Fluid Dynamics Approach Research Articles

Parametric evaluation of carbon dioxide and steam co-gasification of sewage sludge and palm kernel shell in a downdraft fixed bed reactor: Computational Fluid Dynamics (CFD) approach

Thermally converting sewage sludge (SS) to harness its energy potential brings challenges like high ash content, which can cause system instability. However, co-gasifying SS with carbon-rich materials has shown to be more advantageous. This study analyses a two-dimensional Eulerian CFD numerical model for a CO2 and steam cogasification of SS and palm kernel shell in a downdraft gasifier by solving the governing equations of mass phases, turbulence, energy, and momentum on a high-resolution mesh model. The devolatilization phase is defined by comprehensive solid carbon pyrolysis kinetic mechanisms and secondary gas reaction mechanisms, whilst the gasification and combustion processes are governed by applying detailed heterogeneous and homogeneous rate-controlled reactions. An experimental assessment with temperature of 1000 °C; ER of 0.28; fuel feed rate of 0.00061 kgs−1; at atmospheric pressure was conducted to validate the current model considering the temperature distribution and gas composition. The validated model is further used to evaluate the effect of mixing ratios, steam-to-fuel ratio (S/F), carbon dioxide-fuel ratio (CO2/F), and gasification temperature on syngas composition, lower heating value, hot gas efficiency, gas yield, H2/CO and synergistic coefficient. The predicted results agree well with the experimental data with the maximum deviational error of 9.52 %. The highest H2 production was recorded during steam gasification, whilst CO was favored by CO2 gasification. Synergistic analysis presented the highest synergy coefficient for the SS mixing ratio of 25 % at 1.91 and 50 % at 1.93 for steam and CO2 gasification respectively.

Investigation on the performance and vapor injection characteristics of a scroll compressor for electric vehicles based on computational fluid dynamics approach

Investigation on the performance and vapor injection characteristics of a scroll compressor for electric vehicles based on computational fluid dynamics approach

Numerical analysis of collision mechanism that causes particle tribocharging in dry powder inhaler

Chronic obstructive pulmonary disease (COPD) is induced by inhalation of toxic substances such as cigarettes and air pollution. Dry powder inhalers (DPIs) are the primary treatment for these diseases. However, they have some problems, such as residuals in a capsule caused by electrostatic force before reaching the human lungs. This study investigated the particle tribocharging mechanism in a DPI using a tandem differential mobility analyzer (TDMA) and a combined discrete element method and computational fluid dynamics (DEM-CFD) approach. In the TDMA experiment, the charging state of the particles changed from negative to positive charge in the DPI device fabricated by the 3D printer. This is because tribocharging is caused by particle–particle collisions and particle–wall collisions. In the numerical simulation, particle–wall collisions occurred more frequently than particle–particle collisions. Therefore, the particle–wall collisions change the charging state of the particle in the DPI device. These results suggest that collisions between particles and walls of the device cause the particles to become charged, leading to a decrease in their deposition in the deeper regions of the lungs. Moreover, the large turbulence kinetic energy of the airflow in the DPI device caused particle–wall collisions because the particles were widely dispersed in the DPI device. These results suggest that optimum turbulence kinetic energy is necessary to reduce particle aggregation and improve the delivery efficiency of DPIs to the human lungs.Graphical

Analysis of Rounded Interceptor Effects on Ship Resistance of High-Speed Planing Vessel using Computational Fluid Dynamics

The primary objective of the interceptor is to control the trim of the vessel, thereby enhancing fuel efficiency and stability. However, at high speeds, the interceptor induces adverse effects. This research aims to mitigate these negative impacts by modifying the geometric configuration of the interceptor. The shape modifications of the rounded interceptor evaluated through numerical simulations include radii of R10.00, R12.50, and R15.00. This study aims to contribute to an enhanced understanding of the effects on drag, heave, and trim performance of the planing hull vessel. The methodology employs a Computational Fluid Dynamics (CFD) approach using Reynolds-Averaged Navier-Stokes (RANS) equations. The simulation verification was conducted regarding prior experimental studies, and the simulation procedures adhered to the guidelines set by the International Towing Tank Conference (ITTC). The interceptor's height is a key factor in reducing trim, heave, and consequently, drag. The modified rounded interceptor effectively reduces drag at high speeds.

Three-Dimensional Aeroelastic Investigation of a Novel Convex Bladed H-Darrieus Wind Turbine Based on a Two-Way Coupled Computational Fluid Dynamics and Finite Element Analysis Approach

Three-Dimensional Aeroelastic Investigation of a Novel Convex Bladed H-Darrieus Wind Turbine Based on a Two-Way Coupled Computational Fluid Dynamics and Finite Element Analysis Approach

Effect of Inter Turbine Spacing in Omnidirectional Wind for Savonius Cluster: A Computational Fluid Dynamics and Artificial Neural Network Approach

Effect of Inter Turbine Spacing in Omnidirectional Wind for Savonius Cluster: A Computational Fluid Dynamics and Artificial Neural Network Approach

Rotor-Fuselage-Intake Aerodynamics and Icing Using Vortex and Eulerian–Lagrangian Computational Fluid Dynamics Methods

Rotorcraft rotor-fuselage-intake aerodynamics and icing present unique challenges associated with rotor-wake dynamics and the interaction of rotor wake with the fuselage and the intake. The effects of the rotor wake are dominant in low forward flight, and performing high-fidelity simulations of the rotor-fuselage-intake simultaneously is expensive. This study presents a novel hybrid nonlinear vortex–computational fluid dynamics (CFD) approach to rotor-fuselage-intake aerodynamics and icing. The method combines nonlinear vortex–lattice, Lagrangian vortex–particle, and Eulerian CFD methods on airflow and droplet impingement with a PDE-based ice-accretion model. The Lagrangian description of rotor wake preserves the wake structure independently of the Eulerian grid, whereas the Eulerian description of the flowfield naturally computes nonlinear flow phenomena and surface properties. The algorithm allowed the ice accretion to be computed much faster than existing methods. The method was validated by considering airflow, surface pressure, and ice accretion around a model rotorcraft. We investigated ice accretion with strong rotor wakes for different advance ratios and rotor thrust coefficients. We also investigated the effects of the suction of airflow in the intake and the differences between with and without the rotor. It was found that the advance ratio had a dominant effect compared to the rotor thrust coefficient.

Numerical study of a horizontal shower water heat recovery system

The objective of this work is to numerically study the performance of a drain water heat recovery (DWHR) device prototype intended for small shower trays. The numerical model is based on Computational Fluid Dynamics (CFD) approach. The simulations were performed for unbalanced and balanced configurations in terms of waste water flow rate and cold water flow rate. The results achieved show that the thermal effectiveness of the proposed DWHR system is between 15-27% and the Number of Transfer Units (NTU) is among 17-37%, with higher values for the unbalanced configuration. Based on these values, it can be concluded that the designed DWHR unit leads to satisfactory results considering cost-effectiveness reasons and maintenance.

Analysis of heat transfer and AuNPs-mediated photo-thermal inactivation of E. coli at varying laser powers using single-phase CFD modeling

PurposeIn the wake of the COVID-19 pandemics, the demand for innovative and effective methods of bacterial inactivation has become a critical area of research, providing the impetus for this study. The purpose of this research is to analyze the AuNPs-mediated photothermal inactivation of E. coli. Gold nanoparticles irradiated by laser represent a promising technique for combating bacterial infection that combines high-tech and scientific progress. The intermediate aim of the work was to present the calibration of the model with respect to the gold nanorods experiment. The purpose of this work is to study the effect of initial concentration of E. coli bacteria, the design of the chamber and the laser power on heat transfer and inactivation of E. coli bacteria.Design/methodology/approachUsing the CFD simulation, the work combines three main concepts. 1. The conversion of laser light to heat has been described by a combination of three distinctive approximations: a- Discrete particle integration to take into account every nanoparticle within the system, b- Rayleigh-Drude approximation to determine the scattering and extinction coefficients and c- Lambert–Beer–Bourger law to describe the decrease in laser intensity across the AuNPs. 2. The contribution of the presence of E. coli bacteria to the thermal and fluid-dynamic fields in the microdevice was modeled by single-phase approach by determining the effective thermophysical properties of the water-bacteria mixture. 3. An approach based on a temperature threshold attained at which bacteria will be inactivated, has been used to predict bacterial response to temperature increases.FindingsThe comparison of the thermal fields and temporal temperature changes obtained by the CFD simulation with those obtained experimentally confirms the accuracy of the light-heat conversion model derived from the aforementioned approximations. The results show a linear relationship between maximum temperature and variation in laser power over the range studied, which is in line with previous experimental results. It was also found that the temperature inside the microchamber can exceed 55 °C only when a laser power higher than 0.8 W is used, so bacterial inactivation begins.Research limitations/implicationsThe experimental data allows to determinate the concentration of nanoparticles. This parameter is introduced into the mathematical model obtaining the same number of AuNPs. However, this assumption introduces a certain simplification, as in the mathematical model the distribution of nanoparticles is uniform.Practical implicationsThis work is directly connected to the use of gold nanoparticles for energy conversion, as well as the field of bacterial inactivation in microfluidic systems such as lab-on-a-chip. Presented mathematical and numerical models can be extended to the entire spectrum of wavelengths with particular use of white light in the inactivation of bacteria.Originality/valueThis work represents a significant advancement in the field, as to the best of the authors’ knowledge, it is the first to employ a single-phase computational fluid dynamics (CFD) approach specifically combined with the thermal inactivation of bacteria. Moreover, this research pioneers the use of a numerical simulation to analyze the temperature threshold of photothermal inactivation of E. coli mediated by gold nanorods (AuNRs). The integration of these methodologies offers a new perspective on optimizing bacterial inactivation techniques, making this study a valuable contribution to both computational modeling and biomedical applications.

Effects of Evaporation and Body Thermal Plume on Cough Droplet Dispersion and Exposure Risk for Queuing People.

The transmission of virus-containing droplets among multiple people in an outdoor environment is seldom evaluated. In this study, an Euler-Lagrange computational fluid dynamics approach was used to investigate the effects of evaporation and the body thermal plume on the dispersion of coughed droplets under various wind conditions, and the infection risk was evaluated for various arrangements of individuals queuing outdoors using virtual manikin models. The evaporation time was longer for larger droplets and in a more humid environment. Transient evaporation strongly affected the motion of droplets ranging in diameter from 60 to 150 μm. The body thermal plume affected airflow and particle dispersion under weak wind conditions, but its effect was negligible at wind speeds greater than 0.8 m/s. Droplets smaller than 100 μm could reach the head of a susceptible person, suggesting a high exposure risk. The exposure fraction and body deposition were highest in an all-male queue sequence and lowest for a male-female-male-female-male queue sequence.

EFFECTIVENESS OF PHYSICAL DISTANCING IN A MOSQUE DURING CONGREGATIONAL PRAYER USING CFD SIMULATION APPROACH

This study aims to investigate the effectiveness of physical distancing in a mosque during congregational prayer using the Computational Fluid Dynamic (CFD) simulation approach. A three-dimensional (3D) model of a mosque, prayer, and assailant was designed using Computer Aided Design (CAD) software. Then, a simulation is run using CFD software to simulate the pathogen transmission during the congregation prayer. The simulation is run with the fix of air movement, temperature, and humidity at variable distances, as distancing is the main focus of the study. This is to avoid other factors affecting the results of this study, as what matters the most is the distance among the prayers. The mesh sensitivity study has been done to get a good simulation result that is close to the real world using the numerical computational method. A correct turbulent model is then chosen, and the simulation data obtained were pre validated by the previous literature study. The simulations showed that the pathogen tends to move to the front right side of the mosque. Particles deposition showed that prayer at the front of the assailant received the most percentage of the particles deposition which is the highest 1.3% particles at 3m physical distancing and prayers at the side received least percentage of particles deposition for all physical distancing. The particles also mostly deposited at the ceiling and the mosque's ground. Finally, the result showed that the further distance among the prayers will minimise the virus reproduction number, Ro value during the congregational prayer. The highest value of Ro for without physical distancing is 3 at the interval of 40s to 50s, while the value of Ro for 3m and 4m physical distancing is 0 at the interval of 80s to 100s. This is because the virus cannot be transmitted to many people as the distance between humans increases. The percentage of probability infected prayers is the highest for without physical distancing, which is 26.63% out of total prayers, while at the lowest for 4m physical distancing, which is 14.29% out of all prayers. In conclusion, the pathogen transmission among prayers can be reduced by applying physical distancing as the pathogens are droplet nuclei that are sufficiently small to remain suspended in the air for an extended period and can travel more than 2m distance.

Effect of the Cross-Sectional Geometry of the Mixed Particle Zone on the Spiral Separation Process and Its Structural Optimization

Cross-sectional geometry is of significance in determining the flow characteristics and the particles separation in spiral concentrators. The effects of the cross-sectional geometry within the mixed particle zone on the secondary flow and the separation process of hematite and quartz particles with a size of 89.5 μm were investigated via a computational fluid dynamics (CFD) approach. The optimization of the line segment slopes was conducted using response surface methodology (RSM). The results indicate that the peak radial fluxes and average radial velocities of the secondary flow are positively correlated with the corresponding line segment slope. The independent adjustment of line slopes in regions I and II, and the interaction of line slopes in regions I and III, influence the separation efficiency of hematite and quartz particles significantly. The separation performance of the experimental spiral concentrator with a cross-sectional profile of the optimized line segments for a feed of hematite and quartz with a size range of −100 + 75 μm is remarkably improved by nearly 5%. This study provides insights for the cross-section design of spiral concentrators for the effective separation of coarse-grained hematite and quartz.

A low-cost space-time finite element for free-surface flows under total Lagrangian description

In this work, we propose a position-based space-time finite element formulation for incompressible Newtonian flows under a total Lagrangian description. This formulation is suggested within the context of finite strain free-surface flows and differs from the traditional finite element approach for fluid dynamics by utilizing current nodal positions as the main variables instead of nodal velocities. In contrast to time-marching methods, space-time formulations involve applying the finite element technique not only to the spatial domain but also to the temporal domain. The proposed approach employs a finite element discretization that can be unstructured or structured in space, but is always structured in time. Thus, the space-time shape functions are expressed as a tensor product of linear shape functions in the spatial direction and specially designed quadratic shape functions in the temporal direction. Consequently, the space-time domain is divided into time slabs that are solved progressively, with the final velocities and positions from the previous time slab serving as initial conditions for the current one, thereby reducing the dimension of the discrete system of equations. The proposed shape functions in the temporal direction yield a system of equations of the same size as standard time-marching methods, but with advantages stemming from the space-time discretization: different stability and high-frequency dissipation can be achieved based on the selection of the time test functions. To solve the incompressible problem stably, we employ mixed equal-order position-pressure finite elements with Petrov-Galerkin/pressure stabilization (PSPG). This formulation possesses several significant features that justify its development: 1) the space-time formulation facilitates dynamic re-meshing by permitting the spatial discretization at the end of one time slab to differ entirely from the spatial discretization at its beginning, thus extending its applicability to flows with undefined distortion and topological changes; 2) by considering positions as variational parameters, it becomes straightforward to couple with Lagrangian hyper-elastic solid solvers, which may also be formulated in terms of positions or displacements in a monolithic way. Numerical examples conducted to validate the formulation demonstrate its robustness and efficiency for finite strain free surface flows, including phenomena such as dam breaks with smooth surfaces and sloshing.

Predicting the passive control of fluid forces over circular cylinder in a time dependent flow using neuro-computing

The objective of this research is to combine Artificial Neural Networks (ANNs) and Computational Fluid Dynamics (CFD) approaches to leverage the advantages of both methods. To achieve this goal, we introduce a new artificial neural network architecture designed specifically for predicting fluid forces within the CFD framework, aiming to reduce computational costs. Initially, time-dependent simulations around a rigid cylinder and a passive device (attached and detached) were conducted, followed by a thorough analysis of the hydrodynamic drag and lift forces encountered by the cylinder and passive device with various length L=0.1,0.2,0.3 and gap spacing Gi=0.1,0.2,0.3. The inhibition of vortex shedding is noted for gap separations of 0.1 and 0.2. However, a splitter plate of insufficient length or placed at an unsuitable distance from an obstacle yields no significant benefits. The finite element method is employed as a computational technique to address complex nonlinear governing equations. The nonlinear partial differential equations are spatially discretized with the finite element method, while temporal derivatives are addressed using a backward implicit Euler scheme. Velocity and pressure plots are provided to illustrate the physical aspects of the problem. The results indicate that the introduction of a splitter plate has reduced vortex shedding, leading to a steady flow regime, as evidenced by the stable drag and lift coefficients. The data obtained from simulations were utilized to train a neural network architecture based on the feed-forward backpropagation algorithm of Levenberg–Marquardt. Following training and validation stages, predictions for drag and lift coefficients were made without the need for additional CFD simulations. These results show that the mean square error values are very close to zero, indicating a strong correlation between the fluid force coefficients obtained from CFD and those predicted by the ANN. Additionally, a significant reduction in computational time was achieved without sacrificing the accuracy of the drag and lift coefficient predictions.

Optimizing Biomass Briquette Drying: A Computational Fluid Dynamics Approach with a Case Study in Mozambique

Biomass fuels remain the primary cooking energy source in many developing regions, contributing to deforestation and greenhouse gas emissions. Briquettes made from waste biomass are a sustainable alternative; however, their production is hindered by inefficient drying methods, such as open sun drying, which can take 5 to 7 days. This study evaluates the thermal and airflow performance of a solar tunnel dryer (STD) designed to accelerate drying times for charcoal briquettes under Mozambique's climatic conditions. Using Computational Fluid Dynamics (CFD) simulations, temperature and airflow distributions were analyzed to optimize dryer performance. Moisture and temperature profiles of hexagonal briquettes with inner holes indicated effective drying, achieving uniform moisture reduction to 10% from an initial 50%. Drying time was projected based on simulated airflow and temperature conditions, showing a significant reduction compared to traditional methods. The STD, operating with air temperatures of 36.5°C to 65°C and velocities up to 33.5 m/s at a mass flow rate of 1.36 kg/s, demonstrated its potential to enhance briquette production efficiency while maintaining environmental sustainability. The findings underscore the viability of solar drying technology for biomass fuel processing.

Design Optimisation of a Screw Compressor with a Focus on Rotor Depth: A Computational Fluid Dynamics Approach

Design Optimisation of a Screw Compressor with a Focus on Rotor Depth: A Computational Fluid Dynamics Approach

CFD Analysis into the Breakdown of Catamaran Resistance Based on the Original Formula by Insel and Molland

Over the last 40 years, the use of fast catamaran has progressively developed attributed to its unique characteristics on resistance and seakeeping. The advantages have also been applied to military vessels to gain both resistance and seakeeping benefits. The current study focuses on the resistance of catamaran warships to provide less resistance, therefore, the size of engine and emission of toxic gases to the atmosphere. The total resistance of a catamaran will be different from a monohull of equal displacement. There are several factors including viscous interference factors such as φ, which is introduced to take account of the pressure field change around the hull, σ takes account of the velocity augmentation between the two hulls and calculated from an integration of local frictional resistance over the wetted surface, and τ is the wave resistance interference factor change. Those resistance components were developed by Insel and Molland in the 1990s. The investigation discusses the derivation of those components numerically using Computational Fluid Dynamics (CFD) approach. The speeds (hence, the Froude numbers) are varied from 0.2 to 0.6 and the separations between the hulls (S/L) are made between 0.2 and 0.4 so the comparative purposes can be done against the classical work of Insel and Molland and other published data.

CFD Investigation of Toluene Emission In a Printing Room

Volatile organic compounds (VOCs) comprise several harmful chemical such as benzene and toluene, that can cause acute and chronic health effects for individuals. One of contributors of VOC are printers, photocopiers, and fax machine that use ink that when it is heated during printing operations will emit VOC. Printing shops heavily operate these devices (machines) and often several of them at the same time and this will cause the VOC level inside the premises to be higher compared to home and offices that have similar equipment. This study estimates the VOC, particularly toluene, concentration, and distribution inside a printing room, by using Computer Fluid Dynamic (CFD) analysis approach software. The software aid in physical modelling of the emission flow based on copiers machine numbers and influence of parameters like concentration levels and anthropometric data. Despite implementing ventilation and at a minimum number of operating copiers, the study reveals that toluene emissions exceed the recommended limit, particularly among females who have higher exposure than males due to height. The quantity of copiers and the positioning influenced the dispersion of toluene in the investigated area.

Heat Transfer in The Energy Storage During Solidification

Phase-change materials combined with thermal energy storage technology can improve energy efficiency. This study aims to analyse heat transfer in thermal energy storage tanks under solidification conditions. This involves developing storage tanks with three different numbers of paraffin balls: 4, 6, and 8 balls) in the TES tank. The tanks were designed for residential use, and the analysis will use Computational Fluid Dynamics (CFD) approaches to evaluate heat transfer efficiency. This comprehensive investigation seeks to optimise the configuration and operation of PCM-based thermal energy storage systems for residential applications. Increasing the number of paraffin balls resulted in a more uniform temperature distribution and a larger total heat transfer rate due to the larger surface area available for heat transfer; however, fewer paraffin balls led to a more significant pressure drop in the tank. Based on these findings, it is suggested to use a TES tank with a larger number of paraffin balls to improve heat transfer efficiency and temperature uniformity in residential applications.

Real-Time Environmental Design Parameters and their Impact on the Performance of Passive Basin Solar Still: A Dynamic CFD Modeling Approach

A computational fluid dynamics (CFD) approach was used in this work to investigate various design and environmental factors and their impact on the performance of passive basin solar stills (PBSS). This requires using the ANSYS software to build a sophisticated geometrical solar still model with the associated solar cells. The impact of solar cell configuration on energy optimization was determined by analyzing the developed system in both series and parallel configurations. Accuracy of simulation results was ensured in the model by introducing a meshing technique that consisted of>2 million components. The results (for static pressure analysis) indicated the absence of any high-pressure-induced strains after evaluating the performance metrics (static pressure, velocity, and energy distribution) for impact on the system using > 200 iterations; this suggests that the system design is balanced. Hence, the performance of solar stills can be improved by using new materials and design configurations as shown in this work. This study has improved knowledge of solar water desalination and other forms of renewable energy sources for related applications.