Average Velocity Distribution Research Articles

Aerodynamic Analysis of Variable Camber-Morphing Airfoils with Substantial Camber Deflections

In recent years, morphing wings have become not only a concept, but an aerodynamic solution for the aviation industry to take a step forward toward future technologies. However, continuously morphing airfoils became an interesting answer to provide green energy solutions. In this paper, the authors conducted experimental research on a continuously camber-morphing airfoil using the Particle Image Velocimetry (PIV) and Computational Fluid Dynamics (CFD) methods. The main objective of this work was to research a variety of morphing airfoils with different camber deflections. An average velocity distribution and turbulence distribution were compared and are discussed. The two-dimensional PIV results were compared to the CFD simulations to validate the numerical method’s accuracy and obtain the aerodynamic coefficient’s trends. A further comparison revealed that morphing airfoils have better aerodynamic performance than conventional airfoils for very low camber deflections and create substantial amounts of drag for significant camber deflections.

Parameter Investigation of Flyash Jet Mill with Superheated Steam

To improve the utilization rate of flyash, refining flyash is an important approach, and steam power grinding with superheated steam is an important equipment to meet the fine particle size requirements of flyash grinding. A 2.4 m height jet mill with four Laval nozzles has been employed here, and FLUENT is adopted to numerically simulate the distribution of fluid velocity and pressure in the flow field within the model. Meanwhile, parameter investigation is also carried out to reveal the effect of nozzle spacing and nozzle inclination angle on fluid filed and average particle velocity distribution. It is found that both spacing and nozzle inclination angle can affect the average particle velocity simultaneously. From the present parameter investigation, it can be concluded that Model 2 (nozzle spacing is 455 mm) with an inclination angle of 4° is the best choice since it can provide largest particle velocity distribution along the vertical direction.

CFD simulation of flyash fluidized-bed pulverization with superheated steam

The supersonic pulverization technology uses superheated steam generated by the boiler to generate supersonic airflow through the Laval nozzle, and accelerates the flyash fed into the crushing chamber by the screw feeder, and then the flyash can be crushed in mutual collision and friction process. The present paper conducted CFD simulation of fluidized-bed pulverization with superheated steam, and both the velocity filed and the particle tracks are obtained. Convergence test was performed firstly to verify the numerical results, and three different meshes and several different numbers of particles are employed here to show the average velocity of the particles through a certain horizontal plane. The effect of some key parameters, such as distance between the two opposite nozzles and feeding locations of the flyash to the velocity filed and the particle velocity are also numerically investigated. Results show that, the best distance between the two opposite nozzles of the four-nozzle case is 142 mm and the average particle velocity distribution varies little with the flyash feeding position for the present jet mill model.

Evaluation of the earth-air heat exchanger's performance in improving the indoor conditions of an industrial poultry house using computational fluid dynamics verified with field tests

This paper aims to investigate the performance of an Earth Air Heat Exchanger (EAHE) to improve the indoor conditions of an industrial poultry building after its installation, considering the optimal position and installation configuration (separate or collected inlets), which have not been addressed previously. In this regard, an industrial broiler house containing 20,000 chickens equipped with four cooling pads operated by a mechanical ventilation system located in Biskra, Algeria, was simulated with six scenarios, including the original. The model developed is verified with the field test measurements and experimental and numerical data in the literature. The results showed that optimizing the cooling pad position increases average indoor air temperature and velocity distribution by 0.1% and 8%, respectively. Moreover, the position and configuration of installing the EAHE inlets play an important role in uniforming indoor air distribution. Scenario 3, with 80 EAHE inlets versus exhaust fans, has the best indoor air uniformity, with a maximum velocity and temperature difference between its sections of 1.15 m s−1 and 1.4 K, respectively. Overall, EAHE showed a good ability to cool and maintain appropriate indoor air temperatures, achieving a difference of 15 °C between inside and outside, in addition to providing annual energy savings of 921,600 kWh/year and reducing 30,643 tons of CO2 emissions during its lifespan, in contrast, its simple payback time estimated 4 years.

Study on the Formation Characteristics and Disaster Mitigation Mechanisms of Rip Currents on Arc-Shaped Beach

Rip currents are fast offshore currents generated during the breaking process of waves propagating nearshore, posing a potential life safety threat to coastal bathers. This study utilizes a Boussinesq phase-resolving model to investigate the formation mechanism of rip currents at Dadonghai Beach, based on its actual topography, and explores the characteristics of rip current formation under various wave conditions, with an emphasis on analyzing vortices, the mean water level and the spatial distribution of average velocity. The results indicate that rip current formation is significantly influenced by wave height and period. The increase in wave height and period results in more intense rip currents and higher water level fluctuations on arc-shaped beaches and on both sides of the bay, leading to complex vortex distributions. An increase in the angle of wave incidence hinders rip current formation in arc-shaped beach areas but is favorable to the generation of deflection rips on both sides of the bay. Furthermore, an increase in bottom friction inhibits rip current formation. When the water depth decreases in the channels, rip currents transition into longshore currents. The findings of this research offer valuable scientific insights into the formation mechanisms of rip currents and contribute to their prediction and prevention.

Spatial search weighting information contained in cell velocity distribution

Cell migration plays a significant role in physiological and pathological processes. Understanding the characteristics of cell movement is crucial for comprehending biological processes such as cell functionality, cell migration, and cell–cell interactions. One of the fundamental characteristics of cell movement is the specific distribution of cell speed, containing valuable information that still requires comprehensive understanding. This article investigates the distribution of mean velocities along cell trajectories, with a focus on optimizing the efficiency of cell food search in the context of the entire colony. We confirm that the specific velocity distribution in the experiments corresponds to an optimal search efficiency when spatial weighting is considered. The simulation results indicate that the distribution of average velocity does not align with the optimal search efficiency when employing average spatial weighting. However, when considering the distribution of central spatial weighting, the specific velocity distribution in the experiment is shown to correspond to the optimal search efficiency. Our simulations reveal that for any given distribution of average velocity, a specific central spatial weighting can be identified among the possible central spatial weighting that aligns with the optimal search strategy. Additionally, our work presents a method for determining the spatial weights embedded in the velocity distribution of cell movement. Our results have provided new avenues for further investigation of significant topics, such as relationship between cell behavior and environmental conditions throughout their evolutionary history, and how cells achieve collective cooperation through cell-cell communication.

Mixing performance of an expansive mixer on viscoelastic solutions under alternating current electric field

Development of effective technologies for mixing viscoelastic solutions with reagents is still a challenge, which plays an important role in the fields of disease diagnosis, water desalination, and immunoassay. The purpose of this paper is to numerically study the mixing performance of an expansive mixer on the viscoelastic solution under the impact of an alternating current (AC) electric field through the analyzation of mixing efficiency, the concentration distribution, and average outlet velocity. A poly acrylic acid (PAA) water solution with different concentrations characterized by the Oldroyd-B constitutive model is used as a mixed medium, and an open-source toolbox called rheoTool based on finite volume algorithm is applied to solve the governing equations. We quantitatively determine the mixing efficiency for different PAA concentrations, AC electric field strengths, and frequencies and compare the mixing efficiency created by AC and direct current (DC) electric fields. Our investigation indicates that the mixing efficiency of the mixer diminishes with the PAA concentrations but enhances with the AC electric field strengths for a relatively high polymer concentration, and AC electric fields with different frequencies lead to a larger mixing efficiency than DC electric fields for a low polymer concentration. Additionally, the influence of the model parameters on the average outlet velocity and concentration distribution is discussed at length. Our numerical simulation results show that the mixer has an excellent mixing performance for both Newtonian and viscoelastic solutions, with a mixing efficiency of more than 99% at a low polymer concentration and a stable outflow velocity.

Numerical study the effect of air barriers height inside the air conditioning ducting to satisfy the regulation of Indonesia Minister of Transportation number 69 of 2019

The Indonesian smart hybrid light train is a train under development by the government and will operate in Makassar-Parepare, Indonesia track. The authors conducted a numerical study on CFD to investigate the air flow distribution inside the air conditioning ducting and the air velocity and air temperature distribution on Motor Engine and Compartment (MEC) car to achieve the passenger comfort criteria based on the regulation standard of Indonesia Minister of Transportation Number 69 of 2019. This study was conducted by simulating 5 variations of air barriers height inside the supply ducts. The input of air into the ducting has the parameters of mass flow rate, static temperature, static pressure, and density with the values of 1 kg/s, 20 °C, 1 atm, and 1.2 kg/m 3 , respectively. The simulation results show that variation E is the best design which generated the average air velocity and air temperature distribution in the executive passenger cabin with the values of 0.25 m/s and 21.91 °C, respectively. Meanwhile, the other 4 variations did not satisfy the standard. The results also show that the ducting geometry can accommodate the air temperature difference on the MEC car that does not exceed 1.5 °C and the air supply is sufficient from the air conditioner unit to the driver room.

CFD Calculations of Average Flow Parameters around the Rotor of a Savonius Wind Turbine

The geometry of a conventional two-bladed Savonius rotor was used in this study based on a report available in the literature. A two-dimensional rotor model consisting of two buckets and an overlap ratio of 0.1 was prepared. The unsteady Reynolds averaged Navier-Stokes (URANS) equations and the eddy-viscosity turbulence model SST k-ω were employed in order to solve the fluid motion equations numerically. Instantaneous velocities and pressures were calculated at defined points around the rotor and then averaged. The research shows that the operating rotor significantly modifies the flow on the downwind part of the rotor and in the wake, but the impact of the tip speed ratio on the average velocity distribution is small. This parameter has a much greater influence on the characteristics of the aerodynamic moment and the distribution of static pressure in the wake. In the upwind part of the rotor, the average velocity parallel to the direction of undisturbed flow is 29% lower than in the downwind part.

Prospects for Using Wind Energy in the Western Sector of the Arctic

The aim of the study is to estimate the wind energy potential in the western sector of the Arctic and to identify possible ways for using wind resources for power and heat supply to regional consumers. The data of long-term wind velocity observation series at meteorological stations in the western sector of the Arctic were processed. Based on the obtained results, a map showing the distribution of annual average wind velocities in the coastal regions of the Barents and White Seas has been drawn; the recurrence of wind velocities has been studied, and the wind energy resources in the region have been estimated. It has been established that in the majority of coastal regions, the annual average wind velocities at a height of 10 m above the ground level are in the range 5 to 8 m/s. The highest wind intensity is observed during the winter months. The seasonal maximum of wind velocities coincides with the maximum demand for heat and electricity in the cold season, which is a favorable prerequisite for successful use of wind energy for meeting the consumers’ electricity and heat supply needs. The presented data testify the possibility of efficiently using wind power plants (WPPs) in the following three main areas: the development of systemic wind energy (operation of large wind farms as part of the power system), participation of WPPs in supplying power to autonomous consumers (joint operation with local diesel power plants), and heat supply to consumers (joint operation with boiler units). Based on the study results, promising sites have been determined for construction of large wind farms on the Kola Peninsula northern coast near the hydroelectric power plants operating as part of the Kola power system. The indicators characterizing possible joint operation of WPPs with local diesel power plants and boiler units in decentralized power supply areas have been obtained. It has been shown that the major effect from using wind energy boils down to saving expensive fossil fuel, which is delivered to consumers in the Arctic regions at high transportation costs. In the areas of decentralized power supply, the use of WPPs helps save from 20 to 70% of annual fuel consumption depending on the wind energy potential.

Effective Elastic Stiffness Tensor and Ultrasonic Velocities for 3D Printed Polycrystals with Pores and Texture

ABSTRACT This paper focuses on the micromechanical modeling of pores and texture in 3D-printed polycrystals. A Gaussian-shape approximation is used to describe the orientation distribution function (ODF) and construct the initial homogenization model of the representative volume element (RVE). Spherical and ellipsoidal pores of varying sizes are added in stages to the RVE for homogenization, utilizing the modified Mori-Tanaka (MT) scheme in conjunction with the stepwise iterative method. Wherein, the mechanical interactions between pores and the spatial distribution of pore locations could be taken into account, when developing a cross-scale model from microstructure to macroelasticity. After obtaining the final elastic stiffness tensor, the Christoffel equation is combined with the Cardano’s formula to derive a closed form solution for ultrasonic velocities depending on microstructure. According to the numerical results, this method can effectively capture the behavior characteristics of pores and texture on the elastic stiffness tensor, average velocity, and velocity distribution.

Pore-scale direct numerical simulation of fluid dynamics, conduction and convection heat transfer in open-cell Voronoi porous foams

The pore-scale analysis includes the pore network simulation and direct numerical simulation, which the latter is more accurate and provides more details about the problem. This study presents a pore-scale direct numerical simulation of flow and convection-conduction heat transfer in open-cell metal foams with a complex structure. First, using the Laguerre–Voronoi tessellations (LVT) algorithm, three foam samples with various porosities (76.6%, 84.4%, and 93.8%) and a constant pore density of 20 pores per inch (PPI) are generated. Next, the open-source library of OpenFOAM is employed to perform heat transfer and flow analysis in Darcy and non-Darcy regimes. Results were verified through comparison with available experimental and numerical data. The effects of foams' porosity, solid material, and Reynolds number on flow characteristics and heat transfer are investigated. Results are presented in terms of the permeability, Forchheimer coefficient, the volumetric and average heat transfer coefficient, and temperature and velocity distribution. By decreasing porosity, the flow complexity increases with subsequent increments in heat transfer and pressure drop. Also, the conductive heat transfer through the foam plays a vital role in the total heat transfer rate. These pore-scale outcomes could be used in macro-scale thermo-fluid models to perform more accurate simulations with less computational costs.

Modelling and Comparison of the Thermohydraulic Performance with an Economical Evaluation for a Parabolic Trough Solar Collector Using Different Nanofluids

This study examines the three-dimensional heat transfer and flow characteristics of nanofluids in a parabolic trough solar collector under turbulent flow conditions, whereas a non-uniform focused heat flux was applied to the absorption pipe. CuO/water, Al2O3/water, TiO2/water, and SiO2/water are studied numerically. The dynamic and thermal fields are determined by the Reynolds number varying between 50000 ≤ Re ≤ 250000, while the volume concentration of nanofluids is the following: 3% CuO, 6% Al2O3, 4.82% SiO2 and 3.15% TiO2, the nanoparticle size of 30 nm by means of Finite Element Method (FEM). Effects of various parameters such as volume fraction of nanoparticles (φ), various Reynolds numbers and type of nanoparticle on thermo-hydraulic performance of the parabolic solar collector are studied. The average Nusselt number, heat transfer coefficient, average friction factor, pressure drop, temperature and velocity distribution are illustrated using four different types of nanofluids and four different volume fractions of nanoparticles with various Reynolds numbers. According to the final results, both TiO2 and CuO nanofluids have better performance in terms of thermal and hydraulic efficiency and evaluation economic performance compared with other nanofluids studied.

Numerical analysis of layout of air conditioning in data center considering seasonal factors

In this paper, a better layout of the computer room air conditioning (CRAC) units in the data center (DC) is obtained by comparatively analyzing the indices about velocity and temperature in the room. First, Computational Fluid Dynamics (CFD) is utilized to model the computer room of DC, and two layout schemes of air conditioners are presented. Then, to determine the better layout, the distribution of average air velocity and temperature field of the two layout schemes are compared. Besides, a uniformity index is proposed to conduct the quantitative analysis of the temperature uniformity at the inlet of racks under two layout modes. Considering the influences of seasonal factors on the cooling efficiency, the temperature distribution analysis with different outdoor temperature under two layouts is carried out contrastively.

Computational and experimental investigation of flow fields in a Rushton turbine stirred tank with shear‐thinning fluid

AbstractThe flow feature and local shear rate distribution near the impeller blade in a standard Rushton turbine stirred tank with the aqueous solution of sodium polyacrylate were studied by using particle image velocimetry experiments and computational fluid dynamics simulations. Experimental and simulated results, including average velocity and local shear rate distribution at different rotational speeds, were compared, and good agreement was achieved. On this basis, the numerical methods were used to predict the effects of liquid rheology on the velocity and shear rate distribution. The consistency coefficient affects obviously the velocity fluctuation level but has a limited impact on the flow structure. The power‐law index influences significantly the radial jet structure. In addition, the liquid rheology almost has no effect on the average value of the local shear rate near the impeller region, which is proportional to the rotational speed.

A Study on Current Characteristics Based on Design and Performance Test of Current Generator of KRISO's Deep Ocean Engineering Basin

To build an environment facility of a large-scale ocean basin, various detailed reviews are required, but it is difficult to find data that introduces the related research or construction processes on the environment facility. The current generator facility for offshore structure safety evaluation tests should be implemented by rotating the water of the basin. However, when the water in the large basin rotates, relatively large flow irregularities may occur and the uniformity may not be adequate. In this paper, design and review were conducted to satisfy the performance goals of the DOEB through computational numerical analysis on the shape of the waterway and the flow straightening devices to form the current in the large tank. Based on this, the head loss, which decreases the flow rate when the large tank water rotates through the water channel, was estimated and used as the pump capacity (impeller) design data. The impeller of the DOEB current generator was designed through computational numerical analysis (CFD) based on the lift surface theory from the axial-type impeller shape for satisfying the head loss of the waterway and maximum current velocity. In order to confirm the performance of the designed impeller system, the flow rate and flow velocity performance were checked through factory test operation. And, after installing DOEB, the current flow rate and velocity performance were reviewed compare with the original design target values.</br>Finally, by measuring the current velocity of the test area in DOEB formed through the current generator, the spatial current distribution characteristics in the test area were analyzed. Through the analysis of the current distribution characteristics of the DOEB test area, it was confirmed that the realization of the maximum current velocity and the average flow velocity distribution, the main performance goals in the waterway design process, were satisfied.

Pore-scale mechanisms and simulations for gas–water two-phase transport processes in natural gas reservoirs

During the development of natural gas reservoirs, predicting the bubble size distribution and transport velocity in the study of gas-water two-phase flow through porous media is extremely important in natural gas recovery. Considering the different forces that act on small and elongated bubbles, a double-bubble phase population balance model was introduced to establish an improved bubble flow model. Accordingly, a two-dimensional visualized model was designed to analyze the bubble diameter distribution and average velocity of bubbles. Dominant bubble coalescence, breakup, and coexistence flows were simulated to evaluate the uniqueness of the diameter distribution of bubbles, the change in the median bubble size at different dimensionless distances, and the average velocity distribution. The peak distribution of the bubble diameter was different in the three flow conditions. Owing to the difference in the bubble breakup and coalescence rates, the peak values of bubbles varied with the increase in the dimensionless distance. Higher bubble breakup or coalescence rates were accompanied by a rapid change in the median bubble size. Furthermore, the average velocity of the transition from small bubbles to elongated bubbles decreased significantly. Thus, the proposed pore-scale gas-water two-phase model can effectively predict the occurrence and transport processes in natural gas reservoirs.

Systematic Validation Study of an Unsteady Cavitating Flow over a Hydrofoil Using Conditional Averaging: LES and PIV

We present results of Large-eddy simulations (LES) modeling of steady sheet and unsteady cloud cavitation on a two-dimensional hydrofoil which are validated against Particle image velocimetry (PIV) data. The study is performed for the angle of attack of 9° and high Reynolds numbers ReC of the order of 106 providing a strong adverse pressure gradient along the surface. We employ the Schnerr–Sauer and Kunz cavitation models together with the adaptive mesh refinement in critical flow regions where intensive phase transitions occur. Comparison of the LES and visualization results confirms that the flow dynamics is adequately reproduced in the calculations. To correctly match averaged velocity distributions, we propose a new methodology based on conditional averaging of instantaneous velocity fields measured by PIV which only provides information on the liquid phase. This approach leads to an excellent overall agreement between the conditionally averaged fields of the mean velocity and turbulence intensity obtained experimentally and numerically. The benefits of second-order discretization schemes are highlighted as opposed to the lower-order TVD scheme.

The mean wake model and its novel characteristic parameter of H-rotor VAWTs based on random forest method

Using the random forest (RF) algorithm, this study presented a key parameter to characterize the mean wake of H-rotor VAWTs while modelling the wake. First, the RF algorithm was used to establish the regression relationship between the average wake velocity distribution and the rotor features. Next, the feature crosses method was combined with the RF algorithm to analyze the interaction and importance of the inputs. It was found that the normalized importance of a synthetic feature in wake modelling occupied a considerable significance, reaching 0.884 out of 1. The RF wake model with this parameter as the only input feature could successfully reconstruct the wake. It was found that this feature may reflect the ability of incident wind passing through the operating rotor and played a decisive role in the wake velocity distribution, including initial velocity deficit and wake recovery rate. The universality of this parameter was proved through cases analysis of wind turbines under different sizes and operating conditions. The study of the wake field is important for the modelling of the H-rotor VAWT wake field, and hence affects the optimal configuration of the wind farm.

Investigating heat transfer in an upward flow of liquid metal in the mercury facility with a loop of natural circulation

Research of heat transfer is performed in an upward flow of liquid metal in a vertical channel of rectangular cross-section under the condition of one-sided heating and in a vertical pipe in a mercury circuit with a natural circulation loop. Natural circulation loop enables measurements in mixed turbulent convection modes, which are inaccessible on a contour with a forced convection, that is, in the region of small Reynolds (Peclet) numbers of characteristics. Using a two-coordinate probe with a microthermocouple correlation sensor, profiles of averaged velocity and temperature and distribution of a wall temperature are obtained, and heat transfer coefficients are determined. Criterion dependences of Nusselt number on Peclet and Richardson are built. Experimental data on heat transfer are compared with similar data obtained earlier in a loop with a forced flow of mercury.