized as one of the most effective methods to control particulate pollution. A type of 3-D mesh spacer filter (3-D filter) proposed is effective for filtrating the large particles with low pressure drop. This study described the flow characteristics of dust-containing gas within the 3-D filter by means of CFD-DEM model. The influences of air velocity, particle concentration and restitution coefficient of particle on the filtration performance as well as the particles deposition process were simulated. The results showed that the particles capturing efficiency of 3-D filter was increased with the air velocity and particle concentration while the particles rebound made the filtration efficiency decreased when the air speed was increased more than 3.0 m/s. For the particle properties, the smaller restitution coefficient, the higher filtration efficiency. When the quality of particle deposition was increased to 70 g/m2, the filtration efficiency almost remained unchanged.

Conventional ski-jump bucket energy dissipator is the most important structures used when flow velocity at the spillway foot exceeds 20 m/s. The experimental analysis showed that energy dissipation in conventional ski-jump bucket is less. It is due to fact that, in conventional ski-jump bucket, energy is dissipated partly through the interaction of trajectory with air and mostly through the impact of trajectory in the tail water. To improve energy dissipation, it is proposed to modify conventional ski-jump bucket by use of a deflector along both sides of the bucket. The deflector will contract the flow on both side and promote impact of trajectory in air. So in modified ski-jump bucket, energy is dissipated not only by the interaction of trajectory with air and by the impact of trajectory in tail water but also by the impact of trajectory in the air. In the current study, the effects of using deflector on both sides in the ski-jump bucket were investigated experimentally. This experimental study was based on a comparison of the conventional ski-jump bucket (CSB) with the modified ski-jump bucket (MSB). Model tests were carried out in a hydraulic flume of 30 × 30 cm in cross section and 6 m in length for ten distinct discharges. The model was designed on the basis of the Froude similarity condition with a scale of 1:100. Each test consisted of evaluating the trajectory features and energy dissipation. The main challenge of the present research was to get well trajectory along with more energy dissipation in modified (deflector) ski-jump bucket in comparison with conventional ski-jump bucket. The results demonstrated that modified ski-jump bucket (MSB) improves energy dissipation and also well trajectory was formed. Energy dissipation for the CSB is between 47.16 % and 56.66 %. Energy dissipation for MSB ranged from 67.168% to 72.144%.

Fluidic oscillators (FOs) containing no moving parts have received extensive attention in recent decades. Applications with FOs in some complex conditions are generally characterized by a high-speed jet of particle-laden flow that periodically switches between two parallel channels. This oscillating flow makes FOs prone to erosion. Using the CFD method, this study investigated the dynamic erosion behavior coupled with periodic oscillating jets. Three primary locations of erosion were observed, namely, in the vicinities of the nozzle, splitter, and vents. The effects of flow rate, particle size, and solid content on erosion were evaluated. It was found that the location of maximum erosion did not remain same. The amount of erosion in the splitter and vents fluctuated cyclically due to the periodic oscillation of the supply jet. Additional erosion occurred during the start-up process of the vertical feedback oscillator, whereas the curved feedback oscillator showed better performance in this respect.

With the recent advancements in designs and optimization of gas coolers in CO2 transcritical refrigeration and heat pump systems, the impact of the lubricant on the performance of gas coolers has been gaining increasing attention. The existing literature reviews focus on examining the lubricant effect on the heat transfer performance of gas coolers. However, the studies do not present a detailed discussion and a systematic summary of the flow characteristics. The present paper aims to offer an overall review of the lubricant impact on the flow characteristics of CO2 in gas coolers. The authors hope it will help researchers conduct additional research about practically designing and optimizing gas coolers. This paper reveals the flow mechanism by providing critical discussions on how temperature, lubricant type, lubricant concentration, mass flux, operational pressure, tube diameter, and tube configuration influences the flow characteristics of the CO2-lubricant mixture. Then, the paper summarizes and evaluates the latest developments related to CO2-lubricant mixture in the flow and heat transfer analysis models and pressure drop correlations. Moreover, the current research gap is summarized, and the study proposes development directions. These include measuring thermo-physical properties of CO2-lubricant mixture, examining pressure drop characteristics under different tube configurations, developing universal pressure drop correlations, and studying flow characteristics in vertical tubes.

The cooling channel of a scramjet is the fundamental structure of the active thermal protection for an engine. Till now, studies have focused mainly on the steady-state flow and heat transfer process in the cooling channel. However, the vibration intensity of an engine increases sharply as the flight speed increases, because of which, the flow and heat exchange mechanisms based on the cooling channel under stable conditions cannot be applied under vibration. In this study, experimental methods are used to study the characteristics of the forced vibration of a cooling channel on the flow and heat transfer of hydrocarbon fuel at supercritical pressure. In addition, the influences of different vibration frequencies and vibration amplitudes on the flow and heat transfer are analyzed. The research results show that at supercritical pressure, when the fuel temperature is below the critical temperature and the inner wall temperature is above the critical temperature, external vibrations would enhance the heat transfer characteristics of the cooling channel. However, when the pressure and temperature are unstable, the forced vibration of the cooling channel would suppress the instability of temperature and pressure while strengthening the heat exchange.

The drainage of granular assembly from a flat-bottomed silo can be in either funnel flow mode or mixed flow mode. The primary motivation of this work is to investigate whether there exist fundamental differences between the rheological behavior of particles under these two discharge modes. The developments and evolutions of flowing zone and also the characteristics of particle velocity fluctuation during funnel and mixed flow discharges were analyzed and compared by performing 3D Discrete Element Method (DEM) simulations. For funnel flow discharge, the characteristic width of flowing zone at the early discharge state presented a clear history-dependent feature. For mixed flow discharge, the flowing zone sharply shrunk when the upper free surface of the material approached a critical height and the discharge mode then shifted to funnel flow mode. Discrete Fourier transform results demonstrate that resonant motion of particles appeared during both funnel and mixed flow discharges. The correlation analyses indicate that for these two flow modes, there both existed an intermediate region in the converging part of the flowing zone. Its upper boundary located at the position where the flowing zone started to converge along the vertical direction and was featured as the maximum particle compressive force. And its bottom boundary corresponded to the location of free-fall arch and acted as the source of the resonant motion of particles. Our simulation results thus suggest that from the perspective of particle velocity fluctuation, there is no essential difference between granular flows under funnel and mixed discharge modes.

The present work deals with the numerical analysis of thermohydraulic performance of Al 2 O 3 - H 2 O based nanofluid flow through straight slot rib rectangular channel. The integration of the artificial roughness on the heated surface and use of the nanofluid as a heat transferring medium makes the present system efficient. Important parameters such as Reynolds number ( Re ) is selected in the range of 5000–8000, relative slot rib height ( H SSR / D H ) in the range of 0.060–0.084 and other parameters have been fixed are spanwise pitch ( P span / H SSR ) 4.07, streamwise pitch ( P Stream / H SSR ) is 7.6, nanoparticle concentration ( ∅ ) is 3% and nanoparticle diameter ( n d ) of 40 nm. The analysis resulted in the maximum value of Nusselt number ( Nu rough ) and friction factor ( f rough ) at value of Relative height ratio ( H SSR / D H ) of 0.084 and 0.06, respectively. It is found that the value of relative slot rib height 0.084 delivers the highest thermohydraulic performance ( η ) in comparison to other values of geometric parameters.

Gas bubble distribution is considered one of the most critical factors affecting the Industrial Fluid Coking™ process since it influences the formation of wet agglomerates that causes fouling in the stripper section. A multi-phase Eulerian–Eulerian two-fluid method (TFM) coupled with the kinetic theory of the granular flow (KTGF) was used to investigate the hydrodynamics of a bubbling fluidized bed; the goal is to increase the flow of gas bubbles into the first half of the jet cavity formed when liquid is sprayed into the fluidized bed, thus reducing the formation of wet agglomerates. The numerical simulations under different superficial gas velocities, different gas distributor geometries, and different gas distributor inclined angles were carried out. The results showed that the predicted bubble distributions at the injection level under the lab and commercial operating conditions are similar although the particles and gases are different under those two operating conditions. More gas bubbles can be directed to the first half of the jet cavity by either increasing the gas superficial velocity (directing around 20% more gas to the specified area) or using the proposed new gas distributor (directing around 30% more gas to the specified area). The effect of the inlet gas distributor configuration on the bubble distribution is much more substantial when the inclined angle of the gas distributor is large.

The flow nozzle aerator, which is the part of the water tap made up of Acrylonitrile Butadiene Styrene (ABS), can be modified entirely with a new design. The curved and cone-shaped slopes are used to improve the smooth flow at uniform velocity. Simultaneously, discharge is optimum by modified interior design. The smooth laminar delivery of water with optimum pressure, the liquid element at the aerator end becomes smooth. The assembled nozzle aerator solid model has been generated before experimentation. This can promote through the prediction by the modern tool ANSIFLUENT and Computational Fluid Dynamics (CFD) for finding the flow behavior and its outlet characters. The solid model can be fabricated to prototype for accurate dimensions by using 3D printing technology. Comparing fluid motion with the time consumption of filling water has been done over these different kinds of aerator and nozzle models, which are fabricated by 3-dimensional printing.

In the movement process of continuous bubbles, different liquid flow state and initial temperature of bubble shave important influence on bubble movement and heat transfer. In this study, the flow and heat transfer characteristics of high temperature bubbles in normal temperature liquid are investigated. The rising process of and temperature of bubbles are studied by numerical simulation and compared with experimental results for verification. The results show that the shape, velocity and temperature of the bubble are affected by the initial position of the bubble. Because the closer the initial position of the bubble is to the bottom of the cylinder, the greater decrease of the bubble aspect ratio (w*),the faster decrease of bubble temperature, and the larger bubble velocity would be. The increase of the bubble diameter would mitigate the influence of liquid jet on the bubble motion. Finally, as the bubble surface tension increases, the liquid jet would have less influence on the bubble movement.

We report elastocapillary interaction between a long rectangular membrane fixed along its central axis and a liquid drop dispensed at one of its ends. The introduction of the drop results in the elastocapillary-driven wrapping of the membrane along its width and a concomitant flow in the resulting conduit along its length. Depending upon the drop size (d) and capillary length scale (L_c), we identified general criteria for achieving complete wrapping of the membrane in the dry state from energy consideration. For small droplets satisfying d≲L_c, we find that the critical membrane length (W_c) required for complete wrapping is proportional to the elastocapillary length scale (L_ec). In case of large droplets with d>L_c, the wrapping behavior depends on the ratio of membrane width to elastocapillary length scale (W⁄L_ec ) and the ratio of capillary length scale to the elastocapillary length scale (L_c⁄L_ec ). Our study suggests that the critical membrane width for complete wrapping is smaller in the wet state compared to that in the dry state, which can be attributed to the existence of a transmembrane pressure in the wet state. The effect of membrane thickness and width and drop volume on the length and cross-section of the wrapped conduit and attached width of the wrapped membrane is studied. For small droplets, the resulting elastocapillary flow exhibits an inertial regime at small times, followed by a Washburn regime at intermediate times, and finally an inertial regime, and for large droplets, only an inertial regime is observed throughout.

Flow characteristics and the mechanical theory of granular flows in dense sheared granular systems have yet to be fundamentally understood because of the complexities and discreteness of these systems. This study derives the appropriate equations and effects of mechanical parameters on fluctuation velocity, and investigates the solid volume fraction for a dense granular assembly sheared between two parallel plates. Theoretical results are verified via a discrete element method simulation. Thereafter, the mechanical mechanisms of the granular flows in this dense sheared granular system are investigated using this simulation method. Results show that the fluctuation velocity of granules at the boundaries is larger than that in the middle of the clearance, which is opposite the variation tendency of solid volume fraction. A change in the mechanical parameters can directly influence fluctuation velocity, thereby inducing the variation of the solid volume fraction. Moreover, studies on the mechanical mechanisms of granular flows indicate that inertial number has more significant effects on shear dilatancy, micro-contact structures, and coordination coefficient than contact stiffness coefficient. That is, shear dilatancy amplitude, strong force chains, and coordination coefficient decrease with the increased inertial number.

The rotating packed bed (RPB) has been widely used in gas-liquid flow systems as a process intensification device, exhibiting excellent mass transfer enhancement characteristics. However, the complex internal structure and the high-speed rotation of the rotor in RPB bring significant challenges to study the intensification mechanism by experiment methods. In the past two decades, Computational Fluid Dynamics (CFD) has been gradually applied to simulate the hydrodynamics and mass transfer characteristics in RPB and instruct the reactor design. This article covers the development of the CFD simulation of gas-liquid flow in RPB. Firstly, the improvement of the simulation method in the aspect of mathematical models, geometric models, and solving methods is introduced. Secondly, new progress of CFD simulation about hydrodynamic and mass transfer characteristics in RPB is reviewed, including pressure drop, velocity distribution, flow pattern, and concentration distribution, etc. Some new phenomena such as the end effect area with the maximum turbulent have been revealed by this works. In addition, the exploration of developing new reactor structures by CFD simulation is introduced and it is proved that such new structures are competitive to different applications. The defects of current research and future development directions are also discussed at last.

As a subsequent paper for “type-A-choking-oriented unified model for fast fluidization dynamics”, the present work aims to provide more systematic mesoscale analyses on clusters. Starting from theoretical derivations on idealized flow patterns of gas and solids around a single falling cluster; the momentum consumption due to particle circulation in clouds and the modification of flows by the constraint of driving force available in the bed were addressed. Complete compensation of the pressure-drop driven percolated gas in clusters by the reversely-penetrating particles was used for the ultimate closure of the model. An important finding of the present work, different from most empirical correlations, but verified by Wei and Zhu's latest experimental data and others, is that the cluster diameter does not vary monotonically with the mean solids holdup of the bed, but has a maximum value in between. Demonstrative calculations show that it is easy for Group A particles to enter the flow regime of high-density fast-fluidization as the circulating solids flux increases continuously, while fast fluidization for Group B particles tends to be stopped at Type C choking in advance. Compared with Group A particles, the clusters for Group B particles are less dense, but the penetration velocities of particles are higher, resulting in much larger dimensionless diameters of clusters. Finally, issues of pseudo-2D fast-bed modeling were discussed, and modeling of fast-beds with uneven flow fields was outlook briefly.

An avalanche dynamic model is proposed for the three-dimensional simulation of avalanche dynamics that adopts the Navier–Stokes equations as the governing framework and introduces μ(I) granular rheology in the constitutive law. Using the finite–volume method as the numerical scheme, a simulation program based on the OpenFOAM open-source platform was developed. The validity of the model as well as the program was verified by numerical simulations of a laboratory-scale granular flow test. An interface developed between the natural terrain data and the calculation program enables the simulation of natural avalanches. The Baige avalanche, a natural event, was reproduced. Comparisons between simulations and real data further verify the feasibility and accuracy of the full avalanche dynamic model. In addition, the evolution of the hydrostatic pressure, shear strain rate, inertial number, and kinematic viscosity over the duration of the avalanche were analyzed to extract the underlying internal mechanism.

Although the zonal propagation of mesoscale eddies is intrinsically westward in oceans worldwide, eddies occasionally propagate eastward. Westward propagating eddies (WPEs) and eastward propagating eddies (EPEs) have distinctively different characteristics. In this article, the propagation features of WPEs and EPEs were studied using a combination of current, wind, and topographical data. We found that, except for in the North Atlantic, the energetic areas for WPEs and EPEs did not overlap. Furthermore, the propagation channels of WPEs and EPEs were located at different depths. The magnitude of change in current and wind stress simultaneously affected both the spread direction and velocity of eddies. The average translation speeds of eddies increased as subsurface current velocity increased, regardless of the angle between the direction of eddy propagation and flow. Compared with WPEs, increases in wind stress had little effect on the propagation speeds of EPEs. The directions of EPEs were more sensitive to changes in flow and wind speed. Even small changes in bathymetry slowed the propagation speeds of eddies. This topographical inhibition was biggest when the topographic gradients were around 0.02 and 0.04 for WPEs and EPEs, respectively. The propagation directions of EPEs were also sensitive to the surrounding terrain and tended to move along seamounts and ridges. These findings may refine eddy predictions and aid eddy observations in the future.

Captured CO2 from the manufacturing industries and power generation sources are not pure and may contain usually some amount of impure components, which affect the flow dynamics of the CO2 in the pipelines. Major component of impure components includes N2, H2, H2S, O2, Ar etc., depending on the capture technology used for the removal of CO2 streams. To design efficient CO2 pipeline transportation systems, it is imperative to understand the effect of these impure components on the flow behaviour. The simulation of the effect of CO2 binary mixture on pipeline performance is carried out in this study. The steady-state flow in pipeline is described by a set of parabolic mass, momentum and energy conservation equations. To solve the set of equations subject to the boundary and the inlet conditions of the pipeline, the non-linear algebraic solver library DNSQE in Fortran is used to study the behaviour of 90 vol% CO2, and 10 vol% single impure component (N2, H2, H2S, O2 and Ar). The phase diagram and pertinent fluid properties are calculated using the Peng-Robinson (PR) equation of state implemented in NIST Reference Fluid Thermodynamics and Transport Properties database program REFPROP. The results reveal that the bubble point curves were lifted up to higher pressures by impure components. The changes in the bubble point would affect the operating conditions of CO2 pipeline. The presence of impure components also changed the properties of the flowing fluid. From the results, H2 shows the most significant impact on the performance of CO2 pipeline as the highest pressure drop by ca. 0.18 bar/km which has smaller density and greater flow velocity against other CO2 streams. The results also show that Ar had the mildest effect followed by O2, N2 and CO. In the case of H2S, the flow parameters are found to be nearly identical to those for pure CO2. The pressure drop for binary mixture contains H2S shows the same value with pure CO2 stream by ca. 0.13 bar/km.

Discrete element method is used in this work to examine the mechanisms determining powder deposition efficiency during powder spreading in powder bed fusion additive manufacturing. The results reveal that powder flow in the powder pile is critical for the formation and break of transient jamming. The forces on the underlying part increase first with spreading speed then decrease with a large fluctuation. For varied spreader shapes, a small inclined angle of the spreader surface makes the force barrier farther from the discharging gap, creating a larger region which ensure enough powder supply to the gap. Furthermore, a small inclined angle of the spreader surface close to the gap results in less particle motion conflicts at the gap and ensures larger discharging rate through the gap. This mechanism explains why spreaders with inclined or round surfaces help increase powder deposition efficiency.

During the pipeline transportation of backfill slurry, flow velocity has direct effects on the transport properties and then influences pipe blockage and wear. In this paper, a novel flow loop- horizontal electrical resistivity (HER) test system and Eulerian model were used to investigate the flow behavior and HER characteristic of cemented coal gangue-fly ash backfill (CGFB) slurry under different flow velocity. The results showed that: 1) The pressure drop of CGFB slurry increased linearly with flow rate. 2) The increase in flow rate significantly reduced coarse aggregate contents near the bottom of the pipeline. 3) As the flow rate increases, the fluctuation of measured HER with time increased, the HER differences decreased, and the ranges of the high and low resistance area at the bottom and top of the pipeline, respectively, kept decreasing. The results can provide guidance for HER monitoring of flow state of CGFB slurry in pipeline.

Knotless polyethylene (PE) netting is widely used in fisheries because of its excellent hydrodynamic performance and low cost. Netting deformation and the surrounding flow field distribution play an important role in determining the hydrodynamic characteristics of netting in moving water. In order to investigate the effect of solidity ratio and attack angle on drag, netting deformation, and flow field distribution through the netting, a fluid-structure interaction (FSI) model based on a one-way coupling combining the shear stress turbulent (SST) k-omega model and the large deformation nonlinear structural finite element model was evaluated. Our results showed the difference between the parallel and normal drag forces found in the present numerical model and experimental flume tank data were 9.17% and 11.58%, respectively. The mean relative error in the inclined hydrodynamic drag for different flow velocities and attack angles was 8.35%, 6.69%, and 5.37% for the nettings 1, 2, and 3, respectively. These results show that the present numerical simulation based on FSI one-way coupling can be used to examine hydrodynamic forces on netting. The flow simulation results show that there is a noticeable flow velocity decrease through the netting and a rather large velocity reduction region downstream from the netting for different attack angles. These results reveal the existence of turbulent flow due to the netting wake. It was found that the equivalent stress and total deformation increase as the flow velocity increases and solidity ratio decreases.

We report an experimental study of the shear-induced migration of flexible fibers in suspensions confined between two parallel plates. Non-Brownian fiber suspensions are imaged in a rheo-microscopy setup, where the top and the bottom plates counter-rotate and create a Couette flow. Initially, the fibers are near the bottom plate due to sedimentation. Under shear, the fibers move with the flow and migrate towards the center plane between the two walls. Statistical properties of the fibers, such as the mean values of the positions, orientations, and end-to-end lengths of the fibers, are used to characterize the behaviors of the fibers. A dimensionless parameter Λeff, which compares the hydrodynamic shear stress and the fiber stiffness, is used to analyze the effective flexibility of the fibers. The observations show that the fibers that are more likely to bend exhibit faster migration. As Λeff increases (softer fibers and stronger shear stresses), the fibers tend to align in the flow direction and the motions of the fibers transition from tumbling and rolling to bending. The bending fibers drift away from the walls to the center plane. Further increasing Λeff leads to more coiled fiber shapes, and the bending is more frequent and with larger magnitudes, which leads to more rapid migration towards the center. Different behaviors of the fibers are quantified with Λeff, and the structures and the dynamics of the fibers are correlated with the migration.

Symmetrical multi-inlet vortex separators/reactors have been demonstrated to be beneficial for gas-particle separation and mass transfer, but their internal energy dissipation has remained unknown. This work designed a series of microscale vortex separators/reactors with single-, dual-, and quadruple inlet(s), to conduct a comparative investigation on their energy-loss characteristics and nature. The response of energy loss to inlet configuration and flow rate was experimentally determined. It is found that in 30–100 L/min flow rate, the Euler number depends insignificantly upon the Reynolds number. The introduction of the multi-inlets improves the symmetry of the flow pattern but increases the gradients of vortex velocity and static pressure. RSM-based CFD simulation can effectively reveal the effect of multiple inlets on the inside flow, static pressure, and energy-loss composition. Finally, an improved semi-empirical correlation of energy loss was developed. The results may provide a positive reference for the design, optimization, and application of vortex-based separators/reactors.

Materials which can absorb the high energy flow are of great importance. The high pressure waves, generated by an explosion or high impact loading, have a very high energy value and it causes a great damage to the objects which come in its path. Though every material, depending upon its properties, offers certain degree of resistance to the flow of energy, there are some materials which have the ability to absorb much more energy than others. These materials when combined together or when layered with other materials, can act as an entity which if suitably formed and placed, can resist the flow of high energy in a very effective manner. The research in the field of developing new materials and composites, is evolving as one of the promising research area in the field of material science as they can do wonders in saving precious lives and properties from the damaging effects of high pressure waves. In this paper the concept is presented by employing the high energy absorbing materials and their combinations (i.e. layered together), to study their effectiveness against the impact of high pressure waves produced by an explosion of TNT charge kept at a certain distance. Conditions have been simulated using ANSYS Autodyn software. Attenuation of high pressure waves is observed by studying the Energy absorption property of the materials as a key parameter. The deformation of the material plate and other associated parameters are also studied.

A methodology of the entropy production theory is employed in hydro turbine flows to analyze the hydraulic loss characteristics quantitatively. The entropy production theory has its distinctive superiority over than traditional pressure drop method because it calculates energy loss through integrating entire computational domain so that it can identify location of energy loss and reflect energy loss characteristics intuitively. This simulated study was implemented by commercial software ANSYS CFX with shear stress turbulence model for a Francis turbine versus various discharge conditions. After comparing with experimental data, the energy loss in different flow components was analyzed and the ability of flow parts to generate energy loss was evaluated versus various conditions quantitatively. Then, the distributions of entropy production rate (EPR) were displayed in stay&guide vanes, runner and draft tube. The conclusions indicate that draft tube is the main part generating the most energy loss compared with other parts. The energy loss fluctuation of runner was obtained and three dominant frequencies were captured with two low frequencies 11.93 [Hz], 15.9 [Hz] and one high frequency 27.83 [Hz]. This study indicates that entropy production theory can provide sufficient theoretical and engineering guidance for the energy loss analysis in hydro turbine flows.

The ferrofluid transport phenomena have a considerable interest in the boundary layer flow due to its versatility in advancing emerging industrial applications, such as printing. In this concern, the current theoretical model examines the particulate suspension's transport phenomena in the magnetite ferrofluid past a permeable non-isothermal moving surface with the viscous dissipation effect. Self-similarity quantities are applied to ease the solving process in the built-in collocation method, bvp4c function in the MATLAB software. The kerosene-based ferrofluid showed a better convective heat transfer rate than the water-based ferrofluid as the governing parameters vary. The dust particles’ increment in the ferrofluid increases the frictional drag force exerted on the shrinking sheet significantly. Dual solutions are obtainable only when the sheet shrinks to some extent. However, stability analysis confirmed that one of the numerical solutions is not stable.

Characterising powder flowability can be a challenge if only a small quantity of samples is available, e.g. pharmaceutical formulations. The paper focuses on a new method for assessing powder flowability based on physical properties and cohesiveness of particles using a few grams of powders. The technique applies Bond number to represent powder cohesiveness, which detects particle adhesion at median particle size using a mechanical surface energy tester developed at the Wolfson Centre. To establish the method, correlations between the Bond numbers and the flow functions of several powders measured on a shear cell tester have been explored empirically. With the correlations, a prediction model has been developed not only for powder flow functions but also for other flow properties such as compressibility, internal friction angles and true friction angles. This investigation has been undertaken using a wide range of materials from free-flowing to very cohesive for the method establishment and a group of different types of materials for a blind validation of the method. The methodology shows promising results for powder flowability prediction and other flow properties such as compressibility and internal friction angles. The validation results show a good agreement against the results measured using a shear cell tester.

To obtain better quality parts in the stamping process, the important parameter is the flow of material into the die cavity. This flow is controlled by adapting appropriate blank holding force, initial blank shape, and geometry of drawbead. In this paper, a comparative study is carried out using blank holding force and different blank shapes such as rectangular, oblongated, and oval shapes on thinning of the formed part using hyperform as simulation software. From the simulation, it is observed that more thinning is in rectangular blank shapes as compare to oblongated and oval shapes. Formation of oblongated or oval shape blank required extra blanking die which adds more cost. Hence the use of rectangular blank is most preferable along with drawbead. Further research work is carried out to get an optimized solution on rectangular blank using circular drawbead. The result of drawbead with rectangular blank size will give a less thinning with minimum blank holding force compare to oval and oblongated blank shapes. The results obtained by finite element simulation are in good agreement with the experimental results with a permissible error of an average of 6.70%.

Subsurface hydrogen (H2) storage in geological formations is of growing interest for decarbonization. However, there is a knowledge gap in understanding the multiphase flow involved in this process, which can have a significant impact on the recovery performance of H2. Therefore, a full-compositional modeling study was conducted to analyze potential issues and to understand the fundamental hydrodynamic mechanisms of H2 storage. We performed a range of 2D vertical simulations at the decametre scale with a very fine cell size (0.1 m) to observe the detailed flow behaviour of H2 with carbon dioxide (CO2) as cushion gas in various flow regimes. Issues such as viscous instability, capillary bypassing, gas trapping and gravity segregation are analysed here. To generalize our calculations, we have validated and applied the scaling theory in the context of subsurface H2 storage. Since this study is focused on the hydrodynamic behaviour, three dimensionless groups, including aspect factor, capillary/viscous ratio and gravity/viscous ratio were identified to correlate recovery performance between various scales in a fixed heterogeneous system. It was found that H2 could infiltrate the cushion gas in the proximity of the injectors, meaning that CO2 is not displaced away from the injectors in a piston-like fashion. As a result, the purity of the back produced H2 is much degraded, particularly in a viscous-dominated scenario. On the other hand, the injected H2 mostly accumulates at the top forming a highly restricted mixing zone with CO2 in the gravity-dominated case. The recovery performance is therefore much improved in this case. Although the gas distribution can be significantly altered by capillary forces leading to bypassed zones, the recovery performance of H2 is hardly influenced. This is because the back-produced H2 recovery is not dependent on the sweep efficiency of the gas. H2 can be back produced following the same paths which were formed during injection.

Advancements in mechanical expertise and rigorous need for gyratory components of machines expedite scientists towards essentiality of the eternal evolution of modified lubricants to corroborate the reliability, innocuous procedure and stability of sundry bearings. To enhance the performances at heftily ponderous load and high velocity, the high molecular polymers are utilized in mechanical bearings as lubricant. These lubricants are non-Newtonian in characteristics and comply with different constitutive relationships. One of them is the power law lubricant which complies with Ostwald model and is broadly utilized for the engineering lubrication. The derivation of the slip-flow conditions at the interface of bulk Jeffrey fluid and the thin layer non-Newtonian lubricant is performed over a disk spiraling with simultaneous radial stretching and rotation. To obtain a homogeneous solution, the power-law index is suggested 1/3 and no-slip boundary condition is converted into an incipient slip boundary condition. A single dimensionless slip parameter is introduced to regulate the velocity slip. Flow equations are obtained, and the similarity conversion is performed to obtain ordinary differential equations. Numerical results are computed to visually perceive the effects of lubrication on the flow field by incorporating the interfacial slip conditions. The presence of the lubrication enhances the fluid velocity and plays major role in the reduction of the skin friction at disk surface.

Climate is one of the most important factors that determine the energy balance of free-living organisms, and climate is a complex of variables which determine energy gains and losses from organisms. The environment, through climate, transfers energy to and from all living systems. The flow of energy is by one or more of the following processes: radiation (electromagnetic flux), convection (or conduction of heat), or mass transport (of water or other fluids).

Murray-Darling Freshwater Research CentreMDFRC item.Profile conditions were examined in both small experimental and pilot scale sub-surface flow wetlands. The study systems differed in their hydraulic design. The experimental systems had a vertical up-flow design whereas the pilot system was a horizontal flow trench design. Both systems were found to have significant physical, chemical and biological gradients within the sub-surface profile. System age and plant root density appear to be important factors in determining profile differentiation within the experimental systems. Root densities were found to be partitioned between the upper and lower layers on a 70%/30% split respectively. However, in the experimental systems as the systems aged and root densities increased beyond 112-251 g.m(-2) chemical water quality differentiation id the profile disappeared. Pilot scale systems were found to have physical gradients within the profile as evidenced by hydraulic short-circuiting. Vertical root density distribution is proposed as a major cause of this condition in horizontal flow systems.

Floor drains remove surface fluids and provide a physical barrier between building drainage and the sewer. Their function minimises waterborne contaminant impact on connecting drainage. Bacteria are known to thrive in drainage systems, and material selection, drain design, installation specification and maintenance all affect the potential for bacterial harbourage viability. Furthermore, the use of gullies or channels impacts ergonomic, economic and hydraulic considerations. Channel system hydraulic capacity must be assessed using a steady non-uniform flow formula, the use of which highlights that fluid velocities will fall far short of ‘self-cleansing’ velocity. Development areas include the use of passive or automated backflow prevention valves in sub-surface drainage. Whilst slip resistance and fire protection mechanisms can be incorporated in gratings and gully bodies respectively.

For one polar and several apolar working fluids, the vapor-liquid flow and the heat transfer characteristics in a capillary tube are obtained and compared. The polarity of the working fluid has a close relation to the disjoining pressure, which affects the formation of the liquid film profile greatly. For a polar working fluid (water), the length of the evaporating interfacial region is much longer than those for apolar working fluids. And the thickness of its liquid film increases relatively more gently at the end of the evaporating interfacial region. For different apolar working fluids, the calculation results are similar and the above-mentioned lengths are shorter. The difference is due mainly to the fact that the stronger polar working fluid leads to much stronger disjoining pressure, and the evaporation is choked because the liquid molecules of polar working fluids on the vapor-liquid interface are strongly attracted by the solid wall. The effects of other factors on the length of the evaporating interfacial region and the profile of the vapor-liquid interface are more secondary.

Wind energy technology is based on the ability to capture the energy contained in air motion. Wind power quantifies the rate of this kinetic energy extraction. Wind power is also the rate of kinetic energy flow carried by the moving air. Because the motion is both the source of the energy and the means of its transport, the efficiency of wind power extraction is a balance of slowing down the wind while maintaining a sufficient flow. This chapter quantifies these fundamental concepts and discusses the nature of wind.

Publisher Summary This chapter attempts to provide sufficient knowledge to specify burners, critically assess a burner design and optimize furnace performance and heat transfer. The performance of the burners has a huge effect on furnace operation and efficiency, yet it is relatively rarely that burner design is fully integrated with the furnace heat transfer requirements; little wonder then that poor performance is often the result. A burner is a transducer since it transforms one form of energy into another form of energy. In the case of the burner, it transforms the chemical energy in the fuel into heat energy within the furnace using the chemical reactions in a flame. The effectiveness with which this is achieved is a measure of its performance. Gas burners are generally classified as premixed or turbulent jet diffusion burners, such as premixed burners, where the fuel and most of the air are mixed together prior to passing through the nozzle and turbulent jet diffusion burners, where the fuel and most of the air are introduced separately and are mixed within the furnace. Burners and furnaces are also classified by the air delivery system as natural draught, forced draught, induced draught and balanced draught. Oil burners have the added complexity of two-phase flow resulting from the spray of fuel. Pulverized coal firing has many advantages over other forms of coal firing and makes burning coal similar to oil firing from a process viewpoint. Pulverized coal burners are similar to oil burners but the atomizer is replaced with a coal nozzle. The fine coal is air conveyed to the nozzle. Burners are often specified and selected from a catalogue based on little more than the estimated heat liberation required for the furnace, the number of burners needed and the price of the burner.

The microchannel is one of the essential components for the construction of various micro systems. However, it has been reported that the flow and heat transfer behavior in a microchannel deviates from predictions based on the conventional assumption generally accepted in macro-scale channels. Frictional characteristics of nitrogen and helium flows in three different microchannels (hydraulic diameter range 3-10 w m) have been investigated experimentally. The frictional resistance of gaseous flow in a trapezoidalcross-section microchannel was observed to be smaller than that in the conventional-sized channel. The reduced frictional resistance in microchannels is caused by the rarefaction effect due to extremely small dimensions of flow passages. By using Maxwell's first-order slip boundary condition, we can well predict the mass flow rate through microchannels and the friction constant.

In this analysis, the flow and heat transfer characteristics of an aqueous hybrid nanofluid with TiO2 and Cu as the nanoparticles past a horizontal slim needle in the presence of thermal radiation effect is investigated. We hope that the present research is applicable in fiber technology, polymer ejection, blood flow, etc. The Prandtl number of the base fluid is kept constant at 6.2. The needle is considered thin when its thickness does not exceed that of the boundary layer over it. Using the similarity transformation method, the governing PDEs are transformed to a set of non-linear ODEs. Then, the converted ODEs are numerically solved with help of bvp4c routine from MATLAB. Results indicate that the dual similarity solutions are obtained only when the slim needle moves in the opposite direction of the free stream. In addition, the first solutions are stable and physically realizable. Besides, the second nanoparticle's mass and also the magnetic parameter lead to decrease the range of the velocity ratio parameter for which the solution exists.

This study aims to explore the knowledge on fluid flow properties of the aqueous humour (AH), specifically on the anterior segment (AS) of the human eye for a medical condition called Glaucoma. The research objectives are to study on fluid flow characteristics of velocity and pressure of the AH on the AS of the eye using enlarged 3D printed model and computational analysis, and also to analyse the suitability of the 3D generated anterior AS in fluid flow analysis application on particle image velocimetry (PIV). Using polyvinyl alcohol (PVA) as a water-soluble 3D printing filament, a 3D model of the AS of the human eye was generated with SolidWorks 2018 and printed using Creality Ender 3. This printed model serves as the pattern for silicon rubber mould production using vacuum casting process. Analysis of AH flow hydrodynamics are conducted with computational analysis using ANSYS Workbench 19.2. Key findings support that use of PVA material suite the creation of specific shapes and patterns for 3D modelling applications alike, and silicon rubber moulding creates a non-reactive and long-lasting mould for PIV applications. Computational analysis findings support the use of the generated model for PIV applications. Overall, the study successfully supports the use of 3D printed model for PIV application and future work that can be induced include direct experimentation of the mould with PIV.