Average Fluid Velocity Research Articles

Applying numerical and computational methods to investigate the changes in the fluid parameters of the fluid passing over fins of different shapes with the finite element method

This paper examines the velocity and temperature variation in the x-direction as well as the water fluid concentration through triangular, rectangular, and chamfer baffles in the presence of a uniform magnetic field. In this work, the research innovation is using and installing oblong, triangular, and chamfered vanes on a plate so that we can increase the heat transfer and fluid velocity changes in the area of the melting plate. We can also compare the types of vanes. Let us get to the best choice for placing on the screen and use blades to increase the efficiency and speed of work in the industry. The finite Element Method is used to solve the related equations. With numerical investigations, this general result has been obtained that using chamfer-shaped baffles compared to other baffles on the sheet increases the efficiency of heat transfer and concentration efficiency. The average water fluid temperature on the chamfer baffles is 38.5% bigger than rectangular baffles and 75.34% bigger than triangular modes. Water fluid concentration on the chamfer baffles is 36.5% greater than triangular ones and 55.24% greater than chamfer modes. The use of rectangular baffles compared to other vanes causes a change in fluid velocity. The average water fluid velocity on the rectangular baffles is 24.5% greater than triangular ones and 45.34% bigger than chamfer modes.

Computational simulation of the flow dynamic field in a porous ureteric stent

Ureteric stents are employed clinically to manage urinary obstructions or other pathological conditions. Stents made of porous and biodegradable materials have gained increasing interest, because of their excellent biocompatibility and the potential for overcoming the so-called ‘forgotten stent syndrome’. However, there is very limited characterisation of their flow dynamic performance. In this study, a CFD model of the occluded and unoccluded urinary tract was developed to investigate the urinary flow dynamics in the presence of a porous ureteric stent. With increasing the permeability of the porous material (i.e., from 10−18 to 10−10 m2) both the total mass flow rate through the ureter and the average fluid velocity within the stent increased. In the unoccluded ureter, the total mass flow rate increased of 7.7% when a porous stent with permeability of 10−10 m2 was employed instead of an unporous stent. Drainage performance further improved in the presence of a ureteral occlusion, with the porous stent resulting in 10.2% greater mass flow rate compared to the unporous stent. Findings from this study provide fundamental insights into the flow performance of porous ureteric stents, with potential utility in the development pipeline of these medical devices.Graphical abstract

Numerical study of low Reynolds number effect on MHD mixed convection using CNT-oil nanofluid with radiation

An enclosure with a moving lid is commonly used in heat and mass transmission. Also, many investigations have been done so far on a mixed convective flow in a cavity, but no research has been done to observe the low Reynolds number effect in the presence of MHD and radiation in a cavity with a semi-circular heater incorporated kerosine oil-based CNT nanofluid. In addition, oil-based nanofluid makes the working fluid more stable at a higher temperature. This study numerically investigates the time-dependent effect of low Reynolds number on Kerosene oil-based CNT nanofluid with magnetic field and radiation. The governing equations were employed with the finite element method based Galerkin residual technique. Brownian motion of nanoparticles was considered to determine the thermal conductivity and dynamic viscosity. Lower values of Reynolds number are taken, such as 50 to 200 with fixed values of radiation parameter, the particle concentration, the Hartmann number, and the Richardson number. The results were illustrated as heat transfer and fluid flow for three dimensionless time conditions. Results indicate that increasing the fluid velocity improves the Nusselt number and drag force. The vorticity rises to 54% while increasing the fluid velocity, however, the pressure gradient and average temperature become lower. It is also found that the average fluid velocity is 2.2 times higher in the Re = 50 than in the Re = 100. For the time dependency of this study, the thermo-hydrodynamics behavior changes with dimensionless time. Finally, this study would be a guide for designing thermal devices related to heat transfer, especially using the Kerosene oil-based CNT nanofluid under different conditions.

Методика и алгоритм расчета и подбора насосных агрегатов для хранилищ жидких продуктов

This article presents a methodology for calculating the basic parameters and selecting of centrifugal pumping units for filling (emptying) storages of liquid products (for example, vegetable oils). Centrifugal pumping units are widely used in the operation of tank farms for various needs of the national economy, in particular, for temporary storage of liquid products in sea and river ports when they are transshipped from land transport to ships, or from ships to land transport. As an example, the projected storage of vegetable oils in the port of Yeysk (Azov sea, Krasnodar region, Russian Federation) is given. The methodology includes the calculation of average fluid velocities, linear and local hydraulic losses in the intake and pressure pipelines, pipeline diameters, pump performance, the pressure created by it, electric drive power; equipment selection. Based on the proposed methodology, an algorithm has been created for calculating and selecting a pumping unit for transporting of liquid products from vehicles to a storage tank, or vice versa. The methodology and algorithm discussed in this article can be used in the design of storage facilities for various liquids at manufacturing plants, transshipment bases, etc.

Pineapple Drying Analysis in Packing Plants Through Computational Fluid Dynamics

The aim of this research is to determine the average fluid velocity values and the average total pressure at the outlet of the ventilation system conduit for the drying, by air impulsion, of pineapples in packing plants, in order to ensure the required humidity level of the crown for its proper packaging. The CAD model of the air conduction was obtained in Solidworks and Computational Fluid Dynamics (CFD) techniques were applied to simulate the performance of the ventilation system. Air was indicated as the type of fluid, and an internal analysis of the pipe with roughness Rz = 3.2 μm. As a computational domain, the pipeline was established, from the connection to the fan to the outlet diffuser. As boundary conditions were established; a W and Z Manufacturing regenerative fan at the inlet of the flow pipe 618,439 m3/h, and at the outlet of the pipe the value of atmospheric pressure. As a result of the simulation, an average velocity value at the diffuser outlet of 127.294 m/s was obtained, higher than the required 96.06 m/s. An average total pressure value of 111718.73 Pa was obtained in the conduit suitable for the proposed purposes. For the conveyor belt, it is recommended to use, in each row of pineapples, the simulated fan with a simple diffuser with a rectangular section of 1 x 20 cm, or a regenerative fan with a flow of 1248.77 m3/h and a diffuser with two-outlet bifurcation.

Heat Transfer Delay Method for the Average Fluid Velocity Evaluation in a Multi-Turn Pulsating Heat Pipe

Heat Transfer Delay Method for the Average Fluid Velocity Evaluation in a Multi-Turn Pulsating Heat Pipe

Nonlocal Cahn–Hilliard–Hele–Shaw Systems with Singular Potential and Degenerate Mobility

We study a Cahn-Hilliard-Hele-Shaw (or Cahn-Hilliard-Darcy) system for an incompressible mixture of two fluids. The relative concentration difference $\varphi$ is governed by a convective nonlocal Cahn-Hilliard equation with degenerate mobility and logarithmic potential. The volume averaged fluid velocity $\mathbf{u}$ obeys a Darcy's law depending on the so-called Korteweg force $\mu\nabla \varphi$, where $\mu$ is the nonlocal chemical potential. In addition, the kinematic viscosity $\eta$ may depend on $\varphi$. We establish first the existence of a global weak solution which satisfies the energy identity. Then we prove the existence of a strong solution. Further regularity results on the pressure and on $\mathbf{u}$ are also obtained. Weak-strong uniqueness is demonstrated in the two dimensional case. In the three-dimensional case, uniqueness of weak solutions holds if $\eta$ is constant. Otherwise, weak-strong uniqueness is shown by assuming that the pressure of the strong solution is $\alpha$-H\"{o}lder continuous in space for $\alpha\in (1/5,1)$.

Permeability Characteristics of Water-Sand Seepage in Fracture by Experiment

Studies on the seepage characteristics of water-sand cracks are of great significance to reveal the mechanisms of water and sand inrush. Using a self-made water-sand fracture seepage test instrument, a water-sand seepage test was carried out, and the permeability of water and sand in the fracture was determined. The hysteresis characteristics of water-sand flow in the fracture were obtained after the required permeability was attained. The results show that the hysteresis curve changes from type I to type IV with the increase in sand particle size and concentration. The hysteresis parameters are described by the maximum hysteresis Gp ∗ and the hysteresis area S, both of which show an increasing trend with the increase in sand particle size and concentration; however, this increase is not synchronous. The average velocity and turbulent kinetic energy distribution of the water-sand fluid on the fracture cross section are greatly affected by the particle size and concentration of the volume of sand. This study can provide a reference for further study of water inrush from a shallow coal seam. Through simulation, it is found that the particle size has a great influence on the seepage velocity, and the influence near the side wall surface is greater than that in the middle position.

Development a novel hexagonal airlift flat plate photobioreactor for the improvement of microalgae growth that simultaneously enhance CO2 bio-fixation and wastewater treatment

A novel hexagonal airlift flat plate (HAFP) photobioreactor was designed to improve microalgae growth rate and compared with traditional flat plate (TFP) photobioreactor. The computational fluid dynamics (CFD) simulation was used to determine hydrodynamic parameters and optimal aeration rate in the photobioreactors. Additionally, the capability of the HAFP photobioreactor to enhance microalgae based CO2 bio-fixation and wastewater treatment were investigated. The results of CFD simulation indicated that the HAFP photobioreactor could improve hydrodynamic parameters of turbulence kinetic energy (TKE), average fluid velocity, dead zone (DZ), and water shear stress (WSS) up to 78 %, 41 %, 44 % and 40 %, respectively, under optimal aeration rate of 0.6 vvm. The proposed HAFP photobioreactor showed a drastic improvement in microalgae growth (up to 61 %). The maximum CO2 removal of 53.8 % and bio-fixation of 0.85 g L−1 d−1 were achieved in the HAFP photobioreactor which were approximately 70 % more than that in the TFP photobioreactor. The results suggested that the HAFP photobioreactor could accelerate nutrients removal and achieve remarkably higher efficiencies of 91 %, 99 %, 97 % and 93 % of ammonia (NH3), nitrate (NO3−), phosphate (PO43−) and chemical oxygen demand (COD) within seven days of cultivation.

Interstitial fluid velocity is decreased around cortical bone vascular pores and depends on osteocyte position in a rat model of disuse osteoporosis.

Muscle paralysis induced with botulinum toxin (Botox) injection increases vascular porosity and reduces osteocyte lacunar density in the tibial cortical bone of skeletally mature rats. These morphological changes potentially affect interstitial fluid flow in the lacunar-canalicular porosity, which is thought to play a role in osteocyte mechanotransduction. The aim of this study was to investigate the effects of disuse-induced morphological changes on interstitial fluid velocity around osteocytes in the bone cortex. Micro-CT images from a previous study that quantified the effects of Botox-induced muscle paralysis on bone microarchitecture in skeletally mature rats were used to create high-resolution, animal-specific finite element models that included the vascular pores and osteocyte lacunae within the tibial metaphysis of Botox-injected (BTX, n = 8) and saline-injected control (CTRL, n = 8) groups. To quantify fluid flow, lacunar and canalicular porosities were modeled as fluid-saturated poroelastic materials, and boundary conditions were applied to simulate physiological loading. This modeling approach allowed a detailed quantification of the fluid flow velocities around osteocytes in a relatively large volume of bone tissue. The analysis demonstrated that interstitial fluid velocity at the vascular pore surfaces was significantly lower in BTX compared to CTRL because of the decreased vascular canal separation. No significant differences in average fluid velocity were observed at the osteocyte lacunae and no correlation was found between the fluid velocity and the lacunar density, which was significantly lower in BTX. Instead, the lacunar fluid velocity was dependent on the osteocyte's specific position in the bone cortex and its proximity to a vascular pore.

Inviscid Suspension Flow along a Flat Boundary

A previously developed self-consistent field method is used to study an arbitrary finite set of identical spherical particles of arbitrary density moving in a uniform inviscid incompressible flow specified at infinity in the presence of a flat wall. For a given initial particle distribution in space, expressions for the particle and fluid velocities are derived taking into account the collective hydrodynamic interaction of the particles with each other and the wall. For a statistically uniform particle distribution in a semibounded inviscid fluid, analytical averaged particle and fluid velocity profiles are obtained in the first approximation with respect to the particle volume fraction in the suspension.

Parametric study of gas-solid flow characteristic by using integration computational fluid dynamics and dynamic simulation

The multiphase gas-solid in the FCC Riser system is a complex flow. The particle flow influenced by superficial velocity. Some researchers showed that it needs a method to solve the advanced analysis in solid-particle characteristics, for example, Reynold number particle, the difference of height fluidization, coefficient of drag, and particle forces. This research gives an alternative method by integrating the CFD method and dynamic simulation method. We used EES as dynamic simulation software. The simulation data need some data such as average fluid velocity, average solid velocity, a maximum height of fluidization, and void fraction. The mathematical model is performed and the simulation data is copied to EES to analyst the gas-solid flow characteristic. This parametric study has been carried out with several superficial velocity 0.35 m s−1, 0.45 m−1, 0.5 m−1, and 0.7 m s−1. The results show that there are fluctuations in the forces received by the particles due to changes in the superficial velocity. However, the tendency of fluctuation trend to be directly proportional to the increase in the superficial velocity. The dynamic simulation calculations have a good agreement compare to literature studies and basic theory for solid flow behaviour in bubbling regimes.

Mathematical Model of a Hyperbolic Hydraulic Fracture with Tortuosity

The aim of the research is to study the propagation of a hydraulic fracture with tortuosity due to contact areas between touching asperities on opposite crack walls. The tortuous fracture is replaced by a model symmetric partially open fracture with a hyperbolic crack law and a modified Reynolds flow law. The normal stress at the crack walls is assumed to be proportional to the half-width of the model fracture. The Lie point symmetry of the nonlinear diffusion equation for the fracture half-width is derived and the general form of the group invariant solution is obtained. It was found that the fluid flux at the fracture entry cannot be prescribed arbitrarily, because it is determined by the group invariant solution and that the exponent n in the modified Reynolds flow power law must lie in the range 2 n δ ≪ 1 to avoid singularities, to the fracture entry. The numerical results showed that the tortuosity and the pressure due to the contact regions both have the effect of increasing the fracture length. The spatial gradient of the half-width was found to be singular at the fracture tip for 3 n n = 3 and to be zero for 2 n n n < 3. The effect of the touching asperities is to decrease the width averaged fluid velocity. An approximate analytical solution for the half-width, which was found to agree well with the numerical solution, is derived by making the approximation that the width averaged fluid velocity increases linearly with distance along the fracture.

The mechanism of vortex bifurcation vis-à-vis axial switching in rectangular synthetic jets

The present study investigates the vortex dynamics of the rectangular shaped synthetic jet and reports the occurrence of vortex ring bifurcation along with other reported modes such as axial switching and the vortex suction. The novel finding of vortex ring bifurcation of rectangular synthetic jets has been observed without any other mode of excitation except the periodic axial actuation. The experiments on synthetic jets have been conducted at different actuation frequencies and both qualitative and quantitative characterization of the flow structures has been carried out using Laser Induced Fluorescence (LIF) and Laser Doppler Velocimetry, respectively. LIF flow visualization provides insights into the size of the vortex and the vortex evolution with respect to time, enabling us to propose the flow physics behind the axial switching and the vortex bifurcation processes for rectangular synthetic jets. The proposed flow physics is then quantitatively evidenced by the time-averaged velocity measurements. Vortex splitting or bifurcation is found to occur in the minor axis plane of orifice and the divergence angle depends on the actuation frequency and average velocity of fluid expelled through the orifice in the forward stroke of diaphragm. In the case of occurrence of axial switching, a maximum of three axial switching events are observed before vortex breakup. Finally, by systematically carrying out experiments across a wide range of operational parameters, a narrow region corresponding to the vortex bifurcation has been identified on a Reynolds Number–Strouhal Number map, along with other modes such as axial switching regime and the vortex suction regime. Based on our measurements, a mechanism of vortex bifurcation vis-à-vis axial switching has also been suggested.

Numerical study on turbulent natural convection and radiation heat transfer of nanofluids in a differentially heated square enclosure

Due to the low performance observed during natural convection with fluids such as air and water, nanofluid research was carried out to analyse them for convective heat transfer applications. Heat transfer comparison between water and different water-based nanofluids comprising of MWCNT, alumina and silver has been established for Rayleigh Number 1.5 × 109. Numerical analysis of 2-D differentially heated square cavity has been performed under turbulent natural convection. The top and bottom walls are considered to be at constant temperatures, while the side walls are adiabatic in nature. Based on previous research, nanofluid volume concentration of 0.1 vol% has been considered for this study, and the nature of flow physics and natural convection heat transfer has been explored. It is observed that multiple vortices (almost similar size) exist and evenly speared within the computational domain for air. The viscosity of the fluid was observed to be a deciding factor for the degree of turbulence, thickness and velocity variations within the boundary layer. The average fluid velocity and vortex circulation strength are highest for alumina nanofluid and least for water. The other two nanofluids lie in between with the velocity and vorticity variations of 12.8 and 16.5%, respectively. In terms of heat transfer, alumina nanofluid performs admirably well, followed by MWCNT nanofluid with a variation in radiation heat transfer of 60.8 and 53.19% when compared to air, while for convective heat transfer the variation observed was 98.4 and 97.8%, respectively. Due to the high densities of these nanofluids as compared to air, achieving thermal stratification is difficult. Alumina nanofluid performs admirably well in enhancing convection and radiation heat transfer.

Computational Fluid Dynamics in 3D-Printed Scaffolds with Different Strand-Orientation in Perfusion Bioreactors

Bone tissue engineering strategies use fluid flow dynamics inside 3D-scaffolds in perfusion, bioreactors mechanically stimulate cells in these scaffolds. Fluid flow dynamics depends on the bioreactor’s inlet flow rate and 3D-scaffold architecture. We aimed to employ a computational evaluation to assess fluid dynamics in 3D-printed scaffolds with different angular orientations between strands in each layer inside a perfusion bioreactor at different inlet flow rates. 3D-printed cubic scaffolds (0.6×0.6×0.6 cm; total volume 216×10-3 cm3) containing strands (diameter 100 µm) with regular internal structure and different angular orientation (30°, 45°, 60°, and 90° between strands in each layer) were used for modeling. The finite element method showed that the perfusion bioreactor’s inlet flow rate (0.02, 0.1, 0.5 mL/min) was linearly related to average fluid velocity, average fluid shear stress, and average wall shear stress inside 3D-printed scaffolds with different angular orientation (30°, 45°, 60°, 90°) between strands in each layer. At all inlet flow rates, strands at 30° angular orientation increased average fluid velocity (1.2-1.5-fold), average fluid shear stress (6-10-fold), and average wall shear stress (1.4-2-fold) compared to strands at 45°, 60°, and 90° angular orientation providing similar results. In conclusion, significant local changes in fluid dynamics inside 3D-printed scaffolds result from varying the degree of angular orientation between strands in each layer, and the perfusion bioreactor’s inlet flow rate. By decreasing the angular orientation between strands in each layer and increasing the inlet flow rate of a perfusion bioreactor, the magnitude and distribution of fluid velocity, fluid shear stress, and wall shear stress inside the scaffold increased. The average fluid velocity, average fluid shear stress, and average wall shear stress inside the scaffold within the bioreactor increased linearly with the inlet flow rate. This might have important implications for bone tissue engineering strategies using cells, scaffolds, and bioreactors.

Small-Scale Fluidized Bed Bioreactor for Long-Term Dynamic Culture of 3D Cell Constructs and in vitro Testing.

With the increasing interest in three-dimensional (3D) cell constructs that better represent native tissues, comes the need to also invest in devices, i.e., bioreactors, that provide a controlled dynamic environment similar to the perfusion mechanism observed in vivo. Here a laboratory-scale fluidized bed bioreactor (sFBB) was designed for hydrogel (i.e., alginate) encapsulated cells to generate a dynamic culture system that produced a homogenous milieu and host substantial biomass for long-term evolution of tissue-like structures and “per cell” performance analysis. The bioreactor design, conceptualized through scale-down empirical similarity rules, was initially validated through computational fluid dynamics analysis for the distributor capacity of homogenously dispersing the flow with an average fluid velocity of 4.596 × 10–4 m/s. Experimental tests then demonstrated a consistent fluidization of hydrogel spheres, while maintaining shape and integrity (606.9 ± 99.3 μm diameter and 0.96 shape factor). It also induced mass transfer in and out of the hydrogel at a faster rate than static conditions. Finally, the sFBB sustained culture of alginate encapsulated hepatoblastoma cells for 12 days promoting proliferation into highly viable (>97%) cell spheroids at a high final density of 27.3 ± 0.78 million cells/mL beads. This was reproducible across multiple units set up in parallel and operating simultaneously. The sFBB prototype constitutes a simple and robust tool to generate 3D cell constructs, expandable into a multi-unit setup for simultaneous observations and for future development and biological evaluation of in vitro tissue models and their responses to different agents, increasing the complexity and speed of R&D processes.

Analyzing the Fluid Flow of Transit-Time Ultrasonic Flowmeter with Image Processing Technique and Developing a Quality Metric Depending on Pipe Profile

The ultrasonic transit-time method measures the velocity and quantity of fluids in circular type pipes by using the difference of transit time between the ultrasonic pulses propagating with and against the flow direction. This method gives the average velocity of the fluid along a particular acoustic path. At least two ultrasonic transducers are used for an acoustic path. The multipath ultrasonic flowmeters have more acoustic paths. In this paper, the acoustic path between two transducers is described as pixels for the turbulent flow and formed a flow map for ideal flow conditions such as no elbow or bend depending on pipe profile. Using the obtained pixel values, the average fluid velocity is calculated between two transducers. Finally, a quality metric that calculates the ideal average fluid velocity ratio between the acoustic paths for the turbulent flow is developed. Thus, researchers can evaluate their designs with this quality metric.

Comprehensive analysis of the thermohydraulic performance of cooling networks subject to fouling and undergoing retrofit projects

The aim of this paper is to develop guidelines for the placing of new coolers in cooling systems subject to retrofit. The effects of the accumulation of scale on the flow system are considered. A methodology to assess the interconnected effect of local fluid velocity and fouling deposition is developed. The local average fluid velocity depends on the water flow rate distribution across the piping network. The methodology has four main calculation components: a) the determination of the flow rate distribution across the piping network, b) the prediction of fouling deposition, c) determination of the hydraulic changes and the effect on fouling brought about by the placing of new exchangers into an existing structure, and d) the calculation of the total cooling load and pressure drop of the system. The set of disturbances introduced to the system through fouling and the incorporation of new coolers, create network responses that eventually influence the cooling capacity and the pressure drop. In this work, these interactions are analysed using two case studies. The results indicate that, from the thermal point of view, the incorporation of new heat exchangers is recommended in series. The limit is the point where the increase of the total pressure drop causes a reduction in the overall volumetric flow rate. New coolers added in parallel create a reduction of pressure drop and an increase in the overall water flow rate; however, this increase is not enough to counteract the reduction of fluid velocity and heat capacity removal.

Increasing the energy flexibility of existing district heating networks through flow rate variations

The possibility of recovering waste and renewable heat in urban areas has made district heating networks one of the key infrastructures for decarbonising the heating sector in Europe. The ability to shift the heat production over time is an important asset to improve the competitiveness of both new and existing networks. To this purpose, the present study evaluates the flexibility potential provided by the water volume enclosed in the network pipelines using the district heating network of Verona (Italy) as a case study.Given the users heat demand in two representative weeks, computer simulations were carried out to calculate the network's thermal response to circulating flow rate variations. The latter were designed to cause an early or late shift in the daily peak thermal load. The local temperature drop at the users substations compared to the current situation was used as a relative discomfort indicator. The simulations were carried out using the model NeMo, which has been attached as supplementary material to this publication. The simulation results show that the network pre-charge strategy achieves significant benefits in terms of both peak shaving and load shifting with a limited impact on discomfort for the users. Furthermore, the paper shows that the available storage capacity of the network is significantly influenced by the duration of the flow adjustment, by the average velocity of the heat carrier fluid and by the daily heat demand pattern. Finally, it is shown that the energy flexibility of the network also depends on its topology. In this regard, the article provides preliminary indications on the number and position of the bypass pipes needed to implement the proposed flow rate variations.In conclusion, the article shows that the thermal inertia of the heat carrier fluid is an interesting source of flexibility for existing networks, and the results highlight its potential and limitations.