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Heat characteristics of air vehicle motors are essential for the design of electric aircraft because of heat generation when air vehicle takes off. In this study, the numerical simulation of a water-cooled AFPM motor was carried out to obtain heat transfer characteristics. A simplified computational domain was adopted with coolant passages, and electromagnetic losses of copper, iron, and eddy currents were considered. The steady-state and incompressible flows were assumed to represent the cruising flying condition of the 150-kW power rating in the motor. The system pressure loss and coil temperature were analyzed by changing passage configurations in 4-partition cases. To resolve thermal imbalance, it is best to have the number of channel partitions increase upstream and gradually decrease as you go downstream. This study allows motor designers for air vehicles to evaluate various coolant passage configurations numerically in advance. [ABSTRACT FROM AUTHOR]

In this study, the flow characteristics of two-dimensional corrugated walls with perforation are investigated using particle image velocimetry (PIV) experiments. Analysis of the flow on perforated corrugated walls at perforation ratios φ = 1%, 2.5%, 5%, 10% and the same wavelength Reynolds number, Reλ, shows that the friction coefficient, Cf, decreases with increasing perforation ratio, φ, and the followability becomes more obvious, indicating that perforations on the corrugated wall can reduce the drag. Analysis of the dimensionless circulation, G+ Q, reveals that the perforation effectively controls separation on the corrugated wall, which is consistent with observations of the recirculation area. After elucidating the mechanism of action of the perforation on the corrugated wall, the turbulence characteristics at different Reynolds numbers are explored for φ = 2.5% by varying the velocity of the flow field. When Reλ = 8800, the free flow velocity is insufficient to achieve the inverse pressure gradient required to produce stable separation in the flow field. With an increase in Reλ, the recirculation region in the time-averaged flow field becomes incomplete due to the effect of the perforation, and the turbulent fluctuation is also weakened. The following behavior of the friction coefficient, Cf, with the oscillations of the wave crest and trough also differs from the behavior observed with increasing wavelength Reynolds number, Reλ.

Vortex shedding is commonly observed in both natural and artificial situations. Two key variables, the blockage ratio and the Reynolds number, determine the flow characteristics around a confined bluff body. The goal of the current study was to apply numerical simulation to examine the development of vortices in a continuous turbulence flow at the distanced position of a single splitter plate. As a starting point, the flow around a fixed circular cylinder and plate is examined at various spaced position ratios, where *L ratios are defined as the distance between the cylinder's centre and the plate's front edge. In the wake of the cylinder, when *L is raised, positive and negative vortices are generated. The pressure distribution following the vortex shedding core strike is felt at the plate face tip (starting edge). Compared to the other two positions, the CL created by L2 is larger and receives better cortex hits. [ABSTRACT FROM AUTHOR]

The log-wake law for turbulent current has been developed and tested with laboratory data on turbulent flow in smooth pipes. However, flow with turbulence and vortices in a stepped spillway have not been described. Therefore, in this study, a log-wake law has been developed for use in stepped spillway systems. It can be divided into three parts. The first part, a logarithmic equation, describes the effect of shear stress between the flow layers with a von Kármán constant of 0.41. The second part, a third-degree polynomial, describes the effect of the shear stress on the wall. The last part, a fourth-degree polynomial, describes the effect of changing the flow pressure distribution, similar to the wall-free shear stress. Calibration tests (68 datasets) are used with a flow rate between 0.0233 and 3.285 m3/s, a spillway slope of 14–30°, and a step height of 0.0380–0.610 m. The developed log-wake law characterized the flow in a stepped spillway well. The limitation of the equation is a maximum flow velocity of 4 m/s; the accuracy of this equation decreases as the step height increases. HIGHLIGHTS The developed log-wake law for the spillway is provided.; Related experimental data are included.;

Temperature management in turbomachines is a critical factor for improving power plant efficiency and service life. Air gap clearances between combustion chamber rings assist its installation and expansion while partially modifying the inlet air path to stave off mixing in the flame tube of the combustion chamber. Changes in clearance dimensions can cause geometric asymmetry and result in asymmetric flow and temperature distribution imbalances in the combustion chambers creating hot spots at the outlet of the combustion chamber. Hence, in this paper, the effects of four clearance dimensions with four values on temperature distribution in two combustion chambers attached to the compressor have been numerically studied using Ansys Fluent 17. Taguchi method is applied for optimization and decreasing the outlet semi-circles temperature difference using Minitab software. The optimization results illustrate that the radial clearance between the flame tube and the mixing chamber is the most significant variable in controlling the air flow rate and producing symmetrical temperature distribution in the two chambers. So, one-millimeter radial clearance between two chambers leads to an increase of the temperature distribution by 15oC and 100oC in average and point mode, respectively. Also, results show that as the average clearance of the combustion chamber decreases by 5 millimeters, the point mode temperature of its corresponding outlet semi-circle decreases around 100°C.

In this paper, based on the Mixture model, the numerical computations of the internal flow field in a sewage pump are carried out. Through numerical simulation, the turbulence flow characteristics in the sewage pump are obtained. Results show that when the particle diameter is 0.10 mm, the solid-phase concentration on the volute surface is high, and the wear is more severe. When the particle diameters are 0.15 mm and 0.20 mm, the solid-phase concentration on the volute surface is significantly higher, especially when the over-current cross-section enlarges constantly. [ABSTRACT FROM AUTHOR]

With the extensive construction of ultra-high voltage (UHV) transmission lines, the fatigue damage of steel tube members caused by vortex-induced vibration (VIV) in tubular towers has received growing attention. Although some progress has been made in the research of the VIV of steel tubes in uniform flow, there is still relatively scarce research on the VIV of steel tubes at various inflow conditions. In this paper, a series of wind tunnel tests are conducted to investigate the VIV of the steel tube subjected to uniform, turbulent, and oblique flows. Three turbulence intensities (Iu = 5.9%, 9.7%, and 12.6%), and four yaw angles (α = 10°, 20°, 30°, and 40°) are considered. The results show that the VIV response of the steel tube in the in-line (IL) direction is negligible compared to that in the cross-flow (CF) direction. The displacement amplitude gradually decreases as the turbulence intensity increases, accompanied by a more unstable response. For the inclined steel tube, the VIV maximum amplitude almost remains constant when α ≤ 20°, while it sharply decreased in the case of α = 30° and α = 40°. Furthermore, it was found that the so-called independent principle is applicable for α ≤ 10°. [ABSTRACT FROM AUTHOR]

The indoor environment has a significant impact on our wellbeing. Accurate prediction of the indoor air distribution can help to create a good indoor environment. Reynolds‐averaged Navier–Stokes (RANS) models are commonly used for indoor airflow prediction. However, the Boussinesq hypothesis used in the RANS model fails to account for indoor anisotropic flows. To solve this problem, this study developed a data‐driven RANS model by using a nonlinear model from the literature. An artificial neural network (ANN) was used to determine the coefficients of high‐order terms. Three typical indoor airflows were selected as the training set to develop the model. Four other cases were used as testing sets to verify the generalizability of the model. The results show that the data‐driven model can better predict the distributions of air velocity, temperature, and turbulent kinetic energy for the indoor anisotropic flows than the original RANS model. This is because the nonlinear terms are accurately simulated by the ANN. This investigation concluded that the data‐driven model can correctly predict indoor anisotropic flows and has reasonably good generalizability. [ABSTRACT FROM AUTHOR]

A study on separation control mechanisms of tandemly arranged wing with linear leading edge (LLE) and leading edge protuberance (LEP) in low Reynolds number was conducted. In this study, to investigate the separation control mechanism, we carried out the visualization experiment using smoke-wire method, the streamwise and spanwise velocity measurements above the upper surface of the backward wing by using hotwire anemometer, and the numerical simulation. From the results of flow visualization experiment, it was found that the high lift coefficient obtained by tandemly arranged wing with LLE and singly and tandemly arranged wing with LEP were caused by reducing the flow separation region. From the results of velocity measurements and numerical simulation, it was found that in the case of wing with LLE, the turbulence generated by forward wing, which had mainly streamwise component with peak frequency of 230Hz and broadband frequency over than 30Hz, controled the flow separation. Whereas in the case of wing with LEP, regardless of the wing arrangement, separation control was brought by the separation bubble that caused by the longitudinal vortices generated by the LEP. It was also found that the turbulence from forward wing affected the position of the valley part where the separation bubble and the strong negative pressure were formed.

The numerical procedure for turbulence fluid flow and heat transfer in a twisted flat tube is presented in this work. For the cross-section of the flat tube, three different geometries are investigated. Water is a working fluid with constant thermophysical properties. The Reynolds number ranges from 5000 to 20000. Results show that by using twisted flat tubes, the efficiency has increased nearly 70% compared to the smooth tubes with the same surface area and hydraulic diameter. Also, the alternating helical direction has caused almost 60%, which seems to be a good choice. Due to the effect of helical pitch that affects the flow path, the alternating geometry was better in some Reynolds and not others. The results are explained using flow characteristics contours such as turbulent kinetic energy, tangential velocity, and temperature. Moreover, the results are presented in numbers and plots for a more accurate comparison.

The low-aspect-ratio cylindrical structures represented by oil tanks is a kind of wind sensitive structure, which is prone to buckling under wind-loads. A wind tunnel test was conducted to investigate the properties of wind-loads acting on smooth cylinders with an aspect ratio AR = 0.323 and 0.875, respectively. Some parameters, such as Reynolds number (Re) and turbulence intensity, were taken into account. The results reveal that low-aspect-ratio cylinders have a Re effect, and the effect rises with AR. AR is the main factor affecting the value of the base pressure coefficient and positive pressure range, and the former increases with AR, while the latter decreases with AR. Moreover, due to the influence of the free end and turbulence, which may suppress vortex shedding, the power spectrum of the lift coefficient essentially shows broad spectral peaks with Re and turbulence. Increasing the incoming turbulence made the flow round cylinders at a higher Re state, that is, the supercritical regime is reached at a smaller Re. When turbulence is greater than 4.0%, turbulence and Re have little effect on the mean base force coefficient of low-aspect-ratio cylinders. [ABSTRACT FROM AUTHOR]

Heat transfer enhancement is by far an important component in the design of numerous industrial applications of Taylor-Couette flow including electric motors and particularly rotating machinery. To optimize the performances of these machines, superior knowledge of the fluid flow is vital to better estimate the heat transfer distribution. This study will specifically consider the effect the slit number and width possess on the distribution of turbulent Taylor- Couette flow and the resulting heat transfer correlation in the annulus of two concentric cylinders under varying conditions. A numerical simulation method is intended for the study using varying slit structure parameters of widths (2.5 ≤ w≤ 7.5) mm and fitted with 6, 9, and 12 number of slits. The slit effect is then investigated under both isotherm and non-isotherm conditions considering the interactions between fluid flow regions in the mainstream area and the annulus. The small-scale vortex that appears in the annulus region improves the heat transfer ability between the fluid in the annulus and the main region as well as the heat transfer performance of the model with a gradual increase in Reynolds number. [ABSTRACT FROM AUTHOR]

With the extensive construction of ultra-high voltage (UHV) transmission lines, the fatigue damage of steel tube members caused by vortex-induced vibration (VIV) in tubular towers has received growing attention. Although some progress has been made in the research of the VIV of steel tubes in uniform flow, there is still relatively scarce research on the VIV of steel tubes at various inflow conditions. In this paper, a series of wind tunnel tests are conducted to investigate the VIV of the steel tube subjected to uniform, turbulent, and oblique flows. Three turbulence intensities (Iu = 5.9%, 9.7%, and 12.6%), and four yaw angles (α = 10°, 20°, 30°, and 40°) are considered. The results show that the VIV response of the steel tube in the in-line (IL) direction is negligible compared to that in the cross-flow (CF) direction. The displacement amplitude gradually decreases as the turbulence intensity increases, accompanied by a more unstable response. For the inclined steel tube, the VIV maximum amplitude almost remains constant when α ≤ 20°, while it sharply decreased in the case of α = 30° and α = 40°. Furthermore, it was found that the so-called independent principle is applicable for α ≤ 10°.

As a result of the recent events associated with the SARS-CoV-2 around the world, there has been a need for research to strengthen health care. The use of masks or respirators has been an effective measure, reducing the risk of contagion caused by the spread of the virus in public places. Currently, there are masks that retain up to 99% of particles >0.3 microns; however, they lack an airtight seal with the face, leading to discomfort and poor protection in conditions without social distancing and areas without ventilation. The device proposed in this study includes a geometric design of static valves with convergent spirals and interior baffles that promotes enhanced aerodynamics with bidirectional flow. According to the analysis and CFD simulation of the proposed reusable, washable, and economic mask and valve system for breathing, coughing, and sneezing events, enhanced air exchange could be maintained, facilitating a higher inhalation flow through the side of the mask (62%) and a higher exhalation through the front of the mask (74%), thereby avoiding the recirculation of the flow to the interior of the mask. The inclusion of filters with KN95 characteristics in the inlets and outlets maintains velocities below 10 cm/s, reducing the probability of infection. [ABSTRACT FROM AUTHOR]

Large-eddy simulation has been increasingly applied to internal combustion engine flows because of their improved potential to capture the spatial and temporal evolution of turbulent flow structures compared with Reynolds-averaged Navier Stokes simulation. Furthermore, large-eddy simulation is universally recognized as capable of simulating highly unsteady and random phenomena, which drive cycle-to-cycle variability and cycle-resolved events such as knocks and misfires. To identify large-scale structure fluctuations, many methods have been proposed in the literature. This article describes the application of several analysis methods for the comparison between different datasets (experimental or numerical) and the identification of large-structure fluctuations. The reference engine is the well-known TCC-III singlecylinder optical unit from the University of Michigan and GM Global R&D center; the analyses were carried out under motored engine conditions. A deep analysis of in-cylinder gas dynamics and flow structure evolution was performed by comparing the experimental results (particle image velocimetry of the velocity fields) with a dataset of consecutive largeeddy simulation cycles on four different cutting planes at engine-relevant crank angle positions. Phase-dependent proper orthogonal decomposition was used to obtain further conclusions regarding the accuracy of the simulation results and to apply conditional averaging methods. A two-point correlation and an analysis of the tumble center are proposed. Finally, conclusions are drawn to be used as guidelines in future large-eddy simulation analyses of internal combustion engines. [ABSTRACT FROM AUTHOR]

The low-aspect-ratio cylindrical structures represented by oil tanks is a kind of wind sensitive structure, which is prone to buckling under wind-loads. A wind tunnel test was conducted to investigate the properties of wind-loads acting on smooth cylinders with an aspect ratio AR = 0.323 and 0.875, respectively. Some parameters, such as Reynolds number (Re) and turbulence intensity, were taken into account. The results reveal that low-aspect-ratio cylinders have a Re effect, and the effect rises with AR. AR is the main factor affecting the value of the base pressure coefficient and positive pressure range, and the former increases with AR, while the latter decreases with AR. Moreover, due to the influence of the free end and turbulence, which may suppress vortex shedding, the power spectrum of the lift coefficient essentially shows broad spectral peaks with Re and turbulence. Increasing the incoming turbulence made the flow round cylinders at a higher Re state, that is, the supercritical regime is reached at a smaller Re. When turbulence is greater than 4.0%, turbulence and Re have little effect on the mean base force coefficient of low-aspect-ratio cylinders.

A better understanding of the flow field of the cross-flow turbine (CFT) will be useful in its design and operation. As far as is known, no comprehensive study carried out relating to the effect of Reynolds number to turbulent shear stress, shear wall, energy kinetic turbulent, dissipation rate and Reynolds stress, and the occurrence of vortices around the runners of the CFTs. This study was designed to investigate the flow field in the nozzle and runner of the CFT using computational fluid dynamics (CFD) method. CFD methods were chosen because they can visualize detailed flow patterns that other methods cannot. The setups used in the CFD method such as two-dimensional unsteady simulations, six degrees of freedom features, shear stress transport k-ω turbulent model, and pressure-based solver. Based on results, for the nozzle, the shape of the velocity profile shows that the highest momentum flux occurs at the end of the nozzle, near the runner. Distribution of shear wall was highest at the base and tip of the nozzle; it was lowest at the centre. The turbulent kinetic energy profile at the nozzle was proportional to the turbulent boundary layer profile, Reynolds stress and eddy viscosity. This indicated that nozzle shape affects the momentum flux; therefore, good nozzle geometry can transfer the maximum water energy into the blade. The nozzle's optimum geometry can be achieved by discharge and direction, optimizing velocity magnitude. This minimizes energy loss due to friction between the stream, vortex and mass of wasted fluid. For the runner, the highest turbulent kinetic energy, dissipations rate and Reynolds stress were located at the runner. Not all the water's energy converted into mechanic energy because the part of that energy was used in mixing between water and air. The establishment of lift force on the active blades was not caused by the flow field that crosses the upper part of the blade, but by the momentum of water that hit the lower part of the blade. A vortex formed due to separation of the flow from the blade significantly affected the runner's performance rather than rotational flow (air phase) in the CFT. [ABSTRACT FROM AUTHOR]

As a result of the recent events associated with the SARS-CoV-2 around the world, there has been a need for research to strengthen health care. The use of masks or respirators has been an effective measure, reducing the risk of contagion caused by the spread of the virus in public places. Currently, there are masks that retain up to 99% of particles >0.3 microns; however, they lack an airtight seal with the face, leading to discomfort and poor protection in conditions without social distancing and areas without ventilation. The device proposed in this study includes a geometric design of static valves with convergent spirals and interior baffles that promotes enhanced aerodynamics with bidirectional flow. According to the analysis and CFD simulation of the proposed reusable, washable, and economic mask and valve system for breathing, coughing, and sneezing events, enhanced air exchange could be maintained, facilitating a higher inhalation flow through the side of the mask (62%) and a higher exhalation through the front of the mask (74%), thereby avoiding the recirculation of the flow to the interior of the mask. The inclusion of filters with KN95 characteristics in the inlets and outlets maintains velocities below 10 cm/s, reducing the probability of infection.

Application of agrochemicals on crops is important for plants protection. Multiple factors influence the application of agrochemicals on plants such as climatic conditions, crop characteristics and spraying system design. There is a need for reliable methods to investigate these properties more precisely with low cost and in reasonable time. In the present study, the velocity distribution of an extended flat fan nozzle is investigated to determine the weak jet areas, which have high risks of droplet drift. Two methods are used and compared: the Particle Image Velocimetry (PIV) method used as an experimental approach versus a Computational Fluid Dynamics (CFD) with volume of fluid (VOF) integrating k-epsilon model as a simulation approach. The nozzle was operated at eight different pressures on a custom-made nozzle operating prototype while ANSYS 16 Fluent software was employed for the simulation approach. The obtained findings showed three significant results. First, the spray sheet (jet) has maximum velocity in its center. Second, the particles present in the central region of spray sheet have maximum kinetic energy and this region has the ability to hit the right target on the plant surface, while liquid particles present in the surroundings of this central area have less velocity with minimum kinetic energy and have maximum chances to be off-target during spraying. These particles can move away from the targeted surfaces easily even with very low wind velocity. Third, the study also showed that PIV and CFD simulation methods were in agreement and both showed reliable ways to measure the jet velocity and plot the velocity distribution under the sprayer nozzle. The applications of these findings are also discussed. [ABSTRACT FROM AUTHOR]

Accurate tidal current prediction plays a critical role with increasing utilization of tidal energy. The classical prediction approach of the tidal current velocity adopts the harmonic analysis (HA) method. The performance of the HA approach is not ideal to predict the high frequency components of tidal currents due to the lack of capability processing the non-astronomic factor. Recently, machine learning algorithms have been applied to process the non-astronomic factor in the prediction of tidal current. In this paper, a tidal current velocity prediction considering the effect of the multi-layer current velocity method is proposed. The proposed method adopts three machine learning algorithms to establish the prediction models for comparative investigations, namely long-short term memory (LSTM), back-propagation (BP) neural network, and the Elman regression network. In the case study, the tidal current data collected from the real ocean environment were used to validate the proposed method. The results show that the proposed method combined with the LSTM algorithm had higher accuracy than both the commercial tidal prediction tool (UTide) and the other two algorithms. This paper presents a novel tidal current velocity prediction considering the effect of the multi-layer current velocity method, which improves the accuracy of the power flow prediction and contributes to the research in the field of tidal current velocity prediction and the capture of tidal energy.

In the production and gathering process of coal gas, the complex composition of the coal gas, harsh environments, the complex medium, and high content of solid particles in slurry cause the equipment malfunctions and even failure because of erosion and corrosion. In the present study, COMSOL multi-physics finite element simulation software is used to simulate the erosion–corrosion behaviors of elbow in key chemical equipments. The electrochemical corrosion, solid particle erosion, chemical reaction, and turbulent flow are coupled together. The particle count method is proposed to clarify the erosion phenomenon. The simulation results show that particles with high turbulent intensity hit the wall of elbow directly, which forms a slanted elliptical erosion zone on the extrados surface at 40°–50°. The chemical reaction in turbulence has a difference in the concentration distribution of substances, and this phenomenon leads to different magnitudes of the corrosion current densities in the tube. Moreover, 1/6 released particles hit the extrados surface of the elbow. These findings are beneficial to understand the erosion–corrosion phenomena and design the elbow in key chemical equipment.

In a previous study, several computational fluid dynamics (CFD) simulations of fuel assembly thermal-hydraulic problems were presented that contained fewer fuel rods, such as 3 × 3 and 5 × 5, due to limited computer capacity. However, a typical AFA-3G fuel assembly consists of 17 × 17 rods. The pressure drop levels and flow details in the whole fuel assembly, and even in the pressurized water reactor (PWR), are not available. Hence, an appropriate CFD method for a full-scale 17 × 17 fuel assembly was the focus of this study. The spacer grids with mixing vanes, springs, and dimples were considered. The polyhedral and extruded mesh was generated using Star-CCM+ software and the total mesh number was about 200 million. The axial and lateral velocity distribution in the sub-channels was investigated. The pressure distribution downstream of different spacer grids were also obtained. As a result, an appropriate method for full-scale rod bundle simulations was obtained. The CFD analysis of thermal-hydraulic problems in a reactor coolant system can be widely conducted by using real-size fuel assembly models.

The Spalart-Allmaras (SA) model is a turbulence model for modeling different types of turbulent flows, especially in aerodynamics. Until 1992, when it was published by Spalart and Allmaras, there had been modified different terms of the governing equation of this model (prediction, diffusion and destruction). In this literature review, one can go through the details of the governing equation of this model and the role of each term and reasoning behind it. The model is implemented in three-dimensional compressible supersonic flows, and validated for two different configurations: a ballistic missile and a cruciform missile simulations show the ability of the method to snap the interaction between the fuselage vortices and the winglets.

The initiation features of wedge-induced oblique detonation waves (ODWs) in supersonic turbulence flows are studied with numerical simulations based on the SST k-ω model. The results show that the ignition delays are smaller in turbulence flows which results in a decrease in the initiation lengths of ODWs, and the initiation length decreases with the increase of the turbulence intensity. The effects of turbulence on the initiation limits of ODWs are analyzed with the energetic limit and the kinetic limit. It is shown that the initiation limit is not affected by the energetic limit, but affected by the kinetic limit. Because the ignition delay decreases in a turbulence flow, the kinetic limit is more easily to be fulfilled. Therefore, the initiation limit decreases with the increase of the turbulence intensity, that is to say, ODWs in strongly turbulent flows are more easily to be initiated. Besides, the transition structures of ODWs are investigated and the results show that for the same inflow condition, transition structures of ODWs in strongly turbulent flows are smooth while it is abrupt in an inviscid or slightly turbulent flow, and the reasons are discussed. [ABSTRACT FROM AUTHOR]

Conclusion: The obtained simulations support the underlying hypothesis that the hydrostatic caloric drive is dissipated by local convective flow in a hydropic duct. Objective: To develop a computerized model to simulate and predict the internal fluid thermodynamic behavior within both normal and hydropic horizontal ducts. Methods: This study used a computational fluid dynamics software to simulate the effects of cooling and warming of two geometrical models representing normal and hydropic ducts of one semicircular horizontal canal during 120 s. Results: Temperature maps, vorticity, and velocity fields were successfully obtained to characterize the endolymphatic flow during the caloric test in the developed models. In the normal semicircular canal, a well-defined endolymphatic linear flow was obtained, this flow has an opposite direction depending only on the cooling or warming condition of the simulation. For the hydropic model a non-effective endolymphatic flow was predicted; in this model the velocity and vorticity fields show a non-linear flow, with some vortices formed inside the hydropic duct. [ABSTRACT FROM AUTHOR]

In order to improve the performance of trucks and buses during winter and prolong the life of engines, the authors proposed a thermal electric generator that generates and uses the heat of the diesel combustion products of an independent heater for a passenger compartment of a bus or a truck and generates electrical energy capable to provide its own consumption completely. The difference from other developments is the absence of a liquid circuit and, as the consequence, low requirements for tightness. The feature of the proposed TEG is the use of air as a cold heat carrier for the combustion in TEG combustion chamber, and the combustion products of diesel fuel as a hot heat carrier. Having carried out the engineering calculation for the maximum capacity of an autonomous interior heater, the geometric dimensions of the central channel were set, which made 40x40 mm, and a three-dimensional model of the layout solution was developed. In this paper, the authors developed the design of a thermal-electric generator (TEG). Besides, full-size calculation domains were constructed and numerical modeling of TEG operation was performed for various operating modes of an air heater. The values of the temperature fields on the external and internal surfaces of TEG were obtained and the heat fluxes were determined transferred from cold and hot heat carriers. [ABSTRACT FROM AUTHOR]

• The boric acid concentration is accurately measured by using sodium fluorescein for the first time as the indicator based on the LIF. • The mixing behavior of boric acid under the action of turbulent flow in a T-tube were established. • CFD method was proposed to calculate the specific parameters of boric acid transport in the primary circuit. 10B has a large neutron absorption cross section and is commonly used as a neutron poison in the light water reactor (LWR) to adjust the reactivity of nuclear reactors. In this paper, for the first time, a new planar laser-induced fluorescence (PLIF) method with sodium fluorescein as the tracer is used to measure the concentration field of boric acid. In this paper, the injection process is abstracted as a T-tube. The accuracy of LIF is verified by wire mesh sensor. The CFD method is used to simulate the mixing process to come up with proper parameters to consider the influence of turbulence on the flow. The branch velocity of T-tube has a great influence on the diffusion process. The mixing process in the pipeline is mainly driven by turbulence of the side jet. Boric acid is evenly mixed in the pipe within 8 ∼ 10 times of the pipe diameter. [ABSTRACT FROM AUTHOR]

Several studies of compressible flows show that the pressure-strain is the main indicator of the structural compressibility effects. Undoubtedly, this term controls the change in the Reynolds stress anisotropy. Regarding the model of Adumitroiae et al., the slow part of the pressure strain correlation like the Rotta model uses the standard coefficient C1. The model predictions do not show large differences when compressibility increases. Correction of this coefficient using the turbulent Mach number is proposed. The two forms model of Adumitroiae et al. (with and without correction of 1 C ) are considered to study compressible mixing layers . The obtained results show that the predictions of the proposed compressibility correction model agree with the experiment results of Goebel and Dutton.

The paper presents convection heat transfer of a turbulent flow Al2O3/water nanofluid in a circular duct. The duct is a under constant and uniform heat flux. The paper computationally investigates the system's thermal behavior in a wide range of Reynolds number and also volume concentration up to 6%. To obtain the nanofluid thermophysical properties, the Hamilton-Crosser model along with the Brownian motion effect are utilized. Then the thermal performance of the system with the nanofluid is compared to the conventional systems which use water as the working fluid. The results indicate that the use of nanofluid of 6% improves the heat transfer rate up to 36.8% with respect to pure water. Therefore, using the Al2O3/water nanofluid instead of water can be a great choice when better heat transfer is needed. [ABSTRACT FROM AUTHOR]

In this paper we explore the improvement of aerodynamic characteristics of wind turbine airfoils under stall conditions through passive boundary layer control using slots. Baseline S809 airfoil was modified based on CFD calculations. An extensive 2D-numerical study has been done to analyze the effects of slot׳s location, width and slope and the best configuration was determined. Simulations were done using steady RANS equations; the turbulence closure model has been chosen among four possible choices (standard k – ε , Spalart–Allmaras, k – ω and k – ω SST ) based on comparison with experimental results. The lift and drag coefficients and lift-over-drag ratio are compared for the different configurations. The results show that the control system improves aerodynamic performance only over a specific range of angles of attack. However, a significant penalty is observed on the airfoil efficiency for the final configuration, this penalty results from higher drag than the baseline airfoil at low angles of attack. At moderate and high angles of attack, from 10° to 20°, the slot configuration outperforms the baseline configuration. [ABSTRACT FROM AUTHOR]

Although compact separation by a hydrocyclone is popular in the chemical and petro-chemical industry, the separation of dissolved gas from continuous liquid in a hydrocyclone is rarely mentioned, and few investigations consider the gas solubility changes occurring with the cyclone flow. This work investigates dissolved carbon dioxide separation from water by an inner cone hydrocyclone. When the inlet mass flow is less than 1.2 m 3 /h, increasing the inlet mass flow could increase the separation efficiency. When the inlet mass flow is more than 1.2 m 3 /h, increasing the inlet mass flow will decrease the separation efficiency. An optimum inlet mass flow of 1.2 m 3 /h can provide the maximum separation efficiency of 40.2%. Turbulence simulations also assist in analyzing the flow pattern and the separation progress. [ABSTRACT FROM AUTHOR]

Three series of experiments were conducted to improve sediment microbial fuel cell (SMFC) performance. At first, dissolved oxygen level of catholyte was increased with native seaweed of the Caspian Sea. Power output was improved about 2-fold, and maximum power density of 46.14 8mW/m was produced in the presence of seaweed as biocathode in cathode compartment. Secondly, the best depth to embed anode was then determined. Anode was embedded in 3, 6, 9 and 12 cm below the sediment/water interface. The best depth to bury the anode was finally determined in 3 cm below the sediment/water interface, maximum generated power and current density of 42.156 mW/m and 282.92 mA/m, were respectively obtained in this depth. In addition, influence of agitated flow on power generation from SMFC was investigated. [ABSTRACT FROM AUTHOR]