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Renewable energy sources are essential to address climate change, fossil fuel depletion, and stringent environmental regulations in the subsequent decades. Horizontal-axis wind turbines (HAWTs) are particularly suited to meet this demand. However, their efficiency is affected by environmental factors because they operate in open areas. Adverse weather conditions like rain reduce their aerodynamic performance. This study investigates wind turbine power prediction under rainy conditions by integrating Blade Element Momentum (BEM) theory with explainable artificial intelligence (XAI). The S809 airfoil's aerodynamic characteristics, used in NREL wind turbines, were analyzed using ANSYS FLUENT and symbolic regression under varying rain intensities. Simulations at a Reynolds number (Re) of 1 × 106 were performed using the Discrete Phase Model (DPM) and k– ω SST turbulence model, with liquid water content (LWC) values of 0 (dry), 10, 25, and 39 g/m3. The lift and drag coefficients were calculated at various angles of attack for all the conditions. The results indicated that rain led to reduced lift and increased drag. The innovative aspect of this research is the development of machine learning models predicting changes in the airfoil coefficients under rain with an R 2 value of 0.97. The proposed XAI framework models rain effects at a lower computational time, enabling efficient wind farm performance assessment in rainy conditions compared to conventional CFD simulations. It was found that a heavy rain LWC of 39 g/m3 could reduce power output by 5.7% to 7%. These findings highlight the impact of rain on aerodynamic performance and the importance of advanced predictive models for optimizing renewable energy generation. [ABSTRACT FROM AUTHOR]

Focusing and separation of cells by microfluidic techniques are significant steps in many applications, such as single-cell analysis and disease diagnosis. Among the microfluidic techniques, passive magnetophoresis, as a label-free manner, can manipulate samples by means of magnetic field. Nowadays, most magnetic fields are generated by permanent magnets and electromagnets with large size. However, it is difficult to assemble a magnetic array using permanent magnets or electromagnets to optimize the field distribution. To produce a flexible magnetic field, a micro-magnet made by NdFeB powder and polydimethyl siloxane is proposed in this paper, and those magnetized micro-magnets are arranged into different arrays according to the arrangements of their magnetization directions. Meanwhile, a microfluidic chip containing magnetized micro-magnet arrays is designed for focusing and separating polystyrene microbeads with different diameters. The focusing and separation behaviors of microbeads in the designed microfluidic system are numerical and experimental investigated. In addition, the effects of flow rate and the arrangement of the magnetic micro-magnet array on microbead focusing and separation are discussed. Finally, a multistage microfluidic chip is designed to successfully isolate 5 μm-diameter, 10 μm-diameter, and 15 μm-diameter microbeads from their mixture at a flow rate of 240 μL/min with high purity. [ABSTRACT FROM AUTHOR]

The impact of presence of nano-scale particles inside a flow between two flat plates which known as Poiseuille flow is numerically analyzed. Nanofluids have been investigated in the past few years mainly by considering the heat transfer aspect in a fully developed section of internal flows, rather than detailing the hydrodynamic and thermal developing viewpoint of nanofluid. In other words, this research will focus on the fundamental understanding of developing nanoparticles flows in hydrodynamic and thermal boundary layers in the entrance region. Therefore, flow between two flat plates is numerically studied here by injecting and tracking nanoparticles from inlet to outlet of the channel. The flow is kept in the laminar regime with uniform heat flux applied on the plates. ANSYS Fluent 19.3 is used to numerically solve the continuity and momentum equations, as well as discrete phase modeling for particles. The results showed three major stages in vorticity development in the entrance region. It was found that Brownian motion plays an important role in nanoparticles migration, and close to the wall with the involvement of Thermophoresis. Also, nanoparticles can deviate from flow layers after merging boundary layers.

Controlled agglomeration during spray drying offers several advantages for both powder manufacturers and consumers, and thus it is commonly implemented by industry. The implementation, however is largely based on experience, given the scarcity of comprehensive prediction tools. A resource-efficient approach to numerically treat agglomerates and yet provide an indication of their structures is desired to perform realistic simulations without the need for high-performance computing. In this work, a new numerical model for the treatment of coalescence and agglomeration was implemented and evaluated at two distinct scales with significantly different particle number densities within a Eulerian-Lagrangian CFD framework. The model could accurately predict the trends in the final particle size distributions and distinguish realistic agglomerate structures occurring under different conditions. Challenges were encountered as a result of how the underlying collision detection routine handles high particle number density. Several strategies are proposed to overcome these challenges. This work constitutes significant progress towards achieving an efficient prediction tool to estimate final powder properties and will prove useful in performing large-scale simulations to design and control agglomeration. Unlabelled Image • A rigorous modelling approach was developed for agglomeration in spray drying. • The proposed model was found to be resource efficient and yet useful and informative. • Coalescence and agglomeration of particles were distinguished via penetration depth. • Surface area reduction coined as a parameter indicated agglomerate compactness. • Experimental data obtained from lab- and large-scale dryer supported the assessment. [ABSTRACT FROM AUTHOR]

The impact of presence of nano-scale particles inside a flow between two flat plates which known as Poiseuille flow is numerically analyzed. Nanofluids have been investigated in the past few years mainly by considering the heat transfer aspect in a fully developed section of internal flows, rather than detailing the hydrodynamic and thermal developing viewpoint of nanofluid. In other words, this research will focus on the fundamental understanding of developing nanoparticles flows in hydrodynamic and thermal boundary layers in the entrance region. Therefore, flow between two flat plates is numerically studied here by injecting and tracking nanoparticles from inlet to outlet of the channel. The flow is kept in the laminar regime with uniform heat flux applied on the plates. ANSYS Fluent 19.3 is used to numerically solve the continuity and momentum equations, as well as discrete phase modeling for particles. The results showed three major stages in vorticity development in the entrance region. It was found that Brownian motion plays an important role in nanoparticles migration, and close to the wall with the involvement of Thermophoresis. Also, nanoparticles can deviate from flow layers after merging boundary layers. [ABSTRACT FROM AUTHOR]

Microfluidic-based sorting systems are an integral part of many biological applications, where sorting of cells, microorganisms, and particles is of interest. In this paper, a computational fluid dynamics model is established to expand investigations on a hybrid microparticle sorting method, which combines inertia-magnetic focusing and hydrodynamic separation, known as multiplex inertia-magnetic fractionation (MIMF). This microfluidic device consists of two regions, i.e. a narrow microchannel with a magnet on its side for inertial and magnetophoretic focusing of particles and a downstream wide hydrodynamic expansion zone for particles' separation and imaging. A Lagrangian–Eulerian framework was adopted to simulate particle trajectories using the ANSYS-Fluent discrete phase modeling (DPM) approach. Acting forces that were considered to predict particle trajectories included the drag, inertial lift, Saffman lift, gravitational, and magnetophoretic forces. User-defined functions were used for inertial lift and magnetophoretic forces that are not built-in relations in the ANSYS-Fluent DPM. Numerical results were verified and validated against the experimental data for MIMF of 5 and 11 µm magnetic particles at flow rates of 0.5–5 mL/h. Particles fractionation throughput and purity in the expansion region could be predicted with errors of 6% and 2%, respectfully. The validated model was then used to perform a numerical parametric study on the unknown effects of magnetization, particle size, higher flow rates, and fluid viscosity on MIMF. The presented numerical approach can be used as a tool for future experimental design of inertia-magnetophoretic microfluidic particle sorting devices. [ABSTRACT FROM AUTHOR]

Highlights • Fourteen optimal vortex finders have been obtained using genetic algorithms. • The least Euler number obtained is 54.25% lower than that of the Stairmand cyclone. • The highest collection efficiency obtained is 5% higher than that of the Stairmand cyclone. • Optimal shape of the vortex finders obtained is stepped divergent and convergent-divergent. • Optimization using genetic algorithms provide better solutions than response surface methodology. Abstract Multi-objective optimization of vortex finders is performed using Response Surface Methodology (RSM) and Genetic Algorithms (GA) for enhancing the performance of the standard Stairmand cyclone separator. Three diameters at different axial locations and the distance between these locations are optimized for enhancing the performance of the cyclone separator. This approach provides flexibility to the optimization process as the vortex finder is free to assume any shape (convergent or divergent) according to changes in the three diameters at different locations of the vortex finder. Optimization is carried out using five independent parameters and two dependent variables, Euler number and collection efficiency. The optimization results confirm that the present strategy is capable of optimizing the vortex finder for better performance than the standard Stairmand model. Fourteen optimal vortex finders have been obtained in the proposed work to select the required conflicting performance parameters. Genetic algorithms provide better solutions than RSM. Optimal vortex finders are stepped divergent or convergent-divergent in nature. [ABSTRACT FROM AUTHOR]

Performance analysis of 0.29 m diameter cyclone separator was done for cone shaped vortex finders having different in-built tapered angles varying from 0.0°-10.0° in steps of 2.5° at different inlet velocities using Fluent 15.0. Increasing the angle from 0.0° to 10.0° at the lowest inlet velocity decreases the Stokes number (Stk50), which represents the cut-size of a cyclone separator, by 22.1 % at an expense of significant increase in Euler number (Eu), representing the dimensionless pressure drop, by nearly 46.3 %, whereas at the highest inlet velocity of 25 m/s, the Stk50 decreases by 26.1 % and the increase in Eu lowers to 34.3 %. Beyond a critical angle of orientation, 5.0°, a recirculation zone of increasing magnitude develops inside the vortex finder. The axial velocity, tangential velocity, and pressure drop across the cyclone have been validated against published literature; a grid independence test was also done successfully. [ABSTRACT FROM AUTHOR]

A numerical simulation of a cold gas dynamic spray process using a computational fluid dynamic (CFD) technique is presented. Distribution of particulate matter in the immediate surroundings of spray application site is of interest. The flow field inside an oval shaped supersonic nozzle and the surroundings of the nozzle is simulated. Particle trajectories along their flight in the nozzle as well as before and after impact with the target plane are calculated. Fluent is used for the purpose of flow field simulation. A discrete-phase Lagrangian particle trajectory model is used for particle trajectory calculation. A model uses the principles of motion and impact dynamics to predict particle behavior upon impacting the substrate. The locations and concentrations of particle exhaust patterns around the impact location are determined and presented graphically. The dependence of these patterns to variations in the jet-target tilting angle, standoff distance, upstream temperature and particle material is investigated.

In this paper, heavy rain effects on the aerodynamic efficiency of National Advisory Committee for Aeronautics (NACA) 23015 airfoil cruise and landing configurations and NACA 64210 high lift configuration have been studied. For this study, preprocessing software Gridgen has been used for creation of geometry and mesh, and fluent software is used as a solver. Discrete phase modeling (DPM) in a Langrangian frame of reference has been used to simulate the rain particles dispersed in continuous phase using two-phase flow approach. The coupling between the two phases and its impact on both phases has been included. In discrete phase model (DPM), the wall film is modeled by the injected rain particles. In a simulated rain environment all the cruise, landing, and high lift configurations of airfoils showed a significant decrease in lift and increase in drag in heavy rain environment. In this study, it is found that the heavy rain causes premature boundary-layer transition at low angle of attack (AOA) and separation at high AOA. The water film layer formed on the surface of the airfoil is thought to alter the airfoil geometry and increase the mass effectively. In the simulation for NACA 23105 the increase in drag is less contrary to simulations done for NACA 64210 high lift configuration airfoil, for which the aerodynamic efficiency degradation is much higher. The relative differences appeared to be related to the susceptibility of each airfoil to premature boundary-layer transition. Postprocessing software like MATLAB, Tec plot, and Origin are used to see the effects of the heavy rain, and the results obtained are compared with the experimental results. It is strongly believed that this study will be useful for the aviation engineers and scientists to design the airplanes and UAVs capable of flying in severe weather conditions and to train the pilots to control the airplane in heavy rain conditions well. [ABSTRACT FROM AUTHOR]

A cost-effective and efficient technology was developed to remove particulate and fibrous matter from a container while avoiding dispersing the particles in the environment. This paper presents the whole process of computationally developing a conceptual system which can efficiently remove particles in the size range of 5–1000  μm from the container. The present work offers the unique virtue that prototyping can be easily followed and it shows an efficient, safe, low-cost method in the early product design stage. In the presented system, a viscous medium was designed to capture and flocculate the particulate matter. One of the factors which will lower the operating costs is that the viscous medium can be easily recycled and the flocculated particles with minimal volume can be disposed of safely. The ANSYS FLUENT package was used to simulate our proposed design. The effects of various particle size, specific gravity, and pressure-velocity boundary conditions on separation efficiency of the design have been studied by using different multiphase models along with viscous and discreet phase models. [ABSTRACT FROM AUTHOR]

A numerical simulation of a cold gas dynamic spray process using a computational fluid dynamic (CFD) technique is presented. Distribution of particulate matter in the immediate surroundings of spray application site is of interest. The flow field inside an oval shaped supersonic nozzle and the surroundings of the nozzle is simulated. Particle trajectories along their flight in the nozzle as well as before and after impact with the target plane are calculated. Fluent is used for the purpose of flow field simulation. A discrete-phase Lagrangian particle trajectory model is used for particle trajectory calculation. A model uses the principles of motion and impact dynamics to predict particle behavior upon impacting the substrate. The locations and concentrations of particle exhaust patterns around the impact location are determined and presented graphically. The dependence of these patterns to variations in the jet-target tilting angle, standoff distance, upstream temperature and particle material is investigated. [ABSTRACT FROM AUTHOR]

Abstract: The hydrodynamic study of nanofluids in microchannel is carried out. For this, three microchannels of hydraulic diameters of 130, 211 and 300μm are fabricated by photolithographic and wet etching processes on silicon wafers. Alumina nanofluids with concentrations 0.25vol.%, 0.5vol.% and 1.0vol.% with particle sizes 45nm and 150nm are prepared, stabilized and characterized by standard methods like sonication, pH variation, Transmission Electron Microscope (TEM) and Dynamic Light Scattering (DLS) measurements. The base fluids used are water and Ethylene Glycol. The effect of volume fraction, channel size, particle size and base fluids are presented and analyzed. It is shown that there is an early transition to turbulence for 211 and 301μm channels. In addition, numerical modeling is carried out by using mixture rule and discrete phase modeling approach. This approach is found to be more suitable at higher Reynolds numbers whereas at lower Reynolds numbers the conventional mixture model can be used. Shear induced particle migration is identified to be an important phenomenon at higher Reynolds number and hence the reason for difference between these two models. [Copyright &y& Elsevier]

Abstract: Computational fluid dynamics (CFD) is used to model the shock-wave induced spray process (SISP). SISP is a method of applying coatings of various metallic-based materials onto a substrate. It utilizes the kinetic and thermal energy induced by a moving shock-wave to accelerate and heat powder particles. This process is a new cold gas-dynamic spraying (CGDS or simply cold spray) material deposition technique. The basic principles related to the coating formation and bonding mechanism in this process are hypothesized to be similar to those in traditional Cold Spray processes. The distinguishing feature of SISP is a sequence of moving shock-waves created by the fast opening and closing of a valve. A rate of 30 to 50 pulses per second is presently conceivable. When the valve is rapidly opened and closed, a shock-wave propagates into the spraying gun, accelerating and heating the powder present in the gun. Similar to the cold spray process, the particles then impact the substrate and deform plastically to produce a coating. Individual powder particles may reach the substrate at different velocities and temperatures depending on their location within the unsteady flow regime. An existing correlation for the “critical velocity” for bonding and a CFD model are used to predict whether a particle traveling within this unsteady flow regime will adhere to the substrate upon impact. This information is then used to predict if a coating can be formed under a specific set of spray conditions. [Copyright &y& Elsevier]

Abstract: Computational Fluid Dynamics (CFD) analysis of the effects of co-firing biomass with coal is presented in this study. Coal/biomass co-firing is a complex problem that involves gas and particle phases, along with the effect of the turbulence on the chemical reactions. The CFD analysis includes the prediction of volatile evolution and char burnout from the co-pulverized coal/biomass particles along with the simulation of the combustion chemistry occurring in the gas phase. The mathematical models consist of models for turbulent flow (RNG k–ε model); gas phase combustion (two-mixture fractions/PDF model); particles dispersion by turbulent flow (stochastic tracking model); coal/biomass particles devolatilization (two competing rates Kobayashi model); heterogeneous char reaction (kinetics/diffusion-limited rate model); and radiation (P-1 radiation model). The coal used is a Canadian high sulfur bituminous coal. The coal was blended with 5–20% wheat straw (thermal basis) for co-firing. The effect of the percentage of biomass blended with coal on the flow field, gas and particle temperature distribution, particles trajectories and gas emissions (CO2 and NO x ) are presented. One important result is the reduction of NO x and CO2 emissions when using co-combustion. This reduction depends on the proportion of biomass (wheat straw) blended with coal. [Copyright &y& Elsevier]

Within perfusion cell culture systems, scaffold architecture is able to control important biological parameters such as permeability and fluid flow-induced shear stress. As well, one of the main factors affecting the final fate of this process as well as optimal cell differentiation and proliferation in these systems is initial adhesion of cells to scaffolds. In this study, the effect of scaffold architecture on the adhesion of the cells was computationally investigated. For this purpose, four scaffold models including double-diamond, gyroid, FR-D, and Schwarz-primitive were designed using triply periodic minimal surface (TPMS) geometry with a constant porosity of 80%. As well, the inlet velocity of zero to simulate static cell culture and three different inlet velocities for modeling the dynamic cell culture conditions were also selected. The results showed that cell culture efficiency of scaffolds could be changed up to seven times from architecture to architecture under the same conditions. The efficiency of cell culture in scaffolds with tortuous architecture was also reported higher than those with relatively straight microchannels. In terms of culture methods, unlike dynamic cell culture model in which almost a homogeneous cell distribution was observed in static cell culture simulation, more cells adhered, but they had agglomerated in the scaffold entrance regions and had failed to reach all regions. The results of this study shed more light on the selection and design of scaffold architecture for optimal cell culture in tissue engineering., (Copyright © 2019 Elsevier Ltd. All rights reserved.)